1810811 - make the context-fill and context-stroke SVG paint values work in use content

Status: ASSIGNED

(Core :: SVG, enhancement)

Description

[Robert Longson [:longsonr]]

https://www.w3.org/TR/SVG2/painting.html#TermContextElement

bug 752638 covers markers but the specification says we should do use elements too. There's a testcase http://wpt.live/svg/painting/reftests/paint-context-002.svg and a corresponding reference http://wpt.live/svg/painting/reftests/paint-context-002-ref.svg

Comment 1

[Robert Longson [:longsonr]]

Attachment: call stack

Call stack from the testcase

Comment 2

[Robert Longson [:longsonr]]

Attachment: callstack from the testcase

Comment 3

[Robert Longson [:longsonr]]

Attachment: non-functional patch

Comment 4

[Robert Longson [:longsonr]]

My thought was to introduce an nsDisplayUse class and insert that in the call stack somehow so that it could set the paint context from the use frame's style. Then continue to paint the geometry elements somehow and finally when the stack unwinds, remove the paint context. The code I have doesn't work at all though.

Comment 5

[Emilio Cobos Álvarez (:emilio)]

So... looking a bit into how we paint svg, I don't think a new display item is needed? Doesn't overriding SVGUseFrame::PaintSVG and setting up the context there work? If not, why not?

Comment 6

[Robert Longson [:longsonr]]

SVGUseFrame::PaintSVG would only be called in patterns because it would override SVGDisplayContainerFrame::PaintSVG and that already asserts

NS_ASSERTION(HasAnyStateBits(NS_FRAME_IS_NONDISPLAY) ||
PresContext()->Document()->IsSVGGlyphsDocument(),
"Only painting of non-display SVG should take this code path");

I don't think display list painting really touches containers any more at render time.

Comment 7

[Robert Longson [:longsonr]]

Attachment: Bug 1810811 - make the context-fill and context-stroke SVG paint values work in use content

Comment 8

[Robert Longson [:longsonr]]

https://treeherder.mozilla.org/jobs?repo=try&revision=a30e038ef032db25e174ffa0bd15117345c227e9