The Tor Browser: layout/generic/nsCanvasFrame.cpp@b8a032363ba2 (annotated)

layout/generic/nsCanvasFrame.cpp@b8a032363ba2 (annotated)

layout/generic/nsCanvasFrame.cpp

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* 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 that goes directly inside the document's scrollbars */
 #include "nsCanvasFrame.h"
 #include "nsContainerFrame.h"
 #include "nsCSSRendering.h"
 #include "nsPresContext.h"
 #include "nsStyleContext.h"
 #include "nsRenderingContext.h"
 #include "nsGkAtoms.h"
 #include "nsIPresShell.h"
 #include "nsDisplayList.h"
 #include "nsCSSFrameConstructor.h"
 #include "nsFrameManager.h"
 #include "gfxPlatform.h"
 // for focus
 #include "nsIScrollableFrame.h"
 #ifdef DEBUG_CANVAS_FOCUS
 #include "nsIDocShell.h"
 #endif
 //#define DEBUG_CANVAS_FOCUS
 using namespace mozilla;
 using namespace mozilla::layout;
 using namespace mozilla::gfx;
 nsIFrame*
 NS_NewCanvasFrame(nsIPresShell* aPresShell, nsStyleContext* aContext)
 {
   return new (aPresShell) nsCanvasFrame(aContext);
 }
 NS_IMPL_FRAMEARENA_HELPERS(nsCanvasFrame)
 NS_QUERYFRAME_HEAD(nsCanvasFrame)
   NS_QUERYFRAME_ENTRY(nsCanvasFrame)
 NS_QUERYFRAME_TAIL_INHERITING(nsContainerFrame)
 void
 nsCanvasFrame::DestroyFrom(nsIFrame* aDestructRoot)
 {
   nsIScrollableFrame* sf =
     PresContext()->GetPresShell()->GetRootScrollFrameAsScrollable();
   if (sf) {
     sf->RemoveScrollPositionListener(this);
   }
   nsContainerFrame::DestroyFrom(aDestructRoot);
 }
 void
 nsCanvasFrame::ScrollPositionWillChange(nscoord aX, nscoord aY)
 {
   if (mDoPaintFocus) {
     mDoPaintFocus = false;
     PresContext()->FrameManager()->GetRootFrame()->InvalidateFrameSubtree();
   }
 }
 NS_IMETHODIMP
 nsCanvasFrame::SetHasFocus(bool aHasFocus)
 {
   if (mDoPaintFocus != aHasFocus) {
     mDoPaintFocus = aHasFocus;
     PresContext()->FrameManager()->GetRootFrame()->InvalidateFrameSubtree();
     if (!mAddedScrollPositionListener) {
       nsIScrollableFrame* sf =
         PresContext()->GetPresShell()->GetRootScrollFrameAsScrollable();
       if (sf) {
         sf->AddScrollPositionListener(this);
         mAddedScrollPositionListener = true;
       }
     }
   }
   return NS_OK;
 }
 nsresult
 nsCanvasFrame::SetInitialChildList(ChildListID     aListID,
                                    nsFrameList&    aChildList)
 {
   NS_ASSERTION(aListID != kPrincipalList ||
                aChildList.IsEmpty() || aChildList.OnlyChild(),
                "Primary child list can have at most one frame in it");
   return nsContainerFrame::SetInitialChildList(aListID, aChildList);
 }
 nsresult
 nsCanvasFrame::AppendFrames(ChildListID     aListID,
                             nsFrameList&    aFrameList)
 {
   NS_ASSERTION(aListID == kPrincipalList ||
                aListID == kAbsoluteList, "unexpected child list ID");
   NS_PRECONDITION(aListID != kAbsoluteList ||
                   mFrames.IsEmpty(), "already have a child frame");
   if (aListID != kPrincipalList) {
     // We only support the Principal and Absolute child lists.
     return NS_ERROR_INVALID_ARG;
   }
   if (!mFrames.IsEmpty()) {
     // We only allow a single principal child frame.
