GNOME Bugzilla – Bug 700592
pangocairo kerning problem with nonidentity scaling regression
Last modified: 2015-07-09 15:39:22 UTC
Created attachment 244640 [details] Screenshot showing problem with pangocairo-1.32.5 (Ubuntu 13.04) This looks like a regression of Bug #341481 which was fixed back 2009. Kerning does not seem to scale, see attached screenshot.
Created attachment 244641 [details] Screenshot showing working properly with pangocairo-1.30.1 (LinuxMint 14)
Created attachment 244642 [details] Demo program for attached screenshots.
*** Bug 698777 has been marked as a duplicate of this bug. ***
The issue is reproduceable with Dia ( bug 573261 ) and with a slightly modified version of cairosimple.c ( see https://mail.gnome.org/archives/dia-list/2014-February/msg00011.html ). The effect of the kludge from bug 341481 was removed with the port to HarfBuzz.
Only with TrueType kerning, not GPOS, right?
Hans or Jim, any chance you can test?
If I understand the question and Pango code correctly GPOS is only used if explicetly asked for with pango_ot_*() API or maybe with "writing systems requiring sophisticated glyph positioning" [http://www.microsoft.com/typography/otspec/gpos.htm]. Dia is not using pango_ot_*() API (neither does the modified cairosimple.c metioned above) and the text showing the effect for me is e.g. 'Text' or 'circle' (just zoom into render-test.dia with dia-0.97.2 and cairo antialiased rendering). If my understanding is not correct I do not know what test you are asking for.
It looks like we've encountered the same (or similar) problem. After upgrade from Ubuntu 12.10 (libpango1.0-0: 1.30.1-0ubuntu3) to 14.04 (libpango1.0-0: 1.36.3-1ubuntu1), one of our programs started producing broken text with PNG output (PDF files are fine). The actual program is rather complex and uses pangomm, cairomm etc. but I reduced the problem to simple C function.
Created attachment 278201 [details] Simple C program demonstrating the problem
Created attachment 278202 [details] Output from sample program (demo2.c) on Ubuntu 12.10
Created attachment 278203 [details] Output from sample program (demo2.c) on Ubuntu 14.04
Created attachment 286447 [details] screenshot Not sure if this is related, the minifont size seems also affected. It becomes smaller and smaller if larger scaling value (> 100) is used.
Bug still present in 1.36.8-3 in Ubuntu 15.04 alpha.
Humm. Should be fixed again. Please test: commit 061633100aa120262db2acf9486bb590b2e0862e Author: Behdad Esfahbod <behdad@behdad.org> Date: Mon May 11 17:16:40 2015 -0700 Fix PangoFc with non-identity scale matrix (again!) https://bugzilla.gnome.org/show_bug.cgi?id=700592
*** Bug 700664 has been marked as a duplicate of this bug. ***
pango 1.37.1 works for me.