Add Code Block Guidelines in Script Editor & CodeEdit

Add `code_block_guidelines_style` in CodeEdit. When set, lines appear between the start and end of a foldable code block. This line is appropriately indented.

Multiples guides may stack on top of each other, within reason, and prefer to connect to a bottom parenthesis.

The colour of the guide line becomes _slightly_ more noticeable when the caret is inside the code block:

It can be switched between "None", "Line" and "Line (Close)". This feature is set to "None" by default for the Editor. Its colors can be customised in the Editor Settings.

doc/classes/CodeEdit.xml

@@ -451,6 +451,9 @@
 		<member name="code_completion_prefixes" type="String[]" setter="set_code_completion_prefixes" getter="get_code_comletion_prefixes" default="[]">
 			Sets prefixes that will trigger code completion.
 		</member>
+		<member name="codeblock_guidelines_style" type="int" setter="set_codeblock_guidelines_style" getter="get_codeblock_guidelines_style" enum="CodeEdit.CodeblockGuidelinesStyle" default="0">
+			Sets the style to display code block guidelines. See [enum CodeblockGuidelinesStyle].
+		</member>
 		<member name="delimiter_comments" type="String[]" setter="set_comment_delimiters" getter="get_comment_delimiters" default="[]">
 			Sets the comment delimiters. All existing comment delimiters will be removed.
 		</member>
@@ -527,6 +530,15 @@
 		</signal>
 	</signals>
 	<constants>
+		<constant name="CODEBLOCK_GUIDE_STYLE_NONE" value="0" enum="CodeblockGuidelinesStyle">
+			Codeblock guides are not drawn.
+		</constant>
+		<constant name="CODEBLOCK_GUIDE_STYLE_LINE" value="1" enum="CodeblockGuidelinesStyle">
+			Draws guidelines denoting the blocks of code.
+		</constant>
+		<constant name="CODEBLOCK_GUIDE_STYLE_LINE_CLOSE" value="2" enum="CodeblockGuidelinesStyle">
+			Draws guidelines denoting the blocks of code. Additionally, horizontal lines connect from the end of the block to the last letter when applicable.
+		</constant>
 		<constant name="KIND_CLASS" value="0" enum="CodeCompletionKind">
 			Marks the option as a class.
 		</constant>
@@ -580,6 +592,12 @@
 		<theme_item name="code_folding_color" data_type="color" type="Color" default="Color(0.8, 0.8, 0.8, 0.8)">
 			[Color] for all icons related to line folding.
 		</theme_item>
+		<theme_item name="codeblock_guideline_active_color" data_type="color" type="Color" default="Color(0.8, 0.8, 0.8, 0.25)">
+			[Color] for the code block guideline, if enabled, when the caret is inside of it.
+		</theme_item>
+		<theme_item name="codeblock_guideline_color" data_type="color" type="Color" default="Color(0.8, 0.8, 0.8, 0.1)">
+			[Color] for the code block guideline, if enabled.
+		</theme_item>
 		<theme_item name="completion_background_color" data_type="color" type="Color" default="Color(0.17, 0.16, 0.2, 1)">
 			Sets the background [Color] for the code completion popup.
 		</theme_item>

doc/classes/EditorSettings.xml

@@ -661,6 +661,9 @@
 		<member name="text_editor/appearance/caret/type" type="int" setter="" getter="">
 			The shape of the caret to use in the script editor. [b]Line[/b] displays a vertical line to the left of the current character, whereas [b]Block[/b] displays a outline over the current character.
 		</member>
+		<member name="text_editor/appearance/guidelines/codeblock_guidelines_style" type="int" setter="" getter="">
+			The style to use for the line marking the beginning and end of a block of code (see [enum CodeEdit.CodeblockGuidelinesStyle]). To customise the color of the line, see [member text_editor/theme/highlighting/codeblock_guideline_color] and [member text_editor/theme/highlighting/codeblock_guideline_active_color].
+		</member>
 		<member name="text_editor/appearance/guidelines/line_length_guideline_hard_column" type="int" setter="" getter="">
 			The column at which to display a subtle line as a line length guideline for scripts. This should generally be greater than [member text_editor/appearance/guidelines/line_length_guideline_soft_column].
 		</member>
@@ -824,6 +827,12 @@
 		<member name="text_editor/theme/highlighting/code_folding_color" type="Color" setter="" getter="">
 			The script editor's color for the code folding icon (displayed in the gutter).
 		</member>
+		<member name="text_editor/theme/highlighting/codeblock_guideline_active_color" type="Color" setter="" getter="">
+			The script editor's color for the code block guideline, when the caret is inside the code block. See also [member text_editor/appearance/guidelines/codeblock_guidelines_style].
+		</member>
+		<member name="text_editor/theme/highlighting/codeblock_guideline_color" type="Color" setter="" getter="">
+			The script editor's color for the code block guideline. See also [member text_editor/appearance/guidelines/codeblock_guidelines_style].
+		</member>
 		<member name="text_editor/theme/highlighting/comment_color" type="Color" setter="" getter="">
 			The script editor's comment color.
 			[b]Note:[/b] In GDScript, unlike Python, multiline strings are not considered to be comments, and will use the string highlighting color instead.

