Backends: Vulkan: comments about user using VK_DYNAMIC_STATE_VIEWPORT / VK_DYNAMIC_STATE_SCISSOR and not calling vkCmdSetViewport() / vkCmdSetScissor(). (#4644)
diff --git a/backends/imgui_impl_vulkan.cpp b/backends/imgui_impl_vulkan.cpp
index 296304f..280edea 100644
--- a/backends/imgui_impl_vulkan.cpp
+++ b/backends/imgui_impl_vulkan.cpp
@@ -537,6 +537,14 @@
global_idx_offset += cmd_list->IdxBuffer.Size;
global_vtx_offset += cmd_list->VtxBuffer.Size;
}
+
+ // Note: at this point both vkCmdSetViewport() and vkCmdSetScissor() have been called.
+ // Our last values will leak into user/application rendering IF:
+ // - Your app uses a pipeline with VK_DYNAMIC_STATE_VIEWPORT or VK_DYNAMIC_STATE_SCISSOR dynamic state
+ // - 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)
}
bool ImGui_ImplVulkan_CreateFontsTexture(VkCommandBuffer command_buffer)
