Re: [csswg-drafts] [css-inline-3] make `text` of `leading-trim` interoperable? (#3978)

Thank you for the feedback. I was originally thinking about big differences in the 3 ascent/descent metrics, which often gives a largely (>10 pixels) different positions on large font size. But if we can also make rounding behavior interoperable, I think it's a great achievement. It is a bit larger topic, because this issue was talking only about values that derives from ascent/descent, but rounding applies to all values of [`leading-trim`](https://drafts.csswg.org/css-inline-3/#leading-trim-property).

When thinking about rounding behavior, I can think of multiple levels.
1. Floating point rounding when computing ascent/descent by `value * font-size / em_unit`.
2. Rounding it to fixed point.
3. Rounding it to CSS or physical pixel.

I guess you're talking about rounding at step 3, correct? Step 1 produces slightly different values depends on CPU/FPU, and step 2 is known to be different by each browser, I think these two are hard to standardize.

Do you have any preferred way to do this? I don't have much experiences of what kind of rounding to physical pixels can render glyphs best.

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Received on Thursday, 20 June 2019 10:01:44 UTC