Optimize handling of scrolled wallpapers

Swiping the home screen causes the WindowManagerService to do
a bunch of work to keep the wallpapers in sync. First, it lays out
and places all windows. Also, it notifies the SystemUI process that
the wallpaper position has changed.

The layout/place operation is too much work - we only need to set
the position values for the wallpaper, not relayout the whole system.

The notification mechanism must exist, but should be optional. Most
wallpapers don't care (especially static ImageWallpapers). So we'll
give them a new API (WallpaperService.Engine.setWantsOffsets()) to
allow wallpapers to opt out of this process and avoid the performance
overhead.

Change-Id: I66c38375438937f14f6f5550565b28eb204b1e06

1 files changed, 24 insertions, 10 deletions

diff --git a/services/java/com/android/server/wm/WindowManagerService.java b/services/java/com/android/server/wm/WindowManagerService.java
index 792ef70..08797dd 100644
--- a/services/java/com/android/server/wm/WindowManagerService.java
+++ b/services/java/com/android/server/wm/WindowManagerService.java
@@ -1836,7 +1836,8 @@ public class WindowManagerService extends IWindowManager.Stub
             rawChanged = true;
         }
 
-        if (rawChanged) {
+        if (rawChanged && (wallpaperWin.getAttrs().privateFlags &
+                    WindowManager.LayoutParams.PRIVATE_FLAG_WANTS_OFFSET_NOTIFICATIONS) != 0) {
             try {
                 if (DEBUG_WALLPAPER) Slog.v(TAG, "Report new wp offset "
                         + wallpaperWin + " x=" + wallpaperWin.mWallpaperX
@@ -1886,12 +1887,10 @@ public class WindowManagerService extends IWindowManager.Stub
         }
     }
 
-    boolean updateWallpaperOffsetLocked(WindowState changingTarget, boolean sync) {
+    void updateWallpaperOffsetLocked(WindowState changingTarget, boolean sync) {
         final int dw = mAppDisplayWidth;
         final int dh = mAppDisplayHeight;
 
-        boolean changed = false;
-
         WindowState target = mWallpaperTarget;
         if (target != null) {
             if (target.mWallpaperX >= 0) {
@@ -1916,14 +1915,31 @@ public class WindowManagerService extends IWindowManager.Stub
                 WindowState wallpaper = token.windows.get(curWallpaperIndex);
                 if (updateWallpaperOffsetLocked(wallpaper, dw, dh, sync)) {
                     wallpaper.computeShownFrameLocked();
-                    changed = true;
+                    // No need to lay out the windows - we can just set the wallpaper position
+                    // directly.
+                    if (wallpaper.mSurfaceX != wallpaper.mShownFrame.left
+                            || wallpaper.mSurfaceY != wallpaper.mShownFrame.top) {
+                        Surface.openTransaction();
+                        try {
+                            if (SHOW_TRANSACTIONS) logSurface(wallpaper,
+                                    "POS " + wallpaper.mShownFrame.left
+                                    + ", " + wallpaper.mShownFrame.top, null);
+                            wallpaper.mSurfaceX = wallpaper.mShownFrame.left;
+                            wallpaper.mSurfaceY = wallpaper.mShownFrame.top;
+                            wallpaper.mSurface.setPosition(wallpaper.mShownFrame.left,
+                                    wallpaper.mShownFrame.top);
+                        } catch (RuntimeException e) {
+                            Slog.w(TAG, "Error positioning surface of " + wallpaper
+                                    + " pos=(" + wallpaper.mShownFrame.left
+                                    + "," + wallpaper.mShownFrame.top + ")", e);
+                        }
+                        Surface.closeTransaction();
+                    }
                     // We only want to be synchronous with one wallpaper.
                     sync = false;
                 }
             }
         }
-
-        return changed;
     }
 
     void updateWallpaperVisibilityLocked() {
@@ -2436,9 +2452,7 @@ public class WindowManagerService extends IWindowManager.Stub
             window.mWallpaperY = y;
             window.mWallpaperXStep = xStep;
             window.mWallpaperYStep = yStep;
-            if (updateWallpaperOffsetLocked(window, true)) {
-                performLayoutAndPlaceSurfacesLocked();
-            }
+            updateWallpaperOffsetLocked(window, true);
         }
     }