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
17package android.view;
18
19import android.graphics.Outline;
20import android.graphics.drawable.Drawable;
21
22/**
23 * Interface by which a View builds its {@link Outline}, used for shadow casting and clipping.
24 */
25public abstract class ViewOutlineProvider {
26    /**
27     * Default outline provider for Views, which queries the Outline from the View's background,
28     * or generates a 0 alpha, rectangular Outline the size of the View if a background
29     * isn't present.
30     *
31     * @see Drawable#getOutline(Outline)
32     */
33    public static final ViewOutlineProvider BACKGROUND = new ViewOutlineProvider() {
34        @Override
35        public void getOutline(View view, Outline outline) {
36            Drawable background = view.getBackground();
37            if (background != null) {
38                background.getOutline(outline);
39            } else {
40                outline.setRect(0, 0, view.getWidth(), view.getHeight());
41                outline.setAlpha(0.0f);
42            }
43        }
44    };
45
46    /**
47     * Maintains the outline of the View to match its rectangular bounds,
48     * at <code>1.0f</code> alpha.
49     *
50     * This can be used to enable Views that are opaque but lacking a background cast a shadow.
51     */
52    public static final ViewOutlineProvider BOUNDS = new ViewOutlineProvider() {
53        @Override
54        public void getOutline(View view, Outline outline) {
55            outline.setRect(0, 0, view.getWidth(), view.getHeight());
56        }
57    };
58
59    /**
60     * Maintains the outline of the View to match its rectangular padded bounds,
61     * at <code>1.0f</code> alpha.
62     *
63     * This can be used to enable Views that are opaque but lacking a background cast a shadow.
64     */
65    public static final ViewOutlineProvider PADDED_BOUNDS = new ViewOutlineProvider() {
66        @Override
67        public void getOutline(View view, Outline outline) {
68            outline.setRect(view.getPaddingLeft(),
69                    view.getPaddingTop(),
70                    view.getWidth() - view.getPaddingRight(),
71                    view.getHeight() - view.getPaddingBottom());
72        }
73    };
74
75    /**
76     * Called to get the provider to populate the Outline.
77     *
78     * This method will be called by a View when its owned Drawables are invalidated, when the
79     * View's size changes, or if {@link View#invalidateOutline()} is called
80     * explicitly.
81     *
82     * The input outline is empty and has an alpha of <code>1.0f</code>.
83     *
84     * @param view The view building the outline.
85     * @param outline The empty outline to be populated.
86     */
87    public abstract void getOutline(View view, Outline outline);
88}
89