add tests

Author: Kaushik Iska

ci/licenses_golden/licenses_flutter

@@ -579,6 +579,7 @@ FILE: ../../../flutter/shell/common/isolate_configuration.cc
 FILE: ../../../flutter/shell/common/isolate_configuration.h
 FILE: ../../../flutter/shell/common/layer_tree_holder.cc
 FILE: ../../../flutter/shell/common/layer_tree_holder.h
+FILE: ../../../flutter/shell/common/layer_tree_holder_unittests.cc
 FILE: ../../../flutter/shell/common/persistent_cache.cc
 FILE: ../../../flutter/shell/common/persistent_cache.h
 FILE: ../../../flutter/shell/common/persistent_cache_unittests.cc

flow/compositor_context.h

@@ -27,6 +27,10 @@ enum class RasterStatus {
   // Frame needs to be resubmitted for rasterization. This is
   // currently only called when thread configuration change occurs.
   kResubmit,
+  // Frame has been successfully rasterized, but "there are additional items in
+  // the pipeline waiting to be consumed. This is currently
+  // only called when thread configuration change occurs.
+  kEnqueuePipeline,
   // Failed to rasterize the frame.
   kFailed
 };

shell/common/BUILD.gn

@@ -190,6 +190,7 @@ if (enable_unittests) {
       "animator_unittests.cc",
       "canvas_spy_unittests.cc",
       "input_events_unittests.cc",
+      "layer_tree_holder_unittests.cc",
       "persistent_cache_unittests.cc",
       "renderer_context_manager_unittests.cc",
       "renderer_context_test.cc",

shell/common/layer_tree_holder_unittests.cc

@@ -0,0 +1,73 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#define FML_USED_ON_EMBEDDER
+
+#include <functional>
+#include <future>
+#include <memory>
+
+#include "flutter/shell/common/layer_tree_holder.h"
+#include "gtest/gtest.h"
+
+namespace flutter {
+namespace testing {
+
+TEST(LayerTreeHolder, EmptyOnInit) {
+  const LayerTreeHolder layer_tree_holder;
+  ASSERT_TRUE(layer_tree_holder.IsEmpty());
+}
+
+TEST(LayerTreeHolder, PutOneAndGet) {
+  LayerTreeHolder layer_tree_holder;
+  const auto frame_size = SkISize::Make(64, 64);
+  auto layer_tree = std::make_unique<LayerTree>(frame_size, 100.0f, 1.0f);
+  layer_tree_holder.ReplaceIfNewer(std::move(layer_tree));
+  ASSERT_FALSE(layer_tree_holder.IsEmpty());
+  const auto stored = layer_tree_holder.Get();
+  ASSERT_EQ(stored->frame_size(), frame_size);
+}
+
+TEST(LayerTreeHolder, PutMultiGetsLatest) {
+  const auto build_begin = fml::TimePoint::Now();
+  const auto target_time_1 = build_begin + fml::TimeDelta::FromSeconds(2);
+  const auto target_time_2 = build_begin + fml::TimeDelta::FromSeconds(5);
+
+  LayerTreeHolder layer_tree_holder;
+  const auto frame_size_1 = SkISize::Make(64, 64);
+  auto layer_tree_1 = std::make_unique<LayerTree>(frame_size_1, 100.0f, 1.0f);
+  layer_tree_1->RecordBuildTime(build_begin, target_time_1);
+  layer_tree_holder.ReplaceIfNewer(std::move(layer_tree_1));
+
+  const auto frame_size_2 = SkISize::Make(128, 128);
+  auto layer_tree_2 = std::make_unique<LayerTree>(frame_size_2, 100.0f, 1.0f);
+  layer_tree_2->RecordBuildTime(build_begin, target_time_2);
+  layer_tree_holder.ReplaceIfNewer(std::move(layer_tree_2));
+
+  const auto stored = layer_tree_holder.Get();
+  ASSERT_EQ(stored->frame_size(), frame_size_2);
+}
+
+TEST(LayerTreeHolder, RetainsOlderIfNewerFrameHasEarlierTargetTime) {
+  const auto build_begin = fml::TimePoint::Now();
+  const auto target_time_1 = build_begin + fml::TimeDelta::FromSeconds(5);
+  const auto target_time_2 = build_begin + fml::TimeDelta::FromSeconds(2);
+
+  LayerTreeHolder layer_tree_holder;
+  const auto frame_size_1 = SkISize::Make(64, 64);
+  auto layer_tree_1 = std::make_unique<LayerTree>(frame_size_1, 100.0f, 1.0f);
+  layer_tree_1->RecordBuildTime(build_begin, target_time_1);
+  layer_tree_holder.ReplaceIfNewer(std::move(layer_tree_1));
+
+  const auto frame_size_2 = SkISize::Make(128, 128);
+  auto layer_tree_2 = std::make_unique<LayerTree>(frame_size_2, 100.0f, 1.0f);
+  layer_tree_2->RecordBuildTime(build_begin, target_time_2);
+  layer_tree_holder.ReplaceIfNewer(std::move(layer_tree_2));
+
+  const auto stored = layer_tree_holder.Get();
+  ASSERT_EQ(stored->frame_size(), frame_size_1);
+}
+
+}  // namespace testing
+}  // namespace flutter

shell/common/rasterizer.cc

@@ -4,12 +4,11 @@
 
 #include "flutter/shell/common/rasterizer.h"
 
-#include "flutter/shell/common/persistent_cache.h"
-
 #include <utility>
 
 #include "flutter/fml/time/time_delta.h"
 #include "flutter/fml/time/time_point.h"
+#include "flutter/shell/common/persistent_cache.h"
 #include "third_party/skia/include/core/SkEncodedImageFormat.h"
 #include "third_party/skia/include/core/SkImageEncoder.h"
 #include "third_party/skia/include/core/SkPictureRecorder.h"
@@ -294,6 +293,29 @@ RasterStatus Rasterizer::DoDraw(
     );
   }
 
+  // Pipeline pressure is applied from a couple of places:
+  // rasterizer: When there are more items as of the time of Consume.
+  // animator (via shell): Frame gets produces every vsync.
+  // Enqueing here is to account for the following scenario:
+  // T = 1
+  //  - one item (A) in the pipeline
+  //  - rasterizer starts (and merges the threads)
+  //  - pipeline consume result says no items to process
+  // T = 2
+  //  - animator produces (B) to the pipeline
+  //  - applies pipeline pressure via platform thread.
+  // T = 3
+  //   - rasterizes finished (and un-merges the threads)
+  //   - |Draw| for B yields as its on the wrong thread.
+  // This enqueue ensures that we attempt to consume from the right
+  // thread one more time after un-merge.
+  if (raster_thread_merger_) {
+    if (raster_thread_merger_->DecrementLease() ==
+        fml::RasterThreadStatus::kUnmergedNow) {
+      return RasterStatus::kEnqueuePipeline;
+    }
+  }
+
   return raster_status;
 }