Add highlight to the relationship lines of selected Tree items

doc/classes/Tree.xml

@@ -533,6 +533,12 @@
 		<theme_item name="checked" type="Texture2D">
 			The check icon to display when the [constant TreeItem.CELL_MODE_CHECK] mode cell is checked.
 		</theme_item>
+		<theme_item name="children_hl_line_color" type="Color" default="Color( 0.27, 0.27, 0.27, 1 )">
+			The [Color] of the relationship lines between the selected [TreeItem] and its children.
+		</theme_item>
+		<theme_item name="children_hl_line_width" type="int" default="1">
+			The width of the relationship lines between the selected [TreeItem] and its children.
+		</theme_item>
 		<theme_item name="cursor" type="StyleBox">
 			[StyleBox] used for the cursor, when the [Tree] is being focused.
 		</theme_item>
@@ -587,8 +593,20 @@
 		<theme_item name="outline_size" type="int" default="0">
 			The size of the text outline.
 		</theme_item>
+		<theme_item name="parent_hl_line_color" type="Color" default="Color( 0.27, 0.27, 0.27, 1 )">
+			The [Color] of the relationship lines between the selected [TreeItem] and its parents.
+		</theme_item>
+		<theme_item name="parent_hl_line_margin" type="int" default="0">
+			The space between the parent relationship lines for the selected [TreeItem] and the relationship lines to its siblings that are not selected.
+		</theme_item>
+		<theme_item name="parent_hl_line_width" type="int" default="1">
+			The width of the relationship lines between the selected [TreeItem] and its parents.
+		</theme_item>
 		<theme_item name="relationship_line_color" type="Color" default="Color( 0.27, 0.27, 0.27, 1 )">
-			[Color] of the relationship lines.
+			The default [Color] of the relationship lines.
+		</theme_item>
+		<theme_item name="relationship_line_width" type="int" default="1">
+			The default width of the relationship lines.
 		</theme_item>
 		<theme_item name="scroll_border" type="int" default="4">
 			The maximum distance between the mouse cursor and the control's border to trigger border scrolling when dragging.

editor/editor_themes.cpp

@@ -799,8 +799,6 @@ Ref<Theme> create_editor_theme(const Ref<Theme> p_theme) {
 	style_tree_bg->set_border_color(dark_color_3);
 	theme->set_stylebox("bg", "Tree", style_tree_bg);
 
-	const Color guide_color = mono_color * Color(1, 1, 1, 0.05);
-	Color relationship_line_color = mono_color * Color(1, 1, 1, relationship_line_opacity);
 	// Tree
 	theme->set_icon("checked", "Tree", theme->get_icon("GuiChecked", "EditorIcons"));
 	theme->set_icon("unchecked", "Tree", theme->get_icon("GuiUnchecked", "EditorIcons"));
@@ -817,19 +815,33 @@ Ref<Theme> create_editor_theme(const Ref<Theme> p_theme) {
 	theme->set_color("font_color", "Tree", font_color);
 	theme->set_color("font_selected_color", "Tree", mono_color);
 	theme->set_color("title_button_color", "Tree", font_color);
-	theme->set_color("guide_color", "Tree", guide_color);
-	theme->set_color("relationship_line_color", "Tree", relationship_line_color);
 	theme->set_color("drop_position_color", "Tree", accent_color);
 	theme->set_constant("vseparation", "Tree", widget_default_margin.y - EDSCALE);
 	theme->set_constant("hseparation", "Tree", 6 * EDSCALE);
 	theme->set_constant("guide_width", "Tree", border_width);
 	theme->set_constant("item_margin", "Tree", 3 * default_margin_size * EDSCALE);
 	theme->set_constant("button_margin", "Tree", default_margin_size * EDSCALE);
-	theme->set_constant("draw_relationship_lines", "Tree", relationship_line_opacity >= 0.01);
-	theme->set_constant("draw_guides", "Tree", relationship_line_opacity < 0.01);
 	theme->set_constant("scroll_border", "Tree", 40 * EDSCALE);
 	theme->set_constant("scroll_speed", "Tree", 12);
 
