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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.Bitmap;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Rect;
/**
* 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;
DisplayList mDisplayList;
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;
}
/**
* Update the paint used when drawing this layer.
*
* @param paint The paint used when the layer is drawn into the destination canvas.
* @see View#setLayerPaint(android.graphics.Paint)
*/
void setLayerPaint(Paint paint) { }
/**
* 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 the DisplayList for the layer.
*
* @return The DisplayList of the hardware layer
*/
DisplayList getDisplayList() {
return mDisplayList;
}
/**
* Sets the DisplayList for the layer.
*
* @param displayList The new DisplayList for this layer
*/
void setDisplayList(DisplayList displayList) {
mDisplayList = displayList;
}
/**
* Returns whether or not this layer is opaque.
*
* @return True if the layer is opaque, false otherwise
*/
boolean isOpaque() {
return mOpaque;
}
/**
* Sets whether or not this layer should be considered opaque.
*
* @param isOpaque True if the layer is opaque, false otherwise
*/
abstract void setOpaque(boolean isOpaque);
/**
* Indicates whether this layer can be rendered.
*
* @return True if the layer can be rendered into, false otherwise
*/
abstract boolean isValid();
/**
* Resize 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
* @return True if the resulting layer is valid, false otherwise
*/
abstract boolean 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
*
* @see #start(android.graphics.Canvas)
* @see #end(android.graphics.Canvas)
*/
abstract HardwareCanvas getCanvas();
/**
* Destroys resources without waiting for a GC.
*/
abstract void destroy();
/**
* This must be invoked before drawing onto this layer.
*
* @param currentCanvas The canvas whose rendering needs to be interrupted
*/
abstract HardwareCanvas start(Canvas currentCanvas);
/**
* This must be invoked before drawing onto this layer.
*
* @param dirty The dirty area to repaint
* @param currentCanvas The canvas whose rendering needs to be interrupted
*/
abstract HardwareCanvas start(Canvas currentCanvas, Rect dirty);
/**
* This must be invoked after drawing onto this layer.
*
* @param currentCanvas The canvas whose rendering needs to be resumed
*/
abstract void end(Canvas currentCanvas);
/**
* Copies this layer into the specified bitmap.
*
* @param bitmap The bitmap to copy they layer into
*
* @return True if the copy was successful, false otherwise
*/
abstract boolean copyInto(Bitmap bitmap);
/**
* Update the layer's properties. This method should be used
* when the underlying storage is modified by an external entity.
* To change the underlying storage, use the {@link #resize(int, int)}
* method instead.
*
* @param width The new width of this layer
* @param height The new height of this layer
* @param isOpaque Whether this layer is opaque
*/
void update(int width, int height, boolean isOpaque) {
mWidth = width;
mHeight = height;
mOpaque = isOpaque;
}
/**
* Sets an optional transform on this layer.
*
* @param matrix The transform to apply to the layer.
*/
abstract void setTransform(Matrix matrix);
/**
* Specifies the display list to use to refresh the layer.
*
* @param displayList The display list containing the drawing commands to
* execute in this layer
* @param dirtyRect The dirty region of the layer that needs to be redrawn
*/
abstract void redrawLater(DisplayList displayList, Rect dirtyRect);
/**
* Indicates that this layer has lost its underlying storage.
*/
abstract void clearStorage();
}
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