nana/source/gui/widgets/skeletons/text_editor.cpp

/*
 *	A text editor implementation
 *	Nana C++ Library(http://www.nanapro.org)
 *	Copyright(C) 2003-2018 Jinhao(cnjinhao@hotmail.com)
 *
 *	Distributed under the Boost Software License, Version 1.0.
 *	(See accompanying file LICENSE_1_0.txt or copy at
 *	http://www.boost.org/LICENSE_1_0.txt)
 *
 *	@file: nana/gui/widgets/skeletons/text_editor.cpp
 *	@contributors: Ariel Vina-Rodriguez, Oleg Smolsky
 */
#include <nana/gui/widgets/skeletons/text_editor.hpp>
#include <nana/gui/widgets/skeletons/textbase_export_interface.hpp>
#include <nana/gui/element.hpp>
#include <nana/system/dataexch.hpp>
#include <nana/unicode_bidi.hpp>
#include <nana/gui/widgets/widget.hpp>
#include "content_view.hpp"

#include <deque>
#include <numeric>
#include <cwctype>
#include <cstring>
#include <algorithm>
#include <map>

namespace nana{	namespace widgets
{
	namespace skeletons
	{

		template<typename EnumCommand>
		class undoable_command_interface
		{
		public:
			virtual ~undoable_command_interface() = default;

			virtual EnumCommand get() const = 0;
			virtual bool merge(const undoable_command_interface&) = 0;
			virtual void execute(bool redo) = 0;
		};

		template<typename EnumCommand>
		class undoable
		{
		public:
			using command = EnumCommand;
			using container = std::deque<std::unique_ptr<undoable_command_interface<command>>>;

			void clear()
			{
				commands_.clear();
				pos_ = 0;
			}

			void max_steps(std::size_t maxs)
			{
				max_steps_ = maxs;
				if (maxs && (commands_.size() >= maxs))
					commands_.erase(commands_.begin(), commands_.begin() + (commands_.size() - maxs + 1));
			}

			std::size_t max_steps() const
			{
				return max_steps_;
			}

			void enable(bool enb)
			{
				enabled_ = enb;
				if (!enb)
					clear();
			}

			bool enabled() const
			{
				return enabled_;
			}

			void push(std::unique_ptr<undoable_command_interface<command>> && ptr)
			{
				if (!ptr || !enabled_)
					return;

				if (pos_ < commands_.size())
					commands_.erase(commands_.begin() + pos_, commands_.end());
				else if (max_steps_ && (commands_.size() >= max_steps_))
					commands_.erase(commands_.begin(), commands_.begin() + (commands_.size() - max_steps_ + 1));

				pos_ = commands_.size();
				if (!commands_.empty())
				{
					if (commands_.back().get()->merge(*ptr))
						return;
				}

				commands_.emplace_back(std::move(ptr));
				++pos_;
			}

			std::size_t count(bool is_undo) const
			{
				return (is_undo ? pos_ : commands_.size() - pos_);
			}

			void undo()
			{
				if (pos_ > 0)
				{
					--pos_;
					commands_[pos_].get()->execute(false);
				}
			}

			void redo()
			{
				if (pos_ != commands_.size())
					commands_[pos_++].get()->execute(true);
			}

		private:
			container commands_;
			bool		enabled_{ true };
			std::size_t max_steps_{ 30 };
			std::size_t pos_{ 0 };
		};

		template<typename T>
		using undo_command_ptr = std::unique_ptr <undoable_command_interface<T>> ;

		template<typename EnumCommand>
		class text_editor::basic_undoable
			: public undoable_command_interface<EnumCommand>
		{
		public:
			basic_undoable(text_editor& te, EnumCommand cmd)
				: editor_(te), cmd_(cmd)
			{}

			void set_selected_text()
			{
				//sel_a_ and sel_b_ are not sorted, sel_b_ keeps the caret position.
				sel_a_ = editor_.select_.a;
				sel_b_ = editor_.select_.b;

				if (sel_a_ != sel_b_)
				{
					selected_text_ = editor_._m_make_select_string();
				}
			}

			void set_caret_pos()
			{
				pos_ = editor_.caret();
			}
		protected:
			EnumCommand get() const override
			{
				return cmd_;
			}

			virtual bool merge(const undoable_command_interface<EnumCommand>&) override
			{
				return false;
			}
		protected:
			text_editor & editor_;
			upoint			pos_;
			upoint			sel_a_, sel_b_;
			std::wstring	selected_text_;
		private:
			const EnumCommand cmd_;
		};

		class text_editor::undo_backspace
			: public basic_undoable < command >
		{
		public:
			undo_backspace(text_editor& editor)
				:	basic_undoable<command>(editor, command::backspace)
			{
			}

			void set_removed(std::wstring str)
			{
				selected_text_ = std::move(str);
			}

			void execute(bool redo) override
			{
				editor_._m_cancel_select(0);
				editor_.points_.caret = pos_;

				bool is_enter = ((selected_text_.size() == 1) && ('\n' == selected_text_[0]));
				if (redo)
				{
					if (sel_a_ != sel_b_)
					{
						editor_.select_.a = sel_a_;
						editor_.select_.b = sel_b_;
						editor_._m_erase_select();
						editor_.select_.a = editor_.select_.b;
						editor_.points_.caret = sel_a_;
					}
					else
					{
						if (is_enter)
						{
							editor_.points_.caret = nana::upoint(0, pos_.y + 1);
							editor_.backspace(false);
						}
						else
							editor_.textbase().erase(pos_.y, pos_.x, selected_text_.size());
					}
				}
				else
				{
					if (is_enter)
					{
						editor_.enter(false);
					}
					else
					{
						editor_._m_put(selected_text_);
						if (sel_a_ != sel_b_)
						{
							editor_.select_.a = sel_a_;
							editor_.select_.b = sel_b_;
							editor_.points_.caret = sel_b_;
						}
						else
							++editor_.points_.caret.x;
					}
				}

				editor_.reset_caret();
			}
		};

		class text_editor::undo_input_text
			: public basic_undoable <command>
		{
		public:
			undo_input_text(text_editor & editor, const std::wstring& text)
				:	basic_undoable<command>(editor, command::input_text),
					text_(text)
			{
			}

			void execute(bool redo) override
			{
				bool is_enter = (text_.size() == 1 && '\n' == text_[0]);
				editor_._m_cancel_select(0);
				editor_.points_.caret = pos_;	//The pos_ specifies the caret position before input

				if (redo)
				{
					if (is_enter)
					{
						editor_.enter(false);
					}
					else
					{
						if (!selected_text_.empty())
						{
							editor_.select_.a = sel_a_;
							editor_.select_.b = sel_b_;
							editor_._m_erase_select();
						}
						editor_.points_.caret = editor_._m_put(text_); //redo
					}
				}
				else
				{
					if (is_enter)
					{
						editor_.points_.caret.x = 0;
						++editor_.points_.caret.y;
						editor_.backspace(false);
					}
					else
					{
						std::vector<std::pair<std::size_t, std::size_t>> lines;
						if (editor_._m_resolve_text(text_, lines))
						{
							editor_.select_.a = pos_;
							editor_.select_.b = upoint(static_cast<unsigned>(lines.back().second - lines.back().first), static_cast<unsigned>(pos_.y + lines.size() - 1));
							editor_.backspace(false);
							editor_.select_.a = editor_.select_.b;
						}
						else
							editor_.textbase().erase(pos_.y, pos_.x, text_.size());	//undo
					}

					if (!selected_text_.empty())
					{
						editor_.points_.caret = (std::min)(sel_a_, sel_b_);
						editor_._m_put(selected_text_);
						editor_.points_.caret = sel_b_;
						editor_.select_.a = sel_a_;	//Reset the selected text
						editor_.select_.b = sel_b_;
					}
				}
				editor_.reset_caret();
			}
		private:
			std::wstring text_;
		};

		class text_editor::undo_move_text
			: public basic_undoable <command>
		{
		public:
			undo_move_text(text_editor& editor)
				:	basic_undoable<command>(editor, command::move_text)
			{}

			void execute(bool redo) override
			{
				if (redo)
				{
					editor_.select_.a = sel_a_;
					editor_.select_.b = sel_b_;
					editor_.points_.caret = pos_;
					editor_._m_move_select(false);
				}
				else
				{
					editor_.select_.a = dest_a_;
					editor_.select_.b = dest_b_;
					editor_.points_.caret = (sel_a_ < sel_b_ ? sel_a_ : sel_b_);

					const auto text = editor_._m_make_select_string();

					editor_._m_erase_select();
					editor_._m_put(text);

					editor_.select_.a = sel_a_;
					editor_.select_.b = sel_b_;

					editor_.points_.caret = sel_b_;
					editor_.reset_caret();
				}
			}

			void set_destination(const nana::upoint& dest_a, const nana::upoint& dest_b)
			{
				dest_a_ = dest_a;
				dest_b_ = dest_b;
			}
		private:
			nana::upoint dest_a_, dest_b_;
		};

		struct text_editor::text_section
		{
			const wchar_t* begin{ nullptr };
			const wchar_t* end{ nullptr };
			unsigned pixels{ 0 };

			text_section() = default;
			text_section(const wchar_t* ptr, const wchar_t* endptr, unsigned px)
				: begin(ptr), end(endptr), pixels(px)
			{}
		};


		struct keyword_scheme
		{
			::nana::color fgcolor;
			::nana::color bgcolor;
		};

		struct keyword_desc
		{
			std::wstring text;
			std::string scheme;
			bool case_sensitive;
			bool whole_word_matched;

			keyword_desc(const std::wstring& txt, const std::string& schm, bool cs, bool wwm)
				: text(txt), scheme(schm), case_sensitive(cs), whole_word_matched(wwm)
			{}
		};

		struct entity
		{
			const wchar_t* begin;
			const wchar_t* end;
			const keyword_scheme * scheme;
		};

		enum class sync_graph
		{
			none,
			refresh,
			lazy_refresh
		};

		colored_area_access_interface::~colored_area_access_interface(){}

		class colored_area_access
			: public colored_area_access_interface
		{
		public:
			void set_window(window handle)
			{
				window_handle_ = handle;
			}

			std::shared_ptr<colored_area_type> find(std::size_t pos) const
			{
				for (auto & sp : colored_areas_)
				{
					if (sp->begin <= pos && pos < sp->begin + sp->count)
						return sp;
					else if (sp->begin > pos)
						break;
				}
				return{};
			}
		public:
			//Overrides methods of colored_area_access_interface
			std::shared_ptr<colored_area_type> get(std::size_t line_pos) override
			{
#ifdef _MSC_VER
				auto i = colored_areas_.cbegin();
				for (; i != colored_areas_.cend(); ++i)
#else
				auto i = colored_areas_.begin();
				for (; i != colored_areas_.end(); ++i)
#endif
				{
					auto & area = *(i->get());
					if (area.begin <= line_pos && line_pos < area.begin + area.count)
						return *i;

					if (area.begin > line_pos)
						break;
				}

				return *colored_areas_.emplace(i,
						std::make_shared<colored_area_type>(colored_area_type{line_pos, 1, color{}, color{}})
					);
			}

			bool clear() override
			{
				if (colored_areas_.empty())
					return false;

				colored_areas_.clear();
				API::refresh_window(window_handle_);
				return true;
			}

			bool remove(std::size_t pos) override
			{
				bool changed = false;
#ifdef _MSC_VER
				for (auto i = colored_areas_.cbegin(); i != colored_areas_.cend();)
#else
				for (auto i = colored_areas_.begin(); i != colored_areas_.end();)
#endif
				{
					if (i->get()->begin <= pos && pos < i->get()->begin + i->get()->count)
					{
						i = colored_areas_.erase(i);
						changed = true;
					}
					else if (i->get()->begin > pos)
						break;
				}
				if (changed)
					API::refresh_window(window_handle_);

				return changed;
			}

			std::size_t size() const override
			{
				return colored_areas_.size();
			}

			std::shared_ptr<colored_area_type> at(std::size_t index) override
			{
				return colored_areas_.at(index);
			}
		private:
			window window_handle_;
			std::vector<std::shared_ptr<colored_area_type>> colored_areas_;
		};

		struct text_editor::implementation
		{
			undoable<command>	undo;			//undo command
			renderers			customized_renderers;
			std::vector<upoint> text_position;	//positions of text since last rendering.
			int text_position_origin{ -1 };	//origin when last text_exposed

			skeletons::textbase<wchar_t> textbase;

			sync_graph try_refresh{ sync_graph::none };

			colored_area_access colored_area;

			struct inner_capacities
			{
				editor_behavior_interface * behavior;

				accepts acceptive{ accepts::no_restrict };
				std::function<bool(char_type)> pred_acceptive;
			}capacities;

			struct inner_counterpart
			{
				bool enabled{ false };
				paint::graphics buffer;	//A offscreen buffer which keeps the background that painted by external part.
			}counterpart;

			struct indent_rep
			{
				bool enabled{ false };
				std::function<std::string()> generator;
			}indent;

			struct inner_keywords
			{
				std::map<std::string, std::shared_ptr<keyword_scheme>> schemes;
				std::deque<keyword_desc> base;
			}keywords;

			std::unique_ptr<content_view> cview;
		};


		class text_editor::editor_behavior_interface
		{
		public:
			using row_coordinate = std::pair<std::size_t, std::size_t>; ///< A coordinate type for line position. first: the absolute line position of text. second: the secondary line position of a part of line.

