feat(WorkspaceSvg): Ignore gestures when keyboard move in progress (#8963)

* feat(WorkspaceSvg): Ignore gestures during keyboard moves

  Modify WorkspaceSvg.prototype.getGesture to return null when
  there is a keyboard-initiated move in progress.

* chore(WorkspaceSvg): Add TODOs to remove .keyboardMoveInProgress

Author: cpcallen

core/workspace_svg.ts

@@ -314,7 +314,7 @@ export class WorkspaceSvg
   keyboardAccessibilityMode = false;
 
   /** True iff a keyboard-initiated move ("drag") is in progress. */
-  keyboardMoveInProgress = false;
+  keyboardMoveInProgress = false; // TODO(#8960): Delete this.
 
   /** The list of top-level bounded elements on the workspace. */
   private topBoundedElements: IBoundedElement[] = [];
@@ -1471,6 +1471,8 @@ export class WorkspaceSvg
    * removed, at an time without notice and without being treated
    * as a breaking change.
    *
+   * TODO(#8960): Delete this.
+   *
    * @internal
    * @param inProgress Is a keyboard-initated move in progress?
    */
@@ -1494,6 +1496,8 @@ export class WorkspaceSvg
    */
   isDragging(): boolean {
     return (
+      // TODO(#8960): Query Mover.isMoving to see if move is in
+      // progress rather than relying on a status flag.
       this.keyboardMoveInProgress ||
       (this.currentGesture_ !== null && this.currentGesture_.isDragging())
     );
@@ -2403,36 +2407,47 @@ export class WorkspaceSvg
 
   /**
    * Look up the gesture that is tracking this touch stream on this workspace.
-   * May create a new gesture.
+   *
+   * Returns the gesture in progress, except:
+   *
+   * - If there is a keyboard-initiate move in progress then null will
+   *   be returned - after calling event.preventDefault() and
+   *   event.stopPropagation() to ensure the pointer event is ignored.
+   * - If there is a gesture in progress but event.type is
+   *   'pointerdown' then the in-progress gesture will be cancelled;
+   *   this will result in null being returned.
+   * - If no gesutre is in progress but event is a pointerdown then a
+   *   new gesture will be created and returned.
    *
    * @param e Pointer event.
    * @returns The gesture that is tracking this touch stream, or null if no
    *     valid gesture exists.
    * @internal
    */
   getGesture(e: PointerEvent): Gesture | null {
-    const isStart = e.type === 'pointerdown';
-
-    const gesture = this.currentGesture_;
-    if (gesture) {
-      if (isStart && gesture.hasStarted()) {
-        console.warn('Tried to start the same gesture twice.');
-        // That's funny.  We must have missed a mouse up.
-        // Cancel it, rather than try to retrieve all of the state we need.
-        gesture.cancel();
-        return null;
-      }
-      return gesture;
+    // TODO(#8960): Query Mover.isMoving to see if move is in progress
+    // rather than relying on .keyboardMoveInProgress status flag.
+    if (this.keyboardMoveInProgress) {
+      // Normally these would be called from Gesture.doStart.
+      e.preventDefault();
+      e.stopPropagation();
+      return null;
     }
 
-    // No gesture existed on this workspace, but this looks like the start of a
-    // new gesture.
-    if (isStart) {
+    const isStart = e.type === 'pointerdown';
+    if (isStart && this.currentGesture_?.hasStarted()) {
+      console.warn('Tried to start the same gesture twice.');
+      // That's funny.  We must have missed a mouse up.
+      // Cancel it, rather than try to retrieve all of the state we need.
+      this.currentGesture_.cancel(); // Sets this.currentGesture_ to null.
+    }
+    if (!this.currentGesture_ && isStart) {
+      // No gesture existed on this workspace, but this looks like the
+      // start of a new gesture.
       this.currentGesture_ = new Gesture(e, this);
-      return this.currentGesture_;
     }
-    // No gesture existed and this event couldn't be the start of a new gesture.
-    return null;
+
+    return this.currentGesture_;
   }
 
   /**