Started providing the GPU sync switch to Rasterizer.DrawToSurface()

flow/compositor_context.h

@@ -46,8 +46,12 @@ enum class RasterStatus {
   kEnqueuePipeline,
   // Failed to rasterize the frame.
   kFailed,
-  // Layer tree was discarded due to LayerTreeDiscardCallback
-  kDiscarded
+  // Layer tree was discarded due to LayerTreeDiscardCallback or inability to
+  // access the GPU.
+  kDiscarded,
+  // Drawing was yielded to allow the correct thread to draw as a result of the
+  // RasterThreadMerger.
+  kYielded,
 };
 
 class CompositorContext {

flow/embedded_views.cc

@@ -6,10 +6,8 @@
 
 namespace flutter {
 
-void ExternalViewEmbedder::SubmitFrame(
-    GrDirectContext* context,
-    std::unique_ptr<SurfaceFrame> frame,
-    const std::shared_ptr<const fml::SyncSwitch>& gpu_disable_sync_switch) {
+void ExternalViewEmbedder::SubmitFrame(GrDirectContext* context,
+                                       std::unique_ptr<SurfaceFrame> frame) {
   frame->Submit();
 };
 

flow/embedded_views.h

@@ -10,7 +10,6 @@
 #include "flutter/flow/surface_frame.h"
 #include "flutter/fml/memory/ref_counted.h"
 #include "flutter/fml/raster_thread_merger.h"
-#include "flutter/fml/synchronization/sync_switch.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkPath.h"
 #include "third_party/skia/include/core/SkPoint.h"
@@ -313,10 +312,8 @@ class ExternalViewEmbedder {
   // This method can mutate the root Skia canvas before submitting the frame.
   //
   // It can also allocate frames for overlay surfaces to compose hybrid views.
-  virtual void SubmitFrame(
-      GrDirectContext* context,
-      std::unique_ptr<SurfaceFrame> frame,
-      const std::shared_ptr<const fml::SyncSwitch>& gpu_disable_sync_switch);
+  virtual void SubmitFrame(GrDirectContext* context,
+                           std::unique_ptr<SurfaceFrame> frame);
 
   // This method provides the embedder a way to do additional tasks after
   // |SubmitFrame|. For example, merge task runners if `should_resubmit_frame`

flow/surface.cc

@@ -18,4 +18,8 @@ bool Surface::ClearRenderContext() {
   return false;
 }
 
+bool Surface::AllowsDrawingWhenGpuDisabled() const {
+  return true;
+}
+
 }  // namespace flutter

flow/surface.h

@@ -33,6 +33,8 @@ class Surface {
 
   virtual bool ClearRenderContext();
 
+  virtual bool AllowsDrawingWhenGpuDisabled() const;
+
  private:
   FML_DISALLOW_COPY_AND_ASSIGN(Surface);
 };

shell/common/rasterizer.cc

@@ -147,7 +147,7 @@ void Rasterizer::DrawLastLayerTree(
   DrawToSurface(*frame_timings_recorder, *last_layer_tree_);
 }
 
-void Rasterizer::Draw(
+RasterStatus Rasterizer::Draw(
     std::unique_ptr<FrameTimingsRecorder> frame_timings_recorder,
     std::shared_ptr<Pipeline<flutter::LayerTree>> pipeline,
     LayerTreeDiscardCallback discardCallback) {
@@ -156,7 +156,7 @@ void Rasterizer::Draw(
   if (raster_thread_merger_ &&
       !raster_thread_merger_->IsOnRasterizingThread()) {
     // we yield and let this frame be serviced on the right thread.
-    return;
+    return RasterStatus::kYielded;
   }
   FML_DCHECK(delegate_.GetTaskRunners()
                  .GetRasterTaskRunner()
@@ -217,6 +217,8 @@ void Rasterizer::Draw(
     default:
       break;
   }
+
+  return raster_status;
 }
 
