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Ticket UUID:	7579c335f14c9ed4272dbc6bf672c528677b6780
Title:	Text widget: wrong bbox widths for non-ASCII characters with bidi text rendering
Type:	Bug	Version:	9.1b1
Submitter:	serhiy.storchaka	Created on:	2026-09-24 11:24:10
Subsystem:	18. [text]	Assigned To:	jan.nijtmans
Priority:	5 Medium	Severity:	Important
Status:	Closed	Last Modified:	2026-09-26 13:12:36
Resolution:	Fixed	Closed By:	jan.nijtmans
		Closed on:	2026-09-25 14:10:22
Description:	With the bidi text rendering in 9.1 (default X11 build), `$text bbox` returns wrong widths for characters encoded with more than one UTF-8 byte: pack [text .t -font {Helvetica 14}] .t insert end "Доброго ранку, світе" update # width of each character: bbox vs. font measure 11 of the 20 characters differ; most get the width of the previous character (Д:1/13 о:13/11 г:11/7 …). 9.0 and a 9.1 build with `--disable-bidi` are correct. `CharBboxProc` (generic/tkTextDisp.c) measures the character at `byteIndex` as the byte range `[byteIndex, byteIndex+1]`, which ends in the middle of a multi-byte character. The Xft font code tolerates this since [437a4bc8fb] ([1185640fff]), but the bidi measuring code does not.
User Comments:	serhiy.storchaka added on 2026-09-26 13:12:36: textDisp-25.2 fails on macOS CI (both Aqua and X11 with `--disable-bidi`) with result `1.14`: the bbox width of the space after the comma differs from `font measure` of the space. Proposed fix in branch textdisp-bbox-test-macos: the test checks that the bbox of each character ends where the next one begins, without `font measure`. It still fails without the fix (for 10 of the characters). jan.nijtmans added on 2026-09-25 14:10:22: Fixed [5299492cd8c22dc4\|here] Many thanks! serhiy.storchaka added on 2026-09-24 11:28:54: Fix on text-bbox-multibyte: `CharBboxProc` now measures up to the start of the next character. Test textDisp-25.2.