Smoother scrolling

- changed IO.MouseWheel to float, allows smoother scrolling

imgui.cpp

@@ -1431,16 +1431,15 @@ void ImGui::NewFrame()
     g.IO.WantCaptureKeyboard = (g.ActiveId != 0);
 
     // Scale & Scrolling
-    if (g.HoveredWindow && g.IO.MouseWheel != 0)
+    if (g.HoveredWindow && g.IO.MouseWheel != 0.0f)
     {
         ImGuiWindow* window = g.HoveredWindow;
-        const int mouse_wheel_dir = g.IO.MouseWheel > 0 ? +1 : -1;
         if (g.IO.KeyCtrl)
         {
             if (g.IO.FontAllowUserScaling)
             {
                 // Zoom / Scale window
-                float new_font_scale = ImClamp(window->FontWindowScale + mouse_wheel_dir * 0.10f, 0.50f, 2.50f);
+                float new_font_scale = ImClamp(window->FontWindowScale + g.IO.MouseWheel * 0.10f, 0.50f, 2.50f);
                 float scale = new_font_scale / window->FontWindowScale;
                 window->FontWindowScale = new_font_scale;
 
@@ -1455,7 +1454,7 @@ void ImGui::NewFrame()
         {
             // Scroll
             const int scroll_lines = (window->Flags & ImGuiWindowFlags_ComboBox) ? 3 : 5;
-            window->NextScrollY -= mouse_wheel_dir * window->FontSize() * scroll_lines;
+            window->NextScrollY -= g.IO.MouseWheel * window->FontSize() * scroll_lines;
         }
     }
 
@@ -1605,7 +1604,7 @@ void ImGui::Render()
         g.Windows.swap(sorted_windows);
 
         // Clear data for next frame
-        g.IO.MouseWheel = 0;
+        g.IO.MouseWheel = 0.0f;
         memset(g.IO.InputCharacters, 0, sizeof(g.IO.InputCharacters));
     }
 

imgui.h

@@ -488,7 +488,7 @@ struct ImGuiIO
 
     ImVec2      MousePos;                   // Mouse position, in pixels (set to -1,-1 if no mouse / on another screen, etc.)
     bool        MouseDown[5];               // Mouse buttons. ImGui itself only uses button 0 (left button) but you can use others as storage for convenience.
-    int         MouseWheel;                 // Mouse wheel: -1,0,+1
+    float       MouseWheel;                 // Mouse wheel: 1 unit scrolls about 3 lines text.  
     bool        KeyCtrl;                    // Keyboard modifier pressed: Control
     bool        KeyShift;                   // Keyboard modifier pressed: Shift
     bool        KeysDown[512];              // Keyboard keys that are pressed (in whatever order user naturally has access to keyboard data)