Add support for transparent backbuffers to GLFW contexts (OpenGL3 and Vulkan)

examples/example_glfw_opengl3/main.cpp

@@ -58,6 +58,8 @@ int main(int, char**)
     //glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);  // 3.2+ only
     //glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);            // 3.0+ only
 #endif
+
+    glfwWindowHint(GLFW_TRANSPARENT_FRAMEBUFFER, true); // Enable transparent backbuffers
 
     // Create window with graphics context
     GLFWwindow* window = glfwCreateWindow(1280, 720, "Dear ImGui GLFW+OpenGL3 example", NULL, NULL);
@@ -92,6 +94,7 @@ int main(int, char**)
     io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;         // Enable Multi-Viewport / Platform Windows
     //io.ConfigViewportsNoAutoMerge = true;
     //io.ConfigViewportsNoTaskBarIcon = true;
+    io.ConfigFlags |= ImGuiConfigFlags_TransparentBackbuffers;  // Enable transparent backbuffer support
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
@@ -159,8 +162,12 @@ int main(int, char**)
             ImGui::Checkbox("Demo Window", &show_demo_window);      // Edit bools storing our window open/close state
             ImGui::Checkbox("Another Window", &show_another_window);
 
-            ImGui::SliderFloat("float", &f, 0.0f, 1.0f);            // Edit 1 float using a slider from 0.0f to 1.0f
-            ImGui::ColorEdit3("clear color", (float*)&clear_color); // Edit 3 floats representing a color
+            if (ImGui::SliderFloat("Window Opacity", &f, 0.0f, 1.0f)) {
+                ImGuiStyle& style = ImGui::GetStyle();
+                style.Colors[ImGuiCol_WindowBg].w = f;
+            }// Edit 1 float using a slider from 0.0f to 1.0f
+            ImGui::ColorEdit4("clear color", (float*)&clear_color); // Edit 3 floats representing a color
+
 
             if (ImGui::Button("Button"))                            // Buttons return true when clicked (most widgets return true when edited/activated)
                 counter++;

examples/example_glfw_vulkan/main.cpp

@@ -344,6 +344,7 @@ int main(int, char**)
         return 1;
 
     glfwWindowHint(GLFW_CLIENT_API, GLFW_NO_API);
+    glfwWindowHint(GLFW_TRANSPARENT_FRAMEBUFFER, true);
     GLFWwindow* window = glfwCreateWindow(1280, 720, "Dear ImGui GLFW+Vulkan example", NULL, NULL);
 
     // Setup Vulkan
@@ -378,6 +379,7 @@ int main(int, char**)
     io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;         // Enable Multi-Viewport / Platform Windows
     //io.ConfigViewportsNoAutoMerge = true;
     //io.ConfigViewportsNoTaskBarIcon = true;
+    io.ConfigFlags |= ImGuiConfigFlags_TransparentBackbuffers;  // Enable transparent backbuffer support
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
@@ -486,7 +488,7 @@ int main(int, char**)
 
         // 2. Show a simple window that we create ourselves. We use a Begin/End pair to created a named window.
         {
-            static float f = 0.0f;
+            static float f = 1.0f;
             static int counter = 0;
 
             ImGui::Begin("Hello, world!");                          // Create a window called "Hello, world!" and append into it.
@@ -495,8 +497,11 @@ int main(int, char**)
             ImGui::Checkbox("Demo Window", &show_demo_window);      // Edit bools storing our window open/close state
             ImGui::Checkbox("Another Window", &show_another_window);
 
-            ImGui::SliderFloat("float", &f, 0.0f, 1.0f);            // Edit 1 float using a slider from 0.0f to 1.0f
-            ImGui::ColorEdit3("clear color", (float*)&clear_color); // Edit 3 floats representing a color
+            if (ImGui::SliderFloat("Window Opacity", &f, 0.0f, 1.0f)) { // Edit 1 float using a slider from 0.0f to 1.0f
+                ImGuiStyle& style = ImGui::GetStyle();
+                style.Colors[ImGuiCol_WindowBg].w = f;
+            }
+            ImGui::ColorEdit4("clear color", (float*)&clear_color); // Edit 4 floats representing a color
 
             if (ImGui::Button("Button"))                            // Buttons return true when clicked (most widgets return true when edited/activated)
                 counter++;

examples/imgui_impl_glfw.cpp

@@ -54,6 +54,7 @@
 #define GLFW_HAS_FOCUS_WINDOW         (GLFW_VERSION_MAJOR * 1000 + GLFW_VERSION_MINOR * 100 >= 3200) // 3.2+ glfwFocusWindow
 #define GLFW_HAS_FOCUS_ON_SHOW        (GLFW_VERSION_MAJOR * 1000 + GLFW_VERSION_MINOR * 100 >= 3300) // 3.3+ GLFW_FOCUS_ON_SHOW
 #define GLFW_HAS_MONITOR_WORK_AREA    (GLFW_VERSION_MAJOR * 1000 + GLFW_VERSION_MINOR * 100 >= 3300) // 3.3+ glfwGetMonitorWorkarea
+#define GLFW_HAS_TRANSPARENT_FRAMEBUFFERS (GLFW_VERSION_MAJOR * 1000 + GLFW_VERSION_MINOR * 100 >= 3300)
 
