[Gimp-developer] Slow user interface operations in Gimp 2.7.5

[roland65 free fr]

Hi,

when color management is enabled, Gimp 2.7.5 (and previous 2.7.x versions) is *very slow* when using a selection tool (rectangle, ellipse, crop, ...), when zooming in and out, and probably with other user interface operations. This was reported in Bug 645345 (https://bugzilla.gnome.org/show_bug.cgi?id=645345) but I didn't see this issue in the 2.8 bug list.

I tried to investigate a little on this issue. First, Gimp 2.6.x is not affected at all by this issue. Then, disabling color management in Gimp 2.7.x greatly improve things but it's still slower than Gimp 2.6.x.

I digged into the code and found that each move of the mouse on the rectangle selection (for example) triggers an "expose-event" event which calls the "gimp_display_shell_canvas_expose", which in turn is responsible for the slow image refresh (and this process becomes really slow when color management is enabled).

In Gimp 2.6.x, on the contrary, there is no such event triggered by each movement of the mouse, so the user experience is very smooth.

I tried to fix the issue, but I didn't find in the code where the "expose-event" is triggered.

Hoping you could quickly fix this annoying issue,
RB

PS : Gimp 2.7.5 manually compiled for Debian Squeeze on a 3.5 GHz Core 2 Duo computer