Bug 1769805 - Implement axis relocking in the sticky axis locking mode. r=botond,dlrobertson

Differential Revision: https://phabricator.services.mozilla.com/D150496

gfx/layers/apz/src/AsyncPanZoomController.cpp

@@ -3248,21 +3248,24 @@ void AsyncPanZoomController::HandlePanningUpdate(
 
     if (fabs(aPanDistance.x) > breakThreshold ||
         fabs(aPanDistance.y) > breakThreshold) {
-      if (mState == PANNING_LOCKED_X) {
+      switch (mState) {
+        case PANNING_LOCKED_X:
           if (!apz::IsCloseToHorizontal(
                   angle, StaticPrefs::apz_axis_lock_breakout_angle())) {
             mY.SetAxisLocked(false);
             // If we are within the lock angle from the Y axis, lock
             // onto the Y axis.
-          if (apz::IsCloseToVertical(angle,
-                                     StaticPrefs::apz_axis_lock_lock_angle())) {
+            if (apz::IsCloseToVertical(
+                    angle, StaticPrefs::apz_axis_lock_lock_angle())) {
               mX.SetAxisLocked(true);
               SetState(PANNING_LOCKED_Y);
             } else {
               SetState(PANNING);
             }
           }
-      } else if (mState == PANNING_LOCKED_Y) {
+          break;
+
+        case PANNING_LOCKED_Y:
           if (!apz::IsCloseToVertical(
                   angle, StaticPrefs::apz_axis_lock_breakout_angle())) {
             mX.SetAxisLocked(false);
@@ -3276,6 +3279,14 @@ void AsyncPanZoomController::HandlePanningUpdate(
               SetState(PANNING);
             }
           }
+          break;
+
+        case PANNING:
+          HandlePanning(angle);
+          break;
+
+        default:
+          break;
       }
     }
   }

gfx/layers/apz/test/gtest/TestAxisLock.cpp

@@ -334,13 +334,13 @@ TEST_F(APZCAxisLockTester, BreakStickyAxisLock) {
   BreakStickyAxisLockTest(ScrollDirections(ScrollDirection::eHorizontal,
                                            ScrollDirection::eVertical));
 
-  // Once we're no longer locked onto an axis, there is no way back. Run a
-  // gesture that would normally lock us onto the X axis, but we should stay
-  // in a panning state.
-  BreakStickyAxisLockTestGesture(ScrollDirection::eHorizontal);
+  // We should be in a panning state.
   apzc->AssertStateIsPanning();
   apzc->AssertNotAxisLocked();
 
+  // Lock back to the X axis.
+  BreakStickyAxisLockTestGesture(ScrollDirection::eHorizontal);
+
   // End the gesture.
   QueueMockHitResult(ScrollableLayerGuid::START_SCROLL_ID);
   PanGesture(PanGestureInput::PANGESTURE_END, manager, ScreenIntPoint(50, 50),
@@ -361,6 +361,13 @@ TEST_F(APZCAxisLockTester, BreakStickyAxisLock) {
   // Test breaking all axis locks from a X axis lock.
   BreakStickyAxisLockTest(ScrollDirections(ScrollDirection::eHorizontal,
                                            ScrollDirection::eVertical));
+
+  // We should be in a panning state.
+  apzc->AssertStateIsPanning();
+  apzc->AssertNotAxisLocked();
+
+  // Test switch back to locking onto the Y axis.
+  BreakStickyAxisLockTest(ScrollDirection::eVertical);
 }
 
 TEST_F(APZCAxisLockTester, BreakAxisLockByLockAngle) {