[Bug 31134] Pressed taskbar buttons flashing

[seguso]

Public bug reported:
https://launchpad.net/malone/bugs/31134

Affects: libwnck (Ubuntu)
       Severity: Normal
       Priority: (none set)
         Status: Unconfirmed

Description:
Even after the recent fixes in libwnck-2.13.90, the taskbar still starts
flashing without reason.

To reproduce:

1. Open an xmms window and make the playlist visible.

2. Drag the xmms window a few pixels aside.

3. The xmms button starts flashing.

This is not an xmms bug but a libwnck bug, because a pressed taskbar
button should _never_ flash: if the button is pressed, the program has
already got my attention, so the flashing is useless. It is also
puzzling because it is not clear how to stop a pressed taskbar button
from flashing. libwnck should have ignored the flash request simply
because the associated button was pressed.

Proposed solution: all is needed is to do a simple check before starting
a flash: if the taskbar button is pressed, do not start the flashing.
Instead, libwnck seems to be using a much more complex logic where
pressed buttons are allowed to flash (why?).