From 26c28ae4becac7b7029152993ce3eac940c3d998 Mon Sep 17 00:00:00 2001
From: James Bremner <james@ravenspoint.com>
Date: Wed, 16 Jan 2019 16:43:05 -0500
Subject: [PATCH] Slider value handles -ve values by clipping to zero

see http://nanapro.org/en-us/forum/index.php?u=/topic/1092/ggslider-value-range
---
 include/nana/gui/widgets/slider.hpp |  8 +++++++-
 source/gui/widgets/slider.cpp       | 24 ++++++++++++++----------
 2 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/include/nana/gui/widgets/slider.hpp b/include/nana/gui/widgets/slider.hpp
index 8ce9602b..2fc015ce 100644
--- a/include/nana/gui/widgets/slider.hpp
+++ b/include/nana/gui/widgets/slider.hpp
@@ -151,7 +151,13 @@ namespace nana
 		bool vertical() const;
 		void maximum(unsigned);
 		unsigned maximum() const;
-		void value(unsigned);
+
+		/** Set slider value
+            @param[in] v new value for slider.
+            v will be clipped to the range 0 to maximum
+        */
+		void value(int );
+
 		unsigned value() const;
 		unsigned move_step(bool forward);                         ///< Increase or decrease the value of slider.
 		unsigned adorn() const;
diff --git a/source/gui/widgets/slider.cpp b/source/gui/widgets/slider.cpp
index 67a67631..572eba99 100644
--- a/source/gui/widgets/slider.cpp
+++ b/source/gui/widgets/slider.cpp
@@ -245,7 +245,7 @@ namespace nana
 				};
 			public:
 				enum class parts{none, bar, slider};
-				
+
 				using graph_reference = drawer_trigger::graph_reference;
 
 				model()
@@ -256,7 +256,7 @@ namespace nana
 					proto_.renderer = pat::cloneable<renderer_interface>{interior_renderer{}};
 
 					attr_.seek_dir = seekdir::bilateral;
-					
+
 					attr_.is_draw_adorn = false;
 					attr_.vcur = 0;
 					attr_.vmax = 10;
@@ -361,7 +361,7 @@ namespace nana
 				parts seek_where(::nana::point pos) const
 				{
 					nana::rectangle r = _m_bar_area();
-					
+
 					if (attr_.slider.vert)
 					{
 						std::swap(pos.x, pos.y);
@@ -373,7 +373,7 @@ namespace nana
 						return parts::slider;
 
 					sdpos = static_cast<int>(attr_.slider.weight) / 2;
-					
+
 					if (sdpos <= pos.x && pos.x < sdpos + static_cast<int>(r.width))
 					{
 						if(pos.y < r.bottom())
@@ -446,7 +446,7 @@ namespace nana
 				bool move_slider(const ::nana::point& pos)
 				{
 					int adorn_pos = slider_state_.snap_pos + (attr_.slider.vert ? pos.y : pos.x) - slider_state_.refpos.x;
-					
+
 					if (adorn_pos > 0)
 					{
 						int range = static_cast<int>(_m_range());
@@ -691,7 +691,7 @@ namespace nana
 					window wd;
 					nana::slider * widget;
 				}other_;
-				
+
 				struct prototype_tag
 				{
 					pat::cloneable<slider::renderer_interface> renderer;
@@ -759,9 +759,9 @@ namespace nana
 				void trigger::mouse_move(graph_reference graph, const arg_mouse& arg)
 				{
 					// check if slider is disabled
-					if(!API::get_widget(arg.window_handle)->enabled()) 
+					if(!API::get_widget(arg.window_handle)->enabled())
 						return;		// do nothing
-					
+
 					bool updated = false;
 					if (model_ptr_->if_trace_slider())
 					{
@@ -804,7 +804,7 @@ namespace nana
 
 	//class slider
 		slider::slider(){}
-		
+
 		slider::slider(window wd, bool visible)
 		{
 			create(wd, rectangle(), visible);
@@ -844,10 +844,14 @@ namespace nana
 			return get_drawer_trigger().get_model()->attribute().vmax;
 		}
 
-		void slider::value(unsigned v)
+		void slider::value(int v)
 		{
 			if(handle())
 			{
+			    // limit to positive values, vcur expects unsigned
+			    if( v < 0 )
+                    v = 0;
+
 				if(get_drawer_trigger().get_model()->vcur(v))
 					API::refresh_window(handle());
 			}