Improve input event accumulation

- API has been simplified: all events now go through `parse_input_event()`. Whether they are accumulated or not depends on the `use_accumulated_input` flag.
- Event accumulation is now thread-safe (it was not needed so far, but it prepares the ground for the following changes).
- Touch drag events now support accumulation.

4 files changed, 25 insertions, 10 deletions

diff --git a/core/input/input.cpp b/core/input/input.cpp
index 2da50b7dff..ffe2659126 100644
--- a/core/input/input.cpp
+++ b/core/input/input.cpp
@@ -460,10 +460,6 @@ Vector3 Input::get_gyroscope() const {
 	return gyroscope;
 }
 
-void Input::parse_input_event(const Ref<InputEvent> &p_event) {
-	_parse_input_event_impl(p_event, false);
-}
-
 void Input::_parse_input_event_impl(const Ref<InputEvent> &p_event, bool p_is_emulated) {
 	// Notes on mouse-touch emulation:
 	// - Emulated mouse events are parsed, that is, re-routed to this method, so they make the same effects
@@ -472,8 +468,6 @@ void Input::_parse_input_event_impl(const Ref<InputEvent> &p_event, bool p_is_em
 	// - Emulated touch events are handed right to the main loop (i.e., the SceneTree) because they don't
 	//   require additional handling by this class.
 
-	_THREAD_SAFE_METHOD_
-
 	Ref<InputEventKey> k = p_event;
 	if (k.is_valid() && !k->is_echo() && k->get_keycode() != 0) {
 		if (k->is_pressed()) {
@@ -838,11 +832,13 @@ void Input::set_custom_mouse_cursor(const RES &p_cursor, CursorShape p_shape, co
 	set_custom_mouse_cursor_func(p_cursor, p_shape, p_hotspot);
 }
 
-void Input::accumulate_input_event(const Ref<InputEvent> &p_event) {
+void Input::parse_input_event(const Ref<InputEvent> &p_event) {
+	_THREAD_SAFE_METHOD_
+
 	ERR_FAIL_COND(p_event.is_null());
 
 	if (!use_accumulated_input) {
-		parse_input_event(p_event);
+		_parse_input_event_impl(p_event, false);
 		return;
 	}
 	if (!accumulated_events.is_empty() && accumulated_events.back()->get()->accumulate(p_event)) {
@@ -853,8 +849,10 @@ void Input::accumulate_input_event(const Ref<InputEvent> &p_event) {
 }
 
 void Input::flush_accumulated_events() {
+	_THREAD_SAFE_METHOD_
+
 	while (accumulated_events.front()) {
-		parse_input_event(accumulated_events.front()->get());
+		_parse_input_event_impl(accumulated_events.front()->get(), false);
 		accumulated_events.pop_front();
 	}
 }
diff --git a/core/input/input.h b/core/input/input.h
index ee991aa725..d08e6437a5 100644
--- a/core/input/input.h
+++ b/core/input/input.h
@@ -323,7 +323,6 @@ public:
 	String get_joy_guid(int p_device) const;
 	void set_fallback_mapping(String p_guid);
 
-	void accumulate_input_event(const Ref<InputEvent> &p_event);
 	void flush_accumulated_events();
 	void set_use_accumulated_input(bool p_enable);
 
diff --git a/core/input/input_event.cpp b/core/input/input_event.cpp
index 6e5c1a58ae..16bb92d94b 100644
--- a/core/input/input_event.cpp
+++ b/core/input/input_event.cpp
@@ -1210,6 +1210,22 @@ String InputEventScreenDrag::to_string() {
 	return vformat("InputEventScreenDrag: index=%d, position=(%s), relative=(%s), speed=(%s)", index, String(get_position()), String(get_relative()), String(get_speed()));
 }
 
+bool InputEventScreenDrag::accumulate(const Ref<InputEvent> &p_event) {
+	Ref<InputEventScreenDrag> drag = p_event;
+	if (drag.is_null())
+		return false;
+
+	if (get_index() != drag->get_index()) {
+		return false;
+	}
+
+	set_position(drag->get_position());
+	set_speed(drag->get_speed());
+	relative += drag->get_relative();
+
+	return true;
+}
+
 void InputEventScreenDrag::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_index", "index"), &InputEventScreenDrag::set_index);
 	ClassDB::bind_method(D_METHOD("get_index"), &InputEventScreenDrag::get_index);
diff --git a/core/input/input_event.h b/core/input/input_event.h
index 57b6091123..517d63eb40 100644
--- a/core/input/input_event.h
+++ b/core/input/input_event.h
@@ -410,6 +410,8 @@ public:
 	virtual String as_text() const override;
 	virtual String to_string() override;
 
+	virtual bool accumulate(const Ref<InputEvent> &p_event) override;
+
 	InputEventScreenDrag() {}
 };