Make BaseButton not emit press when container is scrolled

This fixes the problem described in #13996 in a proper way.

This also adds "deadzone" property to ScrollContainer. It can be used
on mobile, where taps are not as precise as mouse clicks. Player could
slightly move their finger when tapping, in which case we still want
the button to be pressed rather than the container to be scrolled.

5 files changed, 60 insertions, 24 deletions

diff --git a/scene/gui/base_button.cpp b/scene/gui/base_button.cpp
index 5f541ea16..1c91e9988 100644
--- a/scene/gui/base_button.cpp
+++ b/scene/gui/base_button.cpp
@@ -247,7 +247,7 @@ void BaseButton::_notification(int p_what) {
 		status.hovering = false;
 		update();
 	}
-	if (p_what == NOTIFICATION_DRAG_BEGIN) {
+	if (p_what == NOTIFICATION_DRAG_BEGIN || p_what == NOTIFICATION_SCROLL_BEGIN) {
 
 		if (status.press_attempt) {
 			status.press_attempt = false;
diff --git a/scene/gui/control.cpp b/scene/gui/control.cpp
index a5883863c..d1244bebf 100644
--- a/scene/gui/control.cpp
+++ b/scene/gui/control.cpp
@@ -2886,6 +2886,8 @@ void Control::_bind_methods() {
 	BIND_CONSTANT(NOTIFICATION_FOCUS_EXIT);
 	BIND_CONSTANT(NOTIFICATION_THEME_CHANGED);
 	BIND_CONSTANT(NOTIFICATION_MODAL_CLOSE);
+	BIND_CONSTANT(NOTIFICATION_SCROLL_BEGIN);
+	BIND_CONSTANT(NOTIFICATION_SCROLL_END);
 
 	BIND_ENUM_CONSTANT(CURSOR_ARROW);
 	BIND_ENUM_CONSTANT(CURSOR_IBEAM);
diff --git a/scene/gui/control.h b/scene/gui/control.h
index 51325f27b..75813ce82 100644
--- a/scene/gui/control.h
+++ b/scene/gui/control.h
@@ -271,6 +271,8 @@ public:
 		NOTIFICATION_FOCUS_EXIT = 44,
 		NOTIFICATION_THEME_CHANGED = 45,
 		NOTIFICATION_MODAL_CLOSE = 46,
+		NOTIFICATION_SCROLL_BEGIN = 47,
+		NOTIFICATION_SCROLL_END = 48,
 
 	};
 
diff --git a/scene/gui/scroll_container.cpp b/scene/gui/scroll_container.cpp
index 33b3d4648..217df275b 100644
--- a/scene/gui/scroll_container.cpp
+++ b/scene/gui/scroll_container.cpp
@@ -75,6 +75,12 @@ void ScrollContainer::_cancel_drag() {
 	drag_accum = Vector2();
 	last_drag_accum = Vector2();
 	drag_from = Vector2();
+
+	if (beyond_deadzone) {
+		emit_signal("scroll_ended");
+		propagate_notification(NOTIFICATION_SCROLL_END);
+		beyond_deadzone = false;
+	}
 }
 
 void ScrollContainer::_gui_input(const Ref<InputEvent> &p_gui_input) {
@@ -122,13 +128,7 @@ void ScrollContainer::_gui_input(const Ref<InputEvent> &p_gui_input) {
 		if (mb->is_pressed()) {
 
 			if (drag_touching) {
-				set_physics_process(false);
-				drag_touching_deaccel = false;
-				drag_touching = false;
-				drag_speed = Vector2();
-				drag_accum = Vector2();
-				last_drag_accum = Vector2();
-				drag_from = Vector2();
+				_cancel_drag();
 			}
 
 			if (true) {
@@ -138,6 +138,7 @@ void ScrollContainer::_gui_input(const Ref<InputEvent> &p_gui_input) {
 				drag_from = Vector2(h_scroll->get_value(), v_scroll->get_value());
 				drag_touching = OS::get_singleton()->has_touchscreen_ui_hint();
 				drag_touching_deaccel = false;
+				beyond_deadzone = false;
 				time_since_motion = 0;
 				if (drag_touching) {
 					set_physics_process(true);
@@ -149,9 +150,7 @@ void ScrollContainer::_gui_input(const Ref<InputEvent> &p_gui_input) {
 			if (drag_touching) {
 
 				if (drag_speed == Vector2()) {
-					drag_touching_deaccel = false;
-					drag_touching = false;
-					set_physics_process(false);
+					_cancel_drag();
 				} else {
 
 					drag_touching_deaccel = true;
@@ -168,17 +167,27 @@ void ScrollContainer::_gui_input(const Ref<InputEvent> &p_gui_input) {
 
 			Vector2 motion = Vector2(mm->get_relative().x, mm->get_relative().y);
 			drag_accum -= motion;
-			Vector2 diff = drag_from + drag_accum;
 
