Bug 1551735 - Add a thread-safe composition recorder for WebRender r=kvark,kats

Since WebRender does its rendering on a separate thread from the compositor
thread, we need a composition recorder that can be shared between threads.

Differential Revision: https://phabricator.services.mozilla.com/D32231

--HG--
extra : moz-landing-system : lando

gfx/layers/CompositionRecorder.cpp

@@ -27,8 +27,6 @@ namespace layers {
 CompositionRecorder::CompositionRecorder(TimeStamp aRecordingStart)
     : mRecordingStart(aRecordingStart) {}
 
-CompositionRecorder::~CompositionRecorder() {}
-
 void CompositionRecorder::RecordFrame(RecordedFrame* aFrame) {
   mCollectedFrames.AppendElement(aFrame);
 }

gfx/layers/CompositionRecorder.h

@@ -49,8 +49,8 @@ class RecordedFrame {
  * If GPU-accelerated rendering is used, the frames will not be mapped into
  * memory until |WriteCollectedFrames| is called.
  */
-class CompositionRecorder final {
-  NS_INLINE_DECL_REFCOUNTING(CompositionRecorder)
+class CompositionRecorder {
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(CompositionRecorder)
 
  public:
   explicit CompositionRecorder(TimeStamp aRecordingStart);
@@ -58,15 +58,15 @@ class CompositionRecorder final {
   /**
    * Record a composited frame.
    */
-  void RecordFrame(RecordedFrame* aFrame);
+  virtual void RecordFrame(RecordedFrame* aFrame);
 
   /**
    * Write out the collected frames as a series of timestamped images.
    */
-  void WriteCollectedFrames();
+  virtual void WriteCollectedFrames();
 
  protected:
-  ~CompositionRecorder();
+  virtual ~CompositionRecorder() = default;
 
  private:
   nsTArray<RefPtr<RecordedFrame>> mCollectedFrames;

gfx/layers/moz.build

@@ -255,6 +255,7 @@ EXPORTS.mozilla.layers += [
     'wr/WebRenderBridgeParent.h',
     'wr/WebRenderCanvasRenderer.h',
     'wr/WebRenderCommandBuilder.h',
+    'wr/WebRenderCompositionRecorder.h',
     'wr/WebRenderDrawEventRecorder.h',
     'wr/WebRenderImageHost.h',
     'wr/WebRenderLayerManager.h',
@@ -503,6 +504,7 @@ UNIFIED_SOURCES += [
     'wr/WebRenderBridgeParent.cpp',
     'wr/WebRenderCanvasRenderer.cpp',
     'wr/WebRenderCommandBuilder.cpp',
+    'wr/WebRenderCompositionRecorder.cpp',
     'wr/WebRenderDrawEventRecorder.cpp',
     'wr/WebRenderImageHost.cpp',
     'wr/WebRenderLayerManager.cpp',

