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Java/ZZScene.java

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+/*   
+ZZScene.java
+ *    
+ *    Copyright (c) 2000, Ted Nelson and Tuomas Lukka
+ *
+ *    You may use and distribute under the terms of either the GNU Lesser
+ *    General Public License, either version 2 of the license or,
+ *    at your choice, any later version. Alternatively, you may use and
+ *    distribute under the terms of the XPL.
+ *
+ *    See the LICENSE.lgpl and LICENSE.xpl files for the specific terms of 
+ *    the licenses.
+ *
+ *    This software is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the README
+ *    file for more details.
+ *
+ */
+/*
+ * Written by Tuomas Lukka
+ */
+package org.gzigzag;
+import java.util.*;
+import java.awt.*;
+
+/** An interface for obtaining clicked -objects based on coordinates.
+ * This is what is given with mouse events.
+ */
+
+public interface ZZScene {
+String rcsid = "$Id: ZZScene.java,v 1.4 2000/09/19 10:31:58 ajk Exp $";
+
+    /** Get an identifying object for the given point on this canvas.
+     * This is one point where OO decoupling doesn't work properly:
+     * different things want to return different kinds of information:
+     * CellThings want to return the cell, TextSpans a VStream.Pos and so on.
+     */
+    Object getObjectAt(int x, int y);
+
+    /** Render this canvas, things interpolated with the given other canvas,
+     * on the given graphics context. 
+     * Interpolation is used for great advantage to show the user what the
+     * relationship between two different states is, i.e. which cells
+     * are the same. The modular nature of the ZZCanvas allows Things
+     * to define their own interpolation semantics: for example, by default,
+     * links are not rendered at all when interpolating and cells 
+     * are interpolated linearly.
+     */
+    void renderInterp(Graphics g, ZZScene other, float fract);
+
+
+    /** Paint a cursor-like thing using XOR.
+     * Originally intended for drawing a ghost cursor on text when
+     * moving the mouse in order to show where a click would put the cursor.
+     */
+    void renderXOR(Graphics g, int x, int y);
+
+    /** Is interpolation to the given canvas visually useful.
+     * This routine returns true if there is something in this canvas
+     * which will be seen animated when interpolating to the new canvas.
+     * For example, when only changing a dimension, some cells stay where
+     * they are and all the others are replaced by other cells (usually... 
+     * there are of course situations where some cells move on the screen
+     * when changing a dimension). In this case, the user is better served
+     * by not animating but simply displaying the new state as fast as
+     * possible.
+     */
+    boolean isInterpUseful(ZZScene s2);
+
+    /** Render this scene in the given graphics context.
+     */
+    void render(Graphics g);
+}