 // Data
 enum GlfwClientApi
@@ -438,6 +439,9 @@ static void ImGui_ImplGlfw_CreateWindow(ImGuiViewport* viewport)
     // With GLFW 3.3, the hint GLFW_FOCUS_ON_SHOW fixes this problem
     glfwWindowHint(GLFW_VISIBLE, false);
     glfwWindowHint(GLFW_FOCUSED, false);
+#if GLFW_HAS_TRANSPARENT_FRAMEBUFFERS
+    glfwWindowHint(GLFW_TRANSPARENT_FRAMEBUFFER, true);
+#endif
 #if GLFW_HAS_FOCUS_ON_SHOW
      glfwWindowHint(GLFW_FOCUS_ON_SHOW, false);
  #endif

examples/imgui_impl_opengl3.cpp

@@ -184,7 +184,7 @@ static void ImGui_ImplOpenGL3_SetupRenderState(ImDrawData* draw_data, int fb_wid
     // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, polygon fill
     glEnable(GL_BLEND);
     glBlendEquation(GL_FUNC_ADD);
-    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+    glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
     glDisable(GL_CULL_FACE);
     glDisable(GL_DEPTH_TEST);
     glEnable(GL_SCISSOR_TEST);
@@ -652,7 +652,7 @@ static void ImGui_ImplOpenGL3_RenderWindow(ImGuiViewport* viewport, void*)
 {
     if (!(viewport->Flags & ImGuiViewportFlags_NoRendererClear))
     {
-        ImVec4 clear_color = ImVec4(0.0f, 0.0f, 0.0f, 1.0f);
+        ImVec4 clear_color = ImGui::GetStyle().Colors[ImGuiCol_WindowBg];
         glClearColor(clear_color.x, clear_color.y, clear_color.z, clear_color.w);
         glClear(GL_COLOR_BUFFER_BIT);
     }

examples/imgui_impl_vulkan.cpp

@@ -749,7 +749,7 @@ bool ImGui_ImplVulkan_CreateDeviceObjects()
     color_attachment[0].dstColorBlendFactor = VK_BLEND_FACTOR_ONE_MINUS_SRC_ALPHA;
     color_attachment[0].colorBlendOp = VK_BLEND_OP_ADD;
     color_attachment[0].srcAlphaBlendFactor = VK_BLEND_FACTOR_ONE_MINUS_SRC_ALPHA;
-    color_attachment[0].dstAlphaBlendFactor = VK_BLEND_FACTOR_ZERO;
+    color_attachment[0].dstAlphaBlendFactor = VK_BLEND_FACTOR_ONE;
     color_attachment[0].alphaBlendOp = VK_BLEND_OP_ADD;
     color_attachment[0].colorWriteMask = VK_COLOR_COMPONENT_R_BIT | VK_COLOR_COMPONENT_G_BIT | VK_COLOR_COMPONENT_B_BIT | VK_COLOR_COMPONENT_A_BIT;
 
@@ -1074,6 +1074,8 @@ void ImGui_ImplVulkanH_CreateWindowSwapChain(VkPhysicalDevice physical_device, V
         VkSurfaceCapabilitiesKHR cap;
         err = vkGetPhysicalDeviceSurfaceCapabilitiesKHR(physical_device, wd->Surface, &cap);
         check_vk_result(err);
+        if (cap.supportedCompositeAlpha & VK_COMPOSITE_ALPHA_POST_MULTIPLIED_BIT_KHR)
+            info.compositeAlpha = VK_COMPOSITE_ALPHA_POST_MULTIPLIED_BIT_KHR;
         if (info.minImageCount < cap.minImageCount)
             info.minImageCount = cap.minImageCount;
         else if (cap.maxImageCount != 0 && info.minImageCount > cap.maxImageCount)
@@ -1365,7 +1367,7 @@ static void ImGui_ImplVulkan_RenderWindow(ImGuiViewport* viewport, void*)
             check_vk_result(err);
         }
         {
-            ImVec4 clear_color = ImVec4(0.0f, 0.0f, 0.0f, 1.0f);
+            ImVec4 clear_color = ImGui::GetStyle().Colors[ImGuiCol_WindowBg];
             memcpy(&wd->ClearValue.color.float32[0], &clear_color, 4 * sizeof(float));
 
             VkRenderPassBeginInfo info = {};