236477 2022-02-10 17:29:24 -0800 letter-spacing is totally broken in Burmese and Thai and Lao 2022-02-17 17:30:31 -0800 1 1 1 Unclassified WebKit Text WebKit Nightly Build Unspecified Unspecified NEW InRadar P2 Normal --- 236489 1 mmaxfield webkit-unassigned mmaxfield webkit-bug-importer oldest_to_newest 1840070 0 451625 mmaxfield 2022-02-10 17:29:24 -0800 Created attachment 451625 Test case WebKit destroys the shapes of the letters. Compare to Chrome / Firefox. 1840071 1 451626 mmaxfield 2022-02-10 17:31:26 -0800 Created attachment 451626 Test case 1840073 2 mmaxfield 2022-02-10 17:34:52 -0800 Oh, wow, ComplexTextController applies letter-spacing to _every glyph_. That's totally bogus. 1840225 3 mmaxfield 2022-02-10 23:29:20 -0800 It looks like the correct iterator to use is kCFStringCursorMovementCluster. This is turning out to be harder than I thought it would be. Because Burmese text is so complicated, it looks like I can't: - add space to the right side of a glyph if the character just after the character the glyph corresponds to is a boundary, because of the string "ဂြို". This string has 4 code points, but no glyph corresponds to the last code point - the last glyph corresponds to the second-to-last and last code points together. - add space to the left side of a glyph if the character the glyph corresponds to is a boundary, because of the same string "ဂြို". Here, the leftmost character corresponds to string index 1 and then the next glyph corresponds to string index 0. Therefore, if we did this, we'd inject letter-spacing in the middle of the cluster. I think the solution is to keep track of cluster boundaries as we iterate across glyphs, and insert space to the right of a glyph if the current glyph and the next glyph belong to different clusters. 1840228 4 mmaxfield 2022-02-10 23:43:11 -0800 https://twitter.com/OhBendy/status/1492033041988001837 indicates that this is a problem for Thai and Lao too. 1843203 5 webkit-bug-importer 2022-02-17 17:30:31 -0800 <rdar://problem/89118337> 451625 2022-02-10 17:29:24 -0800 2022-02-10 17:31:12 -0800 Test case test.html text/html 6500 mmaxfield PCFET0NUWVBFIGh0bWw+CjxodG1sPgo8aGVhZD4KPG1ldGEgY2hhcnNldD0idXRmLTgiPgo8c3R5 bGU+CmRpdiB7CiAgICBsZXR0ZXItc3BhY2luZzogNXB4Owp9Cjwvc3R5bGU+CjwvaGVhZD4KPGJv ZHk+CjxkaXY+4YCA4YCZ4YC54YCY4YCs4YCC4YC84YCt4YCv4YCf4YC64YCe4YCK4YC6IOGAnOGA sOGAnuGArOGAuOGAmeGAu+GArOGAuOGBiiDhgJDhgK3hgJvhgIXhgLnhgIbhgKzhgJThgLrhgJnh gLvhgKzhgLjhgJThgL7hgIThgLfhgLog4YCh4YCV4YCE4YC64YCZ4YC74YCs4YC4IOGAm+GAvuGA 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