1 files changed, 534 insertions, 0 deletions
diff --git a/layout/generic/nsHTMLCanvasFrame.cpp b/layout/generic/nsHTMLCanvasFrame.cpp
new file mode 100644
index 0000000000..07aeabec07
--- /dev/null
+++ b/layout/generic/nsHTMLCanvasFrame.cpp
@@ -0,0 +1,534 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+/* rendering object for the HTML <canvas> element */
+
+#include "nsHTMLCanvasFrame.h"
+
+#include "nsGkAtoms.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/dom/HTMLCanvasElement.h"
+#include "mozilla/layers/ImageDataSerializer.h"
+#include "mozilla/layers/WebRenderBridgeChild.h"
+#include "mozilla/layers/WebRenderCanvasRenderer.h"
+#include "mozilla/layers/RenderRootStateManager.h"
+#include "mozilla/webgpu/CanvasContext.h"
+#include "nsDisplayList.h"
+#include "nsLayoutUtils.h"
+#include "nsStyleUtil.h"
+#include "ActiveLayerTracker.h"
+
+#include <algorithm>
+
+using namespace mozilla;
+using namespace mozilla::dom;
+using namespace mozilla::layers;
+using namespace mozilla::gfx;
+
+/* Helper for our nsIFrame::GetIntrinsicSize() impl. Takes the result of
+ * "GetCanvasSize()" as a parameter, which may help avoid redundant
+ * indirect calls to GetCanvasSize().
+ *
+ * @param aCanvasSizeInPx The canvas's size in CSS pixels, as returned
+ *                        by GetCanvasSize().
+ * @return The canvas's intrinsic size, as an IntrinsicSize object.
+ */
+static IntrinsicSize IntrinsicSizeFromCanvasSize(
+    const nsIntSize& aCanvasSizeInPx) {
+  return IntrinsicSize(
+      nsPresContext::CSSPixelsToAppUnits(aCanvasSizeInPx.width),
+      nsPresContext::CSSPixelsToAppUnits(aCanvasSizeInPx.height));
+}
+
+/* Helper for our nsIFrame::GetIntrinsicRatio() impl. Takes the result of
+ * "GetCanvasSize()" as a parameter, which may help avoid redundant
+ * indirect calls to GetCanvasSize().
+ *
+ * @return The canvas's intrinsic ratio.
+ */
+static AspectRatio IntrinsicRatioFromCanvasSize(
+    const nsIntSize& aCanvasSizeInPx) {
+  return AspectRatio::FromSize(aCanvasSizeInPx.width, aCanvasSizeInPx.height);
+}
+
+class nsDisplayCanvas final : public nsPaintedDisplayItem {
+ public:
+  nsDisplayCanvas(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame)
+      : nsPaintedDisplayItem(aBuilder, aFrame) {
+    MOZ_COUNT_CTOR(nsDisplayCanvas);
+  }
+  MOZ_COUNTED_DTOR_OVERRIDE(nsDisplayCanvas)
+
+  NS_DISPLAY_DECL_NAME("nsDisplayCanvas", TYPE_CANVAS)
+
+  virtual nsRegion GetOpaqueRegion(nsDisplayListBuilder* aBuilder,
+                                   bool* aSnap) const override {
+    *aSnap = false;
+    nsHTMLCanvasFrame* f = static_cast<nsHTMLCanvasFrame*>(Frame());
+    HTMLCanvasElement* canvas = HTMLCanvasElement::FromNode(f->GetContent());
+    nsRegion result;
+    if (canvas->GetIsOpaque()) {
+      // OK, the entire region painted by the canvas is opaque. But what is
+      // that region? It's the canvas's "dest rect" (controlled by the
+      // object-fit/object-position CSS properties), clipped to the container's
+      // content box (which is what GetBounds() returns). So, we grab those
+      // rects and intersect them.
