Strange performance problem with full-screen app over Firefox

[Jesse <pianohacker gmail com>]

I've made a small, full-screen, popover HUD using clutter. With compton running to provide compositing, this works wonderfully. The only problem is that the performance of the show/hide animation (http://i.imgur.com/KThGFz6.gif , not real time) decreases noticeably when Firefox is underneath it. The performance seems like ~45 fps on a workspace without Firefox, and ~15 fps on a workspace with it, while CLUTTER_SHOW_FPS only shows a drop from ~60 to ~45 FPS.This happens regardless of whether Flash or compton are currently running.

Does anyone know what might be causing this problem, and what I could do to work around it?

I'm running Debian jessie with Linux 3.9 on a system with Intel 5700MHD graphics.

Thanks,

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Jesse Weaver