Add theme contexts to various parts of the editor

This change defines additional theme contexts for editor
branches to prevent theme leaking between the default
theme, the project theme, and the editor theme.

- Both editor window and EditorNode define an editor-specific
context with the editor theme and the default theme.
- The 2D viewport defines a project-specific context with
the project theme and the default theme.
- Theme editor preview tabs define the default-only context
with the default theme.

Additionally, the default theme context now only includes
the project theme for running projects (both export and debug).
This prevents the project theme from leaking into the editor.

This commit also does a little clean up on the theming aspects
of the EditorNode.

editor/editor_node.h

@@ -295,7 +295,6 @@ class EditorNode : public Node {
 	bool is_main_screen_editing = false;
 
 	PanelContainer *scene_root_parent = nullptr;
-	Control *theme_base = nullptr;
 	Control *gui_base = nullptr;
 	VBoxContainer *main_vbox = nullptr;
 	OptionButton *renderer = nullptr;
@@ -525,6 +524,7 @@ class EditorNode : public Node {
 	static void _resource_saved(Ref<Resource> p_resource, const String &p_path);
 	static void _resource_loaded(Ref<Resource> p_resource, const String &p_path);
 
+	void _update_theme(bool p_skip_creation = false);
 	void _build_icon_type_cache();
 	void _enable_pending_addons();
 
@@ -867,7 +867,6 @@ class EditorNode : public Node {
 	Error export_preset(const String &p_preset, const String &p_path, bool p_debug, bool p_pack_only);
 
 	Control *get_gui_base() { return gui_base; }
-	Control *get_theme_base() { return gui_base->get_parent_control(); }
 
 	void save_scene_to_path(String p_file, bool p_with_preview = true) {
 		if (p_with_preview) {

editor/editor_resource_preview.cpp

@@ -40,6 +40,7 @@
 #include "editor/editor_paths.h"
 #include "editor/editor_scale.h"
 #include "editor/editor_settings.h"
+#include "editor/editor_string_names.h"
 #include "scene/resources/image_texture.h"
 
 bool EditorResourcePreviewGenerator::handles(const String &p_type) const {
@@ -341,7 +342,8 @@ void EditorResourcePreview::_thread() {
 
 void EditorResourcePreview::_update_thumbnail_sizes() {
 	if (small_thumbnail_size == -1) {
-		small_thumbnail_size = EditorNode::get_singleton()->get_theme_base()->get_editor_theme_icon(SNAME("Object"))->get_width(); // Kind of a workaround to retrieve the default icon size
+		// Kind of a workaround to retrieve the default icon size.
+		small_thumbnail_size = EditorNode::get_singleton()->get_editor_theme()->get_icon(SNAME("Object"), EditorStringName(EditorIcons))->get_width();
 	}
 }
 

editor/plugins/script_editor_plugin.cpp

@@ -1612,6 +1612,8 @@ void ScriptEditor::_notification(int p_what) {
 		case NOTIFICATION_TRANSLATION_CHANGED:
 		case NOTIFICATION_LAYOUT_DIRECTION_CHANGED:
 		case NOTIFICATION_THEME_CHANGED: {
+			tab_container->add_theme_style_override("panel", get_theme_stylebox(SNAME("ScriptEditor"), EditorStringName(EditorStyles)));
+
 			help_search->set_icon(get_editor_theme_icon(SNAME("HelpSearch")));
 			site_search->set_icon(get_editor_theme_icon(SNAME("ExternalLink")));
 
@@ -1628,7 +1630,7 @@ void ScriptEditor::_notification(int p_what) {
 			filter_scripts->set_right_icon(get_editor_theme_icon(SNAME("Search")));
 			filter_methods->set_right_icon(get_editor_theme_icon(SNAME("Search")));
 
-			filename->add_theme_style_override("normal", EditorNode::get_singleton()->get_gui_base()->get_theme_stylebox(SNAME("normal"), SNAME("LineEdit")));
+			filename->add_theme_style_override("normal", get_theme_stylebox(SNAME("normal"), SNAME("LineEdit")));
 
 			recent_scripts->reset_size();
 
@@ -1639,6 +1641,9 @@ void ScriptEditor::_notification(int p_what) {
 		} break;
 
 		case NOTIFICATION_READY: {
+			// Can't set own styles in NOTIFICATION_THEME_CHANGED, so for now this will do.
+			add_theme_style_override("panel", get_theme_stylebox(SNAME("ScriptEditorPanel"), SNAME("EditorStyles")));
+
 			get_tree()->connect("tree_changed", callable_mp(this, &ScriptEditor::_tree_changed));
 			InspectorDock::get_singleton()->connect("request_help", callable_mp(this, &ScriptEditor::_help_class_open));
 			EditorNode::get_singleton()->connect("request_help_search", callable_mp(this, &ScriptEditor::_help_search));
@@ -4139,9 +4144,6 @@ ScriptEditor::ScriptEditor(WindowWrapper *p_wrapper) {
 