gfx/layers/wr/WebRenderCompositionRecorder.cpp

@@ -0,0 +1,144 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "WebRenderCompositionRecorder.h"
+
+#include "mozilla/webrender/RenderThread.h"
+
+namespace mozilla {
+
+namespace layers {
+
+class RendererRecordedFrame final : public layers::RecordedFrame {
+ public:
+  RendererRecordedFrame(const TimeStamp& aTimeStamp, wr::Renderer* aRenderer,
+                        const wr::RecordedFrameHandle aHandle,
+                        const gfx::IntSize& aSize)
+      : RecordedFrame(aTimeStamp),
+        mRenderer(aRenderer),
+        mSize(aSize),
+        mHandle(aHandle) {}
+
+  already_AddRefed<gfx::DataSourceSurface> GetSourceSurface() override {
+    if (!mSurface) {
+      mSurface = gfx::Factory::CreateDataSourceSurface(
+          mSize, gfx::SurfaceFormat::B8G8R8A8, /* aZero = */ false);
+
+      gfx::DataSourceSurface::ScopedMap map(mSurface,
+                                            gfx::DataSourceSurface::WRITE);
+
+      if (!wr_renderer_map_recorded_frame(mRenderer, mHandle, map.GetData(),
+                                          mSize.width * mSize.height * 4,
+                                          mSize.width * 4)) {
+        return nullptr;
+      }
+    }
+
+    return do_AddRef(mSurface);
+  }
+
+ private:
+  wr::Renderer* mRenderer;
+  RefPtr<gfx::DataSourceSurface> mSurface;
+  gfx::IntSize mSize;
+  wr::RecordedFrameHandle mHandle;
+};
+
+void WebRenderCompositionRecorder::RecordFrame(RecordedFrame* aFrame) {
+  MOZ_CRASH(
+      "WebRenderCompositionRecorder::RecordFrame should not be called; call "
+      "MaybeRecordFrame instead.");
+}
+
+bool WebRenderCompositionRecorder::MaybeRecordFrame(
+    wr::Renderer* aRenderer, wr::WebRenderPipelineInfo* aFrameEpochs) {
+  MOZ_ASSERT(wr::RenderThread::IsInRenderThread());
+
+  if (!aRenderer || !aFrameEpochs) {
+    return false;
+  }
+
+  if (!mMutex.TryLock()) {
+    // If we cannot lock the mutex, then the |CompositorBridgeParent|
+    // is holding the mutex in |WriteCollectedFrames|.
+    //
+    // In either case we do not want to wait to acquire the mutex to record a
+    // frame since frames recorded now will not be written to disk.
+
+    return false;
+  }
+
+  auto unlockGuard = MakeScopeExit([&]() { mMutex.Unlock(); });
+
+  if (mFinishedRecording) {
+    return true;
+  }
+
+  if (!DidPaintContent(aFrameEpochs)) {
+    return false;
+  }
+
+  wr::RecordedFrameHandle handle{0};
+  gfx::IntSize size(0, 0);
+
+  if (wr_renderer_record_frame(aRenderer, wr::ImageFormat::BGRA8, &handle,
+                               &size.width, &size.height)) {
+    RefPtr<RecordedFrame> frame =
+        new RendererRecordedFrame(TimeStamp::Now(), aRenderer, handle, size);
+
+    CompositionRecorder::RecordFrame(frame);
+  }
+
+  return false;
+}
+
+void WebRenderCompositionRecorder::WriteCollectedFrames() {
+  MutexAutoLock guard(mMutex);
+
+  MOZ_RELEASE_ASSERT(
+      !mFinishedRecording,
+      "WebRenderCompositionRecorder: Attempting to write frames from invalid "
+      "state.");
+
+  CompositionRecorder::WriteCollectedFrames();
+
+  mFinishedRecording = true;
+}
+
+bool WebRenderCompositionRecorder::DidPaintContent(
+    wr::WebRenderPipelineInfo* aFrameEpochs) {
+  const wr::WrPipelineInfo& info = aFrameEpochs->Raw();
+  bool didPaintContent = false;
+
+  for (wr::usize i = 0; i < info.epochs.length; i++) {
+    const wr::PipelineId pipelineId = info.epochs.data[i].pipeline_id;
+
+    if (pipelineId == mRootPipelineId) {
+      continue;
+    }
+
+    const auto it = mContentPipelines.find(AsUint64(pipelineId));
+    if (it == mContentPipelines.end() ||
+        it->second != info.epochs.data[i].epoch) {
+      // This content pipeline has updated list last render or has newly
+      // rendered.
+      didPaintContent = true;
+      mContentPipelines[AsUint64(pipelineId)] = info.epochs.data[i].epoch;
+    }
+  }
+
+  for (wr::usize i = 0; i < info.removed_pipelines.length; i++) {
+    const wr::PipelineId pipelineId =
+        info.removed_pipelines.data[i].pipeline_id;
+    if (pipelineId == mRootPipelineId) {
+      continue;
+    }
+    mContentPipelines.erase(AsUint64(pipelineId));
+  }
+
+  return didPaintContent;
+}
+
+}  // namespace layers
+}  // namespace mozilla

