comparison framework/Document.h @ 371:dfcc5b355f33

Merge from branch warnfix_no_size_t

      * the same order as the transforms are supplied.
      */
     std::vector<Layer *> createDerivedLayers(const Transforms &,
                                              const ModelTransformer::Input &);
 
+    typedef void *LayerCreationAsyncHandle;
+
     class LayerCreationHandler {
     public:
         virtual ~LayerCreationHandler() { }
 
         /**
          * The primary layers are those corresponding 1-1 to the input
          * models, listed in the same order as the input models. The
          * additional layers vector contains any layers (from all
          * models) that were returned separately at the end of
-         * processing.
+         * processing. The handle indicates which async process this
+         * callback was initiated by. It must not be used again after
+         * this function returns.
          */
-        virtual void layersCreated(std::vector<Layer *> primary,
+        virtual void layersCreated(LayerCreationAsyncHandle handle,
+                                   std::vector<Layer *> primary,
                                    std::vector<Layer *> additional) = 0;
     };
 
     /**
      * Create suitable layers for the given transforms, which must be
      * identical apart from the output (i.e. must use the same plugin
      * and configuration). This method returns after initialising the
      * transformer process, and the layers are returned through a
-     * subsequent call to the provided handler (which must be non-null).
-     */
-    void createDerivedLayersAsync(const Transforms &,
-                                  const ModelTransformer::Input &,
-                                  LayerCreationHandler *handler);
+     * subsequent call to the provided handler (which must be
+     * non-null). The handle returned will be passed through to the
+     * handler callback, and may be also used for cancelling the task.
+     */
+    LayerCreationAsyncHandle createDerivedLayersAsync(const Transforms &,
+                                                      const ModelTransformer::Input &,
+                                                      LayerCreationHandler *handler);
+
+    /**
+     * Indicate that the async layer creation task associated with the
+     * given handle should be cancelled. There is no guarantee about
+     * what this will mean, and the handler callback may still be
+     * called.
+     */
+    void cancelAsyncLayerCreation(LayerCreationAsyncHandle handle);
 
     /**
      * Delete the given layer, and also its associated model if no
      * longer used by any other layer.  In general, this should be the
      * only method used to delete layers -- doing so directly is a bit