Backends: Vulkan: Call vkCmdSetScissor() with a full-viewport at end of render. (ocornut#4644)

Author: ocornut

backends/imgui_impl_vulkan.cpp

@@ -23,6 +23,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2021-10-15: Vulkan: Call vkCmdSetScissor() at the end of render a full-viewport to reduce likehood of issues with people using VK_DYNAMIC_STATE_SCISSOR in their app without calling vkCmdSetScissor() explicitly every frame.
 //  2021-06-29: Reorganized backend to pull data from a single structure to facilitate usage with multiple-contexts (all g_XXXX access changed to bd->XXXX).
 //  2021-03-22: Vulkan: Fix mapped memory validation error when buffer sizes are not multiple of VkPhysicalDeviceLimits::nonCoherentAtomSize.
 //  2021-02-18: Vulkan: Change blending equation to preserve alpha in output buffer.
@@ -544,7 +545,9 @@ void ImGui_ImplVulkan_RenderDrawData(ImDrawData* draw_data, VkCommandBuffer comm
     // - And you forgot to call vkCmdSetViewport() and vkCmdSetScissor() yourself to explicitely set that state.
     // If you use VK_DYNAMIC_STATE_VIEWPORT or VK_DYNAMIC_STATE_SCISSOR you are responsible for setting the values before rendering.
     // In theory we should aim to backup/restore those values but I am not sure this is possible.
-    // If we add a call to vkCmdSetScissor() to cover the full viewport that would fix things for majority of users BUT would made it harder to notice your bug. (See github #4644)
+    // We perform a call to vkCmdSetScissor() to set back a full viewport which is likely to fix things for 99% users but technically this is not perfect. (See github #4644)
+    VkRect2D scissor = { { 0, 0 }, { (uint32_t)fb_width, (uint32_t)fb_height } };
+    vkCmdSetScissor(command_buffer, 0, 1, &scissor);
 }
 
 bool ImGui_ImplVulkan_CreateFontsTexture(VkCommandBuffer command_buffer)

docs/CHANGELOG.txt

@@ -38,6 +38,9 @@ Breaking Changes:
 
 Other Changes:
 
+- Backends: Vulkan: Call vkCmdSetScissor() at the end of render with a full-viewport to reduce
+  likehood of issues with people using VK_DYNAMIC_STATE_SCISSOR in their app without calling
+  vkCmdSetScissor() explicitly every frame. (#4644)
 - Misc: Fix MinGW DLL build issue (when IMGUI_API is defined). [@rokups]
 - CI: Add MinGW DLL build to test suite. [@rokups]