[Impeller] presentKHR from background worker. (flutter#43976)

Testing with validation enabled shows no crashes or validation warnings on Pixel 6 or S10. I believe this is safe since we are correctly synchronized in the acquireNextImage via the presentation semaphore. The only loss is that we will finish the raster task before we know that presentation is failed.

Having said that, we can end up waiting multiple ms for the layout transition and presentation, so that doesn't seem worth it.

Author: Jonah Williams

impeller/renderer/backend/vulkan/swapchain_impl_vk.cc

@@ -392,88 +392,97 @@ bool SwapchainImplVK::Present(const std::shared_ptr<SwapchainImageVK>& image,
   }
 
   const auto& context = ContextVK::Cast(*context_strong);
+  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;
+        }
 
-  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;
-    }
-  }
+        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 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;
+          }
+        }
 
-  //----------------------------------------------------------------------------
-  /// Present the image.
-  ///
-  uint32_t indices[] = {static_cast<uint32_t>(index)};
-
-  vk::PresentInfoKHR present_info;
-  present_info.setSwapchains(*swapchain_);
-  present_info.setImageIndices(indices);
-  present_info.setWaitSemaphores(*sync->present_ready);
-
-  switch (auto result = present_queue_.presentKHR(present_info)) {
-    case vk::Result::eErrorOutOfDateKHR:
-      // Caller will recreate the impl on acquisition, not submission.
-      [[fallthrough]];
-    case vk::Result::eErrorSurfaceLostKHR:
-      // Vulkan guarantees that the set of queue operations will still complete
-      // successfully.
-      [[fallthrough]];
-    case vk::Result::eSuccess:
-      is_rotated_ = false;
-      return true;
-    case vk::Result::eSuboptimalKHR:
-      is_rotated_ = true;
-      return true;
-    default:
-      VALIDATION_LOG << "Could not present queue: " << vk::to_string(result);
-      return false;
-  }
-  FML_UNREACHABLE();
-  return false;
+        //----------------------------------------------------------------------------
+        /// Present the image.
+        ///
+        uint32_t indices[] = {static_cast<uint32_t>(index)};
+
+        vk::PresentInfoKHR present_info;
+        present_info.setSwapchains(*swapchain_);
+        present_info.setImageIndices(indices);
+        present_info.setWaitSemaphores(*sync->present_ready);
+
+        switch (auto result = present_queue_.presentKHR(present_info)) {
+          case vk::Result::eErrorOutOfDateKHR:
+            // Caller will recreate the impl on acquisition, not submission.
+            [[fallthrough]];
+          case vk::Result::eErrorSurfaceLostKHR:
+            // Vulkan guarantees that the set of queue operations will still
+            // complete successfully.
+            [[fallthrough]];
+          case vk::Result::eSuccess:
+            is_rotated_ = false;
+            return;
+          case vk::Result::eSuboptimalKHR:
+            is_rotated_ = true;
+            return;
+          default:
+            VALIDATION_LOG << "Could not present queue: "
+                           << vk::to_string(result);
+            return;
+        }
+        FML_UNREACHABLE();
+      });
+  return true;
 }
 
 }  // namespace impeller