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/*
* Copyright (C) 2011 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.view;
import android.graphics.Canvas;
/**
* A hardware layer can be used to render graphics operations into a hardware
* friendly buffer. For instance, with an OpenGL backend, a hardware layer
* would use a Frame Buffer Object (FBO.) The hardware layer can be used as
* a drawing cache when a complex set of graphics operations needs to be
* drawn several times.
*/
abstract class HardwareLayer {
/**
* Indicates an unknown dimension (width or height.)
*/
static final int DIMENSION_UNDEFINED = -1;
int mWidth;
int mHeight;
final boolean mOpaque;
/**
* Creates a new hardware layer with undefined dimensions.
*/
HardwareLayer() {
this(DIMENSION_UNDEFINED, DIMENSION_UNDEFINED, false);
}
/**
* Creates a new hardware layer at least as large as the supplied
* dimensions.
*
* @param width The minimum width of the layer
* @param height The minimum height of the layer
* @param isOpaque Whether the layer should be opaque or not
*/
HardwareLayer(int width, int height, boolean isOpaque) {
mWidth = width;
mHeight = height;
mOpaque = isOpaque;
}
/**
* Returns the minimum width of the layer.
*
* @return The minimum desired width of the hardware layer
*/
int getWidth() {
return mWidth;
}
/**
* Returns the minimum height of the layer.
*
* @return The minimum desired height of the hardware layer
*/
int getHeight() {
return mHeight;
}
/**
* Returns whether or not this layer is opaque.
*
* @return True if the layer is opaque, false otherwise
*/
boolean isOpaque() {
return mOpaque;
}
/**
* Indicates whether this layer can be rendered.
*
* @return True if the layer can be rendered into, false otherwise
*/
abstract boolean isValid();
/**
* Resizes the layer, if necessary, to be at least as large
* as the supplied dimensions.
*
* @param width The new desired minimum width for this layer
* @param height The new desired minimum height for this layer
*/
abstract void resize(int width, int height);
/**
* Returns a hardware canvas that can be used to render onto
* this layer.
*
* @return A hardware canvas, or null if a canvas cannot be created
*/
abstract HardwareCanvas getCanvas();
/**
* Destroys resources without waiting for a GC.
*/
abstract void destroy();
/**
* This must be invoked before drawing onto this layer.
* @param currentCanvas
*/
abstract HardwareCanvas start(Canvas currentCanvas);
/**
* This must be invoked after drawing onto this layer.
* @param currentCanvas
*/
abstract void end(Canvas currentCanvas);
}
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