Unfold tree items on hover while drag-n-dropping

Co-authored-by: suddjian

doc/classes/EditorSettings.xml

@@ -869,6 +869,9 @@
 		<member name="interface/editor/dock_tab_style" type="int" setter="" getter="">
 			Tab style of editor docks.
 		</member>
+		<member name="interface/editor/dragging_hover_wait_seconds" type="float" setter="" getter="">
+			During a drag-and-drop, this is how long to wait over a UI element before it triggers a reaction (e.g. a section unfolds to show nested items).
+		</member>
 		<member name="interface/editor/editor_language" type="String" setter="" getter="">
 			The language to use for the editor interface.
 			Translations are provided by the community. If you spot a mistake, [url=https://contributing.godotengine.org/en/latest/documentation/translation/index.html]contribute to editor translations on Weblate![/url]

doc/classes/Tree.xml

@@ -355,6 +355,9 @@
 			The drop mode as an OR combination of flags. See [enum DropModeFlags] constants. Once dropping is done, reverts to [constant DROP_MODE_DISABLED]. Setting this during [method Control._can_drop_data] is recommended.
 			This controls the drop sections, i.e. the decision and drawing of possible drop locations based on the mouse position.
 		</member>
+		<member name="enable_drag_unfolding" type="bool" setter="set_enable_drag_unfolding" getter="is_drag_unfolding_enabled" default="true">
+			If [code]true[/code], tree items will unfold when hovered over during a drag-and-drop. The delay for when this happens is dictated by [theme_item dragging_unfold_wait_msec].
+		</member>
 		<member name="enable_recursive_folding" type="bool" setter="set_enable_recursive_folding" getter="is_recursive_folding_enabled" default="true">
 			If [code]true[/code], recursive folding is enabled for this [Tree]. Holding down [kbd]Shift[/kbd] while clicking the fold arrow or using [code]ui_right[/code]/[code]ui_left[/code] shortcuts collapses or uncollapses the [TreeItem] and all its descendants.
 		</member>
@@ -546,6 +549,9 @@
 		<theme_item name="children_hl_line_width" data_type="constant" type="int" default="1">
 			The width of the relationship lines between the selected [TreeItem] and its children.
 		</theme_item>
+		<theme_item name="dragging_unfold_wait_msec" data_type="constant" type="int" default="500">
+			During a drag-and-drop, this is how many milliseconds to wait over a section before the section unfolds.
+		</theme_item>
 		<theme_item name="draw_guides" data_type="constant" type="int" default="1">
 			Draws the guidelines if not zero, this acts as a boolean. The guideline is a horizontal line drawn at the bottom of each item.
 		</theme_item>

editor/docks/scene_tree_dock.cpp

@@ -1711,6 +1711,9 @@ void SceneTreeDock::_notification(int p_what) {
 				scene_tree->set_hide_filtered_out_parents(EDITOR_GET("docks/scene_tree/hide_filtered_out_parents"), false);
 				scene_tree->set_accessibility_warnings(EDITOR_GET("docks/scene_tree/accessibility_warnings"), false);
 			}
+			if (EditorSettings::get_singleton()->check_changed_settings_in_group("interface/editor")) {
+				inspect_hovered_node_delay->set_wait_time(EDITOR_GET("interface/editor/dragging_hover_wait_seconds"));
+			}
 		} break;
 
 		case NOTIFICATION_THEME_CHANGED: {
@@ -4854,7 +4857,6 @@ SceneTreeDock::SceneTreeDock(Node *p_scene_root, EditorSelection *p_editor_selec
 
 	inspect_hovered_node_delay = memnew(Timer);
 	inspect_hovered_node_delay->connect("timeout", callable_mp(this, &SceneTreeDock::_inspect_hovered_node));
-	inspect_hovered_node_delay->set_wait_time(.5);
 	inspect_hovered_node_delay->set_one_shot(true);
 	add_child(inspect_hovered_node_delay);
 

editor/editor_node.cpp

@@ -995,6 +995,10 @@ void EditorNode::_notification(int p_what) {
 				recent_scenes->reset_size();
 			}
 
