Fix magnification viewport drifting when scaling

Fixes: 32255388
Test: Ensure viewport no longer drifts when scaling
Change-Id: I1b12aeaa8e1d0282d6c35a27ee061f6cd7b0a667

1 files changed, 4 insertions, 2 deletions

diff --git a/services/accessibility/java/com/android/server/accessibility/MagnificationController.java b/services/accessibility/java/com/android/server/accessibility/MagnificationController.java
index a70b88e87ae4..7250a445487d 100644
--- a/services/accessibility/java/com/android/server/accessibility/MagnificationController.java
+++ b/services/accessibility/java/com/android/server/accessibility/MagnificationController.java
@@ -446,8 +446,10 @@ class MagnificationController implements Handler.Callback {
             mMagnificationRegion.getBounds(viewport);
             final MagnificationSpec spec = mCurrentMagnificationSpec;
             final float oldScale = spec.scale;
-            final float oldCenterX = (viewport.width() / 2.0f - spec.offsetX) / oldScale;
-            final float oldCenterY = (viewport.height() / 2.0f - spec.offsetY) / oldScale;
+            final float oldCenterX
+                    = (viewport.width() / 2.0f - spec.offsetX + viewport.left) / oldScale;
+            final float oldCenterY
+                    = (viewport.height() / 2.0f - spec.offsetY + viewport.top) / oldScale;
             final float normPivotX = (pivotX - spec.offsetX) / oldScale;
             final float normPivotY = (pivotY - spec.offsetY) / oldScale;
             final float offsetX = (oldCenterX - normPivotX) * (oldScale / scale);