+      nsRect constraintRect = GetBounds(aBuilder, aSnap);
+
+      // Need intrinsic size & ratio, for ComputeObjectDestRect:
+      nsIntSize canvasSize = f->GetCanvasSize();
+      IntrinsicSize intrinsicSize = IntrinsicSizeFromCanvasSize(canvasSize);
+      AspectRatio intrinsicRatio = IntrinsicRatioFromCanvasSize(canvasSize);
+
+      const nsRect destRect = nsLayoutUtils::ComputeObjectDestRect(
+          constraintRect, intrinsicSize, intrinsicRatio, f->StylePosition());
+      return nsRegion(destRect.Intersect(constraintRect));
+    }
+    return result;
+  }
+
+  virtual nsRect GetBounds(nsDisplayListBuilder* aBuilder,
+                           bool* aSnap) const override {
+    *aSnap = true;
+    return Frame()->GetContentRectRelativeToSelf() + ToReferenceFrame();
+  }
+
+  virtual bool CreateWebRenderCommands(
+      mozilla::wr::DisplayListBuilder& aBuilder,
+      wr::IpcResourceUpdateQueue& aResources, const StackingContextHelper& aSc,
+      mozilla::layers::RenderRootStateManager* aManager,
+      nsDisplayListBuilder* aDisplayListBuilder) override {
+    HTMLCanvasElement* element =
+        static_cast<HTMLCanvasElement*>(mFrame->GetContent());
+    element->HandlePrintCallback(mFrame->PresContext());
+
+    if (element->IsOffscreen()) {
+      // If we are offscreen, then we either display via an ImageContainer
+      // which is updated asynchronously, likely from a worker thread, or a
+      // CompositableHandle managed inside the compositor process. There is
+      // nothing to paint until the owner attaches it.
+
+      element->FlushOffscreenCanvas();
+
+      nsHTMLCanvasFrame* canvasFrame = static_cast<nsHTMLCanvasFrame*>(mFrame);
+      nsIntSize canvasSizeInPx = canvasFrame->GetCanvasSize();
+      IntrinsicSize intrinsicSize = IntrinsicSizeFromCanvasSize(canvasSizeInPx);
+      AspectRatio intrinsicRatio = IntrinsicRatioFromCanvasSize(canvasSizeInPx);
+      nsRect area = mFrame->GetContentRectRelativeToSelf() + ToReferenceFrame();
+      nsRect dest = nsLayoutUtils::ComputeObjectDestRect(
+          area, intrinsicSize, intrinsicRatio, mFrame->StylePosition());
+      LayoutDeviceRect bounds = LayoutDeviceRect::FromAppUnits(
+          dest, mFrame->PresContext()->AppUnitsPerDevPixel());
+
+      RefPtr<ImageContainer> container = element->GetImageContainer();
+      if (container) {
+        MOZ_ASSERT(container->IsAsync());
+        aManager->CommandBuilder().PushImage(this, container, aBuilder,
+                                             aResources, aSc, bounds, bounds);
+        return true;
+      }
+
+      return true;
+    }
+
+    switch (element->GetCurrentContextType()) {
+      case CanvasContextType::Canvas2D:
+      case CanvasContextType::WebGL1:
+      case CanvasContextType::WebGL2:
+      case CanvasContextType::WebGPU: {
+        bool isRecycled;
+        RefPtr<WebRenderCanvasData> canvasData =
+            aManager->CommandBuilder()
+                .CreateOrRecycleWebRenderUserData<WebRenderCanvasData>(
+                    this, &isRecycled);
+        nsHTMLCanvasFrame* canvasFrame =
+            static_cast<nsHTMLCanvasFrame*>(mFrame);
+        if (!canvasFrame->UpdateWebRenderCanvasData(aDisplayListBuilder,
+                                                    canvasData)) {
+          return true;
+        }
+        WebRenderCanvasRendererAsync* data = canvasData->GetCanvasRenderer();
+        MOZ_ASSERT(data);
+        data->UpdateCompositableClient();
+
+        // Push IFrame for async image pipeline.
+        // XXX Remove this once partial display list update is supported.