+			if (EditorSettings::get_singleton()->check_changed_settings_in_group("interface/editor")) {
+				theme->set_constant("dragging_unfold_wait_msec", "Tree", (float)EDITOR_GET("interface/editor/dragging_hover_wait_seconds") * 1000);
+			}
+
 			if (EditorSettings::get_singleton()->check_changed_settings_in_group("interface/editor/dock_tab_style")) {
 				editor_dock_manager->update_tab_styles();
 			}

editor/inspector/editor_inspector.cpp

@@ -2138,6 +2138,12 @@ void EditorInspectorSection::_notification(int p_what) {
 				queue_redraw();
 			}
 		} break;
+
+		case EditorSettings::NOTIFICATION_EDITOR_SETTINGS_CHANGED: {
+			if (EditorSettings::get_singleton()->check_changed_settings_in_group("interface/editor")) {
+				dropping_unfold_timer->set_wait_time(EDITOR_GET("interface/editor/dragging_hover_wait_seconds"));
+			}
+		} break;
 	}
 }
 
@@ -2466,7 +2472,7 @@ EditorInspectorSection::EditorInspectorSection() {
 	vbox = memnew(VBoxContainer);
 
 	dropping_unfold_timer = memnew(Timer);
-	dropping_unfold_timer->set_wait_time(0.6);
+	dropping_unfold_timer->set_wait_time(EDITOR_GET("interface/editor/dragging_hover_wait_seconds"));
 	dropping_unfold_timer->set_one_shot(true);
 	add_child(dropping_unfold_timer);
 	dropping_unfold_timer->connect("timeout", callable_mp(this, &EditorInspectorSection::unfold));

editor/scene/scene_tree_editor.cpp

@@ -1362,6 +1362,8 @@ void SceneTreeEditor::_notification(int p_what) {
 		} break;
 
 		case NOTIFICATION_THEME_CHANGED: {
+			// Wait for the node to be inspected before triggering the unfolding.
+			tree->add_theme_constant_override("dragging_unfold_wait_msec", (float)EDITOR_GET("interface/editor/dragging_hover_wait_seconds") * 1000 * 2);
 			tree->add_theme_constant_override("icon_max_width", get_theme_constant(SNAME("class_icon_size"), EditorStringName(Editor)));
 			[[fallthrough]];
 		}

editor/settings/editor_settings.cpp

@@ -503,6 +503,7 @@ void EditorSettings::_load_defaults(Ref<ConfigFile> p_extra_config) {
 	EDITOR_SETTING(Variant::STRING, PROPERTY_HINT_GLOBAL_FILE, "interface/editor/main_font", "", "*.ttf,*.otf,*.woff,*.woff2,*.pfb,*.pfm")
 	EDITOR_SETTING(Variant::STRING, PROPERTY_HINT_GLOBAL_FILE, "interface/editor/main_font_bold", "", "*.ttf,*.otf,*.woff,*.woff2,*.pfb,*.pfm")
 	EDITOR_SETTING(Variant::STRING, PROPERTY_HINT_GLOBAL_FILE, "interface/editor/code_font", "", "*.ttf,*.otf,*.woff,*.woff2,*.pfb,*.pfm")
+	EDITOR_SETTING(Variant::FLOAT, PROPERTY_HINT_RANGE, "interface/editor/dragging_hover_wait_seconds", 0.5, "0.01,10,0.01,or_greater,suffix:s");
 	_initial_set("interface/editor/separate_distraction_mode", false, true);
 	_initial_set("interface/editor/automatically_open_screenshots", true, true);
 	EDITOR_SETTING_USAGE(Variant::BOOL, PROPERTY_HINT_NONE, "interface/editor/single_window_mode", false, "", PROPERTY_USAGE_DEFAULT | PROPERTY_USAGE_RESTART_IF_CHANGED | PROPERTY_USAGE_EDITOR_BASIC_SETTING)

