Bug 1724839 - Don't use BasicLayerManager for painting ImageBitmap <canvas> elements. r=jrmuizel

Differential Revision: https://phabricator.services.mozilla.com/D122171

dom/canvas/ImageBitmapRenderingContext.h

@@ -81,6 +81,9 @@ class ImageBitmapRenderingContext final
   virtual already_AddRefed<Layer> GetCanvasLayer(
       nsDisplayListBuilder* aBuilder, Layer* aOldLayer,
       LayerManager* aManager) override;
+  virtual already_AddRefed<layers::Image> GetAsImage() override {
+    return ClipToIntrinsicSize();
+  }
   bool UpdateWebRenderCanvasData(nsDisplayListBuilder* aBuilder,
                                  WebRenderCanvasData* aCanvasData) override;
   virtual void MarkContextClean() override;

dom/canvas/nsICanvasRenderingContextInternal.h

@@ -39,6 +39,7 @@ class CanvasLayer;
 class CanvasRenderer;
 class CompositableHandle;
 class Layer;
+class Image;
 class LayerManager;
 class LayerTransactionChild;
 class PersistentBufferProvider;
@@ -146,6 +147,9 @@ class nsICanvasRenderingContextInternal : public nsISupports,
   virtual already_AddRefed<Layer> GetCanvasLayer(
       mozilla::nsDisplayListBuilder* builder, Layer* oldLayer,
       LayerManager* manager) = 0;
+  virtual already_AddRefed<mozilla::layers::Image> GetAsImage() {
+    return nullptr;
+  }
   virtual bool UpdateWebRenderCanvasData(
       mozilla::nsDisplayListBuilder* aBuilder,
       WebRenderCanvasData* aCanvasData) {

dom/html/HTMLCanvasElement.cpp

@@ -1142,6 +1142,18 @@ already_AddRefed<Layer> HTMLCanvasElement::GetCanvasLayer(
   return nullptr;
 }
 
+already_AddRefed<Image> HTMLCanvasElement::GetAsImage() {
+  if (mCurrentContext) {
+    return mCurrentContext->GetAsImage();
+  }
+
+  if (mOffscreenCanvas) {
+    MOZ_CRASH("todo");
+  }
+
+  return nullptr;
+}
+
 bool HTMLCanvasElement::UpdateWebRenderCanvasData(
     nsDisplayListBuilder* aBuilder, WebRenderCanvasData* aCanvasData) {
   if (mCurrentContext) {

dom/html/HTMLCanvasElement.h

@@ -301,6 +301,7 @@ class HTMLCanvasElement final : public nsGenericHTMLElement,
   already_AddRefed<Layer> GetCanvasLayer(nsDisplayListBuilder* aBuilder,
                                          Layer* aOldLayer,
                                          LayerManager* aManager);
+  already_AddRefed<layers::Image> GetAsImage();
   bool UpdateWebRenderCanvasData(nsDisplayListBuilder* aBuilder,
                                  WebRenderCanvasData* aCanvasData);
   bool InitializeCanvasRenderer(nsDisplayListBuilder* aBuilder,

layout/generic/nsHTMLCanvasFrame.cpp

@@ -307,6 +307,51 @@ class nsDisplayCanvas final : public nsPaintedDisplayItem {
 
   virtual void Paint(nsDisplayListBuilder* aBuilder,
                      gfxContext* aCtx) override {
+    nsHTMLCanvasFrame* f = static_cast<nsHTMLCanvasFrame*>(Frame());
+    HTMLCanvasElement* canvas = HTMLCanvasElement::FromNode(f->GetContent());
+
+    nsRect area = f->GetContentRectRelativeToSelf() + ToReferenceFrame();
+    nsIntSize canvasSizeInPx = f->GetCanvasSize();
+
+    nsPresContext* presContext = f->PresContext();
+    canvas->HandlePrintCallback(presContext);
+
+    if (canvasSizeInPx.width <= 0 || canvasSizeInPx.height <= 0 ||
+        area.IsEmpty()) {
+      return;
+    }
+
+    IntrinsicSize intrinsicSize = IntrinsicSizeFromCanvasSize(canvasSizeInPx);
+    AspectRatio intrinsicRatio = IntrinsicRatioFromCanvasSize(canvasSizeInPx);
+
+    nsRect dest = nsLayoutUtils::ComputeObjectDestRect(
+        area, intrinsicSize, intrinsicRatio, f->StylePosition());
+
+    gfxRect destGFXRect = presContext->AppUnitsToGfxUnits(dest);
+
+    // Transform the canvas into the right place
+    gfxPoint p = destGFXRect.TopLeft();
+    Matrix transform = Matrix::Translation(p.x, p.y);
+    transform.PreScale(destGFXRect.Width() / canvasSizeInPx.width,
+                       destGFXRect.Height() / canvasSizeInPx.height);
+
+    if (RefPtr<layers::Image> image = canvas->GetAsImage()) {
+      RefPtr<gfx::SourceSurface> surface = image->GetAsSourceSurface();
+      if (!surface || !surface->IsValid()) {
+        return;
+      }
+
+      gfxContextMatrixAutoSaveRestore saveMatrix(aCtx);
+      aCtx->Multiply(transform);
+
+      gfx::IntSize size = surface->GetSize();
+      aCtx->GetDrawTarget()->FillRect(
+          Rect(0, 0, size.width, size.height),
+          SurfacePattern(surface, ExtendMode::CLAMP, Matrix(),
+                         nsLayoutUtils::GetSamplingFilterForFrame(f)));
+      return;
+    }
+
     // This currently uses BasicLayerManager to re-use the code for extracting
     // the current CanvasRenderer/Image and generating DrawTarget rendering
     // commands for it.