Add global touch coords broker

[Thesola10]

This closes #764 by implementing a broker function, Utils.getPointerCoords(), which selects from global.get_cursor() and a memorized set of coordinates from the last touch event on Stage.

Hopefully this approach will also correct future touchscreen misbehavior.

Edit 2024-03-09:

This PR has been repurposed as a continuation for accidentally superseded by the broker partly introduced in #791.

[Thesola10]

Currently does not work as coordinates do not seem to update. The way I understand it, the Stage is somehow not the global vantage point I thought it would be events-wise. What I need is an Actor that can intercept every single touch-event in the entirety of GNOME Shell...

[Thesola10]

Likely unwarranted -- if we want touch coords to remain separate from a UX standpoint, this just won't cut it. Then again, I'm not even sure how that may relate to drag-and-drop softlock, so I'll wait until I get my code to work before I undo this change.

[Thesola10]

Another proposal, which fixes the immediate issue of centering touch window movement, is to discard changes to grab.js in this PR, and instead apply this patch:

diff --git a/grab.js b/grab.js
index 5aee3ec..9956e81 100644
--- a/grab.js
+++ b/grab.js
@@ -63,7 +63,7 @@ export class MoveGrab {
 
         this.initialY = clone.targetY;
         Easer.removeEase(clone);
-        let [gx, gy, $] = global.get_pointer();
+        let [gx, gy, $] = Utils.getPointerCoords();
 
         let px = (gx - actor.x) / actor.width;
         let py = (gy - actor.y) / actor.height;

However this is much less elegant and may cause confusion as to the role of Utils.getPointerCoords(), as well as keeping the fugly warp hack from #736.

[Thesola10]

Might have to use Clutter.GestureAction but that involves building an entire class just for that. Would've loved to use SwipeTracker.TouchSwipeGesture, but that's private.

[Thesola10]

Pushed #791 as an alternate version of this fix, implementing this solution.

[Thesola10]

I wonder if it's because CLUTTER_EVENT_PROPAGATE causes Clutter to omit followups? Behavior is very inconsistent, it works on the panel so why not the root Stage?

[Thesola10]

huh. this is annoying
I had intended to turn this PR into a develop + revert fbca4 for bookkeeping and stuff, but since i accidentally also pushed the merge commit from #791 this PR is marked as merged as well.

[jtaala]

huh. this is annoying I had intended to turn this PR into a develop + revert fbca4 for bookkeeping and stuff, but since i accidentally also pushed the merge commit from #791 this PR is marked as merged as well.

I noticed that - do you need me to revert anything?

[Thesola10]

nah, the branch is still there in the correct state so you can delete it if you want, as long as the comment and commit message are there it's fine