Backends: Vulkan: fixed validation errors during window detach in multi-viewport mode. [docking branch amend] (#8600, #8176)

backends/imgui_impl_vulkan.cpp

@@ -1985,13 +1985,13 @@ static void ImGui_ImplVulkan_RenderWindow(ImGuiViewport* viewport, void*)
             VkImageMemoryBarrier barrier = {};
             barrier.sType = VK_STRUCTURE_TYPE_IMAGE_MEMORY_BARRIER;
             barrier.dstAccessMask = VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT;
-            barrier.oldLayout = VK_IMAGE_LAYOUT_UNDEFINED;
+            barrier.oldLayout = VK_IMAGE_LAYOUT_PRESENT_SRC_KHR;
             barrier.newLayout = VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL;
             barrier.image = fd->Backbuffer;
             barrier.subresourceRange.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
             barrier.subresourceRange.levelCount = 1;
             barrier.subresourceRange.layerCount = 1;
-            vkCmdPipelineBarrier(fd->CommandBuffer, VK_PIPELINE_STAGE_TOP_OF_PIPE_BIT, VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT, 0, 0, nullptr, 0, nullptr, 1, &barrier);
+            vkCmdPipelineBarrier(fd->CommandBuffer, VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT | VK_PIPELINE_STAGE_NONE, VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT, 0, 0, nullptr, 0, nullptr, 1, &barrier);
 
             VkRenderingAttachmentInfo attachmentInfo = {};
             attachmentInfo.sType = VK_STRUCTURE_TYPE_RENDERING_ATTACHMENT_INFO_KHR;