1/*
2 * Copyright (C) 2007 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.graphics;
18
19import java.io.InputStream;
20import java.io.OutputStream;
21
22/**
23 * A picture records drawing calls (via the canvas returned by beginRecording)
24 * and can then play them back (via picture.draw(canvas) or canvas.drawPicture).
25 * The picture's contents can also be written to a stream, and then later
26 * restored to a new picture (via writeToStream / createFromStream). For most
27 * content (esp. text, lines, rectangles), drawing a sequence from a picture can
28 * be faster than the equivalent API calls, since the picture performs its
29 * playback without incurring any java-call overhead.
30 */
31public class Picture {
32    private Canvas mRecordingCanvas;
33    private final int mNativePicture;
34
35    private static final int WORKING_STREAM_STORAGE = 16 * 1024;
36
37    public Picture() {
38        this(nativeConstructor(0));
39    }
40
41    /**
42     * Create a picture by making a copy of what has already been recorded in
43     * src. The contents of src are unchanged, and if src changes later, those
44     * changes will not be reflected in this picture.
45     */
46    public Picture(Picture src) {
47        this(nativeConstructor(src != null ? src.mNativePicture : 0));
48    }
49
50    /**
51     * To record a picture, call beginRecording() and then draw into the Canvas
52     * that is returned. Nothing we appear on screen, but all of the draw
53     * commands (e.g. drawRect(...)) will be recorded. To stop recording, call
54     * endRecording(). At this point the Canvas that was returned must no longer
55     * be referenced, and nothing should be drawn into it.
56     */
57    public Canvas beginRecording(int width, int height) {
58        int ni = nativeBeginRecording(mNativePicture, width, height);
59        mRecordingCanvas = new RecordingCanvas(this, ni);
60        return mRecordingCanvas;
61    }
62
63    /**
64     * Call endRecording when the picture is built. After this call, the picture
65     * may be drawn, but the canvas that was returned by beginRecording must not
66     * be referenced anymore. This is automatically called if Picture.draw() or
67     * Canvas.drawPicture() is called.
68     */
69    public void endRecording() {
70        if (mRecordingCanvas != null) {
71            mRecordingCanvas = null;
72            nativeEndRecording(mNativePicture);
73        }
74    }
75
76    /**
77     * Get the width of the picture as passed to beginRecording. This
78     * does not reflect (per se) the content of the picture.
79     */
80    public native int getWidth();
81
82    /**
83     * Get the height of the picture as passed to beginRecording. This
84     * does not reflect (per se) the content of the picture.
85     */
86    public native int getHeight();
87
88    /**
89     * Draw this picture on the canvas. The picture may have the side effect
90     * of changing the matrix and clip of the canvas.
91     *
92     * @param canvas  The picture is drawn to this canvas
93     */
94    public void draw(Canvas canvas) {
95        if (mRecordingCanvas != null) {
96            endRecording();
97        }
98        nativeDraw(canvas.mNativeCanvas, mNativePicture);
99    }
100
101    /**
102     * Create a new picture (already recorded) from the data in the stream. This
103     * data was generated by a previous call to writeToStream().
104     */
105    public static Picture createFromStream(InputStream stream) {
106        return new Picture(
107            nativeCreateFromStream(stream, new byte[WORKING_STREAM_STORAGE]));
108    }
109
110    /**
111     * Write the picture contents to a stream. The data can be used to recreate
112     * the picture in this or another process by calling createFromStream.
113     */
114    public void writeToStream(OutputStream stream) {
115        // do explicit check before calling the native method
116        if (stream == null) {
117            throw new NullPointerException();
118        }
119        if (!nativeWriteToStream(mNativePicture, stream,
120                             new byte[WORKING_STREAM_STORAGE])) {
121            throw new RuntimeException();
122        }
123    }
124
125    protected void finalize() throws Throwable {
126        nativeDestructor(mNativePicture);
127    }
128
129    /*package*/ final int ni() {
130        return mNativePicture;
131    }
132
133    private Picture(int nativePicture) {
134        if (nativePicture == 0) {
135            throw new RuntimeException();
136        }
137        mNativePicture = nativePicture;
138    }
139
140    // return empty picture if src is 0, or a copy of the native src
141    private static native int nativeConstructor(int nativeSrcOr0);
142    private static native int nativeCreateFromStream(InputStream stream,
143                                                byte[] storage);
144    private static native int nativeBeginRecording(int nativeCanvas,
145                                                    int w, int h);
146    private static native void nativeEndRecording(int nativeCanvas);
147    private static native void nativeDraw(int nativeCanvas, int nativePicture);
148    private static native boolean nativeWriteToStream(int nativePicture,
149                                           OutputStream stream, byte[] storage);
150    private static native void nativeDestructor(int nativePicture);
151
152    private static class RecordingCanvas extends Canvas {
153        private final Picture mPicture;
154
155        public RecordingCanvas(Picture pict, int nativeCanvas) {
156            super(nativeCanvas);
157            mPicture = pict;
158        }
159
160        @Override
161        public void setBitmap(Bitmap bitmap) {
162            throw new RuntimeException(
163                                "Cannot call setBitmap on a picture canvas");
164        }
165
166        @Override
167        public void drawPicture(Picture picture) {
168            if (mPicture == picture) {
169                throw new RuntimeException(
170                            "Cannot draw a picture into its recording canvas");
171            }
172            super.drawPicture(picture);
173        }
174    }
175}
176
177