Not sure if the component (i.e. ft font backend) is correct. I'm seeing this with a GTK+ application on X server without RENDER (VNC), cairo HEAD (something similar happens with 1.0.2): ==30218== Use of uninitialised value of size 4 ==30218== at 0x1B96DC22: fbBltOne (icbltone.c:400) ==30218== by 0x1B96927A: fbCompositeSolidMask_nx1xn (fbpict.c:953) ==30218== by 0x1B96A7E4: INT_pixman_composite (fbpict.c:1894) ==30218== by 0x1B94803E: _cairo_image_surface_composite (cairo-image-surface.c:599) ==30218== by 0x1B94F1DE: _cairo_surface_composite (cairo-surface.c:870) ==30218== by 0x1B94DF6A: _cairo_scaled_font_show_glyphs (cairo-scaled-font.c:890) ==30218== by 0x1B9507A5: _cairo_surface_old_show_glyphs_draw_func (cairo-surface.c:1877) ==30218== by 0x1B945668: _cairo_gstate_clip_and_composite (cairo-gstate.c:1123) ==30218== by 0x1B9508B1: _cairo_surface_show_glyphs (cairo-surface.c:1927) ==30218== by 0x1B9469E6: _cairo_gstate_show_glyphs (cairo-gstate.c:1987) ==30218== by 0x1B9419CB: cairo_show_glyphs (cairo.c:2158) ==30218== by 0x4355419A: (within /usr/lib/libpangocairo-1.0.so.0.1001.0) ==30218== by 0x4363AA67: pango_renderer_draw_glyphs (in /usr/lib/libpango-1.0.so.0.1001.0) ==30218== by 0x43554733: pango_cairo_show_glyph_string (in /usr/lib/libpangocairo-1.0.so.0.1001.0)
Thanks for the report. The complication here is that composite() is such a generic function (it's passed 3 buffer pointers) that identifing the culprit is impossible without at least a minimal test-case (the new valgrind --track-origins=yes tool is a promising, though oft-confusing guide.) Marking as invalid due to its age and lack of necessary info to reproduce. Though please if you can identify problematic cases, I'll add them to the test suite.
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