Particles2D: set emitting if not set before generating Visibility Rect

and removed not needed running zeroing
 in ParticlesEditor::_generate_aabb

editor/plugins/particles_2d_editor_plugin.cpp

@@ -68,6 +68,11 @@ void Particles2DEditorPlugin::_menu_callback(int p_idx) {
 
 	switch (p_idx) {
 		case MENU_GENERATE_VISIBILITY_RECT: {
+			float gen_time = particles->get_lifetime();
+			if (gen_time < 1.0)
+				generate_seconds->set_value(1.0);
+			else
+				generate_seconds->set_value(trunc(gen_time) + 1.0);
 			generate_aabb->popup_centered_minsize();
 		} break;
 		case MENU_LOAD_EMISSION_MASK: {
@@ -90,6 +95,12 @@ void Particles2DEditorPlugin::_generate_visibility_rect() {
 
 	EditorProgress ep("gen_aabb", TTR("Generating AABB"), int(time));
 
+	bool was_emitting = particles->is_emitting();
+	if (!was_emitting) {
+		particles->set_emitting(true);
+		OS::get_singleton()->delay_usec(1000);
+	}
+
 	Rect2 rect;
 	while (running < time) {
 
@@ -106,6 +117,10 @@ void Particles2DEditorPlugin::_generate_visibility_rect() {
 		running += (OS::get_singleton()->get_ticks_usec() - ticks) / 1000000.0;
 	}
 
+	if (!was_emitting) {
+		particles->set_emitting(false);
+	}
+
 	particles->set_visibility_rect(rect);
 }
 

editor/plugins/particles_editor_plugin.cpp

@@ -335,7 +335,6 @@ void ParticlesEditor::_generate_aabb() {
 		OS::get_singleton()->delay_usec(1000);
 	}
 
-	running = 0.0;
 	AABB rect;
 
 	while (running < time) {