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      1 /*
      2  * Copyright (C) 2014 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 
     18 package com.android.internal.widget;
     19 
     20 import android.graphics.Canvas;
     21 import android.graphics.PixelFormat;
     22 import android.graphics.drawable.Drawable;
     23 import android.view.View;
     24 import android.view.ViewGroup;
     25 
     26 /**
     27  * Helper class for drawing a fallback background in framework decor layouts.
     28  * Useful for when an app has not set a window background but we're asked to draw
     29  * an uncovered area.
     30  */
     31 public class BackgroundFallback {
     32     private Drawable mBackgroundFallback;
     33 
     34     public void setDrawable(Drawable d) {
     35         mBackgroundFallback = d;
     36     }
     37 
     38     public boolean hasFallback() {
     39         return mBackgroundFallback != null;
     40     }
     41 
     42     public void draw(ViewGroup root, Canvas c, View content) {
     43         if (!hasFallback()) {
     44             return;
     45         }
     46 
     47         // Draw the fallback in the padding.
     48         final int width = root.getWidth();
     49         final int height = root.getHeight();
     50         int left = width;
     51         int top = height;
     52         int right = 0;
     53         int bottom = 0;
     54 
     55         final int childCount = root.getChildCount();
     56         for (int i = 0; i < childCount; i++) {
     57             final View child = root.getChildAt(i);
     58             final Drawable childBg = child.getBackground();
     59             if (child == content) {
     60                 // We always count the content view container unless it has no background
     61                 // and no children.
     62                 if (childBg == null && child instanceof ViewGroup &&
     63                         ((ViewGroup) child).getChildCount() == 0) {
     64                     continue;
     65                 }
     66             } else if (child.getVisibility() != View.VISIBLE || childBg == null ||
     67                     childBg.getOpacity() != PixelFormat.OPAQUE) {
     68                 // Potentially translucent or invisible children don't count, and we assume
     69                 // the content view will cover the whole area if we're in a background
     70                 // fallback situation.
     71                 continue;
     72             }
     73             left = Math.min(left, child.getLeft());
     74             top = Math.min(top, child.getTop());
     75             right = Math.max(right, child.getRight());
     76             bottom = Math.max(bottom, child.getBottom());
     77         }
     78 
     79         if (left >= right || top >= bottom) {
     80             // No valid area to draw in.
     81             return;
     82         }
     83 
     84         if (top > 0) {
     85             mBackgroundFallback.setBounds(0, 0, width, top);
     86             mBackgroundFallback.draw(c);
     87         }
     88         if (left > 0) {
     89             mBackgroundFallback.setBounds(0, top, left, height);
     90             mBackgroundFallback.draw(c);
     91         }
     92         if (right < width) {
     93             mBackgroundFallback.setBounds(right, top, width, height);
     94             mBackgroundFallback.draw(c);
     95         }
     96         if (bottom < height) {
     97             mBackgroundFallback.setBounds(left, bottom, right, height);
     98             mBackgroundFallback.draw(c);
     99         }
    100     }
    101 }
    102