[Webkit-unassigned] [Bug 245032] Transformed root repeating background should cover the whole canvas size

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=245032

--- Comment #4 from Matt Woodrow <mattwoodrow at apple.com> ---
The bug as originally stated (incorrect number of repeated images for transformed repeated backgrounds) is because BackgroundPainter::calculateBackgroundImageGeometry is computing a destination drawing area in coordinates after the transform has been applied.

We then pass that rectangle to GraphicsContext::drawTiledImage, which expects a destination rectangle in pre-transform coordinates.

I think we'd need to transform all the relevant coordinates by the inverse of the transform on the root element (destinationRect, borderBoxRect, positioningAreaSize, left, top etc).

There's a lot of complexity around which coordinate space to use when computing tiling size, pixel snapping, background-repeat: round/space etc. None of that appears to be specified currently, nor are there any tests.

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