Re: [csswg-drafts] [css-overflow-3] Specify extent of ink overflow (#8649)

@jfkthame  -- you make a good point that the actual font description used by the glyph rendering subsystem might be different from the one requested by the developer, in which case any visual inspection of ink overflow they did during development will not apply. I meant to acknowledge this with the preface “for a given well-defined font” , but the spec text could be more explicit, something like:

“note that there are many factors that may cause the glyph rendering subsystem to use a font other than the one specified in stylesheets when drawing text, including but not limited to UA settings, accessibility features, and the availability of web fonts. The extent of ink overflow derives from the actual font used for rendering text, and developers should allow for the possibility that the actual rendered extent of ink overflow from glyph overhang does not match what they measured during development.

... and then we could add some language to the IntersectionObserver spec along these lines, with links to the css-text spec:

“Note that the extent of ink overflow from text and text decorations cannot always be predicted or measured in advance. In all cases, IntersectionObserver will determine occlusion based on the actual rendered extent of ink overflow.”

@fantasai  -- Although the *concept* of ink overflow is well-defined, the *extent* of it is not, and that’s what I’d like to fix. I hope my previous comment about the utility of “maximum possible extent of ink overflow” shows why the difference between painted extent and occlusion is not a problem – in fact in almost all cases they are the same, and even for blur filters there is an easy practical solution that also agrees with browsers in practice. If we encounter a particular special case where there is a divergence we can note it explicitly in the spec.

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Received on Wednesday, 1 May 2024 01:07:50 UTC