			virtual ~editor_behavior_interface() = default;

			/// Returns the text sections of a specified line
			/**
			 * @param pos The absolute line number.
			 * @return The text sections of this line.
			 */
			virtual std::vector<text_section> line(std::size_t pos) const = 0;
			virtual row_coordinate text_position_from_screen(int top) const = 0;

			virtual unsigned max_pixels() const = 0;

			/// Deletes lines between first and second, and then, second line will be merged into first line.
			virtual void merge_lines(std::size_t first, std::size_t second) = 0;
			//Calculates how many lines the specified line of text takes with a specified pixels of width.
			virtual void add_lines(std::size_t pos, std::size_t lines) = 0;
			virtual void prepare() = 0;
			virtual void pre_calc_line(std::size_t line, unsigned pixels) = 0;
			virtual void pre_calc_lines(unsigned pixels) = 0;
			virtual std::size_t take_lines() const = 0;
			/// Returns the number of lines that the line of text specified by pos takes.
			virtual std::size_t take_lines(std::size_t pos) const = 0;
		};

		inline bool is_right_text(const unicode_bidi::entity& e)
		{
			return ((e.bidi_char_type != unicode_bidi::bidi_char::L) && (e.level & 1));
		}


		class text_editor::behavior_normal
			: public editor_behavior_interface
		{
		public:
			behavior_normal(text_editor& editor)
				: editor_(editor)
			{}

			std::vector<text_section> line(std::size_t pos) const override
			{
				//Every line of normal behavior only has one text_section
				std::vector<text_section> sections;
				sections.emplace_back(this->sections_[pos]);
				return sections;
			}

			row_coordinate text_position_from_screen(int top) const override
			{
				const std::size_t textlines = editor_.textbase().lines();
				const auto line_px = static_cast<int>(editor_.line_height());
				if ((0 == textlines) || (0 == line_px))
					return{};

				if (top < editor_.text_area_.area.y)
					top = (std::max)(editor_._m_text_topline() - 1, 0);
				else
					top = (top - editor_.text_area_.area.y + editor_.impl_->cview->origin().y) / line_px;

				return{ (textlines <= static_cast<std::size_t>(top) ? textlines - 1 : static_cast<std::size_t>(top)),
					0 };
			}

			unsigned max_pixels() const override
			{
				unsigned px = editor_.width_pixels();
				for (auto & sct : sections_)
				{
					if (sct.pixels > px)
						px = sct.pixels;
				}
				return px;
			}

			void merge_lines(std::size_t first, std::size_t second) override
			{
				if (first > second)
					std::swap(first, second);

				if (second < this->sections_.size())
#ifdef _MSC_VER
					this->sections_.erase(this->sections_.cbegin() + (first + 1), this->sections_.cbegin() + second);
#else
					this->sections_.erase(this->sections_.begin() + (first + 1), this->sections_.begin() + second);
#endif
				pre_calc_line(first, 0);

				//textbase is implement by using deque, and the linemtr holds the text pointers
				//If the textbase is changed, it will check the text pointers.
				std::size_t line = 0;

				auto const & const_sections = sections_;
				for (auto & sct : const_sections)
				{
					auto const& text = editor_.textbase().getline(line);
					if (sct.begin < text.c_str() || (text.c_str() + text.size() < sct.begin))
						pre_calc_line(line, 0);

					++line;
				}
			}

			void add_lines(std::size_t pos, std::size_t line_size) override
			{
				if (pos < this->sections_.size())
				{
					for (std::size_t i = 0; i < line_size; ++i)
#ifdef _MSC_VER
						this->sections_.emplace(this->sections_.cbegin() + (pos + i));
#else
						this->sections_.emplace(this->sections_.begin() + (pos + i));
#endif
					//textbase is implement by using deque, and the linemtr holds the text pointers
					//If the textbase is changed, it will check the text pointers.
					std::size_t line = 0;

					auto const & const_sections = sections_;
					for (auto & sct : const_sections)
					{
						if (line < pos || (pos + line_size) <= line)
						{
							auto const & text = editor_.textbase().getline(line);
							if (sct.begin < text.c_str() || (text.c_str() + text.size() < sct.begin))
								pre_calc_line(line, 0);
						}
						++line;
					}
				}
			}

			void prepare() override
			{
				auto const line_count = editor_.textbase().lines();
				this->sections_.resize(line_count);
			}

			void pre_calc_line(std::size_t pos, unsigned) override
			{
				auto const & text = editor_.textbase().getline(pos);
				auto& txt_section = this->sections_[pos];
				txt_section.begin = text.c_str();
				txt_section.end = txt_section.begin + text.size();
				txt_section.pixels = editor_._m_text_extent_size(txt_section.begin, text.size()).width;
			}

			void pre_calc_lines(unsigned) override
			{
				auto const line_count = editor_.textbase().lines();
				this->sections_.resize(line_count);
				for (std::size_t i = 0; i < line_count; ++i)
					pre_calc_line(i, 0);
			}

			std::size_t take_lines() const override
			{
				return editor_.textbase().lines();
			}

			std::size_t take_lines(std::size_t) const override
			{
				return 1;
			}
		private:
			text_editor& editor_;
			std::vector<text_section> sections_;
		}; //end class behavior_normal


		class text_editor::behavior_linewrapped
			: public text_editor::editor_behavior_interface
		{
			struct line_metrics
			{
				std::size_t		take_lines;	//The number of lines that text of this line takes.
				std::vector<text_section>	line_sections;
			};
		public:
			behavior_linewrapped(text_editor& editor)
				: editor_(editor)
			{}

			std::vector<text_section> line(std::size_t pos) const override
			{
				return linemtr_[pos].line_sections;
			}

			row_coordinate text_position_from_screen(int top) const override
			{
				row_coordinate coord;
				const auto line_px = static_cast<int>(editor_.line_height());

				if ((0 == editor_.textbase().lines()) || (0 == line_px))
					return coord;

				auto text_row = (std::max)(0, (top - editor_.text_area_.area.y + editor_.impl_->cview->origin().y) / line_px);

				coord = _m_textline(static_cast<std::size_t>(text_row));
				if (linemtr_.size() <= coord.first)
				{
					coord.first = linemtr_.size() - 1;
					coord.second = linemtr_.back().line_sections.size() - 1;
				}
				return coord;
			}

			unsigned max_pixels() const override
			{
				return editor_.width_pixels();
			}

			void merge_lines(std::size_t first, std::size_t second) override
			{
				if (first > second)
					std::swap(first, second);

				if (second < linemtr_.size())
					linemtr_.erase(linemtr_.begin() + first + 1, linemtr_.begin() + second + 1);

				auto const width_px = editor_.width_pixels();

				pre_calc_line(first, width_px);
			}

			void add_lines(std::size_t pos, std::size_t lines) override
			{
				if (pos < linemtr_.size())
				{
					for (std::size_t i = 0; i < lines; ++i)
						linemtr_.emplace(linemtr_.begin() + pos + i);

					//textbase is implement by using deque, and the linemtr holds the text pointers
					//If the textbase is changed, it will check the text pointers.
					std::size_t line = 0;

					auto const & const_linemtr = linemtr_;
					for (auto & mtr : const_linemtr)
					{
						if (line < pos || (pos + lines) <= line)
						{
							auto & linestr = editor_.textbase().getline(line);
							auto p = mtr.line_sections.front().begin;
							if (p < linestr.c_str() || (linestr.c_str() + linestr.size() < p))
								pre_calc_line(line, editor_.width_pixels());
						}
						++line;
					}
				}
			}

			void prepare() override
			{
				auto const lines = editor_.textbase().lines();
				linemtr_.resize(lines);
			}

			void pre_calc_line(std::size_t line, unsigned pixels) override
			{
				const string_type& lnstr = editor_.textbase().getline(line);
				if (lnstr.empty())
				{
					auto & mtr = linemtr_[line];
					mtr.line_sections.clear();

					mtr.line_sections.emplace_back(lnstr.c_str(), lnstr.c_str(), unsigned{});
					mtr.take_lines = 1;
					return;
				}

				std::vector<text_section> sections;
				_m_text_section(lnstr, sections);

				std::vector<text_section> line_sections;

				unsigned text_px = 0;
				const wchar_t * secondary_begin = nullptr;
				for (auto & ts : sections)
				{
					if (!secondary_begin)
						secondary_begin = ts.begin;

					const unsigned str_w = editor_._m_text_extent_size(ts.begin, ts.end - ts.begin).width;

					text_px += str_w;
					if (text_px >= pixels)
					{
						if (text_px != str_w)
						{
							line_sections.emplace_back(secondary_begin, ts.begin, unsigned{ text_px - str_w });
							text_px = str_w;
							secondary_begin = ts.begin;
						}

						if (str_w > pixels)	//Indicates the splitting of ts string
						{
							std::size_t len = ts.end - ts.begin;
#ifdef _nana_std_has_string_view
							auto pxbuf = editor_.graph_.glyph_pixels({ts.begin, len});
#else
							std::unique_ptr<unsigned[]> pxbuf(new unsigned[len]);
							editor_.graph_.glyph_pixels(ts.begin, len, pxbuf.get());
#endif

							auto pxptr = pxbuf.get();
							auto pxend = pxptr + len;

							secondary_begin = ts.begin;
							text_px = 0;
							for (auto pxi = pxptr; pxi != pxend; ++pxi)
							{
								text_px += *pxi;
								if (text_px < pixels)
									continue;

								const wchar_t * endptr = ts.begin + (pxi - pxptr) + (text_px == pixels ? 1 : 0);
								line_sections.emplace_back(secondary_begin, endptr, unsigned{ text_px - (text_px == pixels ? 0 : *pxi) });
								secondary_begin = endptr;

								text_px = (text_px == pixels ? 0 : *pxi);
							}
						}
						continue;
					}
					else if (text_px == pixels)
					{
						line_sections.emplace_back(secondary_begin, ts.begin, unsigned{ text_px - str_w });
						secondary_begin = ts.begin;
						text_px = str_w;
					}
				}

				auto & mtr = linemtr_[line];

				mtr.take_lines = line_sections.size();
				mtr.line_sections.swap(line_sections);

				if (secondary_begin)
				{
					mtr.line_sections.emplace_back(secondary_begin, sections.back().end, unsigned{ text_px });
					++mtr.take_lines;
				}
			}

			void pre_calc_lines(unsigned pixels) override
			{
				auto const lines = editor_.textbase().lines();
				linemtr_.resize(lines);

				for (std::size_t i = 0; i < lines; ++i)
					pre_calc_line(i, pixels);
			}

			std::size_t take_lines() const override
			{
				std::size_t lines = 0;
				for (auto & mtr : linemtr_)
					lines += mtr.take_lines;

				return lines;
			}

			std::size_t take_lines(std::size_t pos) const override
			{
				return (pos < linemtr_.size() ? linemtr_[pos].take_lines : 0);
			}
		private:
			/// Split a text into multiple sections, a section indicates an english word or a CKJ character
			void _m_text_section(const std::wstring& str, std::vector<text_section>& tsec)
			{
				if (str.empty())
				{
					tsec.emplace_back(str.c_str(), str.c_str(), unsigned{});
					return;
				}
				const auto end = str.c_str() + str.size();

				const wchar_t * word = nullptr;
				for (auto i = str.c_str(); i != end; ++i)
				{
					wchar_t const ch = *i;

					//CKJ characters and whitespace
					if (' ' == ch || '\t' == ch || (0x4E00 <= ch && ch <= 0x9FCF))
					{
						if (word)	//Record the word.
						{
							tsec.emplace_back(word, i, unsigned{});
							word = nullptr;
						}

						tsec.emplace_back(i, i + 1, unsigned{});
						continue;
					}

					if (nullptr == word)
						word = i;
				}

				if(word)
					tsec.emplace_back(word, end, unsigned{});
			}

			row_coordinate _m_textline(std::size_t scrline) const
			{
				row_coordinate coord;
				for (auto & mtr : linemtr_)
				{
					if (mtr.take_lines > scrline)
					{
						coord.second = scrline;
						return coord;
					}
					else
						scrline -= mtr.take_lines;

					++coord.first;
				}
				return coord;
			}
		private:
			text_editor& editor_;
			std::vector<line_metrics> linemtr_;
		}; //end class behavior_linewrapped

		class text_editor::keyword_parser
		{
		public:
			void parse(const wchar_t* c_str, std::size_t len, implementation::inner_keywords& keywords) //need string_view
			{
				if ( keywords.base.empty() || (0 == len) || (*c_str == 0) )
					return;

				std::wstring text{ c_str, len };

				using index = std::wstring::size_type;

				std::vector<entity> entities;

