BaseButton: multitouch support

doc/classes/Button.xml

@@ -33,7 +33,7 @@
 		[/csharp]
 		[/codeblocks]
 		See also [BaseButton] which contains common properties and methods associated with this node.
-		[b]Note:[/b] Buttons do not detect touch input and therefore don't support multitouch, since mouse emulation can only press one button at a given time. Use [TouchScreenButton] for buttons that trigger gameplay movement or actions.
+		[b]Note:[/b] Buttons support multitouch via touch input, allowing multiple buttons to be pressed at the same time. Otherwise, mouse input is used, limiting interaction to one button press at a time.
 	</description>
 	<tutorials>
 		<link title="2D Dodge The Creeps Demo">https://godotengine.org/asset-library/asset/2712</link>

scene/gui/base_button.cpp

@@ -63,6 +63,45 @@ void BaseButton::gui_input(const Ref<InputEvent> &p_event) {
 		return;
 	}
 
+	if (p_event->get_device() == InputEvent::DEVICE_ID_EMULATION) {
+		return;
+	}
+
+	if (p_event->is_pressed()) {
+		status.device_id = p_event->get_device();
+	}
+
+	if (p_event->get_device() != status.device_id) {
+		return;
+	}
+
+	Ref<InputEventScreenTouch> touch = p_event;
+	if (touch.is_valid()) {
+		if (status.touch_index == -1) {
+			if (touch->is_pressed()) {
+				status.touch_index = touch->get_index();
+				status.press_attempt = true;
+				status.pressing_inside = has_point(touch->get_position());
+				on_action_event(p_event);
+			}
+		} else if (touch->get_index() == status.touch_index) {
+			if (!touch->is_pressed()) {
+				status.touch_index = -1;
+				on_action_event(p_event);
+			}
+		}
+	}
+
+	Ref<InputEventScreenDrag> drag = p_event;
+	if (drag.is_valid() && drag->get_index() == status.touch_index && status.press_attempt) {
+		bool last_press_inside = status.pressing_inside;
+		status.pressing_inside = has_point(drag->get_position());
+
+		if (last_press_inside != status.pressing_inside) {
+			queue_redraw();
+		}
+	}
+
 	Ref<InputEventMouseButton> mouse_button = p_event;
 	bool ui_accept = p_event->is_action("ui_accept", true) && !p_event->is_echo();
 
@@ -154,6 +193,7 @@ void BaseButton::_notification(int p_what) {
 		case NOTIFICATION_SCROLL_BEGIN: {
 			if (status.press_attempt) {
 				status.press_attempt = false;
+				status.touch_index = -1;
 				queue_redraw();
 			}
 		} break;
@@ -165,6 +205,7 @@ void BaseButton::_notification(int p_what) {
 		case NOTIFICATION_FOCUS_EXIT: {
 			if (status.press_attempt) {
 				status.press_attempt = false;
+				status.touch_index = -1;
 				queue_redraw();
 			} else if (status.hovering) {
 				queue_redraw();
@@ -187,6 +228,7 @@ void BaseButton::_notification(int p_what) {
 			status.hovering = false;
 			status.press_attempt = false;
 			status.pressing_inside = false;
+			status.touch_index = -1;
 		} break;
 	}
 }
@@ -205,8 +247,11 @@ void BaseButton::_toggled(bool p_pressed) {
 
 void BaseButton::on_action_event(Ref<InputEvent> p_event) {
 	Ref<InputEventMouseButton> mouse_button = p_event;
+	Ref<InputEventScreenTouch> screen_touch = p_event;
+	Ref<InputEventScreenDrag> screen_drag = p_event;
 
-	if (p_event->is_pressed() && (mouse_button.is_null() || status.hovering)) {
+	bool is_accept_event = mouse_button.is_null() && screen_touch.is_null() && screen_drag.is_null();
+	if (p_event->is_pressed() && (is_accept_event || status.hovering)) {
 		status.press_attempt = true;
 		status.pressing_inside = true;
 		if (!status.pressed_down_with_focus) {

scene/gui/base_button.h

@@ -63,7 +63,8 @@ class BaseButton : public Control {
 		bool pressing_inside = false;
 		bool pressed_down_with_focus = false;
 		bool disabled = false;
-
+		int touch_index = -1;
+		int device_id = InputEvent::DEVICE_ID_EMULATION;
 	} status;
 
 	Ref<ButtonGroup> button_group;