+
+        nsIntSize canvasSizeInPx = data->GetSize();
+        IntrinsicSize intrinsicSize =
+            IntrinsicSizeFromCanvasSize(canvasSizeInPx);
+        AspectRatio intrinsicRatio =
+            IntrinsicRatioFromCanvasSize(canvasSizeInPx);
+
+        nsRect area =
+            mFrame->GetContentRectRelativeToSelf() + ToReferenceFrame();
+        nsRect dest = nsLayoutUtils::ComputeObjectDestRect(
+            area, intrinsicSize, intrinsicRatio, mFrame->StylePosition());
+
+        LayoutDeviceRect bounds = LayoutDeviceRect::FromAppUnits(
+            dest, mFrame->PresContext()->AppUnitsPerDevPixel());
+
+        // We don't push a stacking context for this async image pipeline here.
+        // Instead, we do it inside the iframe that hosts the image. As a
+        // result, a bunch of the calculations normally done as part of that
+        // stacking context need to be done manually and pushed over to the
+        // parent side, where it will be done when we build the display list for
+        // the iframe. That happens in WebRenderCompositableHolder.s2);
+        aBuilder.PushIFrame(bounds, !BackfaceIsHidden(),
+                            data->GetPipelineId().ref(),
+                            /*ignoreMissingPipelines*/ false);
+
+        LayoutDeviceRect scBounds(LayoutDevicePoint(0, 0), bounds.Size());
+        auto filter = wr::ToImageRendering(mFrame->UsedImageRendering());
+        auto mixBlendMode = wr::MixBlendMode::Normal;
+        aManager->WrBridge()->AddWebRenderParentCommand(
+            OpUpdateAsyncImagePipeline(data->GetPipelineId().value(), scBounds,
+                                       wr::WrRotation::Degree0, filter,
+                                       mixBlendMode));
+        break;
+      }
+      case CanvasContextType::ImageBitmap: {
+        nsHTMLCanvasFrame* canvasFrame =
+            static_cast<nsHTMLCanvasFrame*>(mFrame);
+        nsIntSize canvasSizeInPx = canvasFrame->GetCanvasSize();
+        if (canvasSizeInPx.width <= 0 || canvasSizeInPx.height <= 0) {
+          return true;
+        }
+        bool isRecycled;
+        RefPtr<WebRenderCanvasData> canvasData =
+            aManager->CommandBuilder()
+                .CreateOrRecycleWebRenderUserData<WebRenderCanvasData>(
+                    this, &isRecycled);
+        if (!canvasFrame->UpdateWebRenderCanvasData(aDisplayListBuilder,
+                                                    canvasData)) {
+          canvasData->ClearImageContainer();
+          return true;
+        }
+
+        IntrinsicSize intrinsicSize =
+            IntrinsicSizeFromCanvasSize(canvasSizeInPx);
+        AspectRatio intrinsicRatio =
+            IntrinsicRatioFromCanvasSize(canvasSizeInPx);
+
+        nsRect area =
+            mFrame->GetContentRectRelativeToSelf() + ToReferenceFrame();
+        nsRect dest = nsLayoutUtils::ComputeObjectDestRect(
+            area, intrinsicSize, intrinsicRatio, mFrame->StylePosition());
+
+        LayoutDeviceRect bounds = LayoutDeviceRect::FromAppUnits(
+            dest, mFrame->PresContext()->AppUnitsPerDevPixel());
+
+        aManager->CommandBuilder().PushImage(
+            this, canvasData->GetImageContainer(), aBuilder, aResources, aSc,
+            bounds, bounds);
+        break;
+      }
+      case CanvasContextType::NoContext:
+        break;
+      default:
+        MOZ_ASSERT_UNREACHABLE("unknown canvas context type");
+    }
+    return true;
+  }
+
+  // FirstContentfulPaint is supposed to ignore "white" canvases.  We use
+  // MaybeModified (if GetContext() was called on the canvas) as a standin for
+  // "white"
+  virtual bool IsContentful() const override {
