Introduce editor theme spacing presets

This change adds a new editor setting related to theming
which controls base and additional spacing used in the
generated editor theme. These values can also be changed
manually by the user to customize their experience.

Limited effort was applied to make sure both Compact and
Spacious presets work and look fine, but further tuning
and adjustments are totally expected. Some controls will
require layout changes or additional fixes to their constants.

doc/classes/EditorSettings.xml

@@ -662,12 +662,16 @@
 		<member name="interface/theme/accent_color" type="Color" setter="" getter="">
 			The color to use for "highlighted" user interface elements in the editor (pressed and hovered items).
 		</member>
-		<member name="interface/theme/additional_spacing" type="float" setter="" getter="">
-			The spacing to add for buttons and list items in the editor (in pixels). Increasing this value is useful to improve usability on touch screens, at the cost of reducing the amount of usable screen real estate.
+		<member name="interface/theme/additional_spacing" type="int" setter="" getter="">
+			The extra spacing to add to various GUI elements in the editor (in pixels). Increasing this value is useful to improve usability on touch screens, at the cost of reducing the amount of usable screen real estate.
+			 See also [member interface/theme/spacing_preset].
 		</member>
 		<member name="interface/theme/base_color" type="Color" setter="" getter="">
 			The base color to use for user interface elements in the editor. Secondary colors (such as darker/lighter variants) are derived from this color.
 		</member>
+		<member name="interface/theme/base_spacing" type="int" setter="" getter="">
+			The base spacing used by various GUI elements in the editor (in pixels). See also [member interface/theme/spacing_preset].
+		</member>
 		<member name="interface/theme/border_size" type="int" setter="" getter="">
 			The border size to use for interface elements (in pixels).
 		</member>
@@ -699,6 +703,9 @@
 		<member name="interface/theme/relationship_line_opacity" type="float" setter="" getter="">
 			The opacity to use when drawing relationship lines in the editor's [Tree]-based GUIs (such as the Scene tree dock).
 		</member>
+		<member name="interface/theme/spacing_preset" type="String" setter="" getter="">
+			The editor theme spacing preset to use. See also [member interface/theme/base_spacing] and [member interface/theme/additional_spacing].
+		</member>
 		<member name="interface/touchscreen/enable_long_press_as_right_click" type="bool" setter="" getter="">
 			If [code]true[/code], long press on touchscreen is treated as right click.
 			[b]Note:[/b] Defaults to [code]true[/code] on touchscreen devices.

editor/editor_settings.cpp

@@ -460,6 +460,7 @@ void EditorSettings::_load_defaults(Ref<ConfigFile> p_extra_config) {
 
 	// Theme
 	EDITOR_SETTING(Variant::STRING, PROPERTY_HINT_ENUM, "interface/theme/preset", "Default", "Default,Breeze Dark,Godot 2,Gray,Light,Solarized (Dark),Solarized (Light),Black (OLED),Custom")
+	EDITOR_SETTING(Variant::STRING, PROPERTY_HINT_ENUM, "interface/theme/spacing_preset", "Default", "Compact,Default,Spacious,Custom")
 	EDITOR_SETTING(Variant::INT, PROPERTY_HINT_ENUM, "interface/theme/icon_and_font_color", 0, "Auto,Dark,Light")
 	EDITOR_SETTING(Variant::COLOR, PROPERTY_HINT_NONE, "interface/theme/base_color", Color(0.2, 0.23, 0.31), "")
 	EDITOR_SETTING(Variant::COLOR, PROPERTY_HINT_NONE, "interface/theme/accent_color", Color(0.41, 0.61, 0.91), "")
@@ -469,7 +470,8 @@ void EditorSettings::_load_defaults(Ref<ConfigFile> p_extra_config) {
 	EDITOR_SETTING(Variant::FLOAT, PROPERTY_HINT_RANGE, "interface/theme/relationship_line_opacity", 0.1, "0.00,1,0.01")
 	EDITOR_SETTING(Variant::INT, PROPERTY_HINT_RANGE, "interface/theme/border_size", 0, "0,2,1")
 	EDITOR_SETTING(Variant::INT, PROPERTY_HINT_RANGE, "interface/theme/corner_radius", 3, "0,6,1")
-	EDITOR_SETTING(Variant::FLOAT, PROPERTY_HINT_RANGE, "interface/theme/additional_spacing", 0.0, "0,5,0.1")
+	EDITOR_SETTING(Variant::INT, PROPERTY_HINT_RANGE, "interface/theme/base_spacing", 4, "0,8,1")
+	EDITOR_SETTING(Variant::INT, PROPERTY_HINT_RANGE, "interface/theme/additional_spacing", 0, "0,8,1")
 	EDITOR_SETTING_USAGE(Variant::STRING, PROPERTY_HINT_GLOBAL_FILE, "interface/theme/custom_theme", "", "*.res,*.tres,*.theme", PROPERTY_USAGE_DEFAULT | PROPERTY_USAGE_RESTART_IF_CHANGED)
 
 	// Touchscreen

editor/editor_settings_dialog.cpp

@@ -62,8 +62,12 @@ void EditorSettingsDialog::_settings_changed() {
 void EditorSettingsDialog::_settings_property_edited(const String &p_name) {
 	String full_name = inspector->get_full_item_path(p_name);
 
+	// Set theme presets to Custom when controlled settings change.
+
 	if (full_name == "interface/theme/accent_color" || full_name == "interface/theme/base_color" || full_name == "interface/theme/contrast" || full_name == "interface/theme/draw_extra_borders") {
-		EditorSettings::get_singleton()->set_manually("interface/theme/preset", "Custom"); // set preset to Custom
+		EditorSettings::get_singleton()->set_manually("interface/theme/preset", "Custom");
+	} else if (full_name == "interface/theme/base_spacing" || full_name == "interface/theme/additional_spacing") {
+		EditorSettings::get_singleton()->set_manually("interface/theme/spacing_preset", "Custom");
 	} else if (full_name.begins_with("text_editor/theme/highlighting")) {
 		EditorSettings::get_singleton()->set_manually("text_editor/theme/color_theme", "Custom");
 	}