compiling firefox with --enable-default-toolkit=qt leads to firefox spitting up thousands of lines of "QPainter: Internal error; no available GC" all over the console any time the mouse is moved or anything else happens inside it's window, punctuated with other Qt errors such as: nsDrawingSurfaceQt::Unlock: w/h=1280/993 or QCommonStyle::subRect: widget parameter cannot be zero! when it finally closes it dies with this *** glibc detected *** corrupted double-linked list: 0x00002aaaac8bc6d8 *** /usr/libexec/mozilla-launcher: line 119: 16895 Killed "$mozbin" "$@" firefox-bin exited with non-zero status (137)
I'm a bit confused as to what you've done here. By "compiling firefox with --enable-default-toolkit=qt", do you mean you've edited the ebuild to incorporate this configure argument? Or are you building by hand? I suspect this is more an issue to take up with Mozilla directly, since the ebuilds do not attempt to do this. What version of firefox were you trying to build?
This bug is awaiting user response.