[gnome-shell/wip/carlosg/magnifier-improvements: 3/5] magnifier: Implement pointer motion tracking differently

[Carlos Garnacho <carlosg src gnome org>]

commit 4df9c8a809ba0c2df236da0f7aa7b6937b93c423
Author: Carlos Garnacho <carlosg gnome org>
Date:   Thu Feb 6 13:25:20 2020 +0100

    magnifier: Implement pointer motion tracking differently
    
    The use of the core idle monitor means that focus change events
    are also delayed by keyboard interaction. Since the magnifier is
    already in the business of pointer tracking, it's easy enough to
    fire the pointer rest timeout from here, so focus changes are
    accumulated and delayed.

 js/ui/magnifier.js | 38 +++++++++++++++++++++++---------------
 1 file changed, 23 insertions(+), 15 deletions(-)
---
diff --git a/js/ui/magnifier.js b/js/ui/magnifier.js
index 6ff026cd21..227b1342aa 100644
--- a/js/ui/magnifier.js
+++ b/js/ui/magnifier.js
@@ -1133,6 +1133,13 @@ var ZoomRegion = class ZoomRegion {
         return this._screenPosition;
     }
 
+    _clearScrollContentsTimer() {
+        if (this._scrollContentsTimerId != 0) {
+            GLib.source_remove(this._scrollContentsTimerId);
+            this._scrollContentsTimerId = 0;
+        }
+    }
+
     /**
      * scrollToMousePos:
      * Set the region of interest based on the position of the system pointer.
@@ -1146,28 +1153,29 @@ var ZoomRegion = class ZoomRegion {
         else
             this._updateMousePosition();
 
+        this._clearScrollContentsTimer();
+        this._scrollContentsTimerId = GLib.timeout_add(GLib.PRIORITY_DEFAULT, POINTER_REST_TIME, () => {
+            this._followingCursor = false;
+            if (this._xDelayed != null && this._yDelayed != null) {
+                this._scrollContentsToDelayed(this._xDelayed, this._yDelayed);
+                this._xDelayed = null;
+                this._yDelayed = null;
+            }
+
+            return GLib.SOURCE_REMOVE;
+        });
+
         // Determine whether the system mouse pointer is over this zoom region.
         return this._isMouseOverRegion();
     }
 
-    _clearScrollContentsTimer() {
-        if (this._scrollContentsTimerId != 0) {
-            GLib.source_remove(this._scrollContentsTimerId);
-            this._scrollContentsTimerId = 0;
-        }
-    }
-
     _scrollContentsToDelayed(x, y) {
-        if (this._pointerIdleMonitor.get_idletime() >= POINTER_REST_TIME) {
+        if (this._followingCursor) {
+            this._xDelayed = x;
+            this._yDelayed = y;
+        } else {
             this.scrollContentsTo(x, y);
-            return;
         }
-
-        this._clearScrollContentsTimer();
-        this._scrollContentsTimerId = GLib.timeout_add(GLib.PRIORITY_DEFAULT, POINTER_REST_TIME, () => {
-            this._scrollContentsToDelayed(x, y);
-            return GLib.SOURCE_REMOVE;
-        });
     }
 
     /**