[GraphEdit] Improve UI control scheme by separating scroll_offset from scroll bars

scene/gui/graph_edit.cpp

@@ -115,11 +115,11 @@ Vector2 GraphEditMinimap::_get_render_size() {
 }
 
 Vector2 GraphEditMinimap::_get_graph_offset() {
-	return Vector2(ge->h_scrollbar->get_min(), ge->v_scrollbar->get_min());
+	return ge->min_scroll_offset;
 }
 
 Vector2 GraphEditMinimap::_get_graph_size() {
-	Vector2 graph_size = Vector2(ge->h_scrollbar->get_max(), ge->v_scrollbar->get_max()) - Vector2(ge->h_scrollbar->get_min(), ge->v_scrollbar->get_min());
+	Vector2 graph_size = ge->max_scroll_offset - ge->min_scroll_offset;
 
 	if (graph_size.width == 0) {
 		graph_size.width = 1;
@@ -411,17 +411,25 @@ String GraphEdit::get_connections_description(const StringName &p_node, int p_po
 
 void GraphEdit::set_scroll_offset(const Vector2 &p_offset) {
 	setting_scroll_offset = true;
-	h_scrollbar->set_value(p_offset.x);
-	v_scrollbar->set_value(p_offset.y);
-	_update_scroll();
+	scroll_offset = p_offset.clamp(min_scroll_offset, max_scroll_offset - get_size());
+	if (!awaiting_scroll_offset_update) {
+		callable_mp(this, &GraphEdit::_update_scroll_offset).call_deferred();
+		awaiting_scroll_offset_update = true;
+	}
+	minimap->queue_redraw();
+	queue_redraw();
+	_update_scrollbars();
+	callable_mp(this, &GraphEdit::_update_top_connection_layer).call_deferred();
 	setting_scroll_offset = false;
 }
 
 Vector2 GraphEdit::get_scroll_offset() const {
-	return Vector2(h_scrollbar->get_value(), v_scrollbar->get_value());
+	return scroll_offset;
 }
 
-void GraphEdit::_scroll_moved(double) {
+void GraphEdit::_scrollbar_moved(double) {
+	scroll_offset.x = h_scrollbar->get_value();
+	scroll_offset.y = v_scrollbar->get_value();
 	if (!awaiting_scroll_offset_update) {
 		callable_mp(this, &GraphEdit::_update_scroll_offset).call_deferred();
 		awaiting_scroll_offset_update = true;
@@ -443,14 +451,14 @@ void GraphEdit::_update_scroll_offset() {
 		}
 
 		Point2 pos = graph_element->get_position_offset() * zoom;
-		pos -= Point2(h_scrollbar->get_value(), v_scrollbar->get_value());
+		pos -= scroll_offset;
 		graph_element->set_position(pos);
 		if (graph_element->get_scale() != Vector2(zoom, zoom)) {
 			graph_element->set_scale(Vector2(zoom, zoom));
 		}
 	}
 
-	connections_layer->set_position(-Point2(h_scrollbar->get_value(), v_scrollbar->get_value()));
+	connections_layer->set_position(-scroll_offset);
 	set_block_minimum_size_adjust(false);
 	awaiting_scroll_offset_update = false;
 
@@ -460,14 +468,18 @@ void GraphEdit::_update_scroll_offset() {
 	}
 }
 
-void GraphEdit::_update_scroll() {
+void GraphEdit::_update_scrollbars() {
 	if (updating) {
 		return;
 	}
 	updating = true;
 
+	h_scrollbar->set_value_no_signal(scroll_offset.x);
+	v_scrollbar->set_value_no_signal(scroll_offset.y);
+
 	set_block_minimum_size_adjust(true);
 
+	// Determine the graph "canvas" size in screen space.
 	Rect2 screen_rect;
 	for (int i = 0; i < get_child_count(); i++) {
 		GraphElement *graph_element = Object::cast_to<GraphElement>(get_child(i));
@@ -484,6 +496,9 @@ void GraphEdit::_update_scroll() {
 	screen_rect.position -= get_size();
 	screen_rect.size += get_size() * 2.0;
 
