I made a PDF document with pdftex. When I run evince document.pdf these warnings always appear:
*** BUG ***
In pixman_region32_init_rect: Invalid rectangle passed
Set a breakpoint on '_pixman_log_error' to debug
Similar bug warnings can be seen in Eclipse but I'm not sure if that's related.
OS and DE: Debian 8.5 with Gnome 3.14.
Best Answer
Because someone is a bad programmer. The developer of one of the software layers (either evince itself or one of the many libraries it uses) has either misused a function or programmed a function to emit spurious messages. Somehow it mostly works.
Unfortunately, these messages are extremely common in Gnome software. Just ignore them.