 	ScriptServer::edit_request_func = _open_script_request;
 
-	add_theme_style_override("panel", EditorNode::get_singleton()->get_gui_base()->get_theme_stylebox(SNAME("ScriptEditorPanel"), EditorStringName(EditorStyles)));
-	tab_container->add_theme_style_override("panel", EditorNode::get_singleton()->get_gui_base()->get_theme_stylebox(SNAME("ScriptEditor"), EditorStringName(EditorStyles)));
-
 	Ref<EditorJSONSyntaxHighlighter> json_syntax_highlighter;
 	json_syntax_highlighter.instantiate();
 	register_syntax_highlighter(json_syntax_highlighter);

editor/plugins/theme_editor_plugin.cpp

@@ -1217,7 +1217,7 @@ void ThemeItemEditorDialog::_dialog_about_to_show() {
 	import_default_theme_items->reset_item_tree();
 
 	import_editor_theme_items->set_edited_theme(edited_theme);
-	import_editor_theme_items->set_base_theme(EditorNode::get_singleton()->get_theme_base()->get_theme());
+	import_editor_theme_items->set_base_theme(EditorNode::get_singleton()->get_editor_theme());
 	import_editor_theme_items->reset_item_tree();
 
 	import_other_theme_items->set_edited_theme(edited_theme);

editor/plugins/theme_editor_preview.cpp

@@ -202,8 +202,14 @@ void ThemeEditorPreview::_notification(int p_what) {
 			}
 
 			connect("visibility_changed", callable_mp(this, &ThemeEditorPreview::_preview_visibility_changed));
-			[[fallthrough]];
-		}
+		} break;
+
+		case NOTIFICATION_READY: {
+			List<Ref<Theme>> preview_themes;
+			preview_themes.push_back(ThemeDB::get_singleton()->get_default_theme());
+			ThemeDB::get_singleton()->create_theme_context(preview_root, preview_themes);
+		} break;
+
 		case NOTIFICATION_THEME_CHANGED: {
 			picker_button->set_icon(get_editor_theme_icon(SNAME("ColorPick")));
 
@@ -247,9 +253,8 @@ ThemeEditorPreview::ThemeEditorPreview() {
 	preview_container = memnew(ScrollContainer);
 	preview_body->add_child(preview_container);
 
-	MarginContainer *preview_root = memnew(MarginContainer);
+	preview_root = memnew(MarginContainer);
 	preview_container->add_child(preview_root);
-	preview_root->set_theme(ThemeDB::get_singleton()->get_default_theme());
 	preview_root->set_clip_contents(true);
 	preview_root->set_custom_minimum_size(Size2(450, 0) * EDSCALE);
 	preview_root->set_v_size_flags(SIZE_EXPAND_FILL);

editor/plugins/theme_editor_preview.h

@@ -44,6 +44,7 @@ class ThemeEditorPreview : public VBoxContainer {
 	GDCLASS(ThemeEditorPreview, VBoxContainer);
 
 	ScrollContainer *preview_container = nullptr;
+	MarginContainer *preview_root = nullptr;
 	ColorRect *preview_bg = nullptr;
 	MarginContainer *preview_overlay = nullptr;
 	Control *picker_overlay = nullptr;

scene/theme/theme_db.cpp

@@ -272,7 +272,17 @@ void ThemeDB::_init_default_theme_context() {
 	default_theme_context = memnew(ThemeContext);
 
 	List<Ref<Theme>> themes;
+
+	// Only add the project theme to the default context when running projects.
+
+#ifdef TOOLS_ENABLED
+	if (!Engine::get_singleton()->is_editor_hint()) {
+		themes.push_back(project_theme);
+	}
+#else
 	themes.push_back(project_theme);
+#endif
+
 	themes.push_back(default_theme);
 	default_theme_context->set_themes(themes);
 }
@@ -289,6 +299,14 @@ void ThemeDB::_finalize_theme_contexts() {
 	}
 }
 
+ThemeContext *ThemeDB::get_theme_context(Node *p_node) const {
+	if (!theme_contexts.has(p_node)) {
+		return nullptr;
+	}
+
+	return theme_contexts[p_node];
+}
+
 ThemeContext *ThemeDB::get_default_theme_context() const {
 	return default_theme_context;
 }

scene/theme/theme_db.h

@@ -108,6 +108,7 @@ class ThemeDB : public Object {
 	ThemeContext *create_theme_context(Node *p_node, List<Ref<Theme>> &p_themes);
 	void destroy_theme_context(Node *p_node);
 
+	ThemeContext *get_theme_context(Node *p_node) const;
 	ThemeContext *get_default_theme_context() const;
 	ThemeContext *get_nearest_theme_context(Node *p_for_node) const;