     return NS_ERROR_INVALID_ARG;
   }
   // Insert the new frames
   NS_ASSERTION(aFrameList.FirstChild() == aFrameList.LastChild(),
                "Only one principal child frame allowed");
 #ifdef DEBUG
   nsFrame::VerifyDirtyBitSet(aFrameList);
 #endif
   mFrames.AppendFrames(nullptr, aFrameList);
   PresContext()->PresShell()->
     FrameNeedsReflow(this, nsIPresShell::eTreeChange,
                      NS_FRAME_HAS_DIRTY_CHILDREN);
   return NS_OK;
 }
 nsresult
 nsCanvasFrame::InsertFrames(ChildListID     aListID,
                             nsIFrame*       aPrevFrame,
                             nsFrameList&    aFrameList)
 {
   // Because we only support a single child frame inserting is the same
   // as appending
   NS_PRECONDITION(!aPrevFrame, "unexpected previous sibling frame");
   if (aPrevFrame)
     return NS_ERROR_UNEXPECTED;
   return AppendFrames(aListID, aFrameList);
 }
 nsresult
 nsCanvasFrame::RemoveFrame(ChildListID     aListID,
                            nsIFrame*       aOldFrame)
 {
   NS_ASSERTION(aListID == kPrincipalList ||
                aListID == kAbsoluteList, "unexpected child list ID");
   if (aListID != kPrincipalList && aListID != kAbsoluteList) {
     // We only support the Principal and Absolute child lists.
     return NS_ERROR_INVALID_ARG;
   }
   if (aOldFrame != mFrames.FirstChild())
     return NS_ERROR_FAILURE;
   // Remove the frame and destroy it
   mFrames.DestroyFrame(aOldFrame);
   PresContext()->PresShell()->
     FrameNeedsReflow(this, nsIPresShell::eTreeChange,
                      NS_FRAME_HAS_DIRTY_CHILDREN);
   return NS_OK;
 }
 nsRect nsCanvasFrame::CanvasArea() const
 {
   // Not clear which overflow rect we want here, but it probably doesn't
   // matter.
   nsRect result(GetVisualOverflowRect());
   nsIScrollableFrame *scrollableFrame = do_QueryFrame(GetParent());
   if (scrollableFrame) {
     nsRect portRect = scrollableFrame->GetScrollPortRect();
     result.UnionRect(result, nsRect(nsPoint(0, 0), portRect.Size()));
   }
   return result;
 }
 void
 nsDisplayCanvasBackgroundColor::Paint(nsDisplayListBuilder* aBuilder,
                                       nsRenderingContext* aCtx)
 {
   nsCanvasFrame* frame = static_cast<nsCanvasFrame*>(mFrame);
   nsPoint offset = ToReferenceFrame();
   nsRect bgClipRect = frame->CanvasArea() + offset;
   if (NS_GET_A(mColor) > 0) {
     aCtx->SetColor(mColor);
     aCtx->FillRect(bgClipRect);
   }
 }
 static void BlitSurface(gfxContext* aDest, const gfxRect& aRect, gfxASurface* aSource)
 {
   aDest->Translate(gfxPoint(aRect.x, aRect.y));
   aDest->SetSource(aSource);
   aDest->NewPath();
   aDest->Rectangle(gfxRect(0, 0, aRect.width, aRect.height));
   aDest->Fill();
   aDest->Translate(-gfxPoint(aRect.x, aRect.y));
 }
 static void BlitSurface(DrawTarget* aDest, const gfxRect& aRect, DrawTarget* aSource)
 {
   RefPtr<SourceSurface> source = aSource->Snapshot();
   aDest->DrawSurface(source,
                      Rect(aRect.x, aRect.y, aRect.width, aRect.height),
                      Rect(0, 0, aRect.width, aRect.height));
 }
 void
 nsDisplayCanvasBackgroundImage::Paint(nsDisplayListBuilder* aBuilder,
                                       nsRenderingContext* aCtx)
 {
   nsCanvasFrame* frame = static_cast<nsCanvasFrame*>(mFrame);
   nsPoint offset = ToReferenceFrame();
   nsRect bgClipRect = frame->CanvasArea() + offset;
   nsRefPtr<nsRenderingContext> context;
   nsRefPtr<gfxContext> dest = aCtx->ThebesContext();
   nsRefPtr<gfxASurface> surf;
   RefPtr<DrawTarget> dt;
   nsRefPtr<gfxContext> ctx;
   gfxRect destRect;
 #ifndef MOZ_GFX_OPTIMIZE_MOBILE
   if (IsSingleFixedPositionImage(aBuilder, bgClipRect, &destRect) &&
       aBuilder->IsPaintingToWindow() && !aBuilder->IsCompositingCheap() &&
       !dest->CurrentMatrix().HasNonIntegerTranslation()) {
     // Snap image rectangle to nearest pixel boundaries. This is the right way
     // to snap for this context, because we checked HasNonIntegerTranslation above.
