HardwareLayer.java revision 7077506f9945b87b02bdd47ffce75a5b813c821c 
1/*
2 * Copyright (C) 2011 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.Bitmap;
20import android.graphics.Canvas;
21import android.graphics.Matrix;
22
23/**
24 * A hardware layer can be used to render graphics operations into a hardware
25 * friendly buffer. For instance, with an OpenGL backend, a hardware layer
26 * would use a Frame Buffer Object (FBO.) The hardware layer can be used as
27 * a drawing cache when a complex set of graphics operations needs to be
28 * drawn several times.
29 */
30abstract class HardwareLayer {
31    /**
32     * Indicates an unknown dimension (width or height.)
33     */
34    static final int DIMENSION_UNDEFINED = -1;
35
36    int mWidth;
37    int mHeight;
38
39    boolean mOpaque;
40
41    /**
42     * Creates a new hardware layer with undefined dimensions.
43     */
44    HardwareLayer() {
45        this(DIMENSION_UNDEFINED, DIMENSION_UNDEFINED, false);
46    }
47
48    /**
49     * Creates a new hardware layer at least as large as the supplied
50     * dimensions.
51     *
52     * @param width The minimum width of the layer
53     * @param height The minimum height of the layer
54     * @param isOpaque Whether the layer should be opaque or not
55     */
56    HardwareLayer(int width, int height, boolean isOpaque) {
57        mWidth = width;
58        mHeight = height;
59        mOpaque = isOpaque;
60    }
61
62    /**
63     * Returns the minimum width of the layer.
64     *
65     * @return The minimum desired width of the hardware layer
66     */
67    int getWidth() {
68        return mWidth;
69    }
70
71    /**
72     * Returns the minimum height of the layer.
73     *
74     * @return The minimum desired height of the hardware layer
75     */
76    int getHeight() {
77        return mHeight;
78    }
79
80    /**
81     * Returns whether or not this layer is opaque.
82     *
83     * @return True if the layer is opaque, false otherwise
84     */
85    boolean isOpaque() {
86        return mOpaque;
87    }
88
89    /**
90     * Indicates whether this layer can be rendered.
91     *
92     * @return True if the layer can be rendered into, false otherwise
93     */
94    abstract boolean isValid();
95
96    /**
97     * Resize the layer, if necessary, to be at least as large
98     * as the supplied dimensions.
99     *
100     * @param width The new desired minimum width for this layer
101     * @param height The new desired minimum height for this layer
102     */
103    abstract void resize(int width, int height);
104
105    /**
106     * Returns a hardware canvas that can be used to render onto
107     * this layer.
108     *
109     * @return A hardware canvas, or null if a canvas cannot be created
110     */
111    abstract HardwareCanvas getCanvas();
112
113    /**
114     * Destroys resources without waiting for a GC.
115     */
116    abstract void destroy();
117
118    /**
119     * This must be invoked before drawing onto this layer.
120     * @param currentCanvas
121     */
122    abstract HardwareCanvas start(Canvas currentCanvas);
123
124    /**
125     * This must be invoked after drawing onto this layer.
126     * @param currentCanvas
127     */
128    abstract void end(Canvas currentCanvas);
129
130    /**
131     * Copies this layer into the specified bitmap.
132     *
133     * @param bitmap The bitmap to copy they layer into
134     *
135     * @return True if the copy was successful, false otherwise
136     */
137    abstract boolean copyInto(Bitmap bitmap);
138
139    /**
140     * Update the layer's properties. This method should be used
141     * when the underlying storage is modified by an external entity.
142     * To change the underlying storage, use the {@link #resize(int, int)}
143     * method instead.
144     *
145     * @param width The new width of this layer
146     * @param height The new height of this layer
147     * @param isOpaque Whether this layer is opaque
148     */
149    void update(int width, int height, boolean isOpaque) {
150        mWidth = width;
151        mHeight = height;
152        mOpaque = isOpaque;
153    }
154
155    /**
156     * Sets an optional transform on this layer.
157     *
158     * @param matrix The transform to apply to the layer.
159     */
160    abstract void setTransform(Matrix matrix);
161}
162