+	min_scroll_offset = screen_rect.position;
+	max_scroll_offset = screen_rect.position + screen_rect.size;
+
 	h_scrollbar->set_min(screen_rect.position.x);
 	h_scrollbar->set_max(screen_rect.position.x + screen_rect.size.width);
 	h_scrollbar->set_page(get_size().x);
@@ -849,7 +864,7 @@ void GraphEdit::_notification(int p_what) {
 		} break;
 
 		case NOTIFICATION_RESIZED: {
-			_update_scroll();
+			_update_scrollbars();
 			minimap->queue_redraw();
 			callable_mp(this, &GraphEdit::_update_top_connection_layer).call_deferred();
 		} break;
@@ -1714,7 +1729,7 @@ void GraphEdit::_top_layer_draw() {
 }
 
 void GraphEdit::_update_top_connection_layer() {
-	_update_scroll();
+	_update_scrollbars();
 
 	if (!connecting) {
 		dragged_connection_line->clear_points();
@@ -2302,9 +2317,15 @@ void GraphEdit::key_input(const Ref<InputEvent> &p_ev) {
 void GraphEdit::_pan_callback(Vector2 p_scroll_vec, Ref<InputEvent> p_event) {
 	ERR_FAIL_NULL_MSG(connections_layer, "connections_layer is missing.");
 
-	h_scrollbar->set_value(h_scrollbar->get_value() - p_scroll_vec.x);
-	v_scrollbar->set_value(v_scrollbar->get_value() - p_scroll_vec.y);
+	scroll_offset = (scroll_offset - p_scroll_vec).clamp(min_scroll_offset, max_scroll_offset - get_size());
 
+	if (!awaiting_scroll_offset_update) {
+		callable_mp(this, &GraphEdit::_update_scroll_offset).call_deferred();
+		awaiting_scroll_offset_update = true;
+	}
+	minimap->queue_redraw();
+	queue_redraw();
+	callable_mp(this, &GraphEdit::_update_top_connection_layer).call_deferred();
 	connections_layer->queue_redraw();
 }
 
@@ -2406,7 +2427,7 @@ void GraphEdit::set_zoom_custom(float p_zoom, const Vector2 &p_center) {
 		return;
 	}
 
-	Vector2 scrollbar_offset = (Vector2(h_scrollbar->get_value(), v_scrollbar->get_value()) + p_center) / zoom;
+	Point2 zoom_anchor = (scroll_offset + p_center) / zoom;
 
 	zoom = p_zoom;
 
@@ -2415,14 +2436,12 @@ void GraphEdit::set_zoom_custom(float p_zoom, const Vector2 &p_center) {
 	zoom_minus_button->set_disabled(zoom == zoom_min);
 	zoom_plus_button->set_disabled(zoom == zoom_max);
 
-	_update_scroll();
+	_update_scrollbars();
 	minimap->queue_redraw();
 	connections_layer->queue_redraw();
 
 	if (is_visible_in_tree()) {
-		Vector2 offset = scrollbar_offset * zoom - p_center;
-		h_scrollbar->set_value(offset.x);
-		v_scrollbar->set_value(offset.y);
+		scroll_offset = zoom_anchor * zoom - p_center;
 	}
 
 	_update_zoom_label();
@@ -3193,8 +3212,8 @@ GraphEdit::GraphEdit() {
 	v_scrollbar->set_min(-10000);
 	v_scrollbar->set_max(10000);
 
-	h_scrollbar->connect(SceneStringName(value_changed), callable_mp(this, &GraphEdit::_scroll_moved));
-	v_scrollbar->connect(SceneStringName(value_changed), callable_mp(this, &GraphEdit::_scroll_moved));
+	h_scrollbar->connect(SceneStringName(value_changed), callable_mp(this, &GraphEdit::_scrollbar_moved));
+	v_scrollbar->connect(SceneStringName(value_changed), callable_mp(this, &GraphEdit::_scrollbar_moved));
 
 	// Toolbar menu.
 

scene/gui/graph_edit.h

@@ -228,6 +228,10 @@ private:
 	float zoom_min = 0.0;
 	float zoom_max = 0.0;
 
+	Vector2 min_scroll_offset;
+	Vector2 max_scroll_offset;
+	Vector2 scroll_offset;
+
 	bool box_selecting = false;
 	bool box_selection_mode_additive = false;
 	Point2 box_selecting_from;
@@ -327,9 +331,9 @@ private:
 	void _ensure_node_order_from_root(const StringName &p_node);
 	void _ensure_node_order_from(Node *p_node);
 
-	void _update_scroll();
+	void _update_scrollbars();
 	void _update_scroll_offset();
-	void _scroll_moved(double);
+	void _scrollbar_moved(double);
 	virtual void gui_input(const Ref<InputEvent> &p_ev) override;
 	void _top_connection_layer_input(const Ref<InputEvent> &p_ev);