PutImageData and DrawWindow are similar to FillRect in that they may cover the entire canvas. If it is the case, we can call EnsureTarget with a covered rect parameter the same way we do with FillRect to avoid copying the front buffer.

Comment on attachment 8780387 [details] [diff] [review] set covered rect parameter to EnsureTarget I set the covered rect parameter to EnsureTarget in DrawWindow and PutImageData.

Comment on attachment 8780387 [details] [diff] [review] set covered rect parameter to EnsureTarget Review of attachment 8780387 [details] [diff] [review]: ----------------------------------------------------------------- ::: dom/canvas/CanvasRenderingContext2D.cpp @@ +5641,5 @@ > > + // The canvas spec says that the current path, transformation matrix, shadow attributes, > + // global alpha, the clipping region, and global composition operator must not affect the > + // getImageData() and putImageData() methods. > + const gfx::Rect putRect(dirtyRect.x, dirtyRect.y, dirtyRect.width, dirtyRect.height); nit: you can do const gfx::Rect ptRect(dirtyRect); to avoid the hassle of repeating each member.

(In reply to Nicolas Silva [:nical] from comment #3) > Comment on attachment 8780387 [details] [diff] [review] > set covered rect parameter to EnsureTarget > > Review of attachment 8780387 [details] [diff] [review]: > ----------------------------------------------------------------- > > ::: dom/canvas/CanvasRenderingContext2D.cpp > @@ +5641,5 @@ > > > > + // The canvas spec says that the current path, transformation matrix, shadow attributes, > > + // global alpha, the clipping region, and global composition operator must not affect the > > + // getImageData() and putImageData() methods. > > + const gfx::Rect putRect(dirtyRect.x, dirtyRect.y, dirtyRect.width, dirtyRect.height); > > nit: you can do const gfx::Rect ptRect(dirtyRect); to avoid the hassle of > repeating each member. Okay!

Rebase and address nical's comments.

try server: https://treeherder.mozilla.org/#/jobs?repo=try&revision=671a929dd112

Pushed by ryanvm@gmail.com: https://hg.mozilla.org/integration/mozilla-inbound/rev/ec2202e9607b Avoid copy in CanvasRenderingContext2D::PutImageData and DrawWindow. r=nical