				::nana::ciwstring cistr;
				for (auto & ds : keywords.base)
				{
                    index pos{0} ;
                    for (index rest{text.size()}; rest >= ds.text.size() ; ++pos, rest = text.size() - pos)
                    {
					    if (ds.case_sensitive)
					    {
						    pos = text.find(ds.text, pos);
						    if (pos == text.npos)
							    break;
					    }
					    else
					    {
						    if (cistr.empty())
							    cistr.append(text.c_str(), text.size());

						    pos = cistr.find(ds.text.c_str(), pos);
						    if (pos == cistr.npos)
							    break;
					    }

						if (ds.whole_word_matched && (!_m_whole_word(text, pos, ds.text.size())))
							continue;

					    auto ki = keywords.schemes.find(ds.scheme);
					    if ((ki != keywords.schemes.end()) && ki->second)
					    {
							entities.emplace_back();
							auto & last = entities.back();
							last.begin = c_str + pos;
							last.end = last.begin + ds.text.size();
							last.scheme = ki->second.get();
					    }
                    }
				}

				if (!entities.empty())
				{
					std::sort(entities.begin(), entities.end(), [](const entity& a, const entity& b)
					{
						return (a.begin < b.begin);
					});

					auto i = entities.begin();
					auto bound = i->end;

					for (++i; i != entities.end(); )
					{
						if (bound > i->begin)
							i = entities.erase(i);  // erase overlaping. Left only the first.
						else
							++i;
					}
				}

				entities_.swap(entities);
			}

			const std::vector<entity>& entities() const
			{
				return entities_;
			}
		private:
			static bool _m_whole_word(const std::wstring& text, std::wstring::size_type pos, std::size_t len)
			{
				if (pos)
				{
					auto chr = text[pos - 1];
					if ((std::iswalpha(chr) && !std::iswspace(chr)) || chr == '_')
						return false;
				}

				if (pos + len < text.size())
				{
					auto chr = text[pos + len];
					if ((std::iswalpha(chr) && !std::iswspace(chr)) || chr == '_')
						return false;
				}

				return true;
			}
		private:
			std::vector<entity> entities_;
		};

		//class text_editor

		text_editor::text_editor(window wd, graph_reference graph, const text_editor_scheme* schm)
			:	impl_(new implementation),
				window_(wd),
				graph_(graph),
				scheme_(schm)
		{
			impl_->capacities.behavior = new behavior_normal(*this);

			text_area_.area.dimension(graph.size());

			impl_->cview.reset(new content_view{ wd });
			impl_->cview->disp_area(text_area_.area, {}, {}, {});
			impl_->cview->events().scrolled = [this] {
				this->reset_caret();
			};

			impl_->cview->events().hover_outside = [this](const point& pos) {
				mouse_caret(pos, false);
				if (selection::mode::mouse_selected == select_.mode_selection || selection::mode::method_selected == select_.mode_selection)
					set_end_caret(false);
			};

			API::create_caret(wd, { 1, line_height() });
			API::bgcolor(wd, colors::white);
			API::fgcolor(wd, colors::black);
		}

		text_editor::~text_editor()
		{
			//For instance of unique_ptr pimpl idiom.

			delete impl_->capacities.behavior;
			delete impl_;
		}

		size text_editor::caret_size() const
		{
			return { 1, line_height() };
		}

		const point& text_editor::content_origin() const
		{
			return impl_->cview->origin();
		}

		void text_editor::set_highlight(const std::string& name, const ::nana::color& fgcolor, const ::nana::color& bgcolor)
		{
			if (fgcolor.invisible() && bgcolor.invisible())
			{
				impl_->keywords.schemes.erase(name);
				return;
			}

			auto sp = std::make_shared<keyword_scheme>();
			sp->fgcolor = fgcolor;
			sp->bgcolor = bgcolor;
			impl_->keywords.schemes[name].swap(sp);
		}

		void text_editor::erase_highlight(const std::string& name)
		{
			impl_->keywords.schemes.erase(name);
		}

		void text_editor::set_keyword(const ::std::wstring& kw, const std::string& name, bool case_sensitive, bool whole_word_matched)
		{
			for(auto & ds : impl_->keywords.base)
			{
				if (ds.text == kw)
				{
					ds.scheme = name;
					ds.case_sensitive = case_sensitive;
					ds.whole_word_matched = whole_word_matched;
					return;
				}
			}

			impl_->keywords.base.emplace_back(kw, name, case_sensitive, whole_word_matched);
		}

		void text_editor::erase_keyword(const ::std::wstring& kw)
		{
			for (auto i = impl_->keywords.base.begin(); i != impl_->keywords.base.end(); ++i)
			{
				if (kw == i->text)
				{
					impl_->keywords.base.erase(i);
					return;
				}
			}
		}

		colored_area_access_interface& text_editor::colored_area()
		{
			return impl_->colored_area;
		}

		void text_editor::set_accept(std::function<bool(char_type)> pred)
		{
			impl_->capacities.pred_acceptive = std::move(pred);
		}

		void text_editor::set_accept(accepts acceptive)
		{
			impl_->capacities.acceptive = acceptive;
		}

		bool text_editor::respond_char(const arg_keyboard& arg)	//key is a character of ASCII code
		{
			if (!API::window_enabled(window_))
				return false;

			char_type key = arg.key;
			switch (key)
			{
			case keyboard::end_of_text:
				copy();
				return false;
			case keyboard::select_all:
				select(true);
				return true;
			}

			if (attributes_.editable && (!impl_->capacities.pred_acceptive || impl_->capacities.pred_acceptive(key)))
			{
				switch (key)
				{
				case '\b':
					backspace();	break;
				case '\n': case '\r':
					enter();	break;
				case keyboard::sync_idel:
					paste();	break;
				case keyboard::tab:
					put(static_cast<wchar_t>(keyboard::tab)); break;
				case keyboard::cancel:
					cut();
					break;
				case keyboard::end_of_medium:
					undo(true);
					break;
				case keyboard::substitute:
					undo(false);
					break;
				default:
					if (!_m_accepts(key))
						return false;

					if (key > 0x7F || (32 <= key && key <= 126))
						put(key);
				}
				reset_caret();
				impl_->try_refresh = sync_graph::refresh;
				return true;
			}
			return false;
		}

		bool text_editor::respond_key(const arg_keyboard& arg)
		{
			char_type key = arg.key;
			switch (key)
			{
			case keyboard::os_arrow_left:
			case keyboard::os_arrow_right:
			case keyboard::os_arrow_up:
			case keyboard::os_arrow_down:
			case keyboard::os_home:
			case keyboard::os_end:
			case keyboard::os_pageup:
			case keyboard::os_pagedown:
				_m_handle_move_key(arg);
				break;
			case keyboard::del:
				// send delete to set_accept function
				if (this->attr().editable && (!impl_->capacities.pred_acceptive || impl_->capacities.pred_acceptive(key)))
					del();
				break;
			default:
				return false;
			}
			impl_->try_refresh = sync_graph::refresh;
			return true;
		}

		void text_editor::typeface_changed()
		{
			_m_reset_content_size(true);
		}

		void text_editor::indent(bool enb, std::function<std::string()> generator)
		{
			impl_->indent.enabled = enb;
			impl_->indent.generator = std::move(generator);
		}

		void text_editor::set_event(event_interface* ptr)
		{
			event_handler_ = ptr;
		}

		bool text_editor::load(const char* fs)
		{
			if (!impl_->textbase.load(fs))
				return false;

			_m_reset();

			impl_->try_refresh = sync_graph::refresh;
			_m_reset_content_size(true);
			return true;
		}

		void text_editor::text_align(::nana::align alignment)
		{
			this->attributes_.alignment = alignment;
			this->reset_caret();
			impl_->try_refresh = sync_graph::refresh;
			_m_reset_content_size();
		}

		bool text_editor::text_area(const nana::rectangle& r)
		{
			if(text_area_.area == r)
				return false;

			text_area_.area = r;

			if (impl_->counterpart.enabled)
				impl_->counterpart.buffer.make(r.dimension());

			impl_->cview->disp_area(r, { -1, 1 }, { 1, -1 }, { 2, 2 });
			if (impl_->cview->content_size().empty() || this->attributes_.line_wrapped)
				_m_reset_content_size(true);

			reset_caret();
			return true;
		}

		rectangle text_editor::text_area(bool including_scroll) const
		{
			return (including_scroll ? impl_->cview->view_area() : text_area_.area);
		}

		bool text_editor::tip_string(::std::string&& str)
		{
			if(attributes_.tip_string == str)
				return false;

			attributes_.tip_string = std::move(str);
			return true;
		}

		const text_editor::attributes& text_editor::attr() const noexcept
		{
			return attributes_;
		}

		bool text_editor::line_wrapped(bool autl)
		{
			if (autl != attributes_.line_wrapped)
			{
				attributes_.line_wrapped = autl;

				delete impl_->capacities.behavior;
				if (autl)
					impl_->capacities.behavior = new behavior_linewrapped(*this);
				else
					impl_->capacities.behavior = new behavior_normal(*this);

				_m_reset_content_size(true);

				impl_->cview->move_origin(point{} -impl_->cview->origin());
				move_caret(upoint{});

				impl_->try_refresh = sync_graph::refresh;
				return true;
			}
			return false;
		}

		bool text_editor::multi_lines(bool ml)
		{
			if((ml == false) && attributes_.multi_lines)
			{
				//retain the first line and remove the extra lines
				if (impl_->textbase.erase(1, impl_->textbase.lines() - 1))
					_m_reset();
			}

			if (attributes_.multi_lines == ml)
				return false;

			attributes_.multi_lines = ml;

			if (!ml)
				line_wrapped(false);

			_m_reset_content_size();
			impl_->cview->enable_scrolls(ml ? content_view::scrolls::both : content_view::scrolls::none);
			impl_->cview->move_origin(point{} -impl_->cview->origin());

			impl_->try_refresh = sync_graph::refresh;
			return true;
		}

		void text_editor::editable(bool enable, bool enable_caret)
		{
			attributes_.editable = enable;
			attributes_.enable_caret = (enable || enable_caret);
		}

		void text_editor::enable_background(bool enb)
		{
			attributes_.enable_background = enb;
		}

		void text_editor::enable_background_counterpart(bool enb)
		{
			impl_->counterpart.enabled = enb;
			if (enb)
				impl_->counterpart.buffer.make(text_area_.area.dimension());
			else
				impl_->counterpart.buffer.release();
		}

		void text_editor::undo_enabled(bool enb)
		{
			impl_->undo.enable(enb);
		}

		bool text_editor::undo_enabled() const
		{
			return impl_->undo.enabled();
		}

		void text_editor::undo_max_steps(std::size_t maxs)
		{
			impl_->undo.max_steps(maxs);
		}

		std::size_t text_editor::undo_max_steps() const
		{
			return impl_->undo.max_steps();
		}

		void text_editor::clear_undo()
		{
			auto size = impl_->undo.max_steps();
			impl_->undo.max_steps(0);
			impl_->undo.max_steps(size);
		}

		auto text_editor::customized_renderers() -> renderers&
		{
			return impl_->customized_renderers;
		}

		unsigned text_editor::line_height() const
		{
			unsigned ascent, descent, internal_leading;
			unsigned px = 0;
			if (graph_.text_metrics(ascent, descent, internal_leading))
				px = ascent + descent;

			impl_->cview->step(px, false);
			return px;
		}

		unsigned text_editor::screen_lines(bool completed_line) const
		{
			auto const line_px = line_height();
			if (line_px)
			{
				auto h = impl_->cview->view_area().height;
				if (graph_ && h)
				{
					if (completed_line)
						return (h / line_px);

					return (h / line_px + (h % line_px ? 1 : 0));
				}
			}
			return 0;
		}

		bool text_editor::focus_changed(const arg_focus& arg)
		{
			bool renderred = false;

			if (arg.getting && (select_.a == select_.b)) //Do not change the selected text
			{
				bool select_all = false;
				switch (select_.behavior)
				{
				case text_focus_behavior::select:
					select_all = true;
					break;
				case text_focus_behavior::select_if_click:
					select_all = (arg_focus::reason::mouse_press == arg.focus_reason);
					break;
				case text_focus_behavior::select_if_tabstop:
					select_all = (arg_focus::reason::tabstop == arg.focus_reason);
					break;
				case text_focus_behavior::select_if_tabstop_or_click:
					select_all = (arg_focus::reason::tabstop == arg.focus_reason || arg_focus::reason::mouse_press == arg.focus_reason);
				default:
					break;
				}

				if (select_all)
				{
					select(true);
					move_caret_end(false);
					renderred = true;

					//If the text widget is focused by clicking mouse button, the selected text will be cancelled
					//by the subsequent mouse down event. In this situation, the subsequent mouse down event should
					//be ignored.
					select_.ignore_press = (arg_focus::reason::mouse_press == arg.focus_reason);
				}
			}
			show_caret(arg.getting);
			reset_caret();
			return renderred;
		}

		bool text_editor::mouse_enter(bool entering)
		{
			if ((false == entering) && (false == text_area_.captured))
				API::window_cursor(window_, nana::cursor::arrow);

			return false;
		}

		bool text_editor::mouse_move(bool left_button, const point& scrpos)
		{
			cursor cur = cursor::iterm;
			if(((!hit_text_area(scrpos)) && (!text_area_.captured)) || !attributes_.enable_caret || !API::window_enabled(window_))
				cur = cursor::arrow;

