- From: jfkthame via GitHub <sysbot+gh@w3.org>
- Date: Wed, 07 Nov 2018 16:20:47 +0000
- To: public-houdini-archive@w3.org
> If we want to assign, for a grapheme cluster a left-right bounding box (to be able to draw a background on a single character) Careful with the terminology here... is "character" synonymous with "grapheme cluster" in that sentence? >From a JS point of view, as a user of a Canvas TextMetrics API, I would assume "character" really means "UTF-16 code unit", because that's what JS strings use (and expose). But if so, it's not necessarily possible to "draw a background on a single character", which might be only half of a surrogate pair. So maybe you meant "Unicode codepoint"? That's more logical in terms of acting on "a single character"... but still problematic. A single Unicode character may be rendered as multiple disjoint glyphs, so that drawing a background on that single character is actually much harder than just painting a rectangle. Consider the two-character sequence <U+0D15, U+0D4A> (spelling a simple Malayalam consonant-vowel syllable). This renders as three glyphs, കൊ, where the vowel U+0D4A (ൊ) is split into two parts, one to the left of the consonant U+0D15 (ക) and one to the right of it. What "left-side position and advance" does the character U+0D4A have? OK, so maybe you really meant "grapheme cluster" everywhere, and never some other lower-level version of "character"? Then <U+0D15, U+0D4A> is a single grapheme cluster, it has a single left-side and advance, and you could reasonably use these to paint a background for that single cluster (not character). But is that really what people want? The Malayalam syllable കൊ is made up of two characters, by any common understanding of "character", and to be unable to address those characters as separate units seems wrong. Text is *hard!* -- GitHub Notification of comment by jfkthame Please view or discuss this issue at https://github.com/w3c/css-houdini-drafts/issues/832#issuecomment-436682380 using your GitHub account
Received on Wednesday, 7 November 2018 16:20:49 UTC