xdg_shell, multi-output, remove sprawl, cleanup

[jwinarske]

xdg_shell -replaces wl_shell for xdg_shell

Multiple outputs -Adds support for saving state on multiple outputs -Enables deriving the buffer scaling factor

Cleanup -Remove unused methods/variables -Remove unused headers -Initialize uninitialize variables -rename m_engine to m_flutter_engine in App class

Remove sprawl option -Not required with xdg_shell

Update README.md -Enabling flutter desktop causes App build issue. This has been the case for some time. Only use custom devices for debugging eLinux Flutter.

FPS feature cleanup -Fix narrowing warnings -Update README for usage

Remove pinch gesture references -Dart layer gesture detection being used. Not all targets have this protocol

[mv0]

My initial comments for these are:

• please keep the cleanups in a different patch/patches
• please keep indent changes in a different patch/patches
• keep together the wl_shell to xdg-shell conversion - do not split toplevel configure events from xdg_surface ones. Makes reviewing much easier
• all patches are missing a proper commit description

[jwinarske]

Yeah I agree. This wasn't ready for review when I pointed it out. I refactored the patches for logical grouping.

[mv0]

Had a few minor nitpicks, these now look fine to me now. I (still) need to do a follow-up with the resize, as that will currently will be an issue when starting up in a different state (max, rather than full). Feel free to merge once resolved (the comments).

[jwinarske]

@mv0 I have updates that handle buffering scaling, and setup interface versioning using std::min logic. I've moved forward on wl_seat, etc. I can now drag the window between screens and the buffer scaling changes. It's not to say the Mutter implementation tracks 100% correctly, but the nuance can be addressed at a later date if it shows up else where. There was an issue when display scaling was > 100% it would segfault; without these changes.