+    nsHTMLCanvasFrame* f = static_cast<nsHTMLCanvasFrame*>(Frame());
+    HTMLCanvasElement* canvas = HTMLCanvasElement::FromNode(f->GetContent());
+    return canvas->MaybeModified();
+  }
+
+  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());
+
+    gfxContextMatrixAutoSaveRestore saveMatrix(aCtx);
+
+    if (RefPtr<layers::Image> image = canvas->GetAsImage()) {
+      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);
+
+      aCtx->SetMatrix(
+          gfxUtils::SnapTransformTranslation(aCtx->CurrentMatrix(), nullptr));
+
+      RefPtr<gfx::SourceSurface> surface = image->GetAsSourceSurface();
+      if (!surface || !surface->IsValid()) {
+        return;
+      }
+
+      transform = gfxUtils::SnapTransform(
+          transform, gfxRect(0, 0, canvasSizeInPx.width, canvasSizeInPx.height),
+          nullptr);
+      aCtx->Multiply(transform);
+
+      aCtx->GetDrawTarget()->FillRect(
+          Rect(0, 0, canvasSizeInPx.width, canvasSizeInPx.height),
+          SurfacePattern(surface, ExtendMode::CLAMP, Matrix(),
+                         nsLayoutUtils::GetSamplingFilterForFrame(f)));
+      return;
+    }
+
+    if (canvas->IsOffscreen()) {
+      return;
+    }
+
+    RefPtr<CanvasRenderer> renderer = new CanvasRenderer();
+    if (!canvas->InitializeCanvasRenderer(aBuilder, renderer)) {
+      return;
+    }
+    renderer->FirePreTransactionCallback();
+    const auto snapshot = renderer->BorrowSnapshot();
+    if (!snapshot) {
+      return;
+    }
+    const auto& surface = snapshot->mSurf;
+    DrawTarget& dt = *aCtx->GetDrawTarget();
+    gfx::Rect destRect =
+        NSRectToSnappedRect(dest, presContext->AppUnitsPerDevPixel(), dt);
+
+    if (!renderer->YIsDown()) {
+      // Calculate y-coord that is as far below the bottom of destGFXRect as
+      // the origin was above the top, then reflect about that.
+      float y = destRect.Y() + destRect.YMost();
+      Matrix transform = Matrix::Translation(0.0f, y).PreScale(1.0f, -1.0f);
+      aCtx->Multiply(transform);
+    }
+
+    const auto& srcRect = surface->GetRect();
+    dt.DrawSurface(
+        surface, destRect,
+        Rect(float(srcRect.X()), float(srcRect.Y()), float(srcRect.Width()),
+             float(srcRect.Height())),
+        DrawSurfaceOptions(nsLayoutUtils::GetSamplingFilterForFrame(f)));
+
+    renderer->FireDidTransactionCallback();
+    renderer->ResetDirty();
+  }
+};
+
+nsIFrame* NS_NewHTMLCanvasFrame(PresShell* aPresShell, ComputedStyle* aStyle) {
+  return new (aPresShell)
+      nsHTMLCanvasFrame(aStyle, aPresShell->GetPresContext());
+}
+
+NS_QUERYFRAME_HEAD(nsHTMLCanvasFrame)
+  NS_QUERYFRAME_ENTRY(nsHTMLCanvasFrame)
+NS_QUERYFRAME_TAIL_INHERITING(nsContainerFrame)
+
+NS_IMPL_FRAMEARENA_HELPERS(nsHTMLCanvasFrame)
+
+void nsHTMLCanvasFrame::Destroy(DestroyContext& aContext) {
+  if (IsPrimaryFrame()) {
+    HTMLCanvasElement::FromNode(*mContent)->ResetPrintCallback();
+  }
+  nsContainerFrame::Destroy(aContext);
+}
+
+nsHTMLCanvasFrame::~nsHTMLCanvasFrame() = default;
+
+nsIntSize nsHTMLCanvasFrame::GetCanvasSize() const {
+  nsIntSize size(0, 0);
+  HTMLCanvasElement* canvas = HTMLCanvasElement::FromNodeOrNull(GetContent());
+  if (canvas) {
+    size = canvas->GetSize();
+    MOZ_ASSERT(size.width >= 0 && size.height >= 0,
+               "we should've required <canvas> width/height attrs to be "
+               "unsigned (non-negative) values");
+  } else {
+    MOZ_ASSERT_UNREACHABLE("couldn't get canvas size");
+  }
+
+  return size;
+}
+
+/* virtual */
+nscoord nsHTMLCanvasFrame::GetMinISize(gfxContext* aRenderingContext) {
+  // XXX The caller doesn't account for constraints of the height,
+  // min-height, and max-height properties.
