Bug 22356

Summary:	Spurious "out of memory" error on system without fonts
Product:	cairo	Reporter:	Ben Bullock <benkasminbullock>
Component:	freetype font backend	Assignee:	David Turner <david>
Status:	RESOLVED FIXED	QA Contact:	cairo-bugs mailing list <cairo-bugs>
Severity:	trivial
Priority:	medium
Version:	1.8.8
Hardware:	x86 (IA32)
OS:	FreeBSD
Whiteboard:
i915 platform:		i915 features:

Description Ben Bullock 2009-06-18 18:00:21 UTC

If Cairo tries to write text on a system without any fonts installed, it produces an "out of memory" error.

I installed Cairo on a minimal FreeBSD jail without fonts and tried to use cairo_show_text to write some text (this was a mistake, obviously). The text didn't appear and Cairo stopped drawing anything at all after the text. I checked what was happening using the "cairo_status" of the "cairo_t" and found it had an "out of memory" error. Since I was running the program OK on the same system outside the jail, I was sure there was no problem with memory.

Stepping through the program with a debugger, I found that the "out of memory" error was produced when cairo called "FcFontMatch" on line 1697 of cairo-ft-font.c.

Comment 1 Chris Wilson 2009-06-19 03:25:00 UTC

Thanks for the bug report, it reminded that one of the arguments for including a builtin font was precisely so we could fallback and always show text (even if it was completely the wrong font!)

The fix is relatively easy for 1.9, but requires a fair bit more backporting for 1.8. I'm not sure the necessity justifies the extra risk.

commit d3330d7beba0e0d2543e40a0e0e4d81ea9a78b45
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Fri Jun 19 11:15:30 2009 +0100

    [ft] Substitute twin if there are no fonts
    
    Fixes bug 22356 -- Spurious "out of memory" error on system without fonts
    https://bugs.freedesktop.org/show_bug.cgi?id=22356
    
    If FcFontMatch() fails, then it means that there are no fonts available on
    the system (or it may have been a malloc error, we have no way of telling).
    Instead of report NO_MEMORY and disabling all drawing, one of the
    rationales for including a builtin font was so that we could continue even
    in the face of this error and show *something* to the user. (This being a
    last resort (and especially important for demos!) and hopefully easier to
    diagnose than no output at all.)

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