Clear WMS layer before redraw on OpenLayers

Question

I'm currently successfully displaying multiple layers using OpenLayers (Vector and WMS). My application allow the user to modify some parameters, which will :
* modify bound
* modify map center
* modify the WMS image
I use Ajax to avoid page reload, it works nicely, however when some layers take a while to load, the others which are not yet redrawn are still shown in the background (but aren't related at all to my new context). I would like to clear WMS layers (if possible) before re-asking the server for the new image but didn't find anything yet. I do this on the vector layer by calling removeAllFeature();

Thanks for any help !

Here is my pseudo-code when the user click the button :

$.getJSON("url/updateMapConfig.php",
    {  
      data: $(this).serialize() ,   
      ajax: 'true',   
      cache: 'false'  
    },   
    function(j){  
      if (j.result == 'ok') {  
        var layersToShow = [];  
        // Refresh vector layer  
        for(var i=0;i<map.layers.length;i++) {  
          if (map.layers[i].isVector) {  
            map.layers[i].removeAllFeatures();  
            map.layers[i].refresh({force:true}); // Vector layer  
          }   
        }  
        // Refresh visible layers  
        for(var i=0;i<map.layers.length;i++) {  
          if (map.layers[i].visibility && !map.layers[i].isBaseLayer && !map.layers[i].isVector) { // Refresh visible non base  
              map.layers[i].redraw(true); // Other layer  
          }  
        }  
        // Set new bounds  
        var bounds = new OpenLayers.Bounds();  
          bounds.extend(new OpenLayers.LonLat(j.bounds.xmin-100, j.bounds.ymin-100));  
          bounds.extend(new OpenLayers.LonLat(parseInt(j.bounds.xmax)+100, parseInt(j.bounds.ymax)+100));  
        map.zoomToExtent(bounds);  
        // Move to destination point  
        if (j.poiCenter != "") {  
          eval("map.setCenter(new OpenLayers.LonLat("+j.poiCenter+"))");  
        }  
      }  
    }  
);  

Answer 1

I finally found out an happy ending using the clearGrid() function on every layer before redrawing them.

I also found that this function will stop tile loading if any is running. Example I had two base layer : EmptyLayer and WhateverTiledBGLayer. if it tooks 20s to load WhateverTiledBGLayer tiles, even if the user chose to switch to empty layer, I could see the request done to the server for the remaining tiles on WhateverTiledBGLayer.

Simply calling WhateverTiledBGLayer.clearGrid() will stop requesting layers.

Thanks for help.