			API::window_cursor(window_, cur);

			if(!attributes_.enable_caret)
				return false;

			if(left_button)
			{
				mouse_caret(scrpos, false);

				if (selection::mode::mouse_selected == select_.mode_selection || selection::mode::method_selected == select_.mode_selection)
					set_end_caret(false);
				else if (selection::mode::move_selected == select_.mode_selection)
					select_.mode_selection = selection::mode::move_selected_take_effect;

				impl_->try_refresh = sync_graph::refresh;
				return true;
			}
			return false;
		}

		void text_editor::mouse_pressed(const arg_mouse& arg)
		{
			if(!attributes_.enable_caret)
				return;

			if (event_code::mouse_down == arg.evt_code)
			{
				if (select_.ignore_press || (!hit_text_area(arg.pos)))
				{
					select_.ignore_press = false;
					return;
				}

				if (::nana::mouse::left_button == arg.button)
				{
					API::set_capture(window_, true);
					text_area_.captured = true;

					if (this->hit_select_area(_m_coordinate_to_caret(arg.pos), true))
					{
						//The selected of text can be moved only if it is editable
						if (attributes_.editable)
							select_.mode_selection = selection::mode::move_selected;
					}
					else
					{
						//Set caret pos by screen point and get the caret pos.
						mouse_caret(arg.pos, true);
						if (arg.shift)
						{
							if (points_.shift_begin_caret != points_.caret)
							{
								select_.a = points_.shift_begin_caret;
								select_.b = points_.caret;
							}
						}
						else
						{
							if (!select(false))
							{
								select_.a = points_.caret;	//Set begin caret
								set_end_caret(true);
							}
							points_.shift_begin_caret = points_.caret;
						}
						select_.mode_selection = selection::mode::mouse_selected;
					}
				}

				impl_->try_refresh = sync_graph::refresh;
			}
			else if (event_code::mouse_up == arg.evt_code)
			{
				select_.ignore_press = false;

				if (select_.mode_selection == selection::mode::mouse_selected)
				{
					select_.mode_selection = selection::mode::no_selected;
					set_end_caret(true);
				}
				else if (selection::mode::move_selected == select_.mode_selection || selection::mode::move_selected_take_effect == select_.mode_selection)
				{
					//move_selected indicates the mouse is pressed on the selected text, but the mouse has not moved. So the text_editor should cancel the selection.
					//move_selected_take_effect indicates the text_editor should try to move the selection.

					if ((selection::mode::move_selected == select_.mode_selection) || !move_select())
					{
						//no move occurs
						select(false);
						move_caret(_m_coordinate_to_caret(arg.pos));
					}

					select_.mode_selection = selection::mode::no_selected;
					impl_->try_refresh = sync_graph::refresh;
				}

				API::release_capture(window_);

				text_area_.captured = false;
				if (hit_text_area(arg.pos) == false)
					API::window_cursor(window_, nana::cursor::arrow);
			}
		}

		//Added Windows-style mouse double-click to the textbox(https://github.com/cnjinhao/nana/pull/229)
		//Oleg Smolsky
		bool text_editor::select_word(const arg_mouse& arg)
		{
			if(!attributes_.enable_caret)
				return false;

			// Set caret pos by screen point and get the caret pos.
			mouse_caret(arg.pos, true);

			// Set the initial selection: it is an empty range.
			select_.a = select_.b = points_.caret;
			const auto& line = impl_->textbase.getline(select_.b.y);

			// Expand the selection forward to the word's end.
			while (select_.b.x < line.size() && !std::iswspace(line[select_.b.x]))
				++select_.b.x;

			// Expand the selection backward to the word's start.
			while (select_.a.x > 0 && !std::iswspace(line[select_.a.x - 1]))
				--select_.a.x;

			select_.mode_selection = selection::mode::method_selected;
			impl_->try_refresh = sync_graph::refresh;
			return true;
		}

		textbase<text_editor::char_type> & text_editor::textbase()
		{
			return impl_->textbase;
		}

		const textbase<text_editor::char_type> & text_editor::textbase() const
		{
			return impl_->textbase;
		}

		bool text_editor::try_refresh()
		{
			if (sync_graph::none != impl_->try_refresh)
			{
				if (sync_graph::refresh == impl_->try_refresh)
					render(API::is_focus_ready(window_));

				impl_->try_refresh = sync_graph::none;
				return true;
			}
			return false;
		}

		bool text_editor::getline(std::size_t pos, std::wstring& text) const
		{
			if (impl_->textbase.lines() <= pos)
				return false;

			text = impl_->textbase.getline(pos);
			return true;
		}

		void text_editor::text(std::wstring str, bool end_caret)
		{
			impl_->undo.clear();

			impl_->textbase.erase_all();
			_m_reset();
			_m_reset_content_size(true);

			if (!end_caret)
			{
				auto undo_ptr = std::unique_ptr<undo_input_text>{ new undo_input_text(*this, str) };
				undo_ptr->set_caret_pos();

				_m_put(std::move(str));

				impl_->undo.push(std::move(undo_ptr));

				if (graph_)
				{
					this->_m_adjust_view();

					reset_caret();
					impl_->try_refresh = sync_graph::refresh;

					//_m_put calcs the lines
					_m_reset_content_size(true);
					impl_->cview->sync(false);
				}
			}
			else
				put(std::move(str));
		}

		std::wstring text_editor::text() const
		{
			std::wstring str;
			std::size_t lines = impl_->textbase.lines();
			if(lines > 0)
			{
				str = impl_->textbase.getline(0);
				for(std::size_t i = 1; i < lines; ++i)
				{
					str += L"\n\r";
					str += impl_->textbase.getline(i);
				}
			}
			return str;
		}

		bool text_editor::move_caret(upoint crtpos, bool stay_in_view)
		{
			const unsigned line_pixels = line_height();

			if (crtpos != points_.caret)
			{
				//Check and make the crtpos available
				if (crtpos.y < impl_->textbase.lines())
				{
					crtpos.x = (std::min)(static_cast<decltype(crtpos.x)>(impl_->textbase.getline(crtpos.y).size()), crtpos.x);
				}
				else
				{
					crtpos.y = static_cast<unsigned>(impl_->textbase.lines());
					if (crtpos.y > 0)
						--crtpos.y;

					crtpos.x = static_cast<unsigned>(impl_->textbase.getline(crtpos.y).size());
				}

				points_.caret = crtpos;
			}

			//The coordinate of caret
			auto coord = _m_caret_to_coordinate(crtpos);

			const int line_bottom = coord.y + static_cast<int>(line_pixels);

			if (!API::is_focus_ready(window_))
				return false;

			auto caret = API::open_caret(window_, true);

			bool visible = false;
			auto text_area = impl_->cview->view_area();

			if (text_area.is_hit(coord) && (line_bottom > text_area.y))
			{
				visible = true;
				if (line_bottom > text_area.bottom())
					caret->dimension(nana::size(1, line_pixels - (line_bottom - text_area.bottom())));
				else if (caret->dimension().height != line_pixels)
					reset_caret_pixels();
			}

			if(!attributes_.enable_caret)
				visible = false;

			caret->visible(visible);
			if(visible)
				caret->position(coord);

			//Adjust the caret into screen when the caret position is modified by this function
			if (stay_in_view && (!hit_text_area(coord)))
			{
				if (_m_adjust_view())
					impl_->cview->sync(false);

				impl_->try_refresh = sync_graph::refresh;
				caret->visible(true);
				return true;
			}
			return false;
		}

		void text_editor::move_caret_end(bool update)
		{
			points_.caret.y = static_cast<unsigned>(impl_->textbase.lines());
			if(points_.caret.y) --points_.caret.y;
			points_.caret.x = static_cast<unsigned>(impl_->textbase.getline(points_.caret.y).size());

			if (update)
				this->reset_caret();
		}

		void text_editor::reset_caret_pixels() const
		{
			API::open_caret(window_, true).get()->dimension({ 1, line_height() });
		}

		void text_editor::reset_caret(bool stay_in_view)
		{
			move_caret(points_.caret, stay_in_view);
		}

		void text_editor::show_caret(bool isshow)
		{
			if(isshow == false || API::is_focus_ready(window_))
				API::open_caret(window_, true).get()->visible(isshow);
		}

		bool text_editor::selected() const
		{
			return (select_.a != select_.b);
		}

		bool text_editor::get_selected_points(nana::upoint &a, nana::upoint &b) const
		{
			if (select_.a == select_.b)
				return false;

			if (select_.a < select_.b)
			{
				a = select_.a;
				b = select_.b;
			}
			else
			{
				a = select_.b;
				b = select_.a;
			}

			return true;
		}

		bool text_editor::select(bool yes)
		{
			if(yes)
			{
				select_.a.x = select_.a.y = 0;
				select_.b.y = static_cast<unsigned>(impl_->textbase.lines());
				if(select_.b.y) --select_.b.y;
				select_.b.x = static_cast<unsigned>(impl_->textbase.getline(select_.b.y).size());
				select_.mode_selection = selection::mode::method_selected;
				impl_->try_refresh = sync_graph::refresh;
				return true;
			}

			select_.mode_selection = selection::mode::no_selected;
			if (_m_cancel_select(0))
			{
				impl_->try_refresh = sync_graph::refresh;
				return true;
			}
			return false;
		}

		void text_editor::set_end_caret(bool stay_in_view)
		{
			bool new_sel_end = (select_.b != points_.caret);
			select_.b = points_.caret;

			if (new_sel_end || (stay_in_view && this->_m_adjust_view()))
				impl_->try_refresh = sync_graph::refresh;
		}

		bool text_editor::hit_text_area(const point& pos) const
		{
			return impl_->cview->view_area().is_hit(pos);
		}

		bool text_editor::hit_select_area(nana::upoint pos, bool ignore_when_select_all) const
		{
			nana::upoint a, b;
			if (get_selected_points(a, b))
			{
				if (ignore_when_select_all)
				{
					if (a.x == 0 && a.y == 0 && (b.y + 1) == static_cast<unsigned>(textbase().lines()))
					{
						//is select all
						if (b.x == static_cast<unsigned>(textbase().getline(b.y).size()))
							return false;
					}
				}

				if((pos.y > a.y || (pos.y == a.y && pos.x >= a.x)) && ((pos.y < b.y) || (pos.y == b.y && pos.x < b.x)))
					return true;
			}
			return false;
		}

		bool text_editor::move_select()
		{
			if(hit_select_area(points_.caret, true) || (select_.b == points_.caret))
			{
				points_.caret = select_.b;

				if (this->_m_adjust_view())
					impl_->try_refresh = sync_graph::refresh;

				reset_caret();
				return true;
			}

			if (_m_move_select(true))
			{
				this->_m_adjust_view();
				impl_->try_refresh = sync_graph::refresh;
				return true;
			}
			return false;
		}

		bool text_editor::mask(wchar_t ch)
		{
			if (mask_char_ == ch)
				return false;

			mask_char_ = ch;
			return true;
		}

		unsigned text_editor::width_pixels() const
		{
			unsigned exclude_px = API::open_caret(window_, true).get()->dimension().width;

			if (attributes_.line_wrapped)
				exclude_px += impl_->cview->extra_space(false);

			return (text_area_.area.width > exclude_px ? text_area_.area.width - exclude_px : 0);
		}

		window text_editor::window_handle() const
		{
			return window_;
		}

		const std::vector<upoint>& text_editor::text_position() const
		{
			return impl_->text_position;
		}

		void text_editor::focus_behavior(text_focus_behavior behavior)
		{
			select_.behavior = behavior;
		}

		void text_editor::select_behavior(bool move_to_end)
		{
			select_.move_to_end = move_to_end;
		}

		std::size_t text_editor::line_count(bool text_lines) const
		{
			if (text_lines)
				return textbase().lines();

			return impl_->capacities.behavior->take_lines();
		}

		std::shared_ptr<scroll_operation_interface> text_editor::scroll_operation() const
		{
			return impl_->cview->scroll_operation();
		}

		void text_editor::draw_corner()
		{
			impl_->cview->draw_corner(graph_);
		}

		void text_editor::render(bool has_focus)
		{
			const auto bgcolor = _m_bgcolor();

			auto fgcolor = scheme_->foreground.get_color();
			if (!API::window_enabled(window_))
				fgcolor.blend(bgcolor, 0.5);

			if (API::widget_borderless(window_))
				graph_.rectangle(false, bgcolor);

			//Draw background
			if (!API::dev::copy_transparent_background(window_, graph_))
			{
				if (attributes_.enable_background)
					graph_.rectangle(text_area_.area, true, bgcolor);
			}

			if (impl_->customized_renderers.background)
				impl_->customized_renderers.background(graph_, text_area_.area, bgcolor);

			if(impl_->counterpart.buffer && !text_area_.area.empty())
				impl_->counterpart.buffer.bitblt(rectangle{ text_area_.area.dimension() }, graph_, text_area_.area.position());

