Examples: OpenGL: fix for retina screens + io.DisplayFramebufferScale storage (#287)

examples/opengl3_example/imgui_impl_glfw_gl3.cpp

@@ -42,15 +42,18 @@ static void ImGui_ImplGlfwGL3_RenderDrawLists(ImDrawData* draw_data)
     glEnable(GL_SCISSOR_TEST);
     glActiveTexture(GL_TEXTURE0);
 
+    // Handle cases of screen coordinates != from framebuffer coordinates (e.g. retina displays)
+    ImGuiIO& io = ImGui::GetIO();
+    float fb_height = io.DisplaySize.y * io.DisplayFramebufferScale.y;
+    draw_data->ScaleClipRects(io.DisplayFramebufferScale);
+
     // Setup orthographic projection matrix
-    const float width = ImGui::GetIO().DisplaySize.x;
-    const float height = ImGui::GetIO().DisplaySize.y;
     const float ortho_projection[4][4] =
     {
-        { 2.0f/width,	0.0f,			0.0f,		0.0f },
-        { 0.0f,			2.0f/-height,	0.0f,		0.0f },
-        { 0.0f,			0.0f,			-1.0f,		0.0f },
-        { -1.0f,		1.0f,			0.0f,		1.0f },
+        { 2.0f/io.DisplaySize.x, 0.0f,                   0.0f, 0.0f },
+        { 0.0f,                  2.0f/-io.DisplaySize.y, 0.0f, 0.0f },
+        { 0.0f,                  0.0f,                  -1.0f, 0.0f },
+        {-1.0f,                  1.0f,                   0.0f, 1.0f },
     };
     glUseProgram(g_ShaderHandle);
     glUniform1i(g_AttribLocationTex, 0);
@@ -77,7 +80,7 @@ static void ImGui_ImplGlfwGL3_RenderDrawLists(ImDrawData* draw_data)
             else
             {
                 glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->TextureId);
-                glScissor((int)pcmd->ClipRect.x, (int)(height - pcmd->ClipRect.w), (int)(pcmd->ClipRect.z - pcmd->ClipRect.x), (int)(pcmd->ClipRect.w - pcmd->ClipRect.y));
+                glScissor((int)pcmd->ClipRect.x, (int)(fb_height - pcmd->ClipRect.w), (int)(pcmd->ClipRect.z - pcmd->ClipRect.x), (int)(pcmd->ClipRect.w - pcmd->ClipRect.y));
                 glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, GL_UNSIGNED_SHORT, idx_buffer_offset);
             }
             idx_buffer_offset += pcmd->ElemCount;
@@ -307,7 +310,8 @@ void ImGui_ImplGlfwGL3_NewFrame()
     int display_w, display_h;
     glfwGetWindowSize(g_Window, &w, &h);
     glfwGetFramebufferSize(g_Window, &display_w, &display_h);
-    io.DisplaySize = ImVec2((float)display_w, (float)display_h);
+    io.DisplaySize = ImVec2((float)w, (float)h);
+    io.DisplayFramebufferScale = ImVec2((float)display_w / w, (float)display_h / h);
 
     // Setup time step
     double current_time =  glfwGetTime();
@@ -320,9 +324,7 @@ void ImGui_ImplGlfwGL3_NewFrame()
     {
     	double mouse_x, mouse_y;
     	glfwGetCursorPos(g_Window, &mouse_x, &mouse_y);
-    	mouse_x *= (float)display_w / w;                        // Convert mouse coordinates to pixels
-    	mouse_y *= (float)display_h / h;
-    	io.MousePos = ImVec2((float)mouse_x, (float)mouse_y);   // Mouse position, in pixels (set to -1,-1 if no mouse / on another screen, etc.)
+    	io.MousePos = ImVec2((float)mouse_x, (float)mouse_y);   // Mouse position in screen coordinates (set to -1,-1 if no mouse / on another screen, etc.)
     }
     else
     {

examples/opengl3_example/main.cpp

@@ -53,7 +53,6 @@ int main(int, char**)
     // Main loop
     while (!glfwWindowShouldClose(window))
     {
-        ImGuiIO& io = ImGui::GetIO();
         glfwPollEvents();
         ImGui_ImplGlfwGL3_NewFrame();
 
@@ -86,7 +85,9 @@ int main(int, char**)
         }
 
         // Rendering
-        glViewport(0, 0, (int)io.DisplaySize.x, (int)io.DisplaySize.y);
+        int display_w, display_h;
+        glfwGetFramebufferSize(window, &display_w, &display_h);
+        glViewport(0, 0, display_w, display_h);
         glClearColor(clear_color.x, clear_color.y, clear_color.z, clear_color.w);
         glClear(GL_COLOR_BUFFER_BIT);
         ImGui::Render();

examples/opengl_example/imgui_impl_glfw.cpp

@@ -40,13 +40,16 @@ static void ImGui_ImplGlfw_RenderDrawLists(ImDrawData* draw_data)
     glEnable(GL_TEXTURE_2D);
     //glUseProgram(0); // You may want this if using this code in an OpenGL 3+ context
 