     destRect.Round();
     if (dest->IsCairo()) {
       surf = static_cast<gfxASurface*>(Frame()->Properties().Get(nsIFrame::CachedBackgroundImage()));
       nsRefPtr<gfxASurface> destSurf = dest->CurrentSurface();
       if (surf && surf->GetType() == destSurf->GetType()) {
         BlitSurface(dest, destRect, surf);
         return;
       }
       surf = destSurf->CreateSimilarSurface(
           gfxContentType::COLOR_ALPHA,
           gfxIntSize(ceil(destRect.width), ceil(destRect.height)));
     } else {
       dt = static_cast<DrawTarget*>(Frame()->Properties().Get(nsIFrame::CachedBackgroundImageDT()));
       DrawTarget* destDT = dest->GetDrawTarget();
       if (dt) {
         BlitSurface(destDT, destRect, dt);
         return;
       }
       dt = destDT->CreateSimilarDrawTarget(IntSize(ceil(destRect.width), ceil(destRect.height)), SurfaceFormat::B8G8R8A8);
     }
     if (surf || dt) {
       if (surf) {
         ctx = new gfxContext(surf);
       } else {
         ctx = new gfxContext(dt);
       }
       ctx->Translate(-gfxPoint(destRect.x, destRect.y));
       context = new nsRenderingContext();
       context->Init(aCtx->DeviceContext(), ctx);
     }
   }
 #endif
   PaintInternal(aBuilder,
                 (surf || dt) ? context.get() : aCtx,
                 (surf || dt) ? bgClipRect: mVisibleRect,
                 &bgClipRect);
   if (surf) {
     BlitSurface(dest, destRect, surf);
     frame->Properties().Set(nsIFrame::CachedBackgroundImage(),
                             surf.forget().take());
   }
   if (dt) {
     BlitSurface(dest->GetDrawTarget(), destRect, dt);
     frame->Properties().Set(nsIFrame::CachedBackgroundImageDT(), dt.forget().drop());
   }
 }
 void
 nsDisplayCanvasThemedBackground::Paint(nsDisplayListBuilder* aBuilder,
                                        nsRenderingContext* aCtx)
 {
   nsCanvasFrame* frame = static_cast<nsCanvasFrame*>(mFrame);
   nsPoint offset = ToReferenceFrame();
   nsRect bgClipRect = frame->CanvasArea() + offset;
   PaintInternal(aBuilder, aCtx, mVisibleRect, &bgClipRect);
 }
 /**
  * A display item to paint the focus ring for the document.
  *
  * The only reason this can't use nsDisplayGeneric is overriding GetBounds.
  */
 class nsDisplayCanvasFocus : public nsDisplayItem {
 public:
   nsDisplayCanvasFocus(nsDisplayListBuilder* aBuilder, nsCanvasFrame *aFrame)
     : nsDisplayItem(aBuilder, aFrame)
   {
     MOZ_COUNT_CTOR(nsDisplayCanvasFocus);
   }
   virtual ~nsDisplayCanvasFocus() {
     MOZ_COUNT_DTOR(nsDisplayCanvasFocus);
   }
   virtual nsRect GetBounds(nsDisplayListBuilder* aBuilder,
                            bool* aSnap) MOZ_OVERRIDE
   {
     *aSnap = false;
     // This is an overestimate, but that's not a problem.
     nsCanvasFrame* frame = static_cast<nsCanvasFrame*>(mFrame);
     return frame->CanvasArea() + ToReferenceFrame();
   }
   virtual void Paint(nsDisplayListBuilder* aBuilder,
                      nsRenderingContext* aCtx) MOZ_OVERRIDE
   {
     nsCanvasFrame* frame = static_cast<nsCanvasFrame*>(mFrame);
     frame->PaintFocus(*aCtx, ToReferenceFrame());
   }
   NS_DISPLAY_DECL_NAME("CanvasFocus", TYPE_CANVAS_FOCUS)
 };
 void
 nsCanvasFrame::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
                                 const nsRect&           aDirtyRect,
                                 const nsDisplayListSet& aLists)
 {
   if (GetPrevInFlow()) {
     DisplayOverflowContainers(aBuilder, aDirtyRect, aLists);
   }
   // Force a background to be shown. We may have a background propagated to us,
   // in which case StyleBackground wouldn't have the right background
   // and the code in nsFrame::DisplayBorderBackgroundOutline might not give us
   // a background.