			//Render the content when the text isn't empty or the window has got focus,
			//otherwise draw the tip string.
			if ((false == textbase().empty()) || has_focus)
			{
				auto text_pos = _m_render_text(fgcolor);

				if (text_pos.empty())
					text_pos.emplace_back(upoint{});

				if ((impl_->text_position_origin != impl_->cview->origin().y) || (text_pos != impl_->text_position))
				{
					impl_->text_position_origin = impl_->cview->origin().y;
					impl_->text_position.swap(text_pos);
					if (event_handler_)
						event_handler_->text_exposed(impl_->text_position);
				}
			}
			else //Draw tip string
			{
				graph_.string({ text_area_.area.x - impl_->cview->origin().x, text_area_.area.y }, attributes_.tip_string, static_cast<color_rgb>(0x787878));
			}

			if (impl_->text_position.empty())
				impl_->text_position.emplace_back(upoint{});

			_m_draw_border();
			impl_->try_refresh = sync_graph::none;
		}
	//public:
		void text_editor::put(std::wstring text)
		{
			if (text.empty())
				return;

			auto undo_ptr = std::unique_ptr<undo_input_text>{ new undo_input_text(*this, text) };

			undo_ptr->set_selected_text();

			//Do not forget to assign the _m_erase_select() to caret
			//because _m_put() will insert the text at the position where the caret is.
			points_.caret = _m_erase_select();

			undo_ptr->set_caret_pos();
			points_.caret = _m_put(std::move(text));

			impl_->undo.push(std::move(undo_ptr));

			_m_reset_content_size(true);

			if(graph_)
			{
				if(this->_m_adjust_view())
					impl_->cview->sync(false);

				reset_caret();
				impl_->try_refresh = sync_graph::refresh;
			}
		}

		void text_editor::put(wchar_t ch)
		{
			std::wstring ch_str(1, ch);

			auto undo_ptr = std::unique_ptr<undo_input_text>{new undo_input_text(*this, ch_str)};
			bool refresh = (select_.a != select_.b);

			undo_ptr->set_selected_text();
			if(refresh)
				points_.caret = _m_erase_select();

			undo_ptr->set_caret_pos();

			impl_->undo.push(std::move(undo_ptr));

			auto secondary_before = impl_->capacities.behavior->take_lines(points_.caret.y);
			textbase().insert(points_.caret, std::move(ch_str));
			_m_pre_calc_lines(points_.caret.y, 1);

			points_.caret.x ++;

			_m_reset_content_size();

			if (!refresh)
			{
				if (!_m_update_caret_line(secondary_before))
					draw_corner();
			}
			else
				impl_->try_refresh = sync_graph::refresh;

		}

		void text_editor::copy() const
		{
			//Stops copying text if the text_editor is masked.
			if (mask_char_)
				return;

			auto text = _m_make_select_string();
			if (!text.empty())
				nana::system::dataexch().set(text, API::root(this->window_));
		}

		void text_editor::cut()
		{
			copy();
			del();
		}

		void text_editor::paste()
		{
			auto text = system::dataexch{}.wget();

			if ((accepts::no_restrict == impl_->capacities.acceptive) || !impl_->capacities.pred_acceptive)
			{
				put(move(text));
				return;
			}

			//Check if the input is acceptable
			for (auto i = text.begin(); i != text.end(); ++i)
			{
				if (_m_accepts(*i))
				{
					if (accepts::no_restrict == impl_->capacities.acceptive)
						put(*i);

					continue;
				}

				if (accepts::no_restrict != impl_->capacities.acceptive)
				{
					text.erase(i, text.end());
					put(move(text));
				}
				break;
			}
		}

		void text_editor::enter(bool record_undo)
		{
			if(false == attributes_.multi_lines)
				return;

			auto undo_ptr = std::unique_ptr<undo_input_text>(new undo_input_text(*this, std::wstring(1, '\n')));

			undo_ptr->set_selected_text();
			points_.caret = _m_erase_select();

			undo_ptr->set_caret_pos();

			auto & textbase = this->textbase();

			const string_type& lnstr = textbase.getline(points_.caret.y);
			++points_.caret.y;

			if(lnstr.size() > points_.caret.x)
			{
				//Breaks the line and moves the rest part to a new line
				auto rest_part_len = lnstr.size() - points_.caret.x;	//Firstly get the length of rest part, because lnstr may be invalid after insertln
				textbase.insertln(points_.caret.y, lnstr.substr(points_.caret.x));
				textbase.erase(points_.caret.y - 1, points_.caret.x, rest_part_len);
			}
			else
			{
				if (textbase.lines() == 0)
					textbase.insertln(0, std::wstring{});
				textbase.insertln(points_.caret.y, std::wstring{});
			}

			if (record_undo)
				impl_->undo.push(std::move(undo_ptr));

			impl_->capacities.behavior->add_lines(points_.caret.y - 1, 1);
			_m_pre_calc_lines(points_.caret.y - 1, 2);

			points_.caret.x = 0;

			auto origin = impl_->cview->origin();
			origin.x = 0;

			if (impl_->indent.enabled)
			{
				if (impl_->indent.generator)
				{
					put(to_wstring(impl_->indent.generator()));
				}
				else
				{
					auto & text = textbase.getline(points_.caret.y - 1);
					auto indent_pos = text.find_first_not_of(L"\t ");
					if (indent_pos != std::wstring::npos)
						put(text.substr(0, indent_pos));
					else
						put(text);
				}
			}
			else
				_m_reset_content_size();

			auto origin_moved = impl_->cview->move_origin(origin - impl_->cview->origin());

			if (this->_m_adjust_view() || origin_moved)
				impl_->cview->sync(true);
		}

		void text_editor::del()
		{
			if(select_.a == select_.b)
			{
				if(textbase().getline(points_.caret.y).size() > points_.caret.x)
				{
					++points_.caret.x;
				}
				else if (points_.caret.y + 1 < textbase().lines())
				{	//Move to next line
					points_.caret.x = 0;
					++points_.caret.y;
				}
				else
					return;	//No characters behind the caret
			}

			backspace();
		}

		void text_editor::backspace(bool record_undo)
		{
			auto undo_ptr = std::unique_ptr<undo_backspace>(new undo_backspace(*this));
			bool has_to_redraw = true;
			if(select_.a == select_.b)
			{
				auto & textbase = this->textbase();
				if(points_.caret.x)
				{
					unsigned erase_number = 1;
					--points_.caret.x;

					auto& lnstr = textbase.getline(points_.caret.y);

					undo_ptr->set_caret_pos();
					undo_ptr->set_removed(lnstr.substr(points_.caret.x, erase_number));
					auto secondary = impl_->capacities.behavior->take_lines(points_.caret.y);
					textbase.erase(points_.caret.y, points_.caret.x, erase_number);
					_m_pre_calc_lines(points_.caret.y, 1);

					if (!this->_m_adjust_view())
					{
						_m_update_line(points_.caret.y, secondary);
						has_to_redraw = false;
					}
				}
				else if (points_.caret.y)
				{
					points_.caret.x = static_cast<unsigned>(textbase.getline(--points_.caret.y).size());
					textbase.merge(points_.caret.y);
					impl_->capacities.behavior->merge_lines(points_.caret.y, points_.caret.y + 1);
					undo_ptr->set_caret_pos();
					undo_ptr->set_removed(std::wstring(1, '\n'));
				}
				else
					undo_ptr.reset();
			}
			else
			{
				undo_ptr->set_selected_text();
				points_.caret = _m_erase_select();
				undo_ptr->set_caret_pos();
			}

			if (record_undo)
				impl_->undo.push(std::move(undo_ptr));

			_m_reset_content_size(false);

			if(has_to_redraw)
			{
				this->_m_adjust_view();
				impl_->try_refresh = sync_graph::refresh;
			}
		}

		void text_editor::undo(bool reverse)
		{
			if (reverse)
				impl_->undo.redo();
			else
				impl_->undo.undo();

			_m_reset_content_size(true);

			this->_m_adjust_view();
			impl_->try_refresh = sync_graph::refresh;
		}

		void text_editor::set_undo_queue_length(std::size_t len)
		{
			impl_->undo.max_steps(len);
		}

		void text_editor::move_ns(bool to_north)
		{
			const bool redraw_required = _m_cancel_select(0);
			if (_m_move_caret_ns(to_north) || redraw_required)
				impl_->try_refresh = sync_graph::refresh;
		}

		void text_editor::move_left()
		{
			bool pending = true;
			if(_m_cancel_select(1) == false)
			{
				if(points_.caret.x)
				{
					--points_.caret.x;
					pending = false;
					if (this->_m_adjust_view())
						impl_->try_refresh = sync_graph::refresh;
				}
				else if (points_.caret.y) //Move to previous line
					points_.caret.x = static_cast<unsigned>(textbase().getline(--points_.caret.y).size());
				else
					pending = false;
			}

			if (pending && this->_m_adjust_view())
				impl_->try_refresh = sync_graph::refresh;
		}

		void text_editor::move_right()
		{
			bool do_render = false;
			if (_m_cancel_select(2) == false)
			{
				auto lnstr = textbase().getline(points_.caret.y);
				if (lnstr.size() > points_.caret.x)
				{
					++points_.caret.x;
					do_render = this->_m_adjust_view();
				}
				else if (points_.caret.y + 1 < textbase().lines())
				{	//Move to next line
					points_.caret.x = 0;
					++points_.caret.y;
					do_render = this->_m_adjust_view();
				}
			}
			else
				do_render = this->_m_adjust_view();

			if (do_render)
				impl_->try_refresh = sync_graph::refresh;
		}

		void text_editor::_m_handle_move_key(const arg_keyboard& arg)
		{
			if (arg.shift && (select_.a == select_.b))
				select_.a = select_.b = points_.caret;

			auto origin = impl_->cview->origin();
			auto pos = points_.caret;
			auto coord = _m_caret_to_coordinate(points_.caret, false);

			wchar_t key = arg.key;

			auto const line_px = this->line_height();

			//The number of text lines
			auto const line_count = textbase().lines();

			//The number of charecters in the line of caret
			auto const text_length = textbase().getline(points_.caret.y).size();


			switch (key) {
			case keyboard::os_arrow_left:
				if (select_.move_to_end && (select_.a != select_.b) && (!arg.shift))
				{
					pos = select_.a;
				}
				else if (pos.x != 0)
				{
					--pos.x;
				}
				else if (pos.y != 0) {
					--pos.y;
					pos.x = static_cast<decltype(pos.x)>(textbase().getline(pos.y).size());
				}
				break;
			case keyboard::os_arrow_right:
				if (select_.move_to_end && (select_.a != select_.b) && (!arg.shift))
				{
					pos = select_.b;
				}
				else if (pos.x < text_length)
				{
					++pos.x;
				}
				else if (pos.y != line_count - 1)
				{
					++pos.y;
					pos.x = 0;
				}
				break;
			case keyboard::os_arrow_up:
				coord.y -= static_cast<int>(line_px);
				break;
			case keyboard::os_arrow_down:
				coord.y += static_cast<int>(line_px);
				break;
			case keyboard::os_home:
				//move the caret to the begining of the line
				pos.x = 0;

				//move the caret to the begining of the text if Ctrl is pressed
				if (arg.ctrl)
					pos.y = 0;
				break;
			case keyboard::os_end:
				//move the caret to the end of the line
				pos.x = static_cast<decltype(pos.x)>(text_length);

				//move the caret to the end of the text if Ctrl is pressed
				if(arg.ctrl)
					pos.y = static_cast<unsigned>((line_count - 1) * line_px);
				break;
			case keyboard::os_pageup:
				if(origin.y > 0)
				{
					auto off = coord - origin;
					origin.y -= (std::min)(origin.y, static_cast<int>(impl_->cview->view_area().height));
					coord = off + origin;
				}
				break;
			case keyboard::os_pagedown:
				if (impl_->cview->content_size().height > impl_->cview->view_area().height)
				{
					auto off = coord - origin;
					origin.y = (std::min)(origin.y + static_cast<int>(impl_->cview->view_area().height), static_cast<int>(impl_->cview->content_size().height - impl_->cview->view_area().height));
					coord = off + origin;
				}
				break;
			}

			if (pos == points_.caret)
			{
				impl_->cview->move_origin(origin - impl_->cview->origin());
				pos = _m_coordinate_to_caret(coord, false);
			}

			if (pos != points_.caret) {
				if (arg.shift) {
					switch (key) {
					case keyboard::os_arrow_left:
					case keyboard::os_arrow_up:
					case keyboard::os_home:
					case keyboard::os_pageup:
						select_.b = pos;
						break;
					case keyboard::os_arrow_right:
					case keyboard::os_arrow_down:
					case keyboard::os_end:
					case keyboard::os_pagedown:
						select_.b = pos;
						break;
					}
				}
				else {
					select_.b = pos;
					select_.a = pos;
				}
				points_.caret = pos;
				impl_->try_refresh = sync_graph::refresh;
				this->_m_adjust_view();
				impl_->cview->sync(true);
				this->reset_caret();
			}
		}

		unsigned text_editor::_m_width_px(bool include_vs) const
		{
			unsigned exclude_px = API::open_caret(window_, true).get()->dimension().width;

			if (!include_vs)
				exclude_px += impl_->cview->space();

			return (text_area_.area.width > exclude_px ? text_area_.area.width - exclude_px : 0);
		}

