Shader.java revision 6f085f60e929f4bb5ae7ccbc04cbc23c99ee8850 
1/*
2 * Copyright (C) 2006 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 android.annotation.NonNull;
20import android.annotation.Nullable;
21
22/**
23 * Shader is the based class for objects that return horizontal spans of colors
24 * during drawing. A subclass of Shader is installed in a Paint calling
25 * paint.setShader(shader). After that any object (other than a bitmap) that is
26 * drawn with that paint will get its color(s) from the shader.
27 */
28public class Shader {
29    /**
30     * @deprecated Use subclass constructors directly instead.
31     */
32    @Deprecated
33    public Shader() {}
34
35    /**
36     * Current native shader instance. Created and updated lazily when {@link #getNativeInstance()}
37     * is called - otherwise may be out of date with java setters/properties.
38     */
39    private long mNativeInstance;
40
41    /**
42     * Current matrix - always set to null if local matrix is identity.
43     */
44    private Matrix mLocalMatrix;
45
46    public enum TileMode {
47        /**
48         * replicate the edge color if the shader draws outside of its
49         * original bounds
50         */
51        CLAMP   (0),
52        /**
53         * repeat the shader's image horizontally and vertically
54         */
55        REPEAT  (1),
56        /**
57         * repeat the shader's image horizontally and vertically, alternating
58         * mirror images so that adjacent images always seam
59         */
60        MIRROR  (2);
61
62        TileMode(int nativeInt) {
63            this.nativeInt = nativeInt;
64        }
65        final int nativeInt;
66    }
67
68    /**
69     * Return true if the shader has a non-identity local matrix.
70     * @param localM Set to the local matrix of the shader, if the shader's matrix is non-null.
71     * @return true if the shader has a non-identity local matrix
72     */
73    public boolean getLocalMatrix(@NonNull Matrix localM) {
74        if (mLocalMatrix != null) {
75            localM.set(mLocalMatrix);
76            return true; // presence of mLocalMatrix means it's not identity
77        }
78        return false;
79    }
80
81    /**
82     * Set the shader's local matrix. Passing null will reset the shader's
83     * matrix to identity. If the matrix has scale value as 0, the drawing
84     * result is undefined.
85     *
86     * @param localM The shader's new local matrix, or null to specify identity
87     */
88    public void setLocalMatrix(@Nullable Matrix localM) {
89        if (localM == null || localM.isIdentity()) {
90            if (mLocalMatrix != null) {
91                mLocalMatrix = null;
92                discardNativeInstance();
93            }
94        } else {
95            if (mLocalMatrix == null) {
96                mLocalMatrix = new Matrix(localM);
97                discardNativeInstance();
98            } else if (!mLocalMatrix.equals(localM)) {
99                mLocalMatrix.set(localM);
100                discardNativeInstance();
101            }
102        }
103    }
104
105    long createNativeInstance(long nativeMatrix) {
106        return 0;
107    }
108
109    void discardNativeInstance() {
110        if (mNativeInstance != 0) {
111            nativeSafeUnref(mNativeInstance);
112            mNativeInstance = 0;
113        }
114    }
115
116    /**
117     * Callback for subclasses to call {@link #discardNativeInstance()} if the most recently
118     * constructed native instance is no longer valid.
119     */
120    void verifyNativeInstance() {
121    }
122
123    @Override
124    protected void finalize() throws Throwable {
125        try {
126            if (mNativeInstance != 0) {
127                nativeSafeUnref(mNativeInstance);
128            }
129            mNativeInstance = -1;
130        } finally {
131            super.finalize();
132        }
133    }
134
135    /**
136     * @hide
137     */
138    protected Shader copy() {
139        final Shader copy = new Shader();
140        copyLocalMatrix(copy);
141        return copy;
142    }
143
144    /**
145     * @hide
146     */
147    protected void copyLocalMatrix(Shader dest) {
148        dest.mLocalMatrix.set(mLocalMatrix);
149    }
150
151    /**
152     * @hide
153     */
154    public long getNativeInstance() {
155        if (mNativeInstance == -1) {
156            throw new IllegalStateException("attempting to use a finalized Shader");
157        }
158
159        // verify mNativeInstance is valid
160        verifyNativeInstance();
161
162        if (mNativeInstance == 0) {
163            mNativeInstance = createNativeInstance(mLocalMatrix == null
164                    ? 0 : mLocalMatrix.native_instance);
165        }
166        return mNativeInstance;
167    }
168
169    private static native void nativeSafeUnref(long nativeInstance);
170}
171