graphics/java/android/graphics/ComposeShader.java

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.graphics;

/** A subclass of shader that returns the composition of two other shaders, combined by
    an {@link android.graphics.Xfermode} subclass.
*/
public class ComposeShader extends Shader {

    private static final int TYPE_XFERMODE = 1;
    private static final int TYPE_PORTERDUFFMODE = 2;

    /**
     * Type of the ComposeShader: can be either TYPE_XFERMODE or TYPE_PORTERDUFFMODE
     */
    private int mType;

    private Xfermode mXferMode;
    private PorterDuff.Mode mPorterDuffMode;

    /**
     * Hold onto the shaders to avoid GC.
     */
    @SuppressWarnings({"UnusedDeclaration"})
    private final Shader mShaderA;
    @SuppressWarnings({"UnusedDeclaration"})
    private final Shader mShaderB;

    /** Create a new compose shader, given shaders A, B, and a combining mode.
        When the mode is applied, it will be given the result from shader A as its
        "dst", and the result from shader B as its "src".
        @param shaderA  The colors from this shader are seen as the "dst" by the mode
        @param shaderB  The colors from this shader are seen as the "src" by the mode
        @param mode     The mode that combines the colors from the two shaders. If mode
                        is null, then SRC_OVER is assumed.
    */
    public ComposeShader(Shader shaderA, Shader shaderB, Xfermode mode) {
        mType = TYPE_XFERMODE;
        mShaderA = shaderA;
        mShaderB = shaderB;
        mXferMode = mode;
        init(nativeCreate1(shaderA.getNativeInstance(), shaderB.getNativeInstance(),
                (mode != null) ? mode.native_instance : 0));
    }

    /** Create a new compose shader, given shaders A, B, and a combining PorterDuff mode.
        When the mode is applied, it will be given the result from shader A as its
        "dst", and the result from shader B as its "src".
        @param shaderA  The colors from this shader are seen as the "dst" by the mode
        @param shaderB  The colors from this shader are seen as the "src" by the mode
        @param mode     The PorterDuff mode that combines the colors from the two shaders.
    */
    public ComposeShader(Shader shaderA, Shader shaderB, PorterDuff.Mode mode) {
        mType = TYPE_PORTERDUFFMODE;
        mShaderA = shaderA;
        mShaderB = shaderB;
        mPorterDuffMode = mode;
        init(nativeCreate2(shaderA.getNativeInstance(), shaderB.getNativeInstance(),
                mode.nativeInt));
    }

    /**
     * @hide
     */
    @Override
    protected Shader copy() {
        final ComposeShader copy;
        switch (mType) {
            case TYPE_XFERMODE:
                copy = new ComposeShader(mShaderA.copy(), mShaderB.copy(), mXferMode);
                break;
            case TYPE_PORTERDUFFMODE:
                copy = new ComposeShader(mShaderA.copy(), mShaderB.copy(), mPorterDuffMode);
                break;
            default:
                throw new IllegalArgumentException(
                        "ComposeShader should be created with either Xfermode or PorterDuffMode");
        }
        copyLocalMatrix(copy);
        return copy;
    }

    private static native long nativeCreate1(long native_shaderA, long native_shaderB,
            long native_mode);
    private static native long nativeCreate2(long native_shaderA, long native_shaderB,
            int porterDuffMode);
}