Respect Z-ordering when assigning fullscreen-dim layer.

As an optimization, we use a shared fullscreen dim layer for multiple
users. We need to be careful to look at the Z-order of various users
when choosing who to assign it to.

Bug: 36415615
Test: Ask assistant question, long press power, assistant should be dimmed.
Change-Id: Ifea94fe33d32236b79800c0e7c543aac52c8b69f

diff --git a/services/core/java/com/android/server/wm/DimLayerController.java b/services/core/java/com/android/server/wm/DimLayerController.java
index 4100446..d44cd13 100644 (file)
--- a/services/core/java/com/android/server/wm/DimLayerController.java
+++ b/services/core/java/com/android/server/wm/DimLayerController.java
@@ -188,6 +188,7 @@ class DimLayerController {
     boolean animateDimLayers() {
         int fullScreen = -1;
         int fullScreenAndDimming = -1;
+        int topFullScreenUserLayer = 0;
         boolean result = false;
 
         for (int i = mState.size() - 1; i >= 0; i--) {
@@ -213,8 +214,18 @@ class DimLayerController {
             // and we have to make sure we always animate the layer.
             if (user.dimFullscreen() && state.dimLayer == mSharedFullScreenDimLayer) {
                 fullScreen = i;
-                if (mState.valueAt(i).continueDimming) {
+                if (!state.continueDimming) {
+                    continue;
+                }
+
+                // When choosing which user to assign the shared fullscreen layer to
+                // we need to look at Z-order.
+                if (topFullScreenUserLayer == 0 ||
+                        (state.animator != null && state.animator.mAnimLayer > topFullScreenUserLayer)) {
                     fullScreenAndDimming = i;
+                    if (state.animator != null) {
+                        topFullScreenUserLayer = state.animator.mAnimLayer;
+                    }
                 }
             } else {
                 // We always want to animate the non fullscreen windows, they don't share their