Backends: Vulkan: VK_SUBOPTIMAL_KHR doesn't skip frame. (ocornut#7831, ocornut#7825)

Author: ocornut

backends/imgui_impl_vulkan.cpp

@@ -247,8 +247,9 @@ struct ImGui_ImplVulkan_ViewportData
     ImGui_ImplVulkan_WindowRenderBuffers    RenderBuffers;          // Used by all viewports
     bool                                    WindowOwned;
     bool                                    SwapChainNeedRebuild;   // Flag when viewport swapchain resized in the middle of processing a frame
+    bool                                    SwapChainSuboptimal;    // Flag when VK_SUBOPTIMAL_KHR was returned.
 
-    ImGui_ImplVulkan_ViewportData() { WindowOwned = SwapChainNeedRebuild = false; memset(&RenderBuffers, 0, sizeof(RenderBuffers)); }
+    ImGui_ImplVulkan_ViewportData() { WindowOwned = SwapChainNeedRebuild = SwapChainSuboptimal = false; memset(&RenderBuffers, 0, sizeof(RenderBuffers)); }
     ~ImGui_ImplVulkan_ViewportData() { }
 };
 
@@ -1808,10 +1809,10 @@ static void ImGui_ImplVulkan_RenderWindow(ImGuiViewport* viewport, void*)
     ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;
     VkResult err;
 
-    if (vd->SwapChainNeedRebuild)
+    if (vd->SwapChainNeedRebuild || vd->SwapChainSuboptimal)
     {
         ImGui_ImplVulkanH_CreateOrResizeWindow(v->Instance, v->PhysicalDevice, v->Device, wd, v->QueueFamily, v->Allocator, (int)viewport->Size.x, (int)viewport->Size.y, v->MinImageCount);
-        vd->SwapChainNeedRebuild = false;
+        vd->SwapChainNeedRebuild = vd->SwapChainSuboptimal = false;
     }
 
     ImGui_ImplVulkanH_Frame* fd = nullptr;
@@ -1821,11 +1822,13 @@ static void ImGui_ImplVulkan_RenderWindow(ImGuiViewport* viewport, void*)
             err = vkAcquireNextImageKHR(v->Device, wd->Swapchain, UINT64_MAX, fsd->ImageAcquiredSemaphore, VK_NULL_HANDLE, &wd->FrameIndex);
             if (err == VK_ERROR_OUT_OF_DATE_KHR)
             {
-                // Since we are not going to swap this frame anyway, it's ok that recreation happens on next frame.
-                vd->SwapChainNeedRebuild = true;
+                vd->SwapChainNeedRebuild = true; // Since we are not going to swap this frame anyway, it's ok that recreation happens on next frame.
                 return;
             }
-            check_vk_result(err);
+            if (err == VK_SUBOPTIMAL_KHR)
+                vd->SwapChainSuboptimal = true;
+            else
+                check_vk_result(err);
             fd = &wd->Frames[wd->FrameIndex];
         }
         for (;;)
@@ -1967,11 +1970,14 @@ static void ImGui_ImplVulkan_SwapBuffers(ImGuiViewport* viewport, void*)
     info.pSwapchains = &wd->Swapchain;
     info.pImageIndices = &present_index;
     err = vkQueuePresentKHR(v->Queue, &info);
-    if (err == VK_ERROR_OUT_OF_DATE_KHR || err == VK_SUBOPTIMAL_KHR)
-        vd->SwapChainNeedRebuild = true;
     if (err == VK_ERROR_OUT_OF_DATE_KHR)
+    {
+        vd->SwapChainNeedRebuild = true;
         return;
-    if (err != VK_SUBOPTIMAL_KHR)
+    }
+    if (err == VK_SUBOPTIMAL_KHR)
+        vd->SwapChainSuboptimal = true;
+    else
         check_vk_result(err);
     wd->SemaphoreIndex = (wd->SemaphoreIndex + 1) % wd->SemaphoreCount; // Now we can use the next set of semaphores
 }

docs/CHANGELOG.txt

@@ -46,11 +46,13 @@ Other changes:
 - ImDrawList: texture baked storage for thick line reduced from ~64x64 to ~32x32. (#3245)
 - Examples: DirectX12: Reduced number of frame in flight from 3 to 2 in
   provided example, to reduce latency.
-- Examples: Vulkan: better handle VK_SUBOPTIMAL_KHR being returned by
+- Backends+Examples: Vulkan: better handle VK_SUBOPTIMAL_KHR being returned by
   vkAcquireNextImageKHR() or vkQueuePresentKHR(). (#7825, #7831) [@NostraMagister]
 - Backends: DirectX12: Texture upload use the command queue provided in
   ImGui_ImplDX12_InitInfo instead of creating its own.
 
+Docking+Viewports Branch:
+
 
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  VERSION 1.91.7 (Released 2025-01-14)