editor/themes/editor_theme_manager.cpp

@@ -975,6 +975,7 @@ void EditorThemeManager::_populate_standard_styles(const Ref<EditorTheme> &p_the
 			p_theme->set_constant("inner_item_margin_left", "Tree", p_config.increased_margin * EDSCALE);
 			p_theme->set_constant("inner_item_margin_right", "Tree", p_config.increased_margin * EDSCALE);
 			p_theme->set_constant("button_margin", "Tree", p_config.base_margin * EDSCALE);
+			p_theme->set_constant("dragging_unfold_wait_msec", "Tree", (float)EDITOR_GET("interface/editor/dragging_hover_wait_seconds") * 1000);
 			p_theme->set_constant("scroll_border", "Tree", 40 * EDSCALE);
 			p_theme->set_constant("scroll_speed", "Tree", 12);
 			p_theme->set_constant("outline_size", "Tree", 0);

scene/gui/tree.cpp

@@ -139,7 +139,7 @@ void TreeItem::_change_tree(Tree *p_tree) {
 		}
 
 		if (tree->drop_mode_over == this) {
-			tree->drop_mode_over = nullptr;
+			tree->_reset_drop_mode_over();
 		}
 
 		if (tree->single_select_defer == this) {
@@ -4278,6 +4278,9 @@ void Tree::_determine_hovered_item() {
 		if (drop_mode_flags) {
 			if (it != drop_mode_over) {
 				drop_mode_over = it;
+				if (enable_drag_unfolding) {
+					dropping_unfold_timer->start(theme_cache.dragging_unfold_wait_msec * 0.001);
+				}
 				queue_redraw();
 			}
 			if (it && section != drop_mode_section) {
@@ -4321,6 +4324,19 @@ void Tree::_determine_hovered_item() {
 	}
 }
 
+void Tree::_on_dropping_unfold_timer_timeout() {
+	if (enable_drag_unfolding && drop_mode_over && drop_mode_section == 0) {
+		drop_mode_over->set_collapsed(false);
+	}
+}
+
+void Tree::_reset_drop_mode_over() {
+	drop_mode_over = nullptr;
+	if (!dropping_unfold_timer->is_stopped()) {
+		dropping_unfold_timer->stop();
+	}
+}
+
 void Tree::_queue_update_hovered_item() {
 	if (hovered_update_queued) {
 		return;
@@ -6440,13 +6456,28 @@ bool Tree::is_recursive_folding_enabled() const {
 	return enable_recursive_folding;
 }
 
+void Tree::set_enable_drag_unfolding(bool p_enable) {
+	if (enable_drag_unfolding == p_enable) {
+		return;
+	}
+
+	enable_drag_unfolding = p_enable;
+	if (!enable_drag_unfolding && !dropping_unfold_timer->is_stopped()) {
+		dropping_unfold_timer->stop();
+	}
+}
+
+bool Tree::is_drag_unfolding_enabled() const {
+	return enable_drag_unfolding;
+}
+
 void Tree::set_drop_mode_flags(int p_flags) {
 	if (drop_mode_flags == p_flags) {
 		return;
 	}
 	drop_mode_flags = p_flags;
 	if (drop_mode_flags == 0) {
-		drop_mode_over = nullptr;
+		_reset_drop_mode_over();
 	}
 
 	queue_redraw();
@@ -6567,6 +6598,9 @@ void Tree::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_enable_recursive_folding", "enable"), &Tree::set_enable_recursive_folding);
 	ClassDB::bind_method(D_METHOD("is_recursive_folding_enabled"), &Tree::is_recursive_folding_enabled);
 
+	ClassDB::bind_method(D_METHOD("set_enable_drag_unfolding", "enable"), &Tree::set_enable_drag_unfolding);
+	ClassDB::bind_method(D_METHOD("is_drag_unfolding_enabled"), &Tree::is_drag_unfolding_enabled);
+
 	ClassDB::bind_method(D_METHOD("set_drop_mode_flags", "flags"), &Tree::set_drop_mode_flags);
 	ClassDB::bind_method(D_METHOD("get_drop_mode_flags"), &Tree::get_drop_mode_flags);
 