		void text_editor::_m_draw_border()
		{
			if (!API::widget_borderless(this->window_))
			{
				if (impl_->customized_renderers.border)
				{
					impl_->customized_renderers.border(graph_, _m_bgcolor());
				}
				else
				{
					::nana::facade<element::border> facade;
					facade.draw(graph_, _m_bgcolor(), API::fgcolor(this->window_), ::nana::rectangle{ API::window_size(this->window_) }, API::element_state(this->window_));
				}

				if (!attributes_.line_wrapped)
				{
					auto exclude_px = API::open_caret(window_, true).get()->dimension().width;
					int x = this->text_area_.area.x + static_cast<int>(width_pixels());
					graph_.rectangle(rectangle{ x, this->text_area_.area.y, exclude_px, text_area_.area.height }, true, _m_bgcolor());
				}
			}

			draw_corner();
		}

		const upoint& text_editor::mouse_caret(const point& scrpos, bool stay_in_view)	//From screen position
		{
			points_.caret = _m_coordinate_to_caret(scrpos);

			if (stay_in_view && this->_m_adjust_view())
				impl_->try_refresh = sync_graph::refresh;

			reset_caret();
			return points_.caret;
		}

		const upoint& text_editor::caret() const
		{
			return points_.caret;
		}

		point text_editor::caret_screen_pos() const
		{
			return _m_caret_to_coordinate(points_.caret);
		}

		bool text_editor::scroll(bool upwards, bool vert)
		{
			impl_->cview->scroll(!upwards, !vert);
			return false;
		}

		color text_editor::_m_draw_colored_area(paint::graphics& graph, const std::pair<std::size_t, std::size_t>& row, bool whole_line)
		{
			auto area = impl_->colored_area.find(row.first);
			if (area)
			{
				if (!area->bgcolor.invisible())
				{
					auto const height = line_height();

					auto top = _m_caret_to_coordinate(upoint{ 0, static_cast<unsigned>(row.first) }).y;
					std::size_t lines = 1;

					if (whole_line)
						lines = impl_->capacities.behavior->take_lines(row.first);
					else
						top += static_cast<int>(height * row.second);

					const rectangle area_r = { text_area_.area.x, top, width_pixels(), static_cast<unsigned>(height * lines) };

					if (API::is_transparent_background(this->window_))
						graph.blend(area_r, area->bgcolor, 1);
					else
						graph.rectangle(area_r, true, area->bgcolor);
				}

				return area->fgcolor;
			}
			return{};
		}

		std::vector<upoint> text_editor::_m_render_text(const color& text_color)
		{
			std::vector<upoint> line_indexes;
			auto const behavior = this->impl_->capacities.behavior;
			auto const line_count = textbase().lines();

			auto row = behavior->text_position_from_screen(impl_->cview->view_area().y);

			if (row.first >= line_count || graph_.empty())
				return line_indexes;

			auto sections = behavior->line(row.first);
			if (row.second < sections.size())
			{
				nana::upoint str_pos(0, static_cast<unsigned>(row.first));
				str_pos.x = static_cast<unsigned>(sections[row.second].begin - textbase().getline(row.first).c_str());

				int top = _m_text_top_base() - (impl_->cview->origin().y % line_height());
				const unsigned pixels = line_height();

				const std::size_t scrlines = screen_lines() + 1;
				for (std::size_t pos = 0; pos < scrlines; ++pos, top += pixels)
				{
					if (row.first >= line_count)
						break;

					auto fgcolor = _m_draw_colored_area(graph_, row, false);
					if (fgcolor.invisible())
						fgcolor = text_color;

					sections = behavior->line(row.first);
					if (row.second < sections.size())
					{
						auto const & sct = sections[row.second];

						_m_draw_string(top, fgcolor, str_pos, sct, true);
						line_indexes.emplace_back(str_pos);
						++row.second;
						if (row.second >= sections.size())
						{
							++row.first;
							row.second = 0;
							str_pos.x = 0;
							++str_pos.y;
						}
						else
							str_pos.x += static_cast<unsigned>(sct.end - sct.begin);
					}
					else
						break;
				}
			}

			return line_indexes;
		}

		void text_editor::_m_pre_calc_lines(std::size_t line_off, std::size_t lines)
		{
			unsigned width_px = width_pixels();
			for (auto pos = line_off, end = line_off + lines; pos != end; ++pos)
				this->impl_->capacities.behavior->pre_calc_line(pos, width_px);
		}

		nana::point	text_editor::_m_caret_to_coordinate(nana::upoint pos, bool to_screen_coordinate) const
		{
			auto const behavior = impl_->capacities.behavior;
			auto const sections = behavior->line(pos.y);

			std::size_t lines = 0;	//lines before the caret line;
			for (std::size_t i = 0; i < pos.y; ++i)
			{
				lines += behavior->take_lines(i);
			}

			const text_section * sct_ptr = nullptr;
			nana::point scrpos;
			if (0 != pos.x)
			{
				std::wstring str;

				std::size_t sct_pos = 0;
				for (auto & sct : sections)
				{
					std::size_t chsize = sct.end - sct.begin;
					str.clear();
					if (mask_char_)
						str.append(chsize, mask_char_);
					else
						str.append(sct.begin, sct.end);

					//In line-wrapped mode. If the caret is at the end of a line which is not the last section,
					//the caret should be moved to the beginning of next section line.
					if ((sct_pos + 1 < sections.size()) ? (pos.x < chsize) : (pos.x <= chsize))
					{
						sct_ptr = &sct;
						if (pos.x == chsize)
							scrpos.x = _m_text_extent_size(str.c_str(), sct.end - sct.begin).width;
						else
							scrpos.x = _m_pixels_by_char(str, pos.x);
						break;
					}
					else
					{
						pos.x -= static_cast<unsigned>(chsize);
						++lines;
					}

					++sct_pos;
				}
			}

			if (!sct_ptr)
			{
				if (sections.empty())
					scrpos.x += _m_text_x({});
				else
					scrpos.x += _m_text_x(sections.front());
			}
			else
				scrpos.x += _m_text_x(*sct_ptr);

			scrpos.y = static_cast<int>(lines * line_height());

			if (!to_screen_coordinate)
			{
				//_m_text_x includes origin x and text_area x. remove these factors
				scrpos.x += (impl_->cview->origin().x - text_area_.area.x);
			}
			else
				scrpos.y += this->_m_text_top_base() - impl_->cview->origin().y;

			return scrpos;
		}

		upoint text_editor::_m_coordinate_to_caret(point scrpos, bool from_screen_coordinate) const
		{
			if (!from_screen_coordinate)
				scrpos -= (impl_->cview->origin() - point{ text_area_.area.x, this->_m_text_top_base() });

			auto const behavior = impl_->capacities.behavior;

			auto const row = behavior->text_position_from_screen(scrpos.y);

			auto sections = behavior->line(row.first);
			if (sections.empty())
				return{ 0, static_cast<unsigned>(row.first) };

			//First of all, find the text of secondary.
			auto real_str = sections[row.second];

			auto text_ptr = real_str.begin;
			const auto text_size = real_str.end - real_str.begin;

			std::wstring mask_str;
			if (mask_char_)
			{
				mask_str.resize(text_size, mask_char_);
				text_ptr = mask_str.c_str();
			}

			auto const reordered = unicode_reorder(text_ptr, text_size);

			nana::upoint res(static_cast<unsigned>(real_str.begin - sections.front().begin), static_cast<unsigned>(row.first));

			scrpos.x = (std::max)(0, (scrpos.x - _m_text_x(sections[row.second])));

			for (auto & ent : reordered)
			{
				auto str_px = static_cast<int>(_m_text_extent_size(ent.begin, ent.end - ent.begin).width);
				if (scrpos.x <= str_px)
				{
					res.x += _m_char_by_pixels(ent, scrpos.x) + static_cast<unsigned>(ent.begin - text_ptr);
					return res;
				}
				scrpos.x -= str_px;
			}

			//move the caret to the end of this section.
			res.x = static_cast<unsigned>(text_size);
			for (std::size_t i = 0; i < row.second; ++i)
				res.x += static_cast<int>(sections[i].end - sections[i].begin);

			return res;
		}

		bool text_editor::_m_pos_from_secondary(std::size_t textline, const nana::upoint& secondary, unsigned & pos)
		{
			if (textline >= textbase().lines())
				return false;

			auto sections = impl_->capacities.behavior->line(textline);

			if (secondary.y >= sections.size())
				return false;

			auto const & sct = sections[secondary.y];

			auto chptr = sct.begin + (std::min)(secondary.x, static_cast<unsigned>(sct.end - sct.begin));
			pos = static_cast<unsigned>(chptr - textbase().getline(textline).c_str());
			return true;
		}


		bool text_editor::_m_pos_secondary(const nana::upoint& charpos, nana::upoint& secondary_pos) const
		{
			if (charpos.y >= textbase().lines())
				return false;

			secondary_pos.x = charpos.x;
			secondary_pos.y = 0;

			auto sections = impl_->capacities.behavior->line(charpos.y);
			unsigned len = 0;
			for (auto & sct : sections)
			{
				len = static_cast<unsigned>(sct.end - sct.begin);
				if (len >= secondary_pos.x)
					return true;

				++secondary_pos.y;
				secondary_pos.x -= len;
			}
			--secondary_pos.y;
			secondary_pos.x = len;
			return true;
		}

		bool text_editor::_m_move_caret_ns(bool to_north)
		{
			auto const behavior = impl_->capacities.behavior;

			nana::upoint secondary_pos;
			_m_pos_secondary(points_.caret, secondary_pos);

			if (to_north)	//North
			{
				if (0 == secondary_pos.y)
				{
					if (0 == points_.caret.y)
						return false;

					--points_.caret.y;
					secondary_pos.y = static_cast<unsigned>(behavior->take_lines(points_.caret.y)) - 1;
				}
				else
				{
					//Test if out of screen
					if (static_cast<int>(points_.caret.y) < _m_text_topline())
					{
						auto origin = impl_->cview->origin();
						origin.y = static_cast<int>(points_.caret.y) * line_height();
						impl_->cview->move_origin(origin - impl_->cview->origin());
					}

					--secondary_pos.y;
				}
			}
			else //South
			{
				++secondary_pos.y;
				if (secondary_pos.y >= behavior->take_lines(points_.caret.y))
				{
					secondary_pos.y = 0;
					if (points_.caret.y + 1 >= textbase().lines())
						return false;

					++points_.caret.y;
				}
			}

			_m_pos_from_secondary(points_.caret.y, secondary_pos, points_.caret.x);
			return this->_m_adjust_view();
		}

		void text_editor::_m_update_line(std::size_t pos, std::size_t secondary_count_before)
		{
			auto behavior = impl_->capacities.behavior;
			if (behavior->take_lines(pos) == secondary_count_before)
			{
				auto top = _m_caret_to_coordinate(upoint{ 0, static_cast<unsigned>(pos) }).y;

				const unsigned pixels = line_height();
				const rectangle update_area = { text_area_.area.x, top, width_pixels(), static_cast<unsigned>(pixels * secondary_count_before) };

				if (!API::dev::copy_transparent_background(window_, update_area, graph_, update_area.position()))
				{
					_m_draw_colored_area(graph_, { pos, 0 }, true);
					graph_.rectangle(update_area, true, API::bgcolor(window_));
				}
				else
					_m_draw_colored_area(graph_, { pos, 0 }, true);

				auto fgcolor = API::fgcolor(window_);
				auto text_ptr = textbase().getline(pos).c_str();

				auto sections = behavior->line(pos);
				for (auto & sct : sections)
				{
					_m_draw_string(top, fgcolor, nana::upoint(static_cast<unsigned>(sct.begin - text_ptr), points_.caret.y), sct, true);
					top += pixels;
				}

				_m_draw_border();
				impl_->try_refresh = sync_graph::lazy_refresh;
			}
			else
				impl_->try_refresh = sync_graph::refresh;
		}

		bool text_editor::_m_accepts(char_type ch) const
		{
			if (accepts::no_restrict == impl_->capacities.acceptive)
			{
				if (impl_->capacities.pred_acceptive)
					return impl_->capacities.pred_acceptive(ch);
				return true;
			}

			//Checks the input whether it meets the requirement for a numeric.
			auto str = text();

			if ('+' == ch || '-' == ch)
				return str.empty();

			if((accepts::real == impl_->capacities.acceptive) && ('.' == ch))
				return (str.find(L'.') == str.npos);

			return ('0' <= ch && ch <= '9');
		}

		::nana::color text_editor::_m_bgcolor() const
		{
			return (!API::window_enabled(window_) ? static_cast<color_rgb>(0xE0E0E0) : API::bgcolor(window_));
		}

		void text_editor::_m_reset_content_size(bool calc_lines)
		{
			size csize;

			if (this->attributes_.line_wrapped)
			{
				//detect if vertical scrollbar is required
				auto const max_lines = screen_lines(true);

				if (calc_lines)
				{
					auto text_lines = textbase().lines();
					if (text_lines <= max_lines)
					{
						impl_->capacities.behavior->prepare();

						auto const width_px = _m_width_px(true);

						std::size_t lines = 0;
						for (std::size_t i = 0; i < text_lines; ++i)
						{
							impl_->capacities.behavior->pre_calc_line(i, width_px);
							lines += impl_->capacities.behavior->take_lines(i);

							if (lines > max_lines)
							{
								text_lines = lines;
								break;
							}
						}
					}