   // We don't have any border or outline, and our background draws over
   // the overflow area, so just add nsDisplayCanvasBackground instead of
   // calling DisplayBorderBackgroundOutline.
   if (IsVisibleForPainting(aBuilder)) {
     nsStyleContext* bgSC;
     const nsStyleBackground* bg = nullptr;
     bool isThemed = IsThemed();
     if (!isThemed && nsCSSRendering::FindBackground(this, &bgSC)) {
       bg = bgSC->StyleBackground();
     }
     aLists.BorderBackground()->AppendNewToTop(
         new (aBuilder) nsDisplayCanvasBackgroundColor(aBuilder, this));
     if (isThemed) {
       aLists.BorderBackground()->AppendNewToTop(
         new (aBuilder) nsDisplayCanvasThemedBackground(aBuilder, this));
       return;
     }
     if (!bg) {
       return;
     }
     // Create separate items for each background layer.
     NS_FOR_VISIBLE_BACKGROUND_LAYERS_BACK_TO_FRONT(i, bg) {
       if (bg->mLayers[i].mImage.IsEmpty()) {
         continue;
       }
       aLists.BorderBackground()->AppendNewToTop(
         new (aBuilder) nsDisplayCanvasBackgroundImage(aBuilder, this, i, bg));
     }
   }
   nsIFrame* kid;
   for (kid = GetFirstPrincipalChild(); kid; kid = kid->GetNextSibling()) {
     // Put our child into its own pseudo-stack.
     BuildDisplayListForChild(aBuilder, kid, aDirtyRect, aLists);
   }
 #ifdef DEBUG_CANVAS_FOCUS
   nsCOMPtr<nsIContent> focusContent;
   aPresContext->EventStateManager()->
     GetFocusedContent(getter_AddRefs(focusContent));
   bool hasFocus = false;
   nsCOMPtr<nsISupports> container;
   aPresContext->GetContainer(getter_AddRefs(container));
   nsCOMPtr<nsIDocShell> docShell(do_QueryInterface(container));
   if (docShell) {
     docShell->GetHasFocus(&hasFocus);
     printf("%p - nsCanvasFrame::Paint R:%d,%d,%d,%d  DR: %d,%d,%d,%d\n", this,
             mRect.x, mRect.y, mRect.width, mRect.height,
             aDirtyRect.x, aDirtyRect.y, aDirtyRect.width, aDirtyRect.height);
   }
   printf("%p - Focus: %s   c: %p  DoPaint:%s\n", docShell.get(), hasFocus?"Y":"N",
          focusContent.get(), mDoPaintFocus?"Y":"N");
 #endif
   if (!mDoPaintFocus)
     return;
   // Only paint the focus if we're visible
   if (!StyleVisibility()->IsVisible())
     return;
   aLists.Outlines()->AppendNewToTop(new (aBuilder)
     nsDisplayCanvasFocus(aBuilder, this));
 }
 void
 nsCanvasFrame::PaintFocus(nsRenderingContext& aRenderingContext, nsPoint aPt)
 {
   nsRect focusRect(aPt, GetSize());
   nsIScrollableFrame *scrollableFrame = do_QueryFrame(GetParent());
   if (scrollableFrame) {
     nsRect portRect = scrollableFrame->GetScrollPortRect();
     focusRect.width = portRect.width;
     focusRect.height = portRect.height;
     focusRect.MoveBy(scrollableFrame->GetScrollPosition());
   }
  // XXX use the root frame foreground color, but should we find BODY frame
  // for HTML documents?
