1094174 - Fix up the exposure of our SVG context paint implementation

Status: NEW

(Core :: SVG, defect)

Description

[Jonathan Watt [:jwatt]]

Right now we have support for context-* keywords turned on for fill-opacity, stroke-opacity, stroke-dashoffset and stroke-width, since they're behind the gfx.font_rendering.opentype_svg.enabled pref which is now enabled by default. There are a few issues with this.

The WG only resolved on the context-fill, context-fill-opacity, context-stroke and context-stroke-opacity keywords, not the context-value keyword. (FWIW context-value raises some considerable implementation difficulties which our implementation appears to completely ignore, making it quite broken.)

These values are relevant to <use> and <marker>, not just SVG glyphs, so having them behind the opentype_svg pref seems wrong.

I think we should put the keywords that the WG resolved on behind a new enabled pref, and put the context-value keyword behind a second disabled pref.

The relevant code here is the code in nsCSSPropList.h that adds VARIANT_OPENTYPE_SVG_KEYWORD (where we'd mostly just switch that for VARIANT_KEYWORD), and the code in nsCSSParser.cpp that checks for VARIANT_OPENTYPE_SVG_KEYWORD and adds VARIANT_KEYWORD if the opentype_svg pref is enabled.