Added ability to import multiple files (#2439)

* allow import multiple files at once

* added bool allow_multiple_selection for backwards compatability

* made dialog_open_fil_ext a private method

* all imported files selected in layers list

synfig-studio/src/gui/app.cpp

@@ -2343,7 +2343,7 @@ gint Signal_Open_Ok    (GtkWidget */*widget*/, int *val){*val=1; return 0;}
 gint Signal_Open_Cancel(GtkWidget */*widget*/, int *val){*val=2; return 0;}
 
 bool
-App::dialog_open_file(const std::string &title, std::string &filename, std::string preference)
+App::dialog_open_file_ext(const std::string &title, std::vector<std::string> &filenames, std::string preference, bool allow_multiple_selection)
 {
 	// info("App::dialog_open_file('%s', '%s', '%s')", title.c_str(), filename.c_str(), preference.c_str());
 	// TODO: Win32 native dialod not ready yet
@@ -2402,6 +2402,7 @@ App::dialog_open_file(const std::string &title, std::string &filename, std::stri
 	dialog->set_current_folder(prev_path);
 	dialog->add_button(_("Cancel"), Gtk::RESPONSE_CANCEL)->set_image_from_icon_name("gtk-cancel", Gtk::ICON_SIZE_BUTTON);
 	dialog->add_button(_("Import"), Gtk::RESPONSE_ACCEPT)->set_image_from_icon_name("gtk-open",   Gtk::ICON_SIZE_BUTTON);
+	dialog->set_select_multiple(allow_multiple_selection);
 
 	// 0 All supported files
 	// 0.1 Synfig documents. sfg is not supported to import
@@ -2503,29 +2504,48 @@ App::dialog_open_file(const std::string &title, std::string &filename, std::stri
 	dialog->add_filter(filter_video);
 	dialog->add_filter(filter_lipsync);
 	dialog->add_filter(filter_any);
-	
+
 	dialog->set_extra_widget(*scale_imported_box());
 
-	if (filename.empty())
+	if (filenames.empty())
 		dialog->set_filename(prev_path);
-	else if (is_absolute_path(filename))
-		dialog->set_filename(filename);
+	else if (is_absolute_path(filenames.front()))
+		dialog->set_filename(filenames.front());
 	else
-		dialog->set_filename(prev_path + ETL_DIRECTORY_SEPARATOR + filename);
+		dialog->set_filename(prev_path + ETL_DIRECTORY_SEPARATOR + filenames.front());
 
 	if(dialog->run() == Gtk::RESPONSE_ACCEPT) {
-		filename = dialog->get_filename();
-		// info("Saving preference %s = '%s' in App::dialog_open_file()", preference.c_str(), dirname(filename).c_str());
-		_preferences.set_value(preference, dirname(filename));
+		filenames = dialog->get_filenames();
+		if(!filenames.empty()){
+			// info("Saving preference %s = '%s' in App::dialog_open_file()", preference.c_str(), dirname(filename).c_str());
+			_preferences.set_value(preference, dirname(filenames.front()));
+		}
 		delete dialog;
 		return true;
 	}
-
 	delete dialog;
 	return false;
 #endif   // not USE_WIN32_FILE_DIALOGS
 }
 
+bool
+App::dialog_open_file(const std::string &title, std::string &filename, std::string preference)
+{
+	std::vector<std::string> filenames;
+	if (!filename.empty())
+        filenames.push_back(filename);
+	if(dialog_open_file_ext(title, filenames, preference, false)) {
+		filename = filenames.front();
+		return true;
+	}
+	return false;
+}
+
+bool App::dialog_open_file(const std::string &title, std::vector<std::string> &filenames, std::string preference)
+{
+	return dialog_open_file_ext(title, filenames, preference, true);
+}
+
 bool
 App::dialog_open_file_spal(const std::string &title, std::string &filename, std::string preference)
 {

synfig-studio/src/gui/app.h

@@ -307,6 +307,7 @@ class App : public Gtk::Main, private IconController
 
 private:
 	static void add_recent_file(const std::string &filename, bool emit_signal);
+	static bool dialog_open_file_ext(const std::string &title, std::vector<std::string> &filenames, std::string preference, bool allow_multiple_selection);
 
 	/*
  -- ** -- P U B L I C   M E T H O D S -----------------------------------------
@@ -416,6 +417,7 @@ class App : public Gtk::Main, private IconController
 
 	static bool dialog_select_importer(const std::string& filename, std::string& plugin);
 	static bool dialog_open_file(const std::string &title, std::string &filename, std::string preference);
+	static bool dialog_open_file(const std::string &title, std::vector<std::string> &filenames, std::string preference);
 	static bool dialog_open_file_spal(const std::string &title, std::string &filename, std::string preference);
 	static bool dialog_open_file_sketch(const std::string &title, std::string &filename, std::string preference);
 	static bool dialog_open_file_image(const std::string &title, std::string &filename, std::string preference);

synfig-studio/src/gui/canvasview.cpp

@@ -3570,10 +3570,13 @@ void
 CanvasView::import_file()
 {
 	// String filename(dirname(get_canvas()->get_file_name()));
-	String filename("*.*");
+	std::vector<std::string> filenames;
+	LayerTree::LayerList layers;
+	filenames.push_back("*.*");
 	String errors, warnings;
-	if(App::dialog_open_file(_("Please select files"), filename, IMAGE_DIR_PREFERENCE))
+	if(App::dialog_open_file(_("Please select files"), filenames, IMAGE_DIR_PREFERENCE))
 	{
+		for(const std::string &filename : filenames){
 		// Don't let user import a file to itself
 		// Check if it's the same file of this canvas
 		{
@@ -3621,10 +3624,12 @@ CanvasView::import_file()
 				_("Close"));
 
 		if (layer) {
-			get_selection_manager()->clear_selected_layers();
-			get_selection_manager()->set_selected_layer(layer);
+			layers.push_back(layer);
 		}
 	}
+	get_selection_manager()->clear_selected_layers();
+	get_selection_manager()->set_selected_layers(layers);
+	}
 }
 
 void