+    // Handle cases of screen coordinates != from framebuffer coordinates (e.g. retina displays)
+    ImGuiIO& io = ImGui::GetIO();
+    float fb_height = io.DisplaySize.y * io.DisplayFramebufferScale.y;
+    draw_data->ScaleClipRects(io.DisplayFramebufferScale);
+
     // Setup orthographic projection matrix
-    const float width = ImGui::GetIO().DisplaySize.x;
-    const float height = ImGui::GetIO().DisplaySize.y;
     glMatrixMode(GL_PROJECTION);
     glPushMatrix();
     glLoadIdentity();
-    glOrtho(0.0f, width, height, 0.0f, -1.0f, +1.0f);
+    glOrtho(0.0f, io.DisplaySize.x, io.DisplaySize.y, 0.0f, -1.0f, +1.0f);
     glMatrixMode(GL_MODELVIEW);
     glPushMatrix();
     glLoadIdentity();
@@ -72,7 +75,7 @@ static void ImGui_ImplGlfw_RenderDrawLists(ImDrawData* draw_data)
             else
             {
                 glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->TextureId);
-                glScissor((int)pcmd->ClipRect.x, (int)(height - pcmd->ClipRect.w), (int)(pcmd->ClipRect.z - pcmd->ClipRect.x), (int)(pcmd->ClipRect.w - pcmd->ClipRect.y));
+                glScissor((int)pcmd->ClipRect.x, (int)(fb_height - pcmd->ClipRect.w), (int)(pcmd->ClipRect.z - pcmd->ClipRect.x), (int)(pcmd->ClipRect.w - pcmd->ClipRect.y));
                 glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, GL_UNSIGNED_SHORT, idx_buffer);
             }
             idx_buffer += pcmd->ElemCount;
@@ -231,7 +234,8 @@ void ImGui_ImplGlfw_NewFrame()
     int display_w, display_h;
     glfwGetWindowSize(g_Window, &w, &h);
     glfwGetFramebufferSize(g_Window, &display_w, &display_h);
-    io.DisplaySize = ImVec2((float)display_w, (float)display_h);
+    io.DisplaySize = ImVec2((float)w, (float)h);
+    io.DisplayFramebufferScale = ImVec2((float)display_w / w, (float)display_h / h);
 
     // Setup time step
     double current_time =  glfwGetTime();
@@ -244,9 +248,7 @@ void ImGui_ImplGlfw_NewFrame()
     {
     	double mouse_x, mouse_y;
     	glfwGetCursorPos(g_Window, &mouse_x, &mouse_y);
-    	mouse_x *= (float)display_w / w;                        // Convert mouse coordinates to pixels
-    	mouse_y *= (float)display_h / h;
-    	io.MousePos = ImVec2((float)mouse_x, (float)mouse_y);   // Mouse position, in pixels (set to -1,-1 if no mouse / on another screen, etc.)
+    	io.MousePos = ImVec2((float)mouse_x, (float)mouse_y);   // Mouse position in screen coordinates (set to -1,-1 if no mouse / on another screen, etc.)
     }
     else
     {

examples/opengl_example/main.cpp

@@ -77,7 +77,9 @@ int main(int, char**)
         }
 
         // Rendering
-        glViewport(0, 0, (int)ImGui::GetIO().DisplaySize.x, (int)ImGui::GetIO().DisplaySize.y);
+        int display_w, display_h;
+        glfwGetFramebufferSize(window, &display_w, &display_h);
+        glViewport(0, 0, display_w, display_h);
         glClearColor(clear_color.x, clear_color.y, clear_color.z, clear_color.w);
         glClear(GL_COLOR_BUFFER_BIT);
         ImGui::Render();

imgui.cpp

@@ -678,6 +678,7 @@ ImGuiIO::ImGuiIO()
     LogFilename = "imgui_log.txt";
     Fonts = &GImDefaultFontAtlas;
     FontGlobalScale = 1.0f;
+    DisplayFramebufferScale = ImVec2(1.0f, 1.0f);
     MousePos = ImVec2(-1,-1);
     MousePosPrev = ImVec2(-1,-1);
     MouseDoubleClickTime = 0.30f;

imgui.h

@@ -676,6 +676,7 @@ struct ImGuiIO
     ImFontAtlas*  Fonts;                    // <auto>               // Load and assemble one or more fonts into a single tightly packed texture. Output to Fonts array.
     float         FontGlobalScale;          // = 1.0f               // Global scale all fonts
     bool          FontAllowUserScaling;     // = false              // Allow user scaling text of individual window with CTRL+Wheel.
+    ImVec2        DisplayFramebufferScale;  // = (1.0f,1.0f)        // For retina display or other situations where window coordinates are different from framebuffer coordinates. User storage only, presently not used by ImGui.
     ImVec2        DisplayVisibleMin;        // <unset> (0.0f,0.0f)  // If you use DisplaySize as a virtual space larger than your screen, set DisplayVisibleMin/Max to the visible area.
     ImVec2        DisplayVisibleMax;        // <unset> (0.0f,0.0f)  // If the values are the same, we defaults to Min=(0.0f) and Max=DisplaySize