					//enable vertical scrollbar when text_lines > max_lines
					csize.width = _m_width_px(text_lines <= max_lines);
					impl_->capacities.behavior->pre_calc_lines(csize.width);
				}
				else
				{
					csize.width = impl_->cview->content_size().width;
				}
			}
			else
			{
				if (calc_lines)
					impl_->capacities.behavior->pre_calc_lines(width_pixels());

				auto maxline = textbase().max_line();
				csize.width = _m_text_extent_size(textbase().getline(maxline.first).c_str(), maxline.second).width + caret_size().width;
			}

			csize.height = static_cast<unsigned>(impl_->capacities.behavior->take_lines() * line_height());

			impl_->cview->content_size(csize);
		}

		void text_editor::_m_reset()
		{
			points_.caret.x = points_.caret.y = 0;
			impl_->cview->move_origin(point{} -impl_->cview->origin());
			select_.a = select_.b;
		}

		nana::upoint text_editor::_m_put(std::wstring text)
		{
			auto & textbase = this->textbase();
			auto crtpos = points_.caret;
			std::vector<std::pair<std::size_t, std::size_t>> lines;
			if (_m_resolve_text(text, lines) && attributes_.multi_lines)
			{
				auto str_orig = textbase.getline(crtpos.y);

				auto const subpos = lines.front();
				auto substr = text.substr(subpos.first, subpos.second - subpos.first);

				if (str_orig.size() == crtpos.x)
					textbase.insert(crtpos, std::move(substr));
				else
					textbase.replace(crtpos.y, str_orig.substr(0, crtpos.x) + substr);

				//There are at least 2 elements in lines
				for (auto i = lines.begin() + 1, end = lines.end() - 1; i != end; ++i)
				{
					textbase.insertln(++crtpos.y, text.substr(i->first, i->second - i->first));
				}

				auto backpos = lines.back();
				textbase.insertln(++crtpos.y, text.substr(backpos.first, backpos.second - backpos.first) + str_orig.substr(crtpos.x));
				crtpos.x = static_cast<decltype(crtpos.x)>(backpos.second - backpos.first);

				impl_->capacities.behavior->add_lines(points_.caret.y, lines.size() - 1);
				_m_pre_calc_lines(points_.caret.y, lines.size());
			}
			else
			{
				//Just insert the first line of text if the text is multilines.
				if (lines.size() > 1)
					text = text.substr(lines.front().first, lines.front().second - lines.front().first);

				crtpos.x += static_cast<unsigned>(text.size());
				textbase.insert(points_.caret, std::move(text));

				_m_pre_calc_lines(crtpos.y, 1);
			}

			return crtpos;
		}

		nana::upoint text_editor::_m_erase_select()
		{
			nana::upoint a, b;
			if (get_selected_points(a, b))
			{
				auto & textbase = this->textbase();
				if(a.y != b.y)
				{
					textbase.erase(a.y, a.x, std::wstring::npos);
					textbase.erase(a.y + 1, b.y - a.y - 1);

					textbase.erase(a.y + 1, 0, b.x);
					textbase.merge(a.y);

					impl_->capacities.behavior->merge_lines(a.y, b.y);
				}
				else
				{
					textbase.erase(a.y, a.x, b.x - a.x);
					_m_pre_calc_lines(a.y, 1);
				}

				select_.a = select_.b;
				return a;
			}

			return points_.caret;
		}

		std::wstring text_editor::_m_make_select_string() const
		{
			std::wstring text;

			nana::upoint a, b;
			if (get_selected_points(a, b))
			{
				auto & textbase = this->textbase();

				if (a.y != b.y)
				{
					text = textbase.getline(a.y).substr(a.x);
					text += L"\r\n";
					for (unsigned i = a.y + 1; i < b.y; ++i)
					{
						text += textbase.getline(i);
						text += L"\r\n";
					}
					text += textbase.getline(b.y).substr(0, b.x);
				}
				else
					return textbase.getline(a.y).substr(a.x, b.x - a.x);
			}

			return text;
		}

		std::size_t eat_endl(const wchar_t* str, std::size_t pos)
		{
			auto ch = str[pos];
			if (0 == ch)
				return pos;

			const wchar_t * endlstr;
			switch (ch)
			{
			case L'\n':
				endlstr = L"\n\r";
				break;
			case L'\r':
				endlstr = L"\r\n";
				break;
			default:
				return pos;
			}

			if (std::memcmp(str + pos, endlstr, sizeof(wchar_t) * 2) == 0)
				return pos + 2;

			return pos + 1;
		}

		bool text_editor::_m_resolve_text(const std::wstring& text, std::vector<std::pair<std::size_t, std::size_t>> & lines)
		{
			auto const text_str = text.c_str();
			std::size_t begin = 0;
			while (true)
			{
				auto pos = text.find_first_of(L"\r\n", begin);
				if (text.npos == pos)
				{
					if (!lines.empty())
						lines.emplace_back(begin, text.size());
					break;
				}

				lines.emplace_back(begin, pos);

				pos = eat_endl(text_str, pos);

				begin = text.find_first_not_of(L"\r\n", pos);

				//The number of new lines minus one
				const auto chp_end = text_str + (begin == text.npos ? text.size() : begin);

				for (auto chp = text_str + pos; chp != chp_end; ++chp)
				{
					auto eats = eat_endl(chp, 0);
					if (eats)
					{
						lines.emplace_back();
						chp += (eats - 1);
					}
				}

				if (text.npos == begin)
				{
					lines.emplace_back();
					break;
				}
			}
			return !lines.empty();
		}

		bool text_editor::_m_cancel_select(int align)
		{
			upoint a, b;
			if (get_selected_points(a, b))
			{
				//domain of algin = [0, 2]
				if (align)
				{
					this->points_.caret = (1 == align ? a : b);
					this->_m_adjust_view();
				}

				select_.a = select_.b = points_.caret;
				reset_caret();
				return true;
			}
			return false;
		}

		nana::size text_editor::_m_text_extent_size(const char_type* str, size_type n) const
		{
			if(mask_char_)
			{
				std::wstring maskstr;
				maskstr.append(n, mask_char_);
				return graph_.text_extent_size(maskstr);
			}
#ifdef _nana_std_has_string_view
			return graph_.text_extent_size(std::basic_string_view<char_type>(str, n));
#else
			return graph_.text_extent_size(str, static_cast<unsigned>(n));
#endif
		}

		bool text_editor::_m_adjust_view()
		{
			auto const view_area = impl_->cview->view_area();

			auto const line_px = static_cast<int>(this->line_height());
			auto coord = _m_caret_to_coordinate(points_.caret, true);

			if (view_area.is_hit(coord) && view_area.is_hit({coord.x, coord.y + line_px}))
				return false;

			unsigned extra_count_horz = 4;
			unsigned extra_count_vert = 0;

			auto const origin = impl_->cview->origin();
			coord = _m_caret_to_coordinate(points_.caret, false);

			point moved_origin;

			//adjust x-axis if it isn't line-wrapped mode
			if (!attributes_.line_wrapped)
			{
				auto extra = points_.caret;

				if (coord.x < origin.x)
				{
					extra.x -= (std::min)(extra_count_horz, points_.caret.x);
					moved_origin.x = _m_caret_to_coordinate(extra, false).x - origin.x;
				}
				else if (coord.x + static_cast<int>(caret_size().width) >= origin.x + static_cast<int>(view_area.width))
				{
					extra.x = (std::min)(static_cast<unsigned>(textbase().getline(points_.caret.y).size()), points_.caret.x + extra_count_horz);
					auto new_origin = _m_caret_to_coordinate(extra, false).x + static_cast<int>(caret_size().width) - static_cast<int>(view_area.width);
					moved_origin.x = new_origin - origin.x;
				}
			}

			auto extra_px = static_cast<int>(line_px * extra_count_vert);

			if (coord.y < origin.y)
			{
				//Top of caret is less than the top of view

				moved_origin.y = (std::max)(0, coord.y - extra_px) - origin.y;
			}
			else if (coord.y + line_px >= origin.y + static_cast<int>(view_area.height))
			{
				//Bottom of caret is greater than the bottom of view

				auto const bottom = static_cast<int>(impl_->capacities.behavior->take_lines() * line_px);
				auto new_origin = (std::min)(coord.y + line_px + extra_px, bottom) - static_cast<int>(view_area.height);
				moved_origin.y = new_origin - origin.y;
			}

			return impl_->cview->move_origin(moved_origin);
		}

		bool text_editor::_m_move_select(bool record_undo)
		{
			if (!attributes_.editable)
				return false;

			nana::upoint caret = points_.caret;
			const auto text = _m_make_select_string();
			if (!text.empty())
			{
				auto undo_ptr = std::unique_ptr<undo_move_text>(new undo_move_text(*this));
				undo_ptr->set_selected_text();

				//Determines whether the caret is at left or at right. The select_.b indicates the caret position when finish selection
				const bool at_left = (select_.b < select_.a);

				nana::upoint a, b;
				get_selected_points(a, b);
				if (caret.y < a.y || (caret.y == a.y && caret.x < a.x))
				{//forward
					undo_ptr->set_caret_pos();

					_m_erase_select();
					_m_put(text);

					select_.a = caret;
					select_.b.y = b.y + (caret.y - a.y);
				}
				else if (b.y < caret.y || (caret.y == b.y && b.x < caret.x))
				{
					undo_ptr->set_caret_pos();

					_m_put(text);
					_m_erase_select();

					select_.b.y = caret.y;
					select_.a.y = caret.y - (b.y - a.y);
					select_.a.x = caret.x - (caret.y == b.y ? (b.x - a.x) : 0);
				}
				select_.b.x = b.x + (a.y == b.y ? (select_.a.x - a.x) : 0);

				//restores the caret at the proper end.
				if ((select_.b < select_.a) != at_left)
					std::swap(select_.a, select_.b);

				if (record_undo)
				{
					undo_ptr->set_destination(select_.a, select_.b);
					impl_->undo.push(std::move(undo_ptr));
				}

				points_.caret = select_.b;
				reset_caret();
				return true;
			}
			return false;
		}

		int text_editor::_m_text_top_base() const
		{
			if(false == attributes_.multi_lines)
			{
				unsigned px = line_height();
				if(text_area_.area.height > px)
					return text_area_.area.y + static_cast<int>((text_area_.area.height - px) >> 1);
			}
			return text_area_.area.y;
		}

		int text_editor::_m_text_topline() const
		{
			auto px = static_cast<int>(line_height());
			return (px ? (impl_->cview->origin().y / px) : px);
		}

		int text_editor::_m_text_x(const text_section& sct) const
		{
			auto const behavior = impl_->capacities.behavior;
			int left = this->text_area_.area.x;

			if (::nana::align::left != this->attributes_.alignment)
			{
				auto blank_px = behavior->max_pixels() - sct.pixels;

				if (::nana::align::center == this->attributes_.alignment)
					left += static_cast<int>(blank_px) / 2;
				else
					left += static_cast<int>(blank_px);
			}

			return left - impl_->cview->origin().x;
		}


		void text_editor::_m_draw_parse_string(const keyword_parser& parser, bool rtl, ::nana::point pos, const ::nana::color& fgcolor, const wchar_t* str, std::size_t len) const
		{
#ifdef _nana_std_has_string_view
			graph_.string(pos, { str, len }, fgcolor);
#else
			graph_.palette(true, fgcolor);
			graph_.string(pos, str, len);
#endif
			if (parser.entities().empty())
				return;

#ifdef _nana_std_has_string_view
			auto glyph_px = graph_.glyph_pixels({ str, len });
#else
			std::unique_ptr<unsigned[]> glyph_px(new unsigned[len]);
			graph_.glyph_pixels(str, len, glyph_px.get());
#endif
			auto glyphs = glyph_px.get();

			auto px_h = line_height();
			auto px_w = std::accumulate(glyphs, glyphs + len, unsigned{});

			::nana::paint::graphics canvas;
			canvas.make({ px_w, px_h });
			canvas.typeface(graph_.typeface());
			::nana::point canvas_text_pos;

			auto ent_pos = pos;
			const auto str_end = str + len;
			auto & entities = parser.entities();

			for (auto & ent : entities)
			{
				const wchar_t* ent_begin = nullptr;

				int ent_off = 0;
				if (str <= ent.begin && ent.begin < str_end)
				{
					ent_begin = ent.begin;
					ent_off = static_cast<int>(std::accumulate(glyphs, glyphs + (ent.begin - str), unsigned{}));
				}
				else if (ent.begin <= str && str < ent.end)
					ent_begin = str;

				if (ent_begin)
				{
					auto ent_end = (ent.end < str_end ? ent.end : str_end);
					auto ent_pixels = std::accumulate(glyphs + (ent_begin - str), glyphs + (ent_end - str), unsigned{});

					canvas.palette(false, ent.scheme->bgcolor.invisible() ? _m_bgcolor() : ent.scheme->bgcolor);
					canvas.palette(true, ent.scheme->fgcolor.invisible() ? fgcolor : ent.scheme->fgcolor);

					canvas.rectangle(true);

					ent_pos.x = pos.x + ent_off;