-			if (scroll_h)
-				h_scroll->set_value(diff.x);
-			else
-				drag_accum.x = 0;
-			if (scroll_v)
-				v_scroll->set_value(diff.y);
-			else
-				drag_accum.y = 0;
-			time_since_motion = 0;
+			if (beyond_deadzone || scroll_h && Math::abs(drag_accum.x) > deadzone || scroll_v && Math::abs(drag_accum.y) > deadzone) {
+				if (!beyond_deadzone) {
+					propagate_notification(NOTIFICATION_SCROLL_BEGIN);
+					emit_signal("scroll_started");
+
+					beyond_deadzone = true;
+					// resetting drag_accum here ensures smooth scrolling after reaching deadzone
+					drag_accum = -motion;
+				}
+				Vector2 diff = drag_from + drag_accum;
+				if (scroll_h)
+					h_scroll->set_value(diff.x);
+				else
+					drag_accum.x = 0;
+				if (scroll_v)
+					v_scroll->set_value(diff.y);
+				else
+					drag_accum.y = 0;
+				time_since_motion = 0;
+			}
 		}
 	}
 
@@ -323,9 +332,7 @@ void ScrollContainer::_notification(int p_what) {
 				drag_speed = Vector2(sgn_x * val_x, sgn_y * val_y);
 
 				if (turnoff_h && turnoff_v) {
-					set_physics_process(false);
-					drag_touching = false;
-					drag_touching_deaccel = false;
+					_cancel_drag();
 				}
 
 			} else {
@@ -430,6 +437,14 @@ void ScrollContainer::set_h_scroll(int p_pos) {
 	_cancel_drag();
 }
 
+int ScrollContainer::get_deadzone() const {
+	return deadzone;
+}
+
+void ScrollContainer::set_deadzone(int p_deadzone) {
+	deadzone = p_deadzone;
+}
+
 String ScrollContainer::get_configuration_warning() const {
 
 	int found = 0;
@@ -466,12 +481,20 @@ void ScrollContainer::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("get_h_scroll"), &ScrollContainer::get_h_scroll);
 	ClassDB::bind_method(D_METHOD("set_v_scroll", "value"), &ScrollContainer::set_v_scroll);
 	ClassDB::bind_method(D_METHOD("get_v_scroll"), &ScrollContainer::get_v_scroll);
+	ClassDB::bind_method(D_METHOD("set_deadzone", "deadzone"), &ScrollContainer::set_deadzone);
+	ClassDB::bind_method(D_METHOD("get_deadzone"), &ScrollContainer::get_deadzone);
+
+	ADD_SIGNAL(MethodInfo("scroll_started"));
+	ADD_SIGNAL(MethodInfo("scroll_ended"));
 
 	ADD_GROUP("Scroll", "scroll_");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "scroll_horizontal_enabled"), "set_enable_h_scroll", "is_h_scroll_enabled");
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "scroll_horizontal"), "set_h_scroll", "get_h_scroll");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "scroll_vertical_enabled"), "set_enable_v_scroll", "is_v_scroll_enabled");
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "scroll_vertical"), "set_v_scroll", "get_v_scroll");
+	ADD_PROPERTY(PropertyInfo(Variant::INT, "scroll_deadzone"), "set_deadzone", "get_deadzone");
+
+	GLOBAL_DEF("gui/common/default_scroll_deadzone", 0);
 };
 
 ScrollContainer::ScrollContainer() {
@@ -490,8 +513,11 @@ ScrollContainer::ScrollContainer() {
 	drag_speed = Vector2();
 	drag_touching = false;
 	drag_touching_deaccel = false;
+	beyond_deadzone = false;
 	scroll_h = true;
 	scroll_v = true;
 
+	deadzone = GLOBAL_GET("gui/common/default_scroll_deadzone");
+
 	set_clip_contents(true);
 };
diff --git a/scene/gui/scroll_container.h b/scene/gui/scroll_container.h
index 6e3387918..3fe1ed447 100644
--- a/scene/gui/scroll_container.h
+++ b/scene/gui/scroll_container.h
@@ -56,10 +56,13 @@ class ScrollContainer : public Container {
 	bool drag_touching;
 	bool drag_touching_deaccel;
 	bool click_handled;
+	bool beyond_deadzone;
 
 	bool scroll_h;
 	bool scroll_v;
 
+	int deadzone;
+
 	void _cancel_drag();
 
 protected:
@@ -86,6 +89,9 @@ public:
 	void set_enable_v_scroll(bool p_enable);
 	bool is_v_scroll_enabled() const;
 
+	int get_deadzone() const;
+	void set_deadzone(int p_deadzone);
+
 	virtual bool clips_input() const;
 
 	virtual String get_configuration_warning() const;