editor/code_editor.cpp

@@ -1048,6 +1048,7 @@ void CodeTextEditor::update_editor_settings() {
 	} else {
 		text_editor->set_line_length_guidelines(TypedArray<int>());
 	}
+	text_editor->set_codeblock_guidelines_style((CodeEdit::CodeblockGuidelinesStyle)EditorSettings::get_singleton()->get("text_editor/appearance/guidelines/codeblock_guidelines_style").operator int());
 }
 
 void CodeTextEditor::set_find_replace_bar(FindReplaceBar *p_bar) {

editor/editor_settings.cpp

@@ -518,6 +518,7 @@ void EditorSettings::_load_defaults(Ref<ConfigFile> p_extra_config) {
 	_initial_set("text_editor/appearance/guidelines/show_line_length_guidelines", true);
 	EDITOR_SETTING(Variant::INT, PROPERTY_HINT_RANGE, "text_editor/appearance/guidelines/line_length_guideline_soft_column", 80, "20,160,1")
 	EDITOR_SETTING(Variant::INT, PROPERTY_HINT_RANGE, "text_editor/appearance/guidelines/line_length_guideline_hard_column", 100, "20,160,1")
+	EDITOR_SETTING(Variant::INT, PROPERTY_HINT_ENUM, "text_editor/appearance/guidelines/codeblock_guidelines_style", 0, "None,Line,Line (Close)")
 
 	// Appearance: Gutters
 	_initial_set("text_editor/appearance/gutters/show_line_numbers", true);
@@ -779,6 +780,8 @@ void EditorSettings::_load_godot2_text_editor_theme() {
 	_initial_set("text_editor/theme/highlighting/brace_mismatch_color", Color(1, 0.2, 0.2));
 	_initial_set("text_editor/theme/highlighting/current_line_color", Color(0.3, 0.5, 0.8, 0.15));
 	_initial_set("text_editor/theme/highlighting/line_length_guideline_color", Color(0.3, 0.5, 0.8, 0.1));
+	_initial_set("text_editor/theme/highlighting/codeblock_guideline_color", Color(0.8, 0.8, 0.8, 0.1));
+	_initial_set("text_editor/theme/highlighting/codeblock_guideline_active_color", Color(0.8, 0.8, 0.8, 0.25));
 	_initial_set("text_editor/theme/highlighting/word_highlighted_color", Color(0.8, 0.9, 0.9, 0.15));
 	_initial_set("text_editor/theme/highlighting/number_color", Color(0.92, 0.58, 0.2));
 	_initial_set("text_editor/theme/highlighting/function_color", Color(0.4, 0.64, 0.81));

editor/editor_themes.cpp

@@ -1746,6 +1746,8 @@ Ref<Theme> create_editor_theme(const Ref<Theme> p_theme) {
 	const Color brace_mismatch_color = dark_theme ? error_color : Color(1, 0.08, 0, 1);
 	const Color current_line_color = alpha1;
 	const Color line_length_guideline_color = dark_theme ? base_color : background_color;
+	const Color codeblock_guideline_color = Color(mono_value, mono_value, mono_value, 0.125);
+	const Color codeblock_guideline_active_color = Color(mono_value, mono_value, mono_value, 0.2);
 	const Color word_highlighted_color = alpha1;
 	const Color number_color = dark_theme ? Color(0.63, 1, 0.88) : Color(0, 0.55, 0.28, 1);
 	const Color function_color = dark_theme ? Color(0.34, 0.7, 1.0) : Color(0, 0.225, 0.9, 1);
@@ -1786,6 +1788,8 @@ Ref<Theme> create_editor_theme(const Ref<Theme> p_theme) {
 		setting->set_initial_value("text_editor/theme/highlighting/brace_mismatch_color", brace_mismatch_color, true);
 		setting->set_initial_value("text_editor/theme/highlighting/current_line_color", current_line_color, true);
 		setting->set_initial_value("text_editor/theme/highlighting/line_length_guideline_color", line_length_guideline_color, true);
+		setting->set_initial_value("text_editor/theme/highlighting/codeblock_guideline_color", codeblock_guideline_color, true);
+		setting->set_initial_value("text_editor/theme/highlighting/codeblock_guideline_active_color", codeblock_guideline_active_color, true);
 		setting->set_initial_value("text_editor/theme/highlighting/word_highlighted_color", word_highlighted_color, true);
 		setting->set_initial_value("text_editor/theme/highlighting/number_color", number_color, true);
 		setting->set_initial_value("text_editor/theme/highlighting/function_color", function_color, true);
@@ -1834,6 +1838,8 @@ Ref<Theme> create_editor_theme(const Ref<Theme> p_theme) {
 	theme->set_color("brace_mismatch_color", "CodeEdit", EDITOR_GET("text_editor/theme/highlighting/brace_mismatch_color"));
 	theme->set_color("current_line_color", "CodeEdit", EDITOR_GET("text_editor/theme/highlighting/current_line_color"));
 	theme->set_color("line_length_guideline_color", "CodeEdit", EDITOR_GET("text_editor/theme/highlighting/line_length_guideline_color"));
+	theme->set_color("codeblock_guideline_color", "CodeEdit", EDITOR_GET("text_editor/theme/highlighting/codeblock_guideline_color"));
+	theme->set_color("codeblock_guideline_active_color", "CodeEdit", EDITOR_GET("text_editor/theme/highlighting/codeblock_guideline_active_color"));
 	theme->set_color("word_highlighted_color", "CodeEdit", EDITOR_GET("text_editor/theme/highlighting/word_highlighted_color"));
 	theme->set_color("bookmark_color", "CodeEdit", EDITOR_GET("text_editor/theme/highlighting/bookmark_color"));
 	theme->set_color("breakpoint_color", "CodeEdit", EDITOR_GET("text_editor/theme/highlighting/breakpoint_color"));