#ifdef _nana_std_has_string_view
					std::wstring_view ent_sv;
					if (rtl)
					{
						//draw the whole text if it is a RTL text, because Arbic language is transformable.
						ent_sv = { str, len };
					}
					else
					{
						ent_sv = { ent_begin, static_cast<std::wstring_view::size_type>(ent_end - ent_begin) };
						ent_off = 0;
					}
					canvas.string({}, ent_sv);
#else
					if (rtl)
					{
						//draw the whole text if it is a RTL text, because Arbic language is transformable.
						canvas.string({}, str, len);
					}
					else
					{
						canvas.string({}, ent_begin, ent_end - ent_begin);
						ent_off = 0;
					}
#endif
					graph_.bitblt(rectangle{ ent_pos, size{ ent_pixels, canvas.height() } }, canvas, point{ ent_off, 0 });
				}
			}
		}

		class text_editor::helper_pencil
		{
		public:
			helper_pencil(paint::graphics& graph, const text_editor& editor, keyword_parser& parser):
				graph_( graph ),
				editor_( editor ),
				parser_( parser ),
				line_px_( editor.line_height() )
			{}

			color selection_color(bool fgcolor, bool focused) const
			{
				if (fgcolor)
					return (focused ? editor_.scheme_->selection_text : editor_.scheme_->foreground).get_color();
				
				return (focused ? editor_.scheme_->selection : editor_.scheme_->selection_unfocused).get_color();
			}

			void write_selection(const point& text_pos, unsigned text_px, const wchar_t* text, std::size_t len, bool has_focused)
			{
#ifdef _nana_std_has_string_view
				graph_.rectangle(::nana::rectangle{ text_pos,{ text_px, line_px_ } }, true,
					selection_color(false, has_focused));

				graph_.string(text_pos, { text, len }, selection_color(true, has_focused));
#else
				graph_.palette(true, selection_color(true, has_focused));

				graph_.rectangle(::nana::rectangle{ text_pos, { text_px, line_px_ } }, true,
					selection_color(false, has_focused));

				graph_.string(text_pos, text, len);
#endif
			}

			void rtl_string(point strpos, const wchar_t* str, std::size_t len, std::size_t str_px, unsigned glyph_front, unsigned glyph_selected, bool has_focused)
			{
				editor_._m_draw_parse_string(parser_, true, strpos, selection_color(true, has_focused), str, len);

				//Draw selected part
				paint::graphics graph({ glyph_selected, line_px_ });
				graph.typeface(this->graph_.typeface());
				graph.rectangle(true, selection_color(false, has_focused));

				int sel_xpos = static_cast<int>(str_px - (glyph_front + glyph_selected));

#ifdef _nana_std_has_string_view
				graph.string({ -sel_xpos, 0 }, { str, len }, selection_color(true, has_focused));
#else
				graph.palette(true, selection_color(true, has_focused));
				graph.string({ -sel_xpos, 0 }, str, len);
#endif
				graph_.bitblt(nana::rectangle(strpos.x + sel_xpos, strpos.y, glyph_selected, line_px_), graph);
			};
		private:
			paint::graphics& graph_;
			const text_editor& editor_;
			keyword_parser & parser_;
			unsigned line_px_;
		};

		void text_editor::_m_draw_string(int top, const ::nana::color& clr, const nana::upoint& text_coord, const text_section& sct, bool if_mask) const
		{
			point text_draw_pos{ _m_text_x(sct), top };

			const int text_right = text_area_.area.right();
			auto const text_len = static_cast<unsigned>(sct.end - sct.begin);
			auto text_ptr = sct.begin;

			std::wstring mask_str;
			if (if_mask && mask_char_)
			{
				mask_str.resize(text_len, mask_char_);
				text_ptr = mask_str.c_str();
			}

			const auto focused = API::is_focus_ready(window_);

			auto const reordered = unicode_reorder(text_ptr, text_len);

			//Parse highlight keywords
			keyword_parser parser;
			parser.parse(text_ptr, text_len, impl_->keywords);

			const auto line_h_pixels = line_height();

			helper_pencil pencil(graph_, *this, parser);

			graph_.palette(true, clr);
			graph_.palette(false, scheme_->selection.get_color());


			//Get the selection begin and end position of the current text.
			const wchar_t *sbegin = nullptr, *send = nullptr;

			nana::upoint a, b;
			if (get_selected_points(a, b))
			{
				if (a.y < text_coord.y && text_coord.y < b.y)
				{
					sbegin = sct.begin;
					send = sct.end;
				}
				else if ((a.y == b.y) && a.y == text_coord.y)
				{
					auto sbegin_pos = (std::max)(a.x, text_coord.x);
					auto send_pos = (std::min)(text_coord.x + text_len, b.x);

					if (sbegin_pos < send_pos)
					{
						sbegin = text_ptr + (sbegin_pos - text_coord.x);
						send = text_ptr + (send_pos - text_coord.x);
					}
				}
				else if (a.y == text_coord.y)
				{
					if (a.x < text_coord.x + text_len)
					{
						sbegin = text_ptr;
						if (text_coord.x < a.x)
							sbegin += (a.x - text_coord.x);

						send = text_ptr + text_len;
					}
				}
				else if (b.y == text_coord.y)
				{
					if (text_coord.x < b.x)
					{
						sbegin = text_ptr;
						send = text_ptr + (std::min)(b.x - text_coord.x, text_len);
					}
				}
			}

			//A text editor feature, it draws an extra block at end of line if the end of line is in range of selection.
			bool extra_space = false;

			//Create a flag for indicating whether the whole line is selected
			const bool text_selected = (sbegin == text_ptr && send == text_ptr+ text_len);

			//The text is not selected or the whole line text is selected
			if ((!sbegin || !send) || text_selected)
			{
				for (auto & ent : reordered)
				{
					std::size_t len = ent.end - ent.begin;

#ifdef _nana_std_has_string_view
					unsigned str_w = graph_.text_extent_size(std::wstring_view{ ent.begin, len }).width;
#else
					unsigned str_w = graph_.text_extent_size(ent.begin, len).width;
#endif

					if ((text_draw_pos.x + static_cast<int>(str_w) > text_area_.area.x) && (text_draw_pos.x < text_right))
					{
						if (text_selected)
							pencil.write_selection(text_draw_pos, str_w, ent.begin, len, focused);
						else
							_m_draw_parse_string(parser, is_right_text(ent), text_draw_pos, clr, ent.begin, len);
					}
					text_draw_pos.x += static_cast<int>(str_w);
				}

				extra_space = text_selected;
			}
			else
			{
				for (auto & ent : reordered)
				{
					const auto len = ent.end - ent.begin;
#ifdef _nana_std_has_string_view
					auto ent_px = graph_.text_extent_size(std::wstring_view(ent.begin, len)).width;
#else
					auto ent_px = graph_.text_extent_size(ent.begin, len).width;
#endif

					extra_space = false;

					//Only draw the text which is in the visual rectangle.
					if ((text_draw_pos.x + static_cast<int>(ent_px) > text_area_.area.x) && (text_draw_pos.x < text_right))
					{
						if (send <= ent.begin || ent.end <= sbegin)
						{
							//this string is not selected
							_m_draw_parse_string(parser, false, text_draw_pos, clr, ent.begin, len);
						}
						else if (sbegin <= ent.begin && ent.end <= send)
						{
							//this string is completed selected
							pencil.write_selection(text_draw_pos, ent_px, ent.begin, len, focused);
							extra_space = true;
						}
						else
						{
							//a part of string is selected

							//get the selected range of this string.
							auto ent_sbegin = (std::max)(sbegin, ent.begin);
							auto ent_send = (std::min)(send, ent.end);

							unsigned select_pos = static_cast<unsigned>(ent_sbegin != ent.begin ? ent_sbegin - ent.begin : 0);
							unsigned select_len = static_cast<unsigned>(ent_send - ent_sbegin);

#ifdef _nana_std_has_string_view
							auto pxbuf = graph_.glyph_pixels({ ent.begin, static_cast<std::size_t>(len) });
#else
							std::unique_ptr<unsigned[]> pxbuf{ new unsigned[len] };
							graph_.glyph_pixels(ent.begin, len, pxbuf.get());
#endif

							auto head_px = std::accumulate(pxbuf.get(), pxbuf.get() + select_pos, unsigned{});
							auto select_px = std::accumulate(pxbuf.get() + select_pos, pxbuf.get() + select_pos + select_len, unsigned{});

							graph_.palette(true, clr);
							if (is_right_text(ent))
							{	//RTL
								pencil.rtl_string(text_draw_pos, ent.begin, len, ent_px, head_px, select_px, focused);
							}
							else
							{	//LTR
								_m_draw_parse_string(parser, false, text_draw_pos, clr, ent.begin, select_pos);

								auto part_pos = text_draw_pos;
								part_pos.x += static_cast<int>(head_px);

								pencil.write_selection(part_pos, select_px, ent.begin + select_pos, select_len, focused);

								if (ent_send < ent.end)
								{
									part_pos.x += static_cast<int>(select_px);
									_m_draw_parse_string(parser, false, part_pos, clr, ent_send, ent.end - ent_send);
								}
							}

							extra_space = (select_pos + select_len == text_len);
						}
					}
					text_draw_pos.x += static_cast<int>(ent_px);
				}//end for
			}

			//extra_space is true if the end of line is selected
			if (extra_space)
			{
				//draw the extra space if end of line is not equal to the second selection position.
				auto pos = text_coord.x + text_len;
				if (b.x != pos || text_coord.y != b.y)
				{
#ifdef _nana_std_has_string_view
					auto whitespace_w = graph_.text_extent_size(std::wstring_view{ L" ", 1 }).width;
#else
					auto whitespace_w = graph_.text_extent_size(L" ", 1).width;
#endif
					graph_.rectangle(::nana::rectangle{ text_draw_pos, { whitespace_w, line_h_pixels } }, true);
				}
			}
		}

		bool text_editor::_m_update_caret_line(std::size_t secondary_before)
		{
			if (false == this->_m_adjust_view())
			{
				if (_m_caret_to_coordinate(points_.caret).x < impl_->cview->view_area().right())
				{
					_m_update_line(points_.caret.y, secondary_before);
					return false;
				}
			}
			else
			{
				//The content view is adjusted, now syncs it with active mode to avoid updating.
				impl_->cview->sync(false);
			}
			impl_->try_refresh = sync_graph::refresh;
			return true;
		}

		unsigned text_editor::_m_char_by_pixels(const unicode_bidi::entity& ent, unsigned pos) const
		{
			auto len = static_cast<std::size_t>(ent.end - ent.begin);
#ifdef _nana_std_has_string_view
			auto pxbuf = graph_.glyph_pixels({ ent.begin, len });
			if (pxbuf)
#else
			std::unique_ptr<unsigned[]> pxbuf(new unsigned[len]);
			if (graph_.glyph_pixels(ent.begin, len, pxbuf.get()))
#endif
			{
				const auto px_end = pxbuf.get() + len;

				if (is_right_text(ent))
				{
					auto total_px = std::accumulate(pxbuf.get(), px_end, unsigned{});

					for (auto p = pxbuf.get(); p != px_end; ++p)
					{
						auto chpos = total_px - *p;
						if ((chpos <= pos) && (pos < total_px))
						{
							if ((*p < 2) || (pos <= chpos + (*p >> 1)))
								return static_cast<unsigned>(p - pxbuf.get()) + 1;

							return static_cast<unsigned>(p - pxbuf.get());
						}
						total_px = chpos;
					}
				}
				else
				{
					for (auto p = pxbuf.get(); p != px_end; ++p)
					{
						if (pos <= *p)
						{
							if ((*p > 1) && (pos >(*p >> 1)))
								return static_cast<unsigned>(p - pxbuf.get()) + 1;
							return static_cast<unsigned>(p - pxbuf.get());
						}
						pos -= *p;
					}
				}
			}

			return 0;
		}

		unsigned text_editor::_m_pixels_by_char(const std::wstring& lnstr, std::size_t pos) const
		{
			if (pos > lnstr.size())
				return 0;

			auto const reordered = unicode_reorder(lnstr.c_str(), lnstr.size());

			auto target = lnstr.c_str() + pos;

			unsigned text_w = 0;
			for (auto & ent : reordered)
			{
				std::size_t len = ent.end - ent.begin;
				if (ent.begin <= target && target <= ent.end)
				{
					if (is_right_text(ent))
					{
						//Characters of some bidi languages may transform in a word.
						//RTL
#ifdef _nana_std_has_string_view
						auto pxbuf = graph_.glyph_pixels({ent.begin, len});
#else
						std::unique_ptr<unsigned[]> pxbuf(new unsigned[len]);
						graph_.glyph_pixels(ent.begin, len, pxbuf.get());
#endif
						return std::accumulate(pxbuf.get() + (target - ent.begin), pxbuf.get() + len, text_w);
					}
					//LTR
					return text_w + _m_text_extent_size(ent.begin, target - ent.begin).width;
				}
				else
					text_w += _m_text_extent_size(ent.begin, len).width;
			}
			return text_w;
		}

		//end class text_editor
	}//end namespace skeletons
}//end namespace widgets
}//end namespace nana