gfx/layers/wr/WebRenderCompositionRecorder.h

@@ -0,0 +1,114 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_layers_WebRenderCompositionRecorder_h
+#define mozilla_layers_WebRenderCompositionRecorder_h
+
+#include "CompositionRecorder.h"
+
+#include "mozilla/Mutex.h"
+#include "mozilla/ScopeExit.h"
+
+#include <unordered_map>
+
+namespace mozilla {
+
+namespace wr {
+class WebRenderPipelineInfo;
+}
+
+namespace layers {
+
+/**
+ * A thread-safe version of the |CompositionRecorder|.
+ *
+ * Composition recording for WebRender occurs on the |RenderThread| whereas the
+ * frames are written on the thread holding the |CompositorBridgeParent|.
+ *
+ */
+class WebRenderCompositionRecorder final : public CompositionRecorder {
+ public:
+  explicit WebRenderCompositionRecorder(TimeStamp aRecordingStart,
+                                        wr::WrPipelineId aRootPipelineId)
+      : CompositionRecorder(aRecordingStart),
+        mMutex("CompositionRecorder"),
+        mFinishedRecording(false),
+        mRootPipelineId(aRootPipelineId) {}
+
+  WebRenderCompositionRecorder() = delete;
+  WebRenderCompositionRecorder(WebRenderCompositionRecorder&) = delete;
+  WebRenderCompositionRecorder(WebRenderCompositionRecorder&&) = delete;
+
+  WebRenderCompositionRecorder& operator=(WebRenderCompositionRecorder&) =
+      delete;
+  WebRenderCompositionRecorder& operator=(WebRenderCompositionRecorder&&) =
+      delete;
+
+  /**
+   * Do not call this method.
+   *
+   * Instead, call |MaybeRecordFrame|, which will only attempt to record a
+   * frame if we have not yet written frames to disk.
+   */
+  void RecordFrame(RecordedFrame* aFrame) override;
+
+  /**
+   * Write the collected frames to disk.
+   *
+   * This method should not be called if frames have already been written or if
+   * |ForceFinishRecording| has been called as the object will be in an invalid
+   * state to write to disk.
+   *
+   * Note: This method will block acquiring a lock.
+   */
+  void WriteCollectedFrames() override;
+
+  /**
+   * Attempt to record a frame from the given renderer.
+   *
+   * This method will only record a frame if the following are true:
+   *
+   * - this object's lock was acquired immediately (i.e., we are not currently
+   *   writing frames to disk);
+   * - we have not yet written frames to disk; and
+   * - one of the pipelines in |aFrameEpochs| has updated and it is not the
+   *   root pipeline.
+   *
+   * Returns whether or not the recorder has finished recording frames. If
+   * true, it is safe to release both this object and Web Render's composition
+   * recorder structures.
+   */
+  bool MaybeRecordFrame(wr::Renderer* aRenderer,
+                        wr::WebRenderPipelineInfo* aFrameEpochs);
+
+ protected:
+  ~WebRenderCompositionRecorder() = default;
+
+  /**
+   * Determine if any content pipelines updated.
+   */
+  bool DidPaintContent(wr::WebRenderPipelineInfo* aFrameEpochs);
+
+ private:
+  Mutex mMutex;
+
+  // Whether or not we have finished recording.
+  bool mFinishedRecording;
+
+  // The id of the root WebRender pipeline.
+  //
+  // All other pipelines are considered content.
+  wr::PipelineId mRootPipelineId;
+
+  // A mapping of wr::PipelineId to the epochs when last they updated.
+  //
+  // We need to use uint64_t here since wr::PipelineId is not default
+  // constructable.
+  std::unordered_map<uint64_t, wr::Epoch> mContentPipelines;
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif  // mozilla_layers_WebRenderCompositionRecorder_h

gfx/webrender_bindings/src/bindings.rs

@@ -74,6 +74,7 @@ pub enum OpacityType {
 /// cbindgen:field-names=[mHandle]
 /// cbindgen:derive-lt=true
 /// cbindgen:derive-lte=true
+/// cbindgen:derive-neq=true
 type WrEpoch = Epoch;
 /// cbindgen:field-names=[mHandle]
 /// cbindgen:derive-lt=true