+	const Color guide_color = mono_color * Color(1, 1, 1, 0.05);
+	Color relationship_line_color = mono_color * Color(1, 1, 1, relationship_line_opacity);
+
+	theme->set_constant("draw_guides", "Tree", relationship_line_opacity < 0.01);
+	theme->set_color("guide_color", "Tree", guide_color);
+
+	int relationship_line_width = 1;
+	Color parent_line_color = mono_color * Color(1, 1, 1, CLAMP(relationship_line_opacity + 0.45, 0.0, 1.0));
+	Color children_line_color = mono_color * Color(1, 1, 1, CLAMP(relationship_line_opacity + 0.25, 0.0, 1.0));
+	theme->set_constant("draw_relationship_lines", "Tree", relationship_line_opacity >= 0.01);
+	theme->set_constant("relationship_line_width", "Tree", relationship_line_width);
+	theme->set_constant("parent_hl_line_width", "Tree", relationship_line_width * 2);
+	theme->set_constant("children_hl_line_width", "Tree", relationship_line_width);
+	theme->set_constant("parent_hl_line_margin", "Tree", relationship_line_width * 3);
+	theme->set_color("relationship_line_color", "Tree", relationship_line_color);
+	theme->set_color("parent_hl_line_color", "Tree", parent_line_color);
+	theme->set_color("children_hl_line_color", "Tree", children_line_color);
+
 	Ref<StyleBoxFlat> style_tree_btn = style_default->duplicate();
 	style_tree_btn->set_bg_color(highlight_color);
 	style_tree_btn->set_border_width_all(0);

scene/gui/tree.cpp

@@ -1184,15 +1184,23 @@ void Tree::update_cache() {
 
 	cache.font_color = get_theme_color("font_color");
 	cache.font_selected_color = get_theme_color("font_selected_color");
-	cache.guide_color = get_theme_color("guide_color");
 	cache.drop_position_color = get_theme_color("drop_position_color");
 	cache.hseparation = get_theme_constant("hseparation");
 	cache.vseparation = get_theme_constant("vseparation");
 	cache.item_margin = get_theme_constant("item_margin");
 	cache.button_margin = get_theme_constant("button_margin");
+
 	cache.draw_guides = get_theme_constant("draw_guides");
+	cache.guide_color = get_theme_color("guide_color");
 	cache.draw_relationship_lines = get_theme_constant("draw_relationship_lines");
+	cache.relationship_line_width = get_theme_constant("relationship_line_width");
+	cache.parent_hl_line_width = get_theme_constant("parent_hl_line_width");
+	cache.children_hl_line_width = get_theme_constant("children_hl_line_width");
+	cache.parent_hl_line_margin = get_theme_constant("parent_hl_line_margin");
 	cache.relationship_line_color = get_theme_color("relationship_line_color");
+	cache.parent_hl_line_color = get_theme_color("parent_hl_line_color");
+	cache.children_hl_line_color = get_theme_color("children_hl_line_color");
+
 	cache.scroll_border = get_theme_constant("scroll_border");
 	cache.scroll_speed = get_theme_constant("scroll_speed");
 
@@ -1813,38 +1821,73 @@ int Tree::draw_item(const Point2i &p_pos, const Point2 &p_draw_ofs, const Size2
 
 		TreeItem *c = p_item->first_child;
 
-		int prev_ofs = children_pos.y - cache.offset.y + p_draw_ofs.y;
+		int base_ofs = children_pos.y - cache.offset.y + p_draw_ofs.y;
+		int prev_ofs = base_ofs;
+		int prev_hl_ofs = base_ofs;
 
 		while (c) {
 			if (cache.draw_relationship_lines > 0 && (!hide_root || c->parent != root)) {
 				int root_ofs = children_pos.x + ((p_item->disable_folding || hide_folding) ? cache.hseparation : cache.item_margin);
-				int parent_ofs = p_pos.x + ((p_item->disable_folding || hide_folding) ? cache.hseparation : cache.item_margin);
+				int parent_ofs = p_pos.x + cache.item_margin;
 				Point2i root_pos = Point2i(root_ofs, children_pos.y + label_h / 2) - cache.offset + p_draw_ofs;
 
 				if (c->get_first_child() != nullptr) {
 					root_pos -= Point2i(cache.arrow->get_width(), 0);
 				}
 
