title: Angular UI Grid - Filter on display values within registerRowsProcessor
body: <p>We have a requirement to filter the contents of a grid using values/inputs that are not embedded into the UI Grid Column headers. The filtering must occur on the values that are displayed or in other word have been "filtered" for presentment.  I have been able to successfully filter on values that don't have a cellFilter specified by specifying a filter method using the registerRowsProcessor.</p>
  
  <pre><code>$scope.externalFilterImpl = ( renderableRows ) =&gt; {
      if($scope.externalFilterValues.name.length&gt;0)
      {
          // Case insensitive matching
          var matcher = new RegExp($scope.externalFilterValues.name, "i");
          renderableRows.forEach( function( row ) {
              var match = false;
              debugger;
              if ( row.entity["id"].match(matcher) ){
              //var value = $scope.gridApi.grid.getCellDisplayValue(row, "id");
              //if ( value.match(matcher) ){
                  match = true;
              }
              if ( !match ){
                  row.visible = false;
              }
          });
      }
  
  
      return renderableRows;
  };
  </code></pre>
  
  <p>The code expects to filter on the display value (filtered value) for the column with the columnDef field property of "id". The columnDef for "id" appears as follows:</p>
  
  <pre><code>        {
              field: "id",
              cellClass: "cellContent",
              displayName: $translate.instant('tableHeading.item'),
              enableColumnMenu: false,
              enableHiding: false,
              suppressRemoveSort: true,
              filter: {
                  placeholder: "Enter a name search"
              },      
              cellFilter: 'translateIds:"itemIds"', 
              filterCellFiltered:true, 
              sortCellFiltered:true,                           
              sort: {
                  direction: uiGridConstants.ASC,
                  priority: 0,
              },                
              cellTemplate: `&lt;div class="ui-grid-cell-contents"&gt;
                          {{COL_FIELD CUSTOM_FILTERS}}
                      &lt;/div&gt;`
          }
  </code></pre>
  
  <p>Any assistance would be greatly appreciated.</p>