From ebbda1906f229f33b40e0267eb2c7e51bbccb443 Mon Sep 17 00:00:00 2001
From: Lee Salzman <lsalzman@mozilla.com>
Date: Sat, 5 Aug 2023 01:05:47 +0000
Subject: [PATCH] Bug 1847244 - Finish plumbing will-read-frequently through
 WindowRenderer. r=jrmuizel

Differential Revision: https://phabricator.services.mozilla.com/D185451
---
 dom/canvas/CanvasRenderingContext2D.cpp |  5 +++--
 gfx/layers/wr/WebRenderLayerManager.cpp | 12 ++++++++----
 gfx/layers/wr/WebRenderLayerManager.h   |  3 ++-
 layout/painting/WindowRenderer.cpp      | 13 +++++++++----
 layout/painting/WindowRenderer.h        |  3 ++-
 5 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/dom/canvas/CanvasRenderingContext2D.cpp b/dom/canvas/CanvasRenderingContext2D.cpp
index 2880511f59f8..ea396a41573f 100644
--- a/dom/canvas/CanvasRenderingContext2D.cpp
+++ b/dom/canvas/CanvasRenderingContext2D.cpp
@@ -1683,8 +1683,9 @@ bool CanvasRenderingContext2D::TrySharedTarget(
     return false;
   }
 
-  aOutProvider =
-      renderer->CreatePersistentBufferProvider(GetSize(), GetSurfaceFormat());
+  aOutProvider = renderer->CreatePersistentBufferProvider(
+      GetSize(), GetSurfaceFormat(),
+      !mAllowAcceleration || mWillReadFrequently);
 
   if (!aOutProvider) {
     return false;
diff --git a/gfx/layers/wr/WebRenderLayerManager.cpp b/gfx/layers/wr/WebRenderLayerManager.cpp
index 6ea61b23b648..779c633c0b5a 100644
--- a/gfx/layers/wr/WebRenderLayerManager.cpp
+++ b/gfx/layers/wr/WebRenderLayerManager.cpp
@@ -749,8 +749,12 @@ void WebRenderLayerManager::ScheduleComposite(wr::RenderReasons aReasons) {
 
 already_AddRefed<PersistentBufferProvider>
 WebRenderLayerManager::CreatePersistentBufferProvider(
-    const gfx::IntSize& aSize, gfx::SurfaceFormat aFormat) {
-  if (!gfxPlatform::UseRemoteCanvas()) {
+    const gfx::IntSize& aSize, gfx::SurfaceFormat aFormat,
+    bool aWillReadFrequently) {
+  // Only initialize devices if hardware acceleration may possibly be used.
+  // Remoting moves hardware usage out-of-process, while will-read-frequently
+  // avoids hardware acceleration entirely.
+  if (!aWillReadFrequently && !gfxPlatform::UseRemoteCanvas()) {
 #ifdef XP_WIN
     // Any kind of hardware acceleration is incompatible with Win32k Lockdown
     // We don't initialize devices here so that PersistentBufferProviderShared
@@ -765,8 +769,8 @@ WebRenderLayerManager::CreatePersistentBufferProvider(
   }
 
   RefPtr<PersistentBufferProvider> provider =
-      PersistentBufferProviderShared::Create(aSize, aFormat,
-                                             AsKnowsCompositor());
+      PersistentBufferProviderShared::Create(
+          aSize, aFormat, AsKnowsCompositor(), aWillReadFrequently);
   if (provider) {
     return provider.forget();
   }
diff --git a/gfx/layers/wr/WebRenderLayerManager.h b/gfx/layers/wr/WebRenderLayerManager.h
index e9809ea2236e..f6d73f895d25 100644
--- a/gfx/layers/wr/WebRenderLayerManager.h
+++ b/gfx/layers/wr/WebRenderLayerManager.h
@@ -125,7 +125,8 @@ class WebRenderLayerManager final : public WindowRenderer {
   void SetFocusTarget(const FocusTarget& aFocusTarget);
 
   already_AddRefed<PersistentBufferProvider> CreatePersistentBufferProvider(
-      const gfx::IntSize& aSize, gfx::SurfaceFormat aFormat) override;
+      const gfx::IntSize& aSize, gfx::SurfaceFormat aFormat,
+      bool aWillReadFrequently) override;
 
   bool AsyncPanZoomEnabled() const;
 
diff --git a/layout/painting/WindowRenderer.cpp b/layout/painting/WindowRenderer.cpp
index d695ef8ebae4..942e8564b2f6 100644
--- a/layout/painting/WindowRenderer.cpp
+++ b/layout/painting/WindowRenderer.cpp
@@ -117,13 +117,18 @@ void FrameRecorder::StopFrameTimeRecording(uint32_t aStartIndex,
 
 already_AddRefed<PersistentBufferProvider>
 WindowRenderer::CreatePersistentBufferProvider(
-    const mozilla::gfx::IntSize& aSize, mozilla::gfx::SurfaceFormat aFormat) {
+    const mozilla::gfx::IntSize& aSize, mozilla::gfx::SurfaceFormat aFormat,
+    bool aWillReadFrequently) {
   RefPtr<PersistentBufferProviderBasic> bufferProvider;
   // If we are using remote canvas we don't want to use acceleration in
   // non-remote layer managers, so we always use the fallback software one.
-  if (!gfxPlatform::UseRemoteCanvas() ||
-      !gfxPlatform::IsBackendAccelerated(
-          gfxPlatform::GetPlatform()->GetPreferredCanvasBackend())) {
+  // If will-read-frequently is set, avoid using the preferred backend in
+  // favor of the fallback backend in case the preferred backend provides
+  // acceleration.
+  if (!aWillReadFrequently &&
+      (!gfxPlatform::UseRemoteCanvas() ||
+       !gfxPlatform::IsBackendAccelerated(
+           gfxPlatform::GetPlatform()->GetPreferredCanvasBackend()))) {
     bufferProvider = PersistentBufferProviderBasic::Create(
         aSize, aFormat,
         gfxPlatform::GetPlatform()->GetPreferredCanvasBackend());
diff --git a/layout/painting/WindowRenderer.h b/layout/painting/WindowRenderer.h
index e018a4cf563c..660d2b42ddfc 100644
--- a/layout/painting/WindowRenderer.h
+++ b/layout/painting/WindowRenderer.h
@@ -200,7 +200,8 @@ class WindowRenderer : public FrameRecorder {
    */
   virtual already_AddRefed<layers::PersistentBufferProvider>
   CreatePersistentBufferProvider(const mozilla::gfx::IntSize& aSize,
-                                 mozilla::gfx::SurfaceFormat aFormat);
+                                 mozilla::gfx::SurfaceFormat aFormat,
+                                 bool aWillReadFrequently = false);
 
   // Helper wrappers around cast to impl and then cast again.