-				float line_width = 1.0;
+				float line_width = cache.relationship_line_width;
+				float parent_line_width = cache.parent_hl_line_width;
+				float children_line_width = cache.children_hl_line_width;
+
 #ifdef TOOLS_ENABLED
 				line_width *= Math::round(EDSCALE);
+				parent_line_width *= Math::round(EDSCALE);
+				children_line_width *= Math::round(EDSCALE);
 #endif
 
 				Point2i parent_pos = Point2i(parent_ofs - cache.arrow->get_width() / 2, p_pos.y + label_h / 2 + cache.arrow->get_height() / 2) - cache.offset + p_draw_ofs;
 
+				int more_prev_ofs = 0;
+
 				if (root_pos.y + line_width >= 0) {
 					if (rtl) {
 						root_pos.x = get_size().width - root_pos.x;
 						parent_pos.x = get_size().width - parent_pos.x;
 					}
-					RenderingServer::get_singleton()->canvas_item_add_line(ci, root_pos, Point2i(parent_pos.x - Math::floor(line_width / 2), root_pos.y), cache.relationship_line_color, line_width);
+
-					RenderingServer::get_singleton()->canvas_item_add_line(ci, Point2i(parent_pos.x, root_pos.y), Point2i(parent_pos.x, prev_ofs), cache.relationship_line_color, line_width);
+					// Order of parts on this bend: the horizontal line first, then the vertical line.
+					if (_is_branch_selected(c)) {
+						// If this item or one of its children is selected, we draw the line using parent highlight style.
+						RenderingServer::get_singleton()->canvas_item_add_line(ci, root_pos, Point2i(parent_pos.x + Math::floor(parent_line_width / 2), root_pos.y), cache.parent_hl_line_color, parent_line_width);
+						RenderingServer::get_singleton()->canvas_item_add_line(ci, Point2i(parent_pos.x, root_pos.y + Math::floor(parent_line_width / 2)), Point2i(parent_pos.x, prev_hl_ofs), cache.parent_hl_line_color, parent_line_width);
+
+						more_prev_ofs = cache.parent_hl_line_margin;
+						prev_hl_ofs = root_pos.y + Math::floor(parent_line_width / 2);
+					} else if (p_item->is_selected(0)) {
+						// If parent item is selected (but this item is not), we draw the line using children highlight style.
+						// Siblings of the selected branch can be drawn with a slight offset (and also don't need a vertical line).
+						if (_is_sibling_branch_selected(c)) {
+							RenderingServer::get_singleton()->canvas_item_add_line(ci, root_pos, Point2i(parent_pos.x + Math::floor(parent_line_width / 2), root_pos.y), cache.children_hl_line_color, children_line_width);
+						} else {
+							RenderingServer::get_singleton()->canvas_item_add_line(ci, root_pos, Point2i(parent_pos.x + Math::floor(children_line_width / 2), root_pos.y), cache.children_hl_line_color, children_line_width);
+							RenderingServer::get_singleton()->canvas_item_add_line(ci, Point2i(parent_pos.x, root_pos.y + Math::floor(children_line_width / 2)), Point2i(parent_pos.x, prev_ofs + Math::floor(children_line_width / 2)), cache.children_hl_line_color, children_line_width);
+						}
+					} else {
+						// If nothing of the above is true, we draw the line using normal style.
+						// Siblings of the selected branch can be drawn with a slight offset (and also don't need a vertical line).
+						if (_is_sibling_branch_selected(c)) {
+							RenderingServer::get_singleton()->canvas_item_add_line(ci, root_pos, Point2i(parent_pos.x + cache.parent_hl_line_margin, root_pos.y), cache.relationship_line_color, line_width);
+						} else {
+							RenderingServer::get_singleton()->canvas_item_add_line(ci, root_pos, Point2i(parent_pos.x + Math::floor(line_width / 2), root_pos.y), cache.relationship_line_color, line_width);
+							RenderingServer::get_singleton()->canvas_item_add_line(ci, Point2i(parent_pos.x, root_pos.y + Math::floor(line_width / 2)), Point2i(parent_pos.x, prev_ofs + Math::floor(line_width / 2)), cache.relationship_line_color, line_width);
+						}
+					}
 				}
 
 				if (htotal < 0) {
 					return -1;
 				}
-				prev_ofs = root_pos.y;
+				prev_ofs = root_pos.y + more_prev_ofs;
 			}
 