   nsIFrame* root = mFrames.FirstChild();
   const nsStyleColor* color = root ? root->StyleColor() : StyleColor();
   if (!color) {
     NS_ERROR("current color cannot be found");
     return;
   }
   nsCSSRendering::PaintFocus(PresContext(), aRenderingContext,
                              focusRect, color->mColor);
 }
 /* virtual */ nscoord
 nsCanvasFrame::GetMinWidth(nsRenderingContext *aRenderingContext)
 {
   nscoord result;
   DISPLAY_MIN_WIDTH(this, result);
   if (mFrames.IsEmpty())
     result = 0;
   else
     result = mFrames.FirstChild()->GetMinWidth(aRenderingContext);
   return result;
 }
 /* virtual */ nscoord
 nsCanvasFrame::GetPrefWidth(nsRenderingContext *aRenderingContext)
 {
   nscoord result;
   DISPLAY_PREF_WIDTH(this, result);
   if (mFrames.IsEmpty())
     result = 0;
   else
     result = mFrames.FirstChild()->GetPrefWidth(aRenderingContext);
   return result;
 }
 nsresult
 nsCanvasFrame::Reflow(nsPresContext*           aPresContext,
                       nsHTMLReflowMetrics&     aDesiredSize,
                       const nsHTMLReflowState& aReflowState,
                       nsReflowStatus&          aStatus)
 {
   DO_GLOBAL_REFLOW_COUNT("nsCanvasFrame");
   DISPLAY_REFLOW(aPresContext, this, aReflowState, aDesiredSize, aStatus);
   NS_FRAME_TRACE_REFLOW_IN("nsCanvasFrame::Reflow");
   // Initialize OUT parameter
   aStatus = NS_FRAME_COMPLETE;
   nsCanvasFrame* prevCanvasFrame = static_cast<nsCanvasFrame*>
                                                (GetPrevInFlow());
   if (prevCanvasFrame) {
     AutoFrameListPtr overflow(aPresContext,
                               prevCanvasFrame->StealOverflowFrames());
     if (overflow) {
       NS_ASSERTION(overflow->OnlyChild(),
                    "must have doc root as canvas frame's only child");
       nsContainerFrame::ReparentFrameViewList(*overflow, prevCanvasFrame, this);
       // Prepend overflow to the our child list. There may already be
       // children placeholders for fixed-pos elements, which don't get
       // reflowed but must not be lost until the canvas frame is destroyed.
       mFrames.InsertFrames(this, nullptr, *overflow);
     }
   }
   // Set our size up front, since some parts of reflow depend on it
   // being already set.  Note that the computed height may be
   // unconstrained; that's ok.  Consumers should watch out for that.
   SetSize(nsSize(aReflowState.ComputedWidth(), aReflowState.ComputedHeight()));
   // Reflow our one and only normal child frame. It's either the root
   // element's frame or a placeholder for that frame, if the root element
   // is abs-pos or fixed-pos. We may have additional children which
   // are placeholders for continuations of fixed-pos content, but those
   // don't need to be reflowed. The normal child is always comes before
   // the fixed-pos placeholders, because we insert it at the start
   // of the child list, above.
   nsHTMLReflowMetrics kidDesiredSize(aReflowState);
   if (mFrames.IsEmpty()) {
     // We have no child frame, so return an empty size
     aDesiredSize.Width() = aDesiredSize.Height() = 0;
   } else {
     nsIFrame* kidFrame = mFrames.FirstChild();
     bool kidDirty = (kidFrame->GetStateBits() & NS_FRAME_IS_DIRTY) != 0;
     nsHTMLReflowState kidReflowState(aPresContext, aReflowState, kidFrame,
                                      nsSize(aReflowState.AvailableWidth(),
                                             aReflowState.AvailableHeight()));
     if (aReflowState.mFlags.mVResize &&
         (kidFrame->GetStateBits() & NS_FRAME_CONTAINS_RELATIVE_HEIGHT)) {
       // Tell our kid it's being vertically resized too.  Bit of a
       // hack for framesets.
