New private movePyPx method to avoid going through all the unnecessary pixel-lonlat conversions. p=elemoine,me (closes #3062)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@11535 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/EventPane.js

@@ -211,6 +211,22 @@ OpenLayers.Layer.EventPane = OpenLayers.Class(OpenLayers.Layer, {
         OpenLayers.Layer.prototype.setZIndex.apply(this, arguments);
         this.pane.style.zIndex = parseInt(this.div.style.zIndex) + 1;
     },
+    
+    /**
+     * Method: moveByPx
+     * Move the layer based on pixel vector. To be implemented by subclasses.
+     *
+     * Parameters:
+     * dx - {Number} The x coord of the displacement vector.
+     * dy - {Number} The y coord of the displacement vector.
+     */
+    moveByPx: function(dx, dy) {
+        OpenLayers.Layer.prototype.moveByPx.apply(this, arguments);
+        
+        if (this.dragPanMapObject) {
+            this.dragPanMapObject(dx, -dy);
+        }
+    },
 
     /**
      * Method: moveTo

lib/OpenLayers/Layer/Grid.js

@@ -251,19 +251,37 @@ OpenLayers.Layer.Grid = OpenLayers.Class(OpenLayers.Layer.HTTPRequest, {
                 if (forceReTile || !tilesBounds.containsBounds(bounds, true)) {
                     this.initGriddedTiles(bounds);
                 } else {
-                    // we might have to shift our buffer tiles, schedule
-                    // that
-                    if (this.timerId != null) {
-                        window.clearTimeout(this.timerId);
-                    }
-                    this.timerId = window.setTimeout(
-                        this._moveGriddedTiles,
-                        this.tileLoadingDelay
-                    );
+                    this.scheduleMoveGriddedTiles();
                 }
             }
         }
     },
+
+    /**
+     * Method: moveByPx
+     * Move the layer based on pixel vector.
+     *
+     * Parameters:
+     * dx - {Number}
+     * dy - {Number}
+     */
+    moveByPx: function(dx, dy) {
+        this.scheduleMoveGriddedTiles();
+    },
+
+    /**
+     * Method: scheduleMoveGriddedTiles
+     * Schedule the move of tiles.
+     */
+    scheduleMoveGriddedTiles: function() {
+        if (this.timerId != null) {
+            window.clearTimeout(this.timerId);
+        }
+        this.timerId = window.setTimeout(
+            this._moveGriddedTiles,
+            this.tileLoadingDelay
+        );
+    },
     
     /**
      * APIMethod: setTileSize
@@ -682,7 +700,9 @@ OpenLayers.Layer.Grid = OpenLayers.Class(OpenLayers.Layer.HTTPRequest, {
         var shifted = true;
         var buffer = this.buffer || 1;
         var tlLayer = this.grid[0][0].position;
-        var tlViewPort = this.map.getViewPortPxFromLayerPx(tlLayer);
+        var offsetX = parseInt(this.map.layerContainerDiv.style.left);
+        var offsetY = parseInt(this.map.layerContainerDiv.style.top);
+        tlViewPort = tlLayer.add(offsetX, offsetY);
         if (tlViewPort.x > -this.tileSize.w * (buffer - 1)) {
             this.shiftColumn(true);
         } else if (tlViewPort.x < -this.tileSize.w * buffer) {