When compositing fills / drawImage calls in canvas, and the composite mode is Source-In, Source-Out, Destination-In, Destination-Atop or Copy, the canvas is cleared. For all of these modes apart from Copy a temporary buffer is also used. If the fill / drawImage is covering the entire canvas we can optimise away the clear and the use of a temporary buffer.
Created attachment 113422 [details] Patch
It would be nice to do the same optimization for filling a path, but there doesn't seem to be any easy way to see if a path contains a rectangle.
Comment on attachment 113422 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=113422&action=review Looks good. Thanks for implementing this! r=me > Source/WebCore/html/canvas/CanvasRenderingContext2D.cpp:1566 > + Path transformedPath; > + transformedPath.addRect(rect); > + transformedPath.transform(state().m_transform); > + > + IntRect canvasRect(0, 0, canvas()->width(), canvas()->height()); > + return transformedPath.contains(canvasRect.minXMinYCorner()) && transformedPath.contains(canvasRect.minXMaxYCorner()) > + && transformedPath.contains(canvasRect.maxXMinYCorner()) && transformedPath.contains(canvasRect.maxXMaxYCorner()); This looks fine, but I'm wondering if it would be easier to use FloatQuad: FloatQuad quad(rect); FloatQuad canvasQuad(FloatRect(0, 0, canvas->width(), canvas->height())); return state().m_transform.mapQuad(quad).containsQuad(canvasQuad); OTOH, I've never actually tried it, so feel free to go with what you've already got.
Created attachment 113571 [details] Patch using FloatQuad
Comment on attachment 113571 [details] Patch using FloatQuad Using FloatQuad is much nicer. Thanks for the tip!
Comment on attachment 113571 [details] Patch using FloatQuad Looks great. r=me
Comment on attachment 113571 [details] Patch using FloatQuad Clearing flags on attachment: 113571 Committed r99257: <http://trac.webkit.org/changeset/99257>
All reviewed patches have been landed. Closing bug.