Add ability to set submenu's popup delay time on mouse hovering

This allows to set delay time for the submenu to popup. Setting
this value low can increase responsiveness. If the popup menu is added
as a child of another (acting as a submenu), it will inherit the delay
time of the parent menu item.

doc/classes/PopupMenu.xml

@@ -507,6 +507,9 @@
 		</member>
 		<member name="hide_on_state_item_selection" type="bool" setter="set_hide_on_state_item_selection" getter="is_hide_on_state_item_selection">
 		</member>
+		<member name="submenu_popup_delay" type="real" setter="set_submenu_popup_delay" getter="get_submenu_popup_delay">
+			Sets the delay time for the submenu item to popup on mouse hovering. If the popup menu is added as a child of another (acting as a submenu), it will inherit the delay time of the parent menu item. Default value: [code]0.3[/code] seconds.
+		</member>
 	</members>
 	<signals>
 		<signal name="id_focused">

scene/gui/popup_menu.cpp

@@ -398,6 +398,15 @@ void PopupMenu::_notification(int p_what) {
 
 	switch (p_what) {
 
+		case NOTIFICATION_ENTER_TREE: {
+
+			PopupMenu *pm = Object::cast_to<PopupMenu>(get_parent());
+			if (pm) {
+				// Inherit submenu's popup delay time from parent menu
+				float pm_delay = pm->get_submenu_popup_delay();
+				set_submenu_popup_delay(pm_delay);
+			}
+		} break;
 		case NOTIFICATION_TRANSLATION_CHANGED: {
 
 			for (int i = 0; i < items.size(); i++) {
@@ -1201,6 +1210,19 @@ bool PopupMenu::is_hide_on_multistate_item_selection() const {
 	return hide_on_multistate_item_selection;
 }
 
+void PopupMenu::set_submenu_popup_delay(float p_time) {
+
+	if (p_time <= 0)
+		p_time = 0.01;
+
+	submenu_timer->set_wait_time(p_time);
+}
+
+float PopupMenu::get_submenu_popup_delay() const {
+
+	return submenu_timer->get_wait_time();
+}
+
 String PopupMenu::get_tooltip(const Point2 &p_pos) const {
 
 	int over = _get_mouse_over(p_pos);
@@ -1303,12 +1325,15 @@ void PopupMenu::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_hide_on_state_item_selection", "enable"), &PopupMenu::set_hide_on_multistate_item_selection);
 	ClassDB::bind_method(D_METHOD("is_hide_on_state_item_selection"), &PopupMenu::is_hide_on_multistate_item_selection);
 
+	ClassDB::bind_method(D_METHOD("set_submenu_popup_delay", "seconds"), &PopupMenu::set_submenu_popup_delay);
+	ClassDB::bind_method(D_METHOD("get_submenu_popup_delay"), &PopupMenu::get_submenu_popup_delay);
 	ClassDB::bind_method(D_METHOD("_submenu_timeout"), &PopupMenu::_submenu_timeout);
 
 	ADD_PROPERTY(PropertyInfo(Variant::ARRAY, "items", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NOEDITOR | PROPERTY_USAGE_INTERNAL), "_set_items", "_get_items");
 	ADD_PROPERTYNO(PropertyInfo(Variant::BOOL, "hide_on_item_selection"), "set_hide_on_item_selection", "is_hide_on_item_selection");
 	ADD_PROPERTYNO(PropertyInfo(Variant::BOOL, "hide_on_checkable_item_selection"), "set_hide_on_checkable_item_selection", "is_hide_on_checkable_item_selection");
 	ADD_PROPERTYNO(PropertyInfo(Variant::BOOL, "hide_on_state_item_selection"), "set_hide_on_state_item_selection", "is_hide_on_state_item_selection");
+	ADD_PROPERTY(PropertyInfo(Variant::REAL, "submenu_popup_delay"), "set_submenu_popup_delay", "get_submenu_popup_delay");
 
 	ADD_SIGNAL(MethodInfo("id_pressed", PropertyInfo(Variant::INT, "ID")));
 	ADD_SIGNAL(MethodInfo("id_focused", PropertyInfo(Variant::INT, "ID")));

scene/gui/popup_menu.h

@@ -202,6 +202,9 @@ public:
 	void set_hide_on_multistate_item_selection(bool p_enabled);
 	bool is_hide_on_multistate_item_selection() const;
 
+	void set_submenu_popup_delay(float p_time);
+	float get_submenu_popup_delay() const;
+
 	virtual void popup(const Rect2 &p_bounds = Rect2());
 
 	PopupMenu();