add docs

vtm/src/org/oscim/utils/ScanBox.java

@@ -18,19 +18,26 @@ package org.oscim.utils;
 import org.oscim.core.Tile;
 
 /**
- * Scan-line fill algorithm to retrieve tile-coordinates.
+ * Scan-line fill algorithm to retrieve tile-coordinates from
+ * Viewport.
+ * <p>
+ * ScanBox is used to calculate tile coordinates that intersect the box (or
+ * trapezoid) which is the projection of screen bounds to the map. Usage:
  * 
- * ScanBox is used to calculate tile coordinates that intersect
+ * <pre>
- * the box (or trapezoid) which is the projection of screen
- * bounds to the map.
- *
- * use:
  * Viewport.getMapViewProjection(box)
- * yourScanBox.scan(pos.x, pos.y, pos.scale, zoomLevel, coords);
+ * 	ScanBox sb = new ScanBox(){
+ * 		@Override
+ *          protected void setVisible(int y, int x1, int x2) {
+ *          }
+ * 	};
+ * sb.scan(pos.x, pos.y, pos.scale, * zoomLevel, coords);
  * 
- * where zoomLevel is the zoom-level for which tile coordinates
+ * </pre>
- * should be calculated.
+ * 
- * */
+ * where zoomLevel is the zoom-level for which tile coordinates should be
+ * calculated.
+ */
 public abstract class ScanBox {
 
 	private final float[] mBox = new float[8];