+  nscoord result;
+  if (Maybe<nscoord> containISize = ContainIntrinsicISize()) {
+    result = *containISize;
+  } else {
+    bool vertical = GetWritingMode().IsVertical();
+    result = nsPresContext::CSSPixelsToAppUnits(
+        vertical ? GetCanvasSize().height : GetCanvasSize().width);
+  }
+  DISPLAY_MIN_INLINE_SIZE(this, result);
+  return result;
+}
+
+/* virtual */
+nscoord nsHTMLCanvasFrame::GetPrefISize(gfxContext* aRenderingContext) {
+  // XXX The caller doesn't account for constraints of the height,
+  // min-height, and max-height properties.
+  nscoord result;
+  if (Maybe<nscoord> containISize = ContainIntrinsicISize()) {
+    result = *containISize;
+  } else {
+    bool vertical = GetWritingMode().IsVertical();
+    result = nsPresContext::CSSPixelsToAppUnits(
+        vertical ? GetCanvasSize().height : GetCanvasSize().width);
+  }
+  DISPLAY_PREF_INLINE_SIZE(this, result);
+  return result;
+}
+
+/* virtual */
+IntrinsicSize nsHTMLCanvasFrame::GetIntrinsicSize() {
+  const auto containAxes = GetContainSizeAxes();
+  IntrinsicSize size = containAxes.IsBoth()
+                           ? IntrinsicSize(0, 0)
+                           : IntrinsicSizeFromCanvasSize(GetCanvasSize());
+  return FinishIntrinsicSize(containAxes, size);
+}
+
+/* virtual */
+AspectRatio nsHTMLCanvasFrame::GetIntrinsicRatio() const {
+  if (GetContainSizeAxes().IsAny()) {
+    return AspectRatio();
+  }
+
+  return IntrinsicRatioFromCanvasSize(GetCanvasSize());
+}
+
+/* virtual */
+nsIFrame::SizeComputationResult nsHTMLCanvasFrame::ComputeSize(
+    gfxContext* aRenderingContext, WritingMode aWM, const LogicalSize& aCBSize,
+    nscoord aAvailableISize, const LogicalSize& aMargin,
+    const LogicalSize& aBorderPadding, const StyleSizeOverrides& aSizeOverrides,
+    ComputeSizeFlags aFlags) {
+  return {ComputeSizeWithIntrinsicDimensions(
+              aRenderingContext, aWM, GetIntrinsicSize(), GetAspectRatio(),
+              aCBSize, aMargin, aBorderPadding, aSizeOverrides, aFlags),
+          AspectRatioUsage::None};
+}
+
+void nsHTMLCanvasFrame::Reflow(nsPresContext* aPresContext,
+                               ReflowOutput& aMetrics,
+                               const ReflowInput& aReflowInput,
+                               nsReflowStatus& aStatus) {
+  MarkInReflow();
+  DO_GLOBAL_REFLOW_COUNT("nsHTMLCanvasFrame");
+  DISPLAY_REFLOW(aPresContext, this, aReflowInput, aMetrics, aStatus);
+  MOZ_ASSERT(aStatus.IsEmpty(), "Caller should pass a fresh reflow status!");
+  NS_FRAME_TRACE(
+      NS_FRAME_TRACE_CALLS,
+      ("enter nsHTMLCanvasFrame::Reflow: availSize=%d,%d",
+       aReflowInput.AvailableWidth(), aReflowInput.AvailableHeight()));
+
+  MOZ_ASSERT(HasAnyStateBits(NS_FRAME_IN_REFLOW), "frame is not in reflow");
+
+  WritingMode wm = aReflowInput.GetWritingMode();
+  const LogicalSize finalSize = aReflowInput.ComputedSizeWithBorderPadding(wm);
+
+  aMetrics.SetSize(wm, finalSize);
+  aMetrics.SetOverflowAreasToDesiredBounds();
+  FinishAndStoreOverflow(&aMetrics);
+
+  // Reflow the single anon block child.
