As it was originally reported on https://bugzilla.gnome.org/show_bug.cgi?id=779234#c0, the hottest path was
convert_ubyte() in mesa. Reverting this shows no trace of those hot paths,
nor any higher than usual CPU activity.
As the improvements at the time were real, I can only conclude that pixel
conversion was happening somewhere further the pipeline, and swizzling just
helped indirectly. That got eventually fixed, so swizzling just stayed to
cause grief. And lots it caused.
The function finish_cb can be called as a result of a call to ca_context_cancel
in cancelled_cb. This will result in a deadlock because, as per documentation,
g_cancellable_disconnect cannot be called inside the cancellable handler.
It is possible to detect if the call to finish_cb is caused by ca_context_cancel
checking if error_code == CA_ERROR_CANCELED. To avoid the deadlock we should
call g_signal_handler_disconnect instead g_cancellable_disconnect if this is the
case.
We use the input_method on both branches, but only check for its existence
when enabling the text_input. The case of focusing out shouldn't happen in
practice as we couldn't have focused in ever before, but still make the
check one level above so it's clearer that the text_input's IM focus cannot
be enabled without an IM implementation.
