Minimize/unminimize and ALT+tab animation broken by recent mutter

[Ubuntu budgie]

A separate upload for focal will be made later.

[Impact]

The recent mutter version now in 20.10 removed the deprecated feature that budgie-desktop needed to animate when minimizing and unminimizing windows.

The result was using a default 'fade' effect that is jarring for budgie users.

This patch upload resolves this by replacing the deprecated Clutter based "scaled-gravity" feature that was removed by the equivalent Clutter API calls.

In addition whilst reworking to resolve it was found that 4k desktop users using scaling greater than 1, the existing minimize and unminimize animation was broken. This has also been resolved by taking into account the scale-factor.

[Test Case]

 * For groovy: simply minimize or unminimize windows. Note the fade effect.

 * For groovy & focal: using a 4K display and a scale factor of 2 or more minimize/unminimize windows. Note that the animation should be too and from the invoking icon. The broken effect is that the animation starts around half way up the screen towards the left-side of the screen.

 * Enable the proposed repository via software-properties-gtk. Install the following packages

sudo apt install budgie-desktop budgie-core libbudgie-plugin0 libbudgietheme0 libbudgie-private0 gir1.2-budgie-desktop-1.0

 * Reboot.

 * minimize a window - note the animation should be a shrink effect ending at where the application was first launched (e.g. plank or the icon-task-list)

 * unminmize a window - note the aniation should be an expand effect starting where the icon is minimized (plank or icon-task list) and ending with the window fully open.

 * Using Settings - Display - look at the scaling options. If you have 200% or more - select that. Logout and login.

 * repeat the minimize/unminimize of windows. The same results as above should occur.

[Regression Potential]

 * I suppose the worse case scenario is this introduces a stability issue in the key component of budgie-desktop - its window manager. Crashes in the window manager will result first in a flash of the screen whilst the window manager restarts. After the third time in fairly quick session the user would be thrown out of the session.

 * Ideally we would wait several weeks whilst other distros and upstream test this before SRUing to a LTS release - this is how we will be proceeding for the focal uploading.

 * We don't have the luxury of this approach for groovy.

 * As such we have pushed this as a PPA install to the community and received feedback all looks ok

 * Within the team we have been testing across multiple configurations - nvidia/intel and virtual machines with and without 4K capabilities. We have tested panels in each screen edge, with plank or icon-tasklist.

 * Additionally we have code-reviewed and consider the changes are not high risk - replacing an obsolete API call with the equivalent API calls with exactly the same call values as the obsolete API call.

[Other Info]

 * N/A

[Launchpad Janitor (janitor)]

This bug was fixed in the package budgie-desktop - 10.5.1+git20200824-2.0ubuntu1

---------------
budgie-desktop (10.5.1+git20200824-2.0ubuntu1) groovy; urgency=medium

  * Bug-fix
    Restore budgie window minimize and unminimize animation
    windowanimation.patch (LP: #1900354)

 -- David Mohammed <email address hidden> Sun, 18 Oct 2020 22:11:50 +0100