@@ -6589,6 +6623,7 @@ void Tree::_bind_methods() {
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "allow_search"), "set_allow_search", "get_allow_search");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "hide_folding"), "set_hide_folding", "is_folding_hidden");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "enable_recursive_folding"), "set_enable_recursive_folding", "is_recursive_folding_enabled");
+	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "enable_drag_unfolding"), "set_enable_drag_unfolding", "is_drag_unfolding_enabled");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "hide_root"), "set_hide_root", "is_root_hidden");
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "drop_mode_flags", PROPERTY_HINT_FLAGS, "On Item,In Between"), "set_drop_mode_flags", "get_drop_mode_flags");
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "select_mode", PROPERTY_HINT_ENUM, "Single,Row,Multi"), "set_select_mode", "get_select_mode");
@@ -6687,6 +6722,8 @@ void Tree::_bind_methods() {
 	BIND_THEME_ITEM(Theme::DATA_TYPE_COLOR, Tree, parent_hl_line_color);
 	BIND_THEME_ITEM(Theme::DATA_TYPE_COLOR, Tree, children_hl_line_color);
 
+	BIND_THEME_ITEM(Theme::DATA_TYPE_CONSTANT, Tree, dragging_unfold_wait_msec);
+
 	BIND_THEME_ITEM(Theme::DATA_TYPE_CONSTANT, Tree, scroll_border);
 	BIND_THEME_ITEM(Theme::DATA_TYPE_CONSTANT, Tree, scroll_speed);
 
@@ -6744,6 +6781,11 @@ Tree::Tree() {
 	range_click_timer->connect("timeout", callable_mp(this, &Tree::_range_click_timeout));
 	add_child(range_click_timer, false, INTERNAL_MODE_FRONT);
 
+	dropping_unfold_timer = memnew(Timer);
+	dropping_unfold_timer->set_one_shot(true);
+	dropping_unfold_timer->connect("timeout", callable_mp(this, &Tree::_on_dropping_unfold_timer_timeout));
+	add_child(dropping_unfold_timer);
+
 	h_scroll->connect(SceneStringName(value_changed), callable_mp(this, &Tree::_scroll_moved));
 	v_scroll->connect(SceneStringName(value_changed), callable_mp(this, &Tree::_scroll_moved));
 	line_editor->connect(SceneStringName(text_submitted), callable_mp(this, &Tree::_line_editor_submit));

scene/gui/tree.h

@@ -650,6 +650,8 @@ private:
 		int parent_hl_line_margin = 0;
 		int draw_guides = 0;
 
+		int dragging_unfold_wait_msec = 500;
+
 		int scroll_border = 0;
 		int scroll_speed = 0;
 
@@ -737,6 +739,11 @@ private:
 
 	bool enable_recursive_folding = true;
 
+	bool enable_drag_unfolding = true;
+	Timer *dropping_unfold_timer = nullptr;
+	void _on_dropping_unfold_timer_timeout();
+	void _reset_drop_mode_over();
+
 	bool enable_auto_tooltip = true;
 
 	bool hovered_update_queued = false;
@@ -885,6 +892,9 @@ public:
 	void set_enable_recursive_folding(bool p_enable);
 	bool is_recursive_folding_enabled() const;
 
+	void set_enable_drag_unfolding(bool p_enable);
+	bool is_drag_unfolding_enabled() const;
+
 	void set_drop_mode_flags(int p_flags);
 	int get_drop_mode_flags() const;
 

scene/theme/default_theme.cpp

@@ -912,6 +912,7 @@ void fill_default_theme(Ref<Theme> &theme, const Ref<Font> &default_font, const
 	theme->set_constant("children_hl_line_width", "Tree", 1);
 	theme->set_constant("parent_hl_line_margin", "Tree", 0);
 	theme->set_constant("draw_guides", "Tree", 1);
+	theme->set_constant("dragging_unfold_wait_msec", "Tree", 500);
 	theme->set_constant("scroll_border", "Tree", Math::round(4 * scale));
 	theme->set_constant("scroll_speed", "Tree", 12);
 	theme->set_constant("outline_size", "Tree", 0);