Examples: GLFW+Vulkan, SDL+Vulkan: Fix for handling of minimized windows. (#3259)

docs/CHANGELOG.txt

@@ -70,6 +70,7 @@ Other Changes:
 - Backends: Vulkan: Fixed edge case where render callbacks wouldn't be called if the ImDrawData
   structure didn't have any vertices. (#2697) [@kudaba]
 - Backends: OSX: Added workaround to avoid fast mouse clicks. (#3261, #1992, #2525) [@nburrus]
+- Examples: GLFW+Vulkan, SDL+Vulkan: Fix for handling of minimized windows. (#3259)
 - Examples: Apple: Fixed example_apple_metal and example_apple_opengl2 using imgui_impl_osx.mm
   not forwarding right and center mouse clicks. (#3260) [@nburrus]
 

examples/example_glfw_vulkan/main.cpp

@@ -248,7 +248,7 @@ static void CleanupVulkanWindow()
     ImGui_ImplVulkanH_DestroyWindow(g_Instance, g_Device, &g_MainWindowData, g_Allocator);
 }
 
-static void FrameRender(ImGui_ImplVulkanH_Window* wd)
+static void FrameRender(ImGui_ImplVulkanH_Window* wd, ImDrawData* draw_data)
 {
     VkResult err;
 
@@ -286,8 +286,8 @@ static void FrameRender(ImGui_ImplVulkanH_Window* wd)
         vkCmdBeginRenderPass(fd->CommandBuffer, &info, VK_SUBPASS_CONTENTS_INLINE);
     }
 
-    // Record Imgui Draw Data and draw funcs into command buffer
-    ImGui_ImplVulkan_RenderDrawData(ImGui::GetDrawData(), fd->CommandBuffer);
+    // Record dear imgui primitives into command buffer
+    ImGui_ImplVulkan_RenderDrawData(draw_data, fd->CommandBuffer);
 
     // Submit command buffer
     vkCmdEndRenderPass(fd->CommandBuffer);
@@ -456,7 +456,8 @@ int main(int, char**)
         // Generally you may always pass all inputs to dear imgui, and hide them from your application based on those two flags.
         glfwPollEvents();
 
-        if (g_SwapChainRebuild)
+        // Resize swap chain?
+        if (g_SwapChainRebuild && g_SwapChainResizeWidth > 0 && g_SwapChainResizeHeight > 0)
         {
             g_SwapChainRebuild = false;
             ImGui_ImplVulkan_SetMinImageCount(g_MinImageCount);
@@ -508,11 +509,14 @@ int main(int, char**)
 
         // Rendering
         ImGui::Render();
-        memcpy(&wd->ClearValue.color.float32[0], &clear_color, 4 * sizeof(float));
-        FrameRender(wd);
-
+        ImDrawData* draw_data = ImGui::GetDrawData();
+        const bool is_minimized = (draw_data->DisplaySize.x <= 0.0f || draw_data->DisplaySize.y <= 0.0f);
+        if (!is_minimized)
+        {
+            FrameRender(wd, draw_data);
             FramePresent(wd);
         }
+    }
 
     // Cleanup
     err = vkDeviceWaitIdle(g_Device);

examples/example_sdl_vulkan/main.cpp

@@ -240,7 +240,7 @@ static void CleanupVulkanWindow()
     ImGui_ImplVulkanH_DestroyWindow(g_Instance, g_Device, &g_MainWindowData, g_Allocator);
 }
 
-static void FrameRender(ImGui_ImplVulkanH_Window* wd)
+static void FrameRender(ImGui_ImplVulkanH_Window* wd, ImDrawData* draw_data)
 {
     VkResult err;
 
@@ -278,8 +278,8 @@ static void FrameRender(ImGui_ImplVulkanH_Window* wd)
         vkCmdBeginRenderPass(fd->CommandBuffer, &info, VK_SUBPASS_CONTENTS_INLINE);
     }
 
-    // Record Imgui Draw Data and draw funcs into command buffer
-    ImGui_ImplVulkan_RenderDrawData(ImGui::GetDrawData(), fd->CommandBuffer);
+    // Record dear imgui primitives into command buffer
+    ImGui_ImplVulkan_RenderDrawData(draw_data, fd->CommandBuffer);
 
     // Submit command buffer
     vkCmdEndRenderPass(fd->CommandBuffer);
@@ -447,13 +447,17 @@ int main(int, char**)
                 done = true;
             if (event.type == SDL_WINDOWEVENT && event.window.event == SDL_WINDOWEVENT_RESIZED && event.window.windowID == SDL_GetWindowID(window))
             {
+                // Note: your own application may rely on SDL_WINDOWEVENT_MINIMIZED/SDL_WINDOWEVENT_RESTORED to skip updating all-together.
+                // Here ImGui_ImplSDL2_NewFrame() will set io.DisplaySize to zero which will disable rendering but let application run.
+                // Please note that you can't Present into a minimized window.
                 g_SwapChainResizeWidth = (int)event.window.data1;
                 g_SwapChainResizeHeight = (int)event.window.data2;
                 g_SwapChainRebuild = true;
             }
         }
 
-        if (g_SwapChainRebuild)
+        // Resize swap chain?
+        if (g_SwapChainRebuild && g_SwapChainResizeWidth > 0 && g_SwapChainResizeHeight > 0)
         {
             g_SwapChainRebuild = false;
             ImGui_ImplVulkan_SetMinImageCount(g_MinImageCount);
@@ -505,11 +509,14 @@ int main(int, char**)
 
         // Rendering
         ImGui::Render();
-        memcpy(&wd->ClearValue.color.float32[0], &clear_color, 4 * sizeof(float));
-        FrameRender(wd);
-
+        ImDrawData* draw_data = ImGui::GetDrawData();
+        const bool is_minimized = (draw_data->DisplaySize.x <= 0.0f || draw_data->DisplaySize.y <= 0.0f);
+        if (!is_minimized)
+        {
+            FrameRender(wd, draw_data);
             FramePresent(wd);
         }
+    }
 
     // Cleanup
     err = vkDeviceWaitIdle(g_Device);

examples/imgui_impl_vulkan.cpp

@@ -999,6 +999,7 @@ void ImGui_ImplVulkanH_CreateWindowSwapChain(VkPhysicalDevice physical_device, V
 {
     VkResult err;
     VkSwapchainKHR old_swapchain = wd->Swapchain;
+    wd->Swapchain = NULL;
     err = vkDeviceWaitIdle(device);
     check_vk_result(err);