Only enable hardware layers on visible workspace pages

Change-Id: Id82fc76d00a188556460d1a78388d46be56c9c4e

3 files changed, 48 insertions, 11 deletions

diff --git a/src/com/android/launcher2/CellLayout.java b/src/com/android/launcher2/CellLayout.java
index ccc842e5e..284db1bdb 100644
--- a/src/com/android/launcher2/CellLayout.java
+++ b/src/com/android/launcher2/CellLayout.java
@@ -302,7 +302,15 @@ public class CellLayout extends ViewGroup {
     }
 
     public void enableHardwareLayers() {
-        mShortcutsAndWidgets.enableHardwareLayers();
+        mShortcutsAndWidgets.setLayerType(LAYER_TYPE_HARDWARE, null);
+    }
+
+    public void disableHardwareLayers() {
+        mShortcutsAndWidgets.setLayerType(LAYER_TYPE_NONE, null);
+    }
+
+    public void buildHardwareLayer() {
+        mShortcutsAndWidgets.buildLayer();
     }
 
     public void setGridSize(int x, int y) {
diff --git a/src/com/android/launcher2/ShortcutAndWidgetContainer.java b/src/com/android/launcher2/ShortcutAndWidgetContainer.java
index 8bebdcd45..8daf3954d 100644
--- a/src/com/android/launcher2/ShortcutAndWidgetContainer.java
+++ b/src/com/android/launcher2/ShortcutAndWidgetContainer.java
@@ -44,10 +44,6 @@ public class ShortcutAndWidgetContainer extends ViewGroup {
         mWallpaperManager = WallpaperManager.getInstance(context);
     }
 
-    public void enableHardwareLayers() {
-        setLayerType(LAYER_TYPE_HARDWARE, null);
-    }
-
     public void setCellDimensions(int cellWidth, int cellHeight, int widthGap, int heightGap ) {
         mCellWidth = cellWidth;
         mCellHeight = cellHeight;
diff --git a/src/com/android/launcher2/Workspace.java b/src/com/android/launcher2/Workspace.java
index feb4ed077..829ac20d7 100644
--- a/src/com/android/launcher2/Workspace.java
+++ b/src/com/android/launcher2/Workspace.java
@@ -170,6 +170,7 @@ public class Workspace extends SmoothPagedView
     private Bitmap mDragOutline = null;
     private final Rect mTempRect = new Rect();
     private final int[] mTempXY = new int[2];
+    private int[] mTempVisiblePagesRange = new int[2];
     private float mOverscrollFade = 0;
     private boolean mOverscrollTransformsSet;
     public static final int DRAG_BITMAP_PADDING = 2;
@@ -427,7 +428,6 @@ public class Workspace extends SmoothPagedView
         CellLayout cl = ((CellLayout) child);
         cl.setOnInterceptTouchListener(this);
         cl.setClickable(true);
-        cl.enableHardwareLayers();
         cl.setContentDescription(getContext().getString(
                 R.string.workspace_description_format, getChildCount()));
     }
@@ -1221,6 +1221,7 @@ public class Workspace extends SmoothPagedView
         super.screenScrolled(screenCenter);
 
         updatePageAlphaValues(screenCenter);
+        enableHwLayersOnVisiblePages();
 
         if (mOverScrollX < 0 || mOverScrollX > mMaxScrollX) {
             int index = mOverScrollX < 0 ? 0 : getChildCount() - 1;
@@ -1368,10 +1369,42 @@ public class Workspace extends SmoothPagedView
 
         if (enableChildrenLayers != mChildrenLayersEnabled) {
             mChildrenLayersEnabled = enableChildrenLayers;
-            for (int i = 0; i < getPageCount(); i++) {
-                CellLayout cl = (CellLayout) getChildAt(i);
-                cl.getShortcutsAndWidgets().setLayerType(
-                        mChildrenLayersEnabled ? LAYER_TYPE_HARDWARE : LAYER_TYPE_NONE, null);
+            if (mChildrenLayersEnabled) {
+                enableHwLayersOnVisiblePages();
+            } else {
+                for (int i = 0; i < getPageCount(); i++) {
+                    final CellLayout cl = (CellLayout) getChildAt(i);
+                    cl.disableHardwareLayers();
+                }
+            }
+        }
+    }
+
+    private void enableHwLayersOnVisiblePages() {
+        if (mChildrenLayersEnabled) {
+            final int screenCount = getChildCount();
+            getVisiblePages(mTempVisiblePagesRange);
+            int leftScreen = mTempVisiblePagesRange[0];
+            int rightScreen = mTempVisiblePagesRange[1];
+            if (leftScreen == rightScreen) {
+                // make sure we're caching at least two pages always
+                if (rightScreen < screenCount - 1) {
+                    rightScreen++;
+                } else if (leftScreen > 0) {
+                    leftScreen--;
+                }
+            }
+            for (int i = 0; i < screenCount; i++) {
+                final CellLayout layout = (CellLayout) getChildAt(i);
+                if (!(leftScreen <= i && i <= rightScreen && shouldDrawChild(layout))) {
+                    layout.disableHardwareLayers();
+                }
+            }
+            for (int i = 0; i < screenCount; i++) {
+                final CellLayout layout = (CellLayout) getChildAt(i);
+                if (leftScreen <= i && i <= rightScreen && shouldDrawChild(layout)) {
+                    layout.enableHardwareLayers();
+                }
             }
         }
     }
@@ -1383,7 +1416,7 @@ public class Workspace extends SmoothPagedView
             final int childCount = getChildCount();
             for (int i = 0; i < childCount; i++) {
                 CellLayout cl = (CellLayout) getChildAt(i);
-                cl.getShortcutsAndWidgets().buildLayer();
+                cl.buildHardwareLayer();
             }
         }
         updateChildrenLayersEnabled(false);