Tile.Image improvements and partial rewrite. Thanks erilem for the excellent collaboration during the review phase. p=me,erilem r=erilem (closes #3419)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@12241 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Tile.js

@@ -77,7 +77,7 @@ OpenLayers.Tile = OpenLayers.Class({
      * {<OpenLayers.Pixel>} Top Left pixel of the tile
      */    
     position: null,
-
+    
     /**
      * Property: isLoading
      * {Boolean} Is the tile loading?
@@ -143,54 +143,38 @@ OpenLayers.Tile = OpenLayers.Class({
         this.events = null;
     },
     
-    /**
-     * Method: clone
-     *
-     * Parameters:
-     * obj - {<OpenLayers.Tile>} The tile to be cloned
-     *
-     * Returns:
-     * {<OpenLayers.Tile>} An exact clone of this <OpenLayers.Tile>
-     */
-    clone: function (obj) {
-        if (obj == null) {
-            obj = new OpenLayers.Tile(this.layer, 
-                                      this.position, 
-                                      this.bounds, 
-                                      this.url, 
-                                      this.size);
-        } 
-        
-        // catch any randomly tagged-on properties
-        OpenLayers.Util.applyDefaults(obj, this);
-        
-        return obj;
-    },
-
     /**
      * Method: draw
      * Clear whatever is currently in the tile, then return whether or not 
-     *     it should actually be re-drawn.
+     *     it should actually be re-drawn. This is an example implementation
+     *     that can be overridden by subclasses. The minimum thing to do here
+     *     is to call <clear> and return the result from <shouldDraw>.
      * 
      * Returns:
-     * {Boolean} Whether or not the tile should actually be drawn. Note that 
-     *     this is not really the best way of doing things, but such is 
-     *     the way the code has been developed. Subclasses call this and
-     *     depend on the return to know if they should draw or not.
+     * {Boolean} Whether or not the tile should actually be drawn.
      */
     draw: function() {
-        var maxExtent = this.layer.maxExtent;
-        var withinMaxExtent = (maxExtent &&
-                               this.bounds.intersectsBounds(maxExtent, false));
- 
-        // The only case where we *wouldn't* want to draw the tile is if the 
-        // tile is outside its layer's maxExtent.
-        this.shouldDraw = (withinMaxExtent || this.layer.displayOutsideMaxExtent);
-                
         //clear tile's contents and mark as not drawn
         this.clear();
         
-        return this.shouldDraw;
+        return this.shouldDraw();
+    },
+    
+    /**
+     * Method: shouldDraw
+     * Return whether or not the tile should actually be (re-)drawn. The only
+     * case where we *wouldn't* want to draw the tile is if the tile is outside
+     * its layer's maxExtent
+     * 
+     * Returns:
+     * {Boolean} Whether or not the tile should actually be drawn.
+     */
+    shouldDraw: function() {
+        var maxExtent = this.layer.maxExtent;
+        var withinMaxExtent = (maxExtent &&
+                               this.bounds.intersectsBounds(maxExtent, false));
+        
+        return withinMaxExtent || this.layer.displayOutsideMaxExtent;
     },
     
     /** 
@@ -220,7 +204,7 @@ OpenLayers.Tile = OpenLayers.Class({
      * Clear the tile of any bounds/position-related data so that it can 
      *     be reused in a new location. To be implemented by subclasses.
      */
-    clear: function() {
+    clear: function(draw) {
         // to be implemented by subclasses
     },
     
@@ -260,29 +244,7 @@ OpenLayers.Tile = OpenLayers.Class({
                                        bottomRight.lon, 
                                        topLeft.lat);  
         return bounds;
-    },        
-        
-    /** 
-     * Method: showTile
-     * Show the tile only if it should be drawn.
-     */
-    showTile: function() { 
-        if (this.shouldDraw) {
-            this.show();
-        }
     },
     
-    /** 
-     * Method: show
-     * Show the tile.  To be implemented by subclasses.
-     */
-    show: function() { },
-    
-    /** 
-     * Method: hide
-     * Hide the tile.  To be implemented by subclasses.
-     */
-    hide: function() { },
-    
     CLASS_NAME: "OpenLayers.Tile"
 });