+  nsReflowStatus childStatus;
+  nsIFrame* childFrame = mFrames.FirstChild();
+  WritingMode childWM = childFrame->GetWritingMode();
+  LogicalSize availSize = aReflowInput.ComputedSize(childWM);
+  availSize.BSize(childWM) = NS_UNCONSTRAINEDSIZE;
+  NS_ASSERTION(!childFrame->GetNextSibling(), "HTML canvas should have 1 kid");
+  ReflowOutput childDesiredSize(aReflowInput.GetWritingMode());
+  ReflowInput childReflowInput(aPresContext, aReflowInput, childFrame,
+                               availSize);
+  ReflowChild(childFrame, aPresContext, childDesiredSize, childReflowInput, 0,
+              0, ReflowChildFlags::Default, childStatus, nullptr);
+  FinishReflowChild(childFrame, aPresContext, childDesiredSize,
+                    &childReflowInput, 0, 0, ReflowChildFlags::Default);
+
+  NS_FRAME_TRACE(NS_FRAME_TRACE_CALLS,
+                 ("exit nsHTMLCanvasFrame::Reflow: size=%d,%d",
+                  aMetrics.ISize(wm), aMetrics.BSize(wm)));
+}
+
+bool nsHTMLCanvasFrame::UpdateWebRenderCanvasData(
+    nsDisplayListBuilder* aBuilder, WebRenderCanvasData* aCanvasData) {
+  HTMLCanvasElement* element = static_cast<HTMLCanvasElement*>(GetContent());
+  return element->UpdateWebRenderCanvasData(aBuilder, aCanvasData);
+}
+
+void nsHTMLCanvasFrame::BuildDisplayList(nsDisplayListBuilder* aBuilder,
+                                         const nsDisplayListSet& aLists) {
+  if (!IsVisibleForPainting()) return;
+
+  DisplayBorderBackgroundOutline(aBuilder, aLists);
+
+  if (HidesContent()) {
+    DisplaySelectionOverlay(aBuilder, aLists.Content(),
+                            nsISelectionDisplay::DISPLAY_IMAGES);
+    return;
+  }
+
+  uint32_t clipFlags =
+      nsStyleUtil::ObjectPropsMightCauseOverflow(StylePosition())
+          ? 0
+          : DisplayListClipState::ASSUME_DRAWING_RESTRICTED_TO_CONTENT_RECT;
+
+  DisplayListClipState::AutoClipContainingBlockDescendantsToContentBox clip(
+      aBuilder, this, clipFlags);
+
+  aLists.Content()->AppendNewToTop<nsDisplayCanvas>(aBuilder, this);
+
+  DisplaySelectionOverlay(aBuilder, aLists.Content(),
+                          nsISelectionDisplay::DISPLAY_IMAGES);
+}
+
+void nsHTMLCanvasFrame::AppendDirectlyOwnedAnonBoxes(
+    nsTArray<OwnedAnonBox>& aResult) {
+  MOZ_ASSERT(mFrames.FirstChild(), "Must have our canvas content anon box");
+  MOZ_ASSERT(!mFrames.FirstChild()->GetNextSibling(),
+             "Must only have our canvas content anon box");
+  aResult.AppendElement(OwnedAnonBox(mFrames.FirstChild()));
+}
+
+void nsHTMLCanvasFrame::UnionChildOverflow(
+    mozilla::OverflowAreas& aOverflowAreas) {
+  // Our one child (the canvas content anon box) is unpainted and isn't relevant
+  // for child-overflow purposes. So we need to provide our own trivial impl to
+  // avoid receiving the child-considering impl that we would otherwise inherit.
+}
+
+#ifdef ACCESSIBILITY
+a11y::AccType nsHTMLCanvasFrame::AccessibleType() {
+  return a11y::eHTMLCanvasType;
+}
+#endif
+
+#ifdef DEBUG_FRAME_DUMP
+nsresult nsHTMLCanvasFrame::GetFrameName(nsAString& aResult) const {
+  return MakeFrameName(u"HTMLCanvas"_ns, aResult);
+}
+#endif