       kidReflowState.mFlags.mVResize = true;
     }
     nsPoint kidPt(kidReflowState.ComputedPhysicalMargin().left,
                   kidReflowState.ComputedPhysicalMargin().top);
     kidReflowState.ApplyRelativePositioning(&kidPt);
     // Reflow the frame
     ReflowChild(kidFrame, aPresContext, kidDesiredSize, kidReflowState,
                 kidPt.x, kidPt.y, 0, aStatus);
     // Complete the reflow and position and size the child frame
     FinishReflowChild(kidFrame, aPresContext, kidDesiredSize, &kidReflowState,
                       kidPt.x, kidPt.y, 0);
     if (!NS_FRAME_IS_FULLY_COMPLETE(aStatus)) {
       nsIFrame* nextFrame = kidFrame->GetNextInFlow();
       NS_ASSERTION(nextFrame || aStatus & NS_FRAME_REFLOW_NEXTINFLOW,
         "If it's incomplete and has no nif yet, it must flag a nif reflow.");
       if (!nextFrame) {
         nextFrame = aPresContext->PresShell()->FrameConstructor()->
           CreateContinuingFrame(aPresContext, kidFrame, this);
         SetOverflowFrames(nsFrameList(nextFrame, nextFrame));
         // Root overflow containers will be normal children of
         // the canvas frame, but that's ok because there
         // aren't any other frames we need to isolate them from
         // during reflow.
       }
       if (NS_FRAME_OVERFLOW_IS_INCOMPLETE(aStatus)) {
         nextFrame->AddStateBits(NS_FRAME_IS_OVERFLOW_CONTAINER);
       }
     }
     // If the child frame was just inserted, then we're responsible for making sure
     // it repaints
     if (kidDirty) {
       // But we have a new child, which will affect our background, so
       // invalidate our whole rect.
       // Note: Even though we request to be sized to our child's size, our
       // scroll frame ensures that we are always the size of the viewport.
       // Also note: GetPosition() on a CanvasFrame is always going to return
       // (0, 0). We only want to invalidate GetRect() since Get*OverflowRect()
       // could also include overflow to our top and left (out of the viewport)
       // which doesn't need to be painted.
       nsIFrame* viewport = PresContext()->GetPresShell()->GetRootFrame();
       viewport->InvalidateFrame();
     }
     // Return our desired size. Normally it's what we're told, but
     // sometimes we can be given an unconstrained height (when a window
     // is sizing-to-content), and we should compute our desired height.
     aDesiredSize.Width() = aReflowState.ComputedWidth();
     if (aReflowState.ComputedHeight() == NS_UNCONSTRAINEDSIZE) {
       aDesiredSize.Height() = kidFrame->GetRect().height +
         kidReflowState.ComputedPhysicalMargin().TopBottom();
     } else {
       aDesiredSize.Height() = aReflowState.ComputedHeight();
     }
     aDesiredSize.SetOverflowAreasToDesiredBounds();
     aDesiredSize.mOverflowAreas.UnionWith(
       kidDesiredSize.mOverflowAreas + kidPt);
   }
   if (prevCanvasFrame) {
     ReflowOverflowContainerChildren(aPresContext, aReflowState,
                                     aDesiredSize.mOverflowAreas, 0,
                                     aStatus);
   }
   FinishReflowWithAbsoluteFrames(aPresContext, aDesiredSize, aReflowState, aStatus);
   NS_FRAME_TRACE_REFLOW_OUT("nsCanvasFrame::Reflow", aStatus);
   NS_FRAME_SET_TRUNCATION(aStatus, aReflowState, aDesiredSize);
   return NS_OK;
 }
 nsIAtom*
 nsCanvasFrame::GetType() const
 {
   return nsGkAtoms::canvasFrame;
 }
 nsresult
 nsCanvasFrame::GetContentForEvent(WidgetEvent* aEvent,
                                   nsIContent** aContent)
 {
   NS_ENSURE_ARG_POINTER(aContent);
   nsresult rv = nsFrame::GetContentForEvent(aEvent,
                                             aContent);
   if (NS_FAILED(rv) || !*aContent) {
     nsIFrame* kid = mFrames.FirstChild();
     if (kid) {
       rv = kid->GetContentForEvent(aEvent,
                                    aContent);
     }
   }
   return rv;
 }
 #ifdef DEBUG_FRAME_DUMP
 nsresult
 nsCanvasFrame::GetFrameName(nsAString& aResult) const
 {
   return MakeFrameName(NS_LITERAL_STRING("Canvas"), aResult);
 }
 #endif

The Tor Browser / annotate

layout/generic/nsCanvasFrame.cpp@b8a032363ba2 (annotated)

layout/generic/nsCanvasFrame.cpp