/*
* Copyright (C) 2010 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;
/**
* A display lists records a series of graphics related operation and can replay
* them later. Display lists are usually built by recording operations on a
* {@link android.graphics.Canvas}. Replaying the operations from a display list
* avoids executing views drawing code on every frame, and is thus much more
* efficient.
*
* @hide
*/
public abstract class DisplayList {
/**
* Starts recording the display list. All operations performed on the
* returned canvas are recorded and stored in this display list.
*
* @return A canvas to record drawing operations.
*/
abstract HardwareCanvas start();
/**
* Ends the recording for this display list. A display list cannot be
* replayed if recording is not finished.
*/
abstract void end();
/**
* Invalidates the display list, indicating that it should be repopulated
* with new drawing commands prior to being used again. Calling this method
* causes calls to {@link #isValid()} to return <code>false</code>.
*/
abstract void invalidate();
/**
* Returns whether the display list is currently usable. If this returns false,
* the display list should be re-recorded prior to replaying it.
*
* @return boolean true if the display list is able to be replayed, false otherwise.
*/
abstract boolean isValid();
/**
* Return the amount of memory used by this display list.
*
* @return The size of this display list in bytes
*/
abstract int getSize();
}