1 /* 2 * Copyright (C) 2011 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 17 package android.view; 18 19 import android.graphics.Bitmap; 20 import android.graphics.Canvas; 21 import android.graphics.Matrix; 22 23 /** 24 * A hardware layer can be used to render graphics operations into a hardware 25 * friendly buffer. For instance, with an OpenGL backend, a hardware layer 26 * would use a Frame Buffer Object (FBO.) The hardware layer can be used as 27 * a drawing cache when a complex set of graphics operations needs to be 28 * drawn several times. 29 */ 30 abstract class HardwareLayer { 31 /** 32 * Indicates an unknown dimension (width or height.) 33 */ 34 static final int DIMENSION_UNDEFINED = -1; 35 36 int mWidth; 37 int mHeight; 38 39 boolean mOpaque; 40 41 /** 42 * Creates a new hardware layer with undefined dimensions. 43 */ HardwareLayer()44 HardwareLayer() { 45 this(DIMENSION_UNDEFINED, DIMENSION_UNDEFINED, false); 46 } 47 48 /** 49 * Creates a new hardware layer at least as large as the supplied 50 * dimensions. 51 * 52 * @param width The minimum width of the layer 53 * @param height The minimum height of the layer 54 * @param isOpaque Whether the layer should be opaque or not 55 */ HardwareLayer(int width, int height, boolean isOpaque)56 HardwareLayer(int width, int height, boolean isOpaque) { 57 mWidth = width; 58 mHeight = height; 59 mOpaque = isOpaque; 60 } 61 62 /** 63 * Returns the minimum width of the layer. 64 * 65 * @return The minimum desired width of the hardware layer 66 */ getWidth()67 int getWidth() { 68 return mWidth; 69 } 70 71 /** 72 * Returns the minimum height of the layer. 73 * 74 * @return The minimum desired height of the hardware layer 75 */ getHeight()76 int getHeight() { 77 return mHeight; 78 } 79 80 /** 81 * Returns whether or not this layer is opaque. 82 * 83 * @return True if the layer is opaque, false otherwise 84 */ isOpaque()85 boolean isOpaque() { 86 return mOpaque; 87 } 88 89 /** 90 * Indicates whether this layer can be rendered. 91 * 92 * @return True if the layer can be rendered into, false otherwise 93 */ isValid()94 abstract boolean isValid(); 95 96 /** 97 * Resize the layer, if necessary, to be at least as large 98 * as the supplied dimensions. 99 * 100 * @param width The new desired minimum width for this layer 101 * @param height The new desired minimum height for this layer 102 */ resize(int width, int height)103 abstract void resize(int width, int height); 104 105 /** 106 * Returns a hardware canvas that can be used to render onto 107 * this layer. 108 * 109 * @return A hardware canvas, or null if a canvas cannot be created 110 */ getCanvas()111 abstract HardwareCanvas getCanvas(); 112 113 /** 114 * Destroys resources without waiting for a GC. 115 */ destroy()116 abstract void destroy(); 117 118 /** 119 * This must be invoked before drawing onto this layer. 120 * @param currentCanvas 121 */ start(Canvas currentCanvas)122 abstract HardwareCanvas start(Canvas currentCanvas); 123 124 /** 125 * This must be invoked after drawing onto this layer. 126 * @param currentCanvas 127 */ end(Canvas currentCanvas)128 abstract void end(Canvas currentCanvas); 129 130 /** 131 * Copies this layer into the specified bitmap. 132 * 133 * @param bitmap The bitmap to copy they layer into 134 * 135 * @return True if the copy was successful, false otherwise 136 */ copyInto(Bitmap bitmap)137 abstract boolean copyInto(Bitmap bitmap); 138 139 /** 140 * Update the layer's properties. This method should be used 141 * when the underlying storage is modified by an external entity. 142 * To change the underlying storage, use the {@link #resize(int, int)} 143 * method instead. 144 * 145 * @param width The new width of this layer 146 * @param height The new height of this layer 147 * @param isOpaque Whether this layer is opaque 148 */ update(int width, int height, boolean isOpaque)149 void update(int width, int height, boolean isOpaque) { 150 mWidth = width; 151 mHeight = height; 152 mOpaque = isOpaque; 153 } 154 155 /** 156 * Sets an optional transform on this layer. 157 * 158 * @param matrix The transform to apply to the layer. 159 */ setTransform(Matrix matrix)160 abstract void setTransform(Matrix matrix); 161 } 162