Avoid re-layout on window minimized, since framebuffer is destroyed a…

…nd size is 0

Deprecate Canvas.saveLayer() for future layer compositor and render tree

core/src/main/java/icyllis/modernui/core/ActivityWindow.java

@@ -165,7 +165,12 @@ private void onFramebufferSizeCallback(long w, int width, int height) {
         mWidth = width;
         mHeight = height;
         if (mRoot != null) {
-            mRoot.mHandler.post(() -> mRoot.setFrame(mWidth, mHeight));
+            mRoot.mHandler.post(() -> {
+                // on minimized, window size is 0
+                if (mWidth != 0 && mHeight != 0) {
+                    mRoot.setFrame(mWidth, mHeight);
+                }
+            });
         }
     }
 

core/src/main/java/icyllis/modernui/graphics/Canvas.java

@@ -119,7 +119,10 @@ protected Canvas() {
      * @param alpha  The alpha to apply to the offscreen when it is
      *               drawn during restore()
      * @return value to pass to restoreToCount() to balance this call
+     * @deprecated this method does nothing, you should manually create a layer, or possibly manage a
+     * pool of layers, or use {@link icyllis.modernui.view.View#LAYER_TYPE_HARDWARE}.
      */
+    @Deprecated
     public final int saveLayer(@Nullable RectF bounds, int alpha) {
         if (bounds == null) {
             // ok, it's big enough
@@ -134,7 +137,10 @@ public final int saveLayer(@Nullable RectF bounds, int alpha) {
      * bounds' rectangle.
      *
      * @see #saveLayer(RectF, int)
+     * @deprecated this method does nothing, you should manually create a layer, or possibly manage a
+     * pool of layers, or use {@link icyllis.modernui.view.View#LAYER_TYPE_HARDWARE}.
      */
+    @Deprecated
     public abstract int saveLayer(float left, float top, float right, float bottom, int alpha);
 
     /**