cairo_show_glyphs doesn't work correctly for the NVidia driver 180.22 (original driver from nvidia.com). Haven't test it with other versions.
Ther are no problems with cairo_show_glyphs and a solid color but if you use a pattern or gradient, the complete text is filled with a random color, out of the color-set of the pattern or gradient.
ouput of the cairo test system:
extend-reflect: ps2 ps3
extend-reflect-similar: ps2 ps3
smask: xlib xlib-fallback
smask-text: xlib xlib-fallback
text-pattern: xlib xlib-fallback
text-transform: xlib xlib-fallback
user-font-proxy: ps2 ps3
Created attachment 22066 [details]
Created attachment 22067 [details]
The consensus is that we do not want to add workarounds for bugs in particular X servers and/or drivers. That road is long and gnarly.
But thank you for taking the time to report the bug -- it appears that my fears that this would be widespread and afflict many more people were unfounded.