modules/midp-lcdui/src/main/java/cc/squirreljme/runtime/lcdui/gfx/DoubleBuffer.java

   1 // -*- Mode: Java; indent-tabs-mode: t; tab-width: 4 -*-
   2 // ---------------------------------------------------------------------------
   3 // SquirrelJME
   4 //     Copyright (C) Stephanie Gawroriski <xer@multiphasicapps.net>
   5 // ---------------------------------------------------------------------------
   6 // SquirrelJME is under the GNU General Public License v3+, or later.
   7 // See license.mkd for licensing and copyright information.
   8 // ---------------------------------------------------------------------------
   9
  10 package cc.squirreljme.runtime.lcdui.gfx;
  11
  12 import javax.microedition.lcdui.Graphics;
  13 import javax.microedition.lcdui.Image;
  14
  15 /**
  16  * This class implements a double buffered image which may be used for
  17  * graphics operations.
  18  *
  19  * @since 2022/02/25
  20  */
  21 public final class DoubleBuffer
  22 {
  23         /** The proxy for the off-screen graphics. */
  24         private final ProxyGraphicsTarget _offScreenProxy =
  25                 new ProxyGraphicsTarget(Image.createImage(1, 1)
  26                         .getGraphics());
  27
  28         /** The off-screen buffer. */
  29         private final SingleBuffer _offScreen;
  30
  31         /** The on-screen buffer. */
  32         private final SingleBuffer _onScreen;
  33
  34         /** The last used width. */
  35         private volatile int _lastWidth =
  36                 -1;
  37
  38         /** The last used height. */
  39         private volatile int _lastHeight =
  40                 -1;
  41
  42         /**
  43          * Initializes the double buffer.
  44          *
  45          * @param __resizeFillColor The color to set when resizing, this is to
  46          * prevent skewed graphics from appearing.
  47          * @since 2022/02/25
  48          */
  49         public DoubleBuffer(int __resizeFillColor)
  50         {
  51                 this._offScreen = new SingleBuffer(__resizeFillColor);
  52                 this._onScreen = new SingleBuffer(0);
  53         }
  54
  55         /**
  56          * Clears the off-screen buffer.
  57          *
  58          * @since 2022/02/25
  59          */
  60         public void clear()
  61         {
  62                 this._offScreen.clear();
  63         }
  64
  65         /**
  66          * Flushes the off-screen buffer to be on-screen.
  67          *
  68          * @since 2022/02/25
  69          */
  70         public void flush()
  71         {
  72                 this._onScreen.copyFrom(this._offScreen);
  73         }
  74
  75         /**
  76          * Returns a graphics object for drawing into the off-screen buffer.
  77          *
  78          * @param __width The buffer width.
  79          * @param __height The buffer height.
  80          * @return The graphics to draw onto the image.
  81          * @throws IllegalArgumentException If the width and/or height are invalid.
  82          * @since 2022/02/25
  83          */
  84         public Graphics getGraphics(int __width, int __height)
  85                 throws IllegalArgumentException
  86         {
  87                 // {@squirreljme.error EB32 Invalid buffer dimensions.}
  88                 if (__width <= 0 || __height <= 0)
  89                         throw new IllegalArgumentException("EB32");
  90
  91                 // We use the proxy regardless
  92                 ProxyGraphicsTarget proxy = this._offScreenProxy;
  93                 ProxyGraphics rv = new ProxyGraphics(proxy, __width, __height);
  94
  95                 // If the surface area has not changed, then we can freely use the same
  96                 // graphics object, this will help reduce load on double-buffered
  97                 // operations
  98                 int lastWidth = this._lastWidth;
  99                 int lastHeight = this._lastHeight;
 100                 if (__width == lastWidth && __height == lastHeight)
 101                         return rv;
 102
 103                 // Otherwise, remember our new screen space and use the graphics it
 104                 // produces
 105                 proxy.setGraphics(this._offScreen.getGraphics(__width, __height));
 106                 this._lastWidth = __width;
 107                 this._lastHeight = __height;
 108
 109                 return rv;
 110         }
 111
 112         /**
 113          * Paints the on-screen buffer onto the given graphics instance.
 114          *
 115          * @param __g The graphics to paint onto.
 116          * @since 2022/02/25
 117          */
 118         public void paint(Graphics __g)
 119         {
 120                 this._onScreen.paint(__g);
 121         }
 122 }