fix bugs that button renderer generated bad values if it zero-size

include/nana/basic_types.hpp

@@ -445,7 +445,13 @@ namespace nana
 		size dimension() const noexcept;
 		rectangle& dimension(const size&) noexcept;
 
-		rectangle& pare_off(int pixels);	 ///<Pares the specified pixels off the rectangle. It's equal to x += pixels; y + pixels; width -= (pixels << 1); height -= (pixels << 1);
+		/// Pares the specified pixels off the rectangle.
+		/**
+		 * It's equal to x += pixels; y + pixels; width -= (pixels << 1); height -= (pixels << 1);
+		 * @param pixels The number of pixels to be pared. If the number that multiples pixels twice is larger than width/height, the width/height will be zero. If the pixels is a negative number, the width/height is add the number that multiple pixels twice.
+		 * @return The reference of *this.
+		 */
+		rectangle& pare_off(int pixels);
 
 		int right() const noexcept;
 		int bottom() const noexcept;

source/basic_types.cpp

@@ -591,21 +591,21 @@ namespace nana
 			return *this;
 		}
 
-		/*
-		rectangle& rectangle::set_size(const size& sz)
-		{
-			width = sz.width;
-			height = sz.height;
-			return *this;
-		}
-		*/
-
 		rectangle& rectangle::pare_off(int pixels)
 		{
 			x += pixels;
 			y += pixels;
-			width -= (pixels << 1);
+			auto const px_twice = (pixels << 1);
-			height -= (pixels << 1);
+			if (px_twice > static_cast<int>(width))
+				width = 0;
+			else
+				width -= px_twice;
+
+			if (px_twice > static_cast<int>(height))
+				height = 0;
+			else
+				height -= px_twice;
+
 			return *this;
 		}
 

source/gui/detail/drawer.cpp

@@ -294,7 +294,7 @@ namespace nana
 
 		void drawer::refresh()
 		{
-			if (data_impl_->realizer && !data_impl_->refreshing)
+			if (data_impl_->realizer && (!(data_impl_->refreshing || graphics.size().empty())))
 			{
 				data_impl_->refreshing = true;
 				data_impl_->realizer->refresh(graphics);

source/paint/graphics.cpp

@@ -1196,7 +1196,11 @@ namespace paint
 #elif defined(NANA_X11)
 			if (nullptr == impl_->handle) return;
 
-			double deltapx = double(vertical ? rct.height : rct.width);
+			nana::rectangle good_rct;
+			if(!nana::overlap(nana::rectangle{ size() }, rct, good_rct))
+				return;
+
+			double deltapx = double(vertical ? good_rct.height : good_rct.width);
 			double r, g, b;
 			const double delta_r = (to.r() - (r = from.r())) / deltapx;
 			const double delta_g = (to.g() - (g = from.g())) / deltapx;
@@ -1207,13 +1211,13 @@ namespace paint
 			Display * disp = nana::detail::platform_spec::instance().open_display();
 			impl_->handle->set_color(static_cast<color_rgb>(last_color));
 			impl_->handle->update_color();
-			const int endpos = deltapx + (vertical ? rct.y : rct.x);
+			const int endpos = deltapx + (vertical ? good_rct.y : good_rct.x);
 			if (endpos > 0)
 			{
 				if (vertical)
 				{
-					int x1 = rct.x, x2 = rct.right();
+					int x1 = good_rct.x, x2 = good_rct.right();
-					auto y = rct.y;
+					auto y = good_rct.y;
 					for (; y < endpos; ++y)
 					{
 						::XDrawLine(disp, impl_->handle->pixmap, impl_->handle->context, x1, y, x2, y);
@@ -1228,8 +1232,8 @@ namespace paint
 				}
 				else
 				{
-					int y1 = rct.y, y2 = rct.bottom();
+					int y1 = good_rct.y, y2 = good_rct.bottom();
-					auto x = rct.x;
+					auto x = good_rct.x;
 					for (; x < endpos; ++x)
 					{
 						::XDrawLine(disp, impl_->handle->pixmap, impl_->handle->context, x, y1, x, y2);