Using Steves threadsafe DCRAW to roughly double thumbnail generation speed on multicore CPUs. Now there are two update worker threads. Easy to remove if someone provides code for a more efficient distribution mechanism.

rtgui/filecatalog.cc

@@ -970,3 +970,25 @@ bool FileCatalog::handleShortcutKey (GdkEventKey* event) {
     return false;
 }
 
+void PreviewMultiLoader::setPreviewLoaderListener (PreviewLoaderListener* p) { 
+	loadA.setPreviewLoaderListener(p); loadB.setPreviewLoaderListener(p);
+}
+
+// Simple round robin
+void PreviewMultiLoader::add(DirEntry de) {
+	if (next==0) {
+		loadA.add(de);
+		next=1;
+	} else {
+		loadB.add(de);
+		next=0;
+	}
+}
+
+void PreviewMultiLoader::start () { loadA.start(); loadB.start(); }
+void PreviewMultiLoader::process () { loadA.process (); loadB.process(); }
+void PreviewMultiLoader::remove  (Glib::ustring fname) { loadA.remove(fname); loadB.remove(fname); }
+void PreviewMultiLoader::end () { loadA.end(); loadB.end(); }
+bool PreviewMultiLoader::runs () { return loadA.runs() || loadB.runs(); }
+void PreviewMultiLoader::terminate () { loadA.terminate(); loadB.terminate(); }
+void PreviewMultiLoader::stop () { loadA.stop(); loadB.stop(); }