Compiz alpha blur on by default

[pablomme]

Binary package hint: compiz

This is a feature request. Given the attention being paid to appearance for Lucid I think it might be worth considering. I'm currently running compiz 1:0.8.4-0ubuntu13 and I'm on 32-bit lucid installed afresh from alpha 3.

There are two visual elements that would greatly benefit from alpha blur: notify-osd and tooltips, now that the default theme has tooltip transparency. Now, blurring is costly and framerates can be severely affected, particularly on slow hardware. However, if blurring is restricted to notify-osd and tooltips, which appear on the screen only temporarily, it should be possible to use alpha blurring without perceived slowdowns, improving readability of the elements' contents and overall desktop appearance.

I order to do this, one would need to:
- Change the default value of /apps/compiz/plugins/blur/screen0/options/alpha_blur to true.
- Change the default value of /apps/compiz/plugins/blur/screen0/options/alpha_blur_match to "(class=notify-osd) | (type=tooltip)".
- Change the default value of /apps/gwd/blur_type to "none".
- Possibly change the default value of /apps/gwd/metacity_theme_opacity to a larger value (e.g. 0.75 -> 0.9).

On my laptop, which has an intel 945 display controller, compiz runs at 60fps (the display's refresh rate) when blurring is off. With the above configuration it continues to run at 60fps until a blurred element pops up, when it drops to 30fps (almost exactly, independently of the blurred region size, which is a tad weird...). A second blurred element makes the frame rate drop further. With decoration blur on this becomes rather unpleasant with just a couple of windows open. However with the above configuration it is unlikely that blurring would ever cause jerkiness, at least for long enough to be noticeable - we can have two notifications and one tooltip active at most.

Of course, I'm assuming sane behaviour of the different components:
- compiz should not try to apply blur if not supported by the hardware, even if set to "on" in GConf
- compiz should run at full framerate when no blurred region is present (or, ideally, if not visible)
- tooltips should always disappear
- notify-osd boxes should always disappear
Although rarely, I have seen instances of all of the above not happening at some point. However these are minor bugs in the relevant programs which should be addressed separately.

[Bálint Magyar (balintm)]

This is currently a very bad idea because of the limitations of some (very widespread) integrated Intel graphics adapters. Namely, enabling any kind of blur in Compiz causes immediate fallback to software rendering.