Added Javadoc to TbtQuadComponent Please review whether the part about "all coordinates are relative to the lower-left border" is correct.

lemur-patch-javadoc

Index: com/simsilica/lemur/component/TbtQuadBackgroundComponent.java
===================================================================
--- com/simsilica/lemur/component/TbtQuadBackgroundComponent.java       (Revision 1008)
+++ com/simsilica/lemur/component/TbtQuadBackgroundComponent.java       (Arbeitskopie)
@@ -45,10 +45,45 @@
 import com.simsilica.lemur.core.GuiMaterial;
 import com.simsilica.lemur.geom.TbtQuad;
 
-
 /**
- *
- *  @author    Paul Speed
+ * A texture-covered background quad.<br>
+ * The texture is split up into a three-by-three grid in this fashion:
+ * 
+ * <pre>
+ *    +---+--------------+-------+
+ *    |   |    <----->   |       |
+ * y2 +---+--------------+-------+
+ *    |   |              |       |
+ *    | ^ |       ^      |   ^   |
+ *    | | |       |      |   |   |
+ *    | | |    <----->   |   |   |
+ *    | | |       |      |   |   |
+ *    | v |       v      |   v   |
+ *    |   |              |       |
+ * y1 +---+--------------+-------+
+ *    |   |    <----->   |       |
+ *    +---+--------------+-------+
+ *       x1             x2
+ * </pre>
+ * 
+ * Arrows indicate the direction in which each grid cell will stretch to fill
+ * the area given by the component.<br>
+ * All coordinates are relative to the lower-left border.
+ * <p>
+ * <b>Common pitfalls</b>
+ * <ul>
+ * <li>Placing controls on a fractional coordinate. This usually happens when
+ * centering controls.
+ * <li>Having a contrast at the border between stretched and unstretched texture
+ * zone (e.g. a black border and a white center). Stretching involves
+ * interpolating colors with the neighbouring pixels (i.e. you'll get a
+ * black-to-white color gradient).<br>
+ * The easiest workaround is to make the border one pixel wider so that the
+ * contrast will be safely inside the unstretched area.
+ * <li>Using a texture that is larger than the quad.
+ * </ul>
+ * 
+ * @author Paul Speed, Joachim "Toolforger" Durchholz (Javadoc)
  */
 public class TbtQuadBackgroundComponent extends AbstractGuiComponent 
                                         implements Cloneable, ColoredComponent