Fix main button margins in custom themes

Defined more theme variations and styleboxes for those variations to work around an issue where external editor themes would apply incorrect margins to certain buttons. This should eliminate clipping/alignment issues while a custom theme is in use.

Also simplified the step where margins are copied over thanks to @Rindbee 's suggestion

editor/editor_node.cpp

@@ -517,9 +517,8 @@ void EditorNode::_update_theme(bool p_skip_creation) {
 
 		scene_root_parent->add_theme_style_override("panel", theme->get_stylebox(SNAME("Content"), EditorStringName(EditorStyles)));
 		bottom_panel->add_theme_style_override("panel", theme->get_stylebox(SNAME("BottomPanel"), EditorStringName(EditorStyles)));
-		main_menu->add_theme_style_override("pressed", theme->get_stylebox(SNAME("MenuTransparent"), EditorStringName(EditorStyles)));
 		distraction_free->set_icon(theme->get_icon(SNAME("DistractionFree"), EditorStringName(EditorIcons)));
-		distraction_free->add_theme_style_override("pressed", theme->get_stylebox(SNAME("MenuTransparent"), EditorStringName(EditorStyles)));
+		distraction_free->add_theme_style_override("pressed", theme->get_stylebox("normal", "FlatMenuButton"));
 
 		help_menu->set_item_icon(help_menu->get_item_index(HELP_SEARCH), theme->get_icon(SNAME("HelpSearch"), EditorStringName(EditorIcons)));
 		help_menu->set_item_icon(help_menu->get_item_index(HELP_COPY_SYSTEM_INFO), theme->get_icon(SNAME("ActionCopy"), EditorStringName(EditorIcons)));
@@ -6638,7 +6637,7 @@ EditorNode::EditorNode() {
 
 	main_menu = memnew(MenuBar);
 	title_bar->add_child(main_menu);
-	main_menu->set_theme_type_variation("FlatMenuButton");
+	main_menu->set_theme_type_variation("MainMenuBar");
 	main_menu->set_start_index(0); // Main menu, add to the start of global menu.
 	main_menu->set_prefer_global_menu(global_menu);
 	main_menu->set_switch_on_hover(true);

editor/gui/editor_bottom_panel.cpp

@@ -50,10 +50,6 @@ void EditorBottomPanel::_notification(int p_what) {
 	switch (p_what) {
 		case NOTIFICATION_THEME_CHANGED: {
 			expand_button->set_icon(get_editor_theme_icon(SNAME("ExpandBottomDock")));
-			for (int i = 0; i < items.size(); i++) {
-				items.write[i].button->add_theme_style_override("pressed", get_theme_stylebox(SNAME("MenuTransparent"), EditorStringName(EditorStyles)));
-				items.write[i].button->add_theme_style_override("hover_pressed", get_theme_stylebox(SNAME("MenuHover"), EditorStringName(EditorStyles)));
-			}
 		} break;
 	}
 }
@@ -160,7 +156,7 @@ void EditorBottomPanel::load_layout_from_config(Ref<ConfigFile> p_config_file, c
 
 Button *EditorBottomPanel::add_item(String p_text, Control *p_item, const Ref<Shortcut> &p_shortcut, bool p_at_front) {
 	Button *tb = memnew(Button);
-	tb->set_theme_type_variation("FlatMenuButton");
+	tb->set_theme_type_variation("BottomPanelButton");
 	tb->connect("toggled", callable_mp(this, &EditorBottomPanel::_switch_by_control).bind(p_item));
 	tb->set_drag_forwarding(Callable(), callable_mp(this, &EditorBottomPanel::_button_drag_hover).bind(tb, p_item), Callable());
 	tb->set_text(p_text);

editor/themes/editor_theme_manager.cpp

@@ -1742,29 +1742,40 @@ void EditorThemeManager::_populate_editor_styles(const Ref<EditorTheme> &p_theme
 		p_theme->set_stylebox("ScriptEditorPanelFloating", EditorStringName(EditorStyles), make_empty_stylebox(0, 0, 0, 0));
 		p_theme->set_stylebox("ScriptEditor", EditorStringName(EditorStyles), make_empty_stylebox(0, 0, 0, 0));
 
