[OpenLayers-Trac] Re: [OpenLayers] #3419: Tile simplifications and partial rewrite

[OpenLayers]

#3419: Tile simplifications and partial rewrite
----------------------+-----------------------------------------------------
 Reporter:  ahocevar  |       Owner:  ahocevar    
     Type:  feature   |      Status:  new         
 Priority:  minor     |   Milestone:  2.12 Release
Component:  Tile      |     Version:  2.10        
 Keywords:            |       State:  Review      
----------------------+-----------------------------------------------------

Comment(by erilem):

 Andreas, here's the the {{{updateBackBuffer}}} implementation I've come up
 to. I find it more clear than previously. Tell me what you think. I still
 need to update the tests, and a few things here and there.

 {{{
     /**
      *
      */
     _updateBackBuffer: function() {
         var map = this.layer.map,
             bbData = this.bbData,
             resolution = bbData.resolution;

         // if we have no back buffer data we can't display a back buffer
         if(!resolution) {
             this.setBackBufferData();
             return;
         }

         var ratio = resolution / map.getResolution();

         // now given the back buffer mode determine if we do need
         // to display a back buffer for this ratio
         var backBufferNeeded = ratio === 1 ? this.backBufferMode & 1 :
                                              this.backBufferMode & 2;
         if(!backBufferNeeded) {
             this.setBackBufferData();
             return;
         }

         var bb = this.insertBackBuffer();

         // best effort - if for whatever reason the back buffer
         // couldn't be created or inserted into the DOM  we just
         // update our state and bail out.

         if(!bb) {
             this.setBackBufferData();
             return;
         }

         // Hooray, we have a back buffer and a ratio, we
         // can position and scale the back buffer.

         var pos = map.getPixelFromLonLat({
             lon: bbData.bounds.left,
             lat: bbData.bounds.top});
         var containerStyle = map.layerContainerDiv.style;
         var loffset = parseInt(containerStyle.left, 10);
         var toffset = parseInt(containerStyle.top, 10);
         var style = bb.style;
         style.left = (pos.x - loffset) + "px";
         style.top = (pos.y - toffset) + "px";
         style.width = (this.size.w * ratio) + "px";
         style.height = (this.size.h * ratio) + "px";
     },
 }}}

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Ticket URL: <http://trac.openlayers.org/ticket/3419#comment:25>
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