 namespace {
@@ -385,6 +387,8 @@ RasterStatus Rasterizer::DoDraw(
              raster_status == RasterStatus::kSkipAndRetry) {
     resubmitted_layer_tree_ = std::move(layer_tree);
     return raster_status;
+  } else if (raster_status == RasterStatus::kDiscarded) {
+    return raster_status;
   }
 
   if (persistent_cache->IsDumpingSkp() &&
@@ -465,6 +469,31 @@ RasterStatus Rasterizer::DrawToSurface(
   TRACE_EVENT0("flutter", "Rasterizer::DrawToSurface");
   FML_DCHECK(surface_);
 
+  RasterStatus raster_status;
+  if (surface_->AllowsDrawingWhenGpuDisabled()) {
+    raster_status = DrawToSurfaceUnsafe(frame_timings_recorder, layer_tree);
+  } else {
+    delegate_.GetIsGpuDisabledSyncSwitch()->Execute(
+        fml::SyncSwitch::Handlers()
+            .SetIfTrue([&] { raster_status = RasterStatus::kDiscarded; })
+            .SetIfFalse([&] {
+              raster_status =
+                  DrawToSurfaceUnsafe(frame_timings_recorder, layer_tree);
+            }));
+  }
+
+  return raster_status;
+}
+
+/// Unsafe because it assumes we have access to the GPU which isn't the case
+/// when iOS is backgrounded, for example.
+/// \see Rasterizer::DrawToSurface
+RasterStatus Rasterizer::DrawToSurfaceUnsafe(
+    FrameTimingsRecorder& frame_timings_recorder,
+    flutter::LayerTree& layer_tree) {
+  TRACE_EVENT0("flutter", "Rasterizer::DrawToSurfaceUnsafe");
+  FML_DCHECK(surface_);
+
   compositor_context_->ui_time().SetLapTime(
       frame_timings_recorder.GetBuildDuration());
 
@@ -512,9 +541,8 @@ RasterStatus Rasterizer::DrawToSurface(
     if (external_view_embedder_ &&
         (!raster_thread_merger_ || raster_thread_merger_->IsMerged())) {
       FML_DCHECK(!frame->IsSubmitted());
-      external_view_embedder_->SubmitFrame(
-          surface_->GetContext(), std::move(frame),
-          delegate_.GetIsGpuDisabledSyncSwitch());
+      external_view_embedder_->SubmitFrame(surface_->GetContext(),
+                                           std::move(frame));
     } else {
       frame->Submit();
     }

shell/common/rasterizer.h

@@ -233,9 +233,10 @@ class Rasterizer final : public SnapshotDelegate {
   /// @param[in]  discardCallback if specified and returns true, the layer tree
   ///                             is discarded instead of being rendered
   ///
-  void Draw(std::unique_ptr<FrameTimingsRecorder> frame_timings_recorder,
-            std::shared_ptr<Pipeline<flutter::LayerTree>> pipeline,
-            LayerTreeDiscardCallback discardCallback = NoDiscard);
+  RasterStatus Draw(
+      std::unique_ptr<FrameTimingsRecorder> frame_timings_recorder,
+      std::shared_ptr<Pipeline<flutter::LayerTree>> pipeline,
+      LayerTreeDiscardCallback discardCallback = NoDiscard);
 
   //----------------------------------------------------------------------------
   /// @brief      The type of the screenshot to obtain of the previously
@@ -492,6 +493,9 @@ class Rasterizer final : public SnapshotDelegate {
   RasterStatus DrawToSurface(FrameTimingsRecorder& frame_timings_recorder,
                              flutter::LayerTree& layer_tree);
 
+  RasterStatus DrawToSurfaceUnsafe(FrameTimingsRecorder& frame_timings_recorder,
+                                   flutter::LayerTree& layer_tree);
+
   void FireNextFrameCallbackIfPresent();
 
   static bool NoDiscard(const flutter::LayerTree& layer_tree) { return false; }