 			if (htotal >= 0) {
@@ -1853,10 +1896,10 @@ int Tree::draw_item(const Point2i &p_pos, const Point2 &p_draw_ofs, const Size2
 				if (child_h < 0) {
 					if (cache.draw_relationship_lines == 0) {
 						return -1; // break, stop drawing, no need to anymore
-					} else {
-						htotal = -1;
-						children_pos.y = cache.offset.y + p_draw_size.height;
 					}
+
+					htotal = -1;
+					children_pos.y = cache.offset.y + p_draw_size.height;
 				} else {
 					htotal += child_h;
 					children_pos.y += child_h;
@@ -1889,6 +1932,36 @@ int Tree::_count_selected_items(TreeItem *p_from) const {
 	return count;
 }
 
+bool Tree::_is_branch_selected(TreeItem *p_from) const {
+	for (int i = 0; i < columns.size(); i++) {
+		if (p_from->is_selected(i)) {
+			return true;
+		}
+	}
+
+	TreeItem *child_item = p_from->get_first_child();
+	while (child_item) {
+		if (_is_branch_selected(child_item)) {
+			return true;
+		}
+		child_item = child_item->get_next();
+	}
+
+	return false;
+}
+
+bool Tree::_is_sibling_branch_selected(TreeItem *p_from) const {
+	TreeItem *sibling_item = p_from->get_next();
+	while (sibling_item) {
+		if (_is_branch_selected(sibling_item)) {
+			return true;
+		}
+		sibling_item = sibling_item->get_next();
+	}
+
+	return false;
+}
+
 void Tree::select_single_item(TreeItem *p_selected, TreeItem *p_current, int p_col, TreeItem *p_prev, bool *r_in_range, bool p_force_deselect) {
 	TreeItem::Cell &selected_cell = p_selected->cells.write[p_col];
 

scene/gui/tree.h

@@ -494,6 +494,8 @@ private:
 		Color guide_color;
 		Color drop_position_color;
 		Color relationship_line_color;
+		Color parent_hl_line_color;
+		Color children_hl_line_color;
 		Color custom_button_font_highlight;
 
 		int hseparation = 0;
@@ -502,6 +504,10 @@ private:
 		int button_margin = 0;
 		Point2 offset;
 		int draw_relationship_lines = 0;
+		int relationship_line_width = 0;
+		int parent_hl_line_width = 0;
+		int children_hl_line_width = 0;
+		int parent_hl_line_margin = 0;
 		int draw_guides = 0;
 		int scroll_border = 0;
 		int scroll_speed = 0;
@@ -574,6 +580,8 @@ private:
 	bool hide_folding = false;
 
 	int _count_selected_items(TreeItem *p_from) const;
+	bool _is_branch_selected(TreeItem *p_from) const;
+	bool _is_sibling_branch_selected(TreeItem *p_from) const;
 	void _go_left();
 	void _go_right();
 	void _go_down();

scene/resources/default_theme/default_theme.cpp

@@ -719,6 +719,8 @@ void fill_default_theme(Ref<Theme> &theme, const Ref<Font> &default_font, const
 	theme->set_color("guide_color", "Tree", Color(0, 0, 0, 0.1));
 	theme->set_color("drop_position_color", "Tree", Color(1, 0.3, 0.2));
 	theme->set_color("relationship_line_color", "Tree", Color(0.27, 0.27, 0.27));
+	theme->set_color("parent_hl_line_color", "Tree", Color(0.27, 0.27, 0.27));
+	theme->set_color("children_hl_line_color", "Tree", Color(0.27, 0.27, 0.27));
 	theme->set_color("custom_button_font_highlight", "Tree", control_font_hover_color);
 
 	theme->set_constant("hseparation", "Tree", 4 * scale);
@@ -726,6 +728,10 @@ void fill_default_theme(Ref<Theme> &theme, const Ref<Font> &default_font, const
 	theme->set_constant("item_margin", "Tree", 12 * scale);
 	theme->set_constant("button_margin", "Tree", 4 * scale);
 	theme->set_constant("draw_relationship_lines", "Tree", 0);
+	theme->set_constant("relationship_line_width", "Tree", 1);
+	theme->set_constant("parent_hl_line_width", "Tree", 1);
+	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("scroll_border", "Tree", 4);
 	theme->set_constant("scroll_speed", "Tree", 12);