[Impeller] Don't perform final layout transition on worker thread.

impeller/renderer/backend/vulkan/swapchain_impl_vk.cc

@@ -392,64 +392,65 @@ bool SwapchainImplVK::Present(const std::shared_ptr<SwapchainImageVK>& image,
   }
 
   const auto& context = ContextVK::Cast(*context_strong);
+  const auto& sync = synchronizers_[current_frame_];
+
+  //----------------------------------------------------------------------------
+  /// Transition the image to color-attachment-optimal.
+  ///
+  sync->final_cmd_buffer = context.CreateCommandBuffer();
+  if (!sync->final_cmd_buffer) {
+    return false;
+  }
+
+  auto vk_final_cmd_buffer = CommandBufferVK::Cast(*sync->final_cmd_buffer)
+                                 .GetEncoder()
+                                 ->GetCommandBuffer();
+  {
+    BarrierVK barrier;
+    barrier.new_layout = vk::ImageLayout::ePresentSrcKHR;
+    barrier.cmd_buffer = vk_final_cmd_buffer;
+    barrier.src_access = vk::AccessFlagBits::eColorAttachmentWrite;
+    barrier.src_stage = vk::PipelineStageFlagBits::eColorAttachmentOutput;
+    barrier.dst_access = {};
+    barrier.dst_stage = vk::PipelineStageFlagBits::eBottomOfPipe;
+
+    if (!image->SetLayout(barrier)) {
+      return false;
+    }
+
+    if (vk_final_cmd_buffer.end() != vk::Result::eSuccess) {
+      return false;
+    }
+  }
+
+  //----------------------------------------------------------------------------
+  /// Signal that the presentation semaphore is ready.
+  ///
+  {
+    vk::SubmitInfo submit_info;
+    vk::PipelineStageFlags wait_stage =
+        vk::PipelineStageFlagBits::eColorAttachmentOutput;
+    submit_info.setWaitDstStageMask(wait_stage);
+    submit_info.setWaitSemaphores(*sync->render_ready);
+    submit_info.setSignalSemaphores(*sync->present_ready);
+    submit_info.setCommandBuffers(vk_final_cmd_buffer);
+    auto result =
+        context.GetGraphicsQueue()->Submit(submit_info, *sync->acquire);
+    if (result != vk::Result::eSuccess) {
+      VALIDATION_LOG << "Could not wait on render semaphore: "
+                     << vk::to_string(result);
+      return false;
+    }
+  }
+
   context.GetConcurrentWorkerTaskRunner()->PostTask(
       [&, index, image, current_frame = current_frame_] {
         auto context_strong = context_.lock();
         if (!context_strong) {
           return;
         }
-        const auto& context = ContextVK::Cast(*context_strong);
-        const auto& sync = synchronizers_[current_frame];
-
-        //----------------------------------------------------------------------------
-        /// Transition the image to color-attachment-optimal.
-        ///
-        sync->final_cmd_buffer = context.CreateCommandBuffer();
-        if (!sync->final_cmd_buffer) {
-          return;
-        }
-
-        auto vk_final_cmd_buffer =
-            CommandBufferVK::Cast(*sync->final_cmd_buffer)
-                .GetEncoder()
-                ->GetCommandBuffer();
-        {
-          BarrierVK barrier;
-          barrier.new_layout = vk::ImageLayout::ePresentSrcKHR;
-          barrier.cmd_buffer = vk_final_cmd_buffer;
-          barrier.src_access = vk::AccessFlagBits::eColorAttachmentWrite;
-          barrier.src_stage = vk::PipelineStageFlagBits::eColorAttachmentOutput;
-          barrier.dst_access = {};
-          barrier.dst_stage = vk::PipelineStageFlagBits::eBottomOfPipe;
-
-          if (!image->SetLayout(barrier)) {
-            return;
-          }
-
-          if (vk_final_cmd_buffer.end() != vk::Result::eSuccess) {
-            return;
-          }
-        }
 
-        //----------------------------------------------------------------------------
-        /// Signal that the presentation semaphore is ready.
-        ///
-        {
-          vk::SubmitInfo submit_info;
-          vk::PipelineStageFlags wait_stage =
-              vk::PipelineStageFlagBits::eColorAttachmentOutput;
-          submit_info.setWaitDstStageMask(wait_stage);
-          submit_info.setWaitSemaphores(*sync->render_ready);
-          submit_info.setSignalSemaphores(*sync->present_ready);
-          submit_info.setCommandBuffers(vk_final_cmd_buffer);
-          auto result =
-              context.GetGraphicsQueue()->Submit(submit_info, *sync->acquire);
-          if (result != vk::Result::eSuccess) {
-            VALIDATION_LOG << "Could not wait on render semaphore: "
-                           << vk::to_string(result);
-            return;
-          }
-        }
+        const auto& sync = synchronizers_[current_frame];
 
         //----------------------------------------------------------------------------
         /// Present the image.