[dash] showing/hiding places causing graphical corruption

[Bill Filler]

This is based on research from bug 740387.
I was able to reproduce the corruption with /apps/metacity/general/capture_before_unmap set to false which rules out th e metacity patch being the problem, at least in this case.

I tested on natty using with nvidia graphics and natty beta and latest from unity-2d dpaily ppa. See attached video. This is how I am able to reproduce reliably:

1) make sure you have files on your desktop (not sure if this is required)
2) open two terminals and have them overlap
3) show dash using Super key
4) hide dash using Super key
5) show applications place by clicking on launcher
6) hide it pressing Super key
7) show dash pressing Super key
bang, the windows that were beneath the apps place are corrupted

verified bug occurs on -intel graphics as well

Simplier steps to reproduce:

1) open 2 terminals
2) bring up apps place
3) super key to hide apps place
4) super key to show dash
bang - corruption

[Florian Boucault (fboucault)]

The corruption is 100% reproducible with metacity but does not happen with either xfwm4 or Compiz.

[Ugo Riboni (uriboni)]

The bug is caused by the fact that our dash window is of EWMH type "dock" and likely we're doing something that metacity assumes that a dock shouldn't ever do.

This only happens with metacity,not the xfce wm or compiz.

I have not yet found out why this happens, but I isolated the issue and made a minimal test case to reproduce it.
You can find it in this branch: bzr+ssh://bazaar.launchpad.net/~uriboni/unity-2d/corrupter/
I can get corruption reliably with that app on both the natty VM and natty on a netbook.

I will try to figure out why this happens and what workarounds or fixes we can put in place, tomorrow morning.

[Ferrin (ferrin-riggins)]

sorry, I'm a complete newb here. I have an old T 40 IBM Thinkpad. So... no super key.(windows key) basically, the Dash is constant. i cannot get it to "minimize?" or hide. is this related?

[Olivier Tilloy (osomon)]

Ferrin: the dash should hide whenever you toggle the BFB button off (in the top left corner, with the Ubuntu logo), or when you launch any application. If it doesn’t, it’s a bug, but likely a different one: could you please file a separate bug report? Thanks!