-		// Bottom panel.
-		Ref<StyleBoxFlat> style_bottom_panel = p_config.content_panel_style->duplicate();
-		style_bottom_panel->set_corner_radius_all(p_config.corner_radius * EDSCALE);
-		p_theme->set_stylebox("BottomPanel", EditorStringName(EditorStyles), style_bottom_panel);
-
 		// Main menu.
 		Ref<StyleBoxFlat> menu_transparent_style = p_config.button_style->duplicate();
 		menu_transparent_style->set_bg_color(Color(1, 1, 1, 0));
 		menu_transparent_style->set_border_width_all(0);
-		Ref<StyleBoxFlat> main_screen_button_transparent = menu_transparent_style->duplicate();
+		Ref<StyleBoxFlat> main_screen_button_hover = p_config.button_style_hover->duplicate();
 		for (int i = 0; i < 4; i++) {
-			menu_transparent_style->set_content_margin((Side)i, p_config.button_style->get_margin((Side)i) + p_config.button_style->get_border_width((Side)i));
+			menu_transparent_style->set_content_margin((Side)i, p_config.button_style->get_content_margin((Side)i));
+			main_screen_button_hover->set_content_margin((Side)i, p_config.button_style_hover->get_content_margin((Side)i));
 		}
-		p_theme->set_stylebox("MenuTransparent", EditorStringName(EditorStyles), menu_transparent_style);
-		p_theme->set_stylebox("MenuHover", EditorStringName(EditorStyles), p_config.button_style_hover);
-		p_theme->set_stylebox("normal", "MainScreenButton", main_screen_button_transparent);
-		p_theme->set_stylebox("pressed", "MainScreenButton", main_screen_button_transparent);
-		p_theme->set_stylebox("hover_pressed", "MainScreenButton", p_config.button_style_hover);
+		p_theme->set_stylebox("normal", "MainScreenButton", menu_transparent_style);
+		p_theme->set_stylebox("pressed", "MainScreenButton", menu_transparent_style);
+		p_theme->set_stylebox("hover", "MainScreenButton", main_screen_button_hover);
+		p_theme->set_stylebox("hover_pressed", "MainScreenButton", main_screen_button_hover);
+
+		p_theme->set_type_variation("MainMenuBar", "FlatMenuButton");
+		p_theme->set_stylebox("normal", "MainMenuBar", menu_transparent_style);
+		p_theme->set_stylebox("pressed", "MainMenuBar", main_screen_button_hover);
+		p_theme->set_stylebox("hover", "MainMenuBar", main_screen_button_hover);
+		p_theme->set_stylebox("hover_pressed", "MainMenuBar", main_screen_button_hover);
 
 		// Run bar.
 		p_theme->set_type_variation("RunBarButton", "FlatMenuButton");
 		p_theme->set_stylebox("disabled", "RunBarButton", menu_transparent_style);
 		p_theme->set_stylebox("pressed", "RunBarButton", menu_transparent_style);
+
+		// Bottom panel.
+		Ref<StyleBoxFlat> style_bottom_panel = p_config.content_panel_style->duplicate();
+		style_bottom_panel->set_corner_radius_all(p_config.corner_radius * EDSCALE);
+		p_theme->set_stylebox("BottomPanel", EditorStringName(EditorStyles), style_bottom_panel);
+		p_theme->set_type_variation("BottomPanelButton", "FlatMenuButton");
+		p_theme->set_stylebox("normal", "BottomPanelButton", menu_transparent_style);
+		p_theme->set_stylebox("pressed", "BottomPanelButton", menu_transparent_style);
+		p_theme->set_stylebox("hover_pressed", "BottomPanelButton", main_screen_button_hover);
+		p_theme->set_stylebox("hover", "BottomPanelButton", main_screen_button_hover);
 	}
 
 	// Editor GUI widgets.
@@ -1821,9 +1832,9 @@ void EditorThemeManager::_populate_editor_styles(const Ref<EditorTheme> &p_theme
 			Ref<StyleBoxFlat> style_flat_button_pressed = p_config.button_style_pressed->duplicate();
 
 			for (int i = 0; i < 4; i++) {
-				style_flat_button->set_content_margin((Side)i, p_config.button_style->get_margin((Side)i) + p_config.button_style->get_border_width((Side)i));
-				style_flat_button_hover->set_content_margin((Side)i, p_config.button_style->get_margin((Side)i) + p_config.button_style->get_border_width((Side)i));
-				style_flat_button_pressed->set_content_margin((Side)i, p_config.button_style->get_margin((Side)i) + p_config.button_style->get_border_width((Side)i));
+				style_flat_button->set_content_margin((Side)i, p_config.button_style->get_content_margin((Side)i));
+				style_flat_button_hover->set_content_margin((Side)i, p_config.button_style->get_content_margin((Side)i));
+				style_flat_button_pressed->set_content_margin((Side)i, p_config.button_style->get_content_margin((Side)i));
 			}
 			Color flat_pressed_color = p_config.dark_color_1.lightened(0.24).lerp(p_config.accent_color, 0.2) * Color(0.8, 0.8, 0.8, 0.85);
 			if (p_config.dark_theme) {