Implement titles API, tab selection, regular-layout-select event

src/extensions.ts

@@ -65,6 +65,12 @@ declare global {
 			options?: { signal: AbortSignal },
 		): void;
 
+		addEventListener(
+			name: "regular-layout-select",
+			cb: (e: RegularLayoutSelectEvent) => void,
+			options?: { signal: AbortSignal },
+		): void;
+
 		removeEventListener(
 			name: "regular-layout-update",
 			cb: (e: RegularLayoutEvent) => void,
@@ -79,8 +85,14 @@ declare global {
 			name: "regular-layout-before-resize",
 			cb: (e: RegularLayoutPresizeEvent) => void,
 		): void;
+
+		removeEventListener(
+			name: "regular-layout-select",
+			cb: (e: RegularLayoutSelectEvent) => void,
+		): void;
 	}
 }
 
 export type RegularLayoutEvent = CustomEvent<Layout>;
 export type RegularLayoutPresizeEvent = CustomEvent<PresizeDetail>;
+export type RegularLayoutSelectEvent = CustomEvent<{ name: string }>;

src/layout/generate_grid.ts

@@ -264,3 +264,21 @@ export function create_css_grid_layout(
 
 	return css.join("\n");
 }
+
+/**
+ * Generates CSS Grid styles that render a single panel maximized to fill the
+ * entire layout, hiding all other slotted children.
+ *
+ * @param name - The name of the panel to maximize.
+ * @param physics - Instance constants (defaults to {@link DEFAULT_PHYSICS}).
+ * @returns CSS string showing only `name`, full-size.
+ */
+export function create_css_maximize_layout(
+	name: string,
+	physics: Physics = DEFAULT_PHYSICS,
+): string {
+	return [
+		host_template("100%", "100%"),
+		child_template(physics, name, "1", "1"),
+	].join("\n");
+}

src/model/overlay_controller.ts

@@ -58,7 +58,6 @@ export class OverlayController {
 
 		const [col, row, box, style] = host.relativeCoordinates(event, true);
 		let drop_target = calculate_intersection(col, row, panel);
-		console.log(row, col, drop_target);
 		if (drop_target) {
 			drop_target = calculate_edge(
 				col,

src/regular-layout-frame.ts

@@ -31,6 +31,20 @@ const HTML_TEMPLATE = `
 
 type DragState = { moved?: boolean; path: LayoutPath };
 
+/**
+ * Escapes a string for safe use as a CSS `<string>` token (the `content`
+ * fallback), handling backslashes, double-quotes, and newlines.
+ */
+const css_string = (value: string): string =>
+	`"${value.replace(/[\\"\n]/g, (c) => (c === "\n" ? "\\A " : `\\${c}`))}"`;
+
+/**
+ * The per-slot CSS custom property a consumer sets to override a tab's label,
+ * e.g. `regular-layout { --regular-layout-my-panel--title: "My Panel"; }`.
+ */
+const title_variable = (slot: string): string =>
+	`--regular-layout-${globalThis.CSS.escape(slot)}--title`;
+
 /**
  * A custom element that represents a draggable panel within a
  * `<regular-layout>`.
@@ -47,8 +61,17 @@ type DragState = { moved?: boolean; path: LayoutPath };
  * [named `slot`s](https://developer.mozilla.org/en-US/docs/Web/API/Web_components/Using_templates_and_slots)
  * for wholesale replacement of the underlying Shadow DOM.
  *
+ * The `name` attribute identifies the panel within the layout. The tab label
+ * defaults to `name`, but can be overridden with pure CSS by setting the
+ * `--regular-layout-<name>--title` custom property to a CSS string - the label
+ * is rendered via the tab title's `::before` `content`, so the override
+ * applies reactively with no JavaScript.
+ *
  * @example
  * ```html
+ * <style>
+ *     regular-layout { --regular-layout-panel-1--title: "Panel 1"; }
+ * </style>
  * <regular-layout>
  *     <regular-layout-frame name="panel-1">
  *         <!-- Panel content here -->
@@ -59,6 +82,7 @@ type DragState = { moved?: boolean; path: LayoutPath };
 export class RegularLayoutFrame extends HTMLElement {
 	private _shadowRoot!: ShadowRoot;
 	private _container_sheet!: CSSStyleSheet;
+	private _title_sheet!: CSSStyleSheet;
 	private _layout!: RegularLayout;
 	private _header!: HTMLElement;
 	private _drag: DragState | null = null;
@@ -72,8 +96,12 @@ export class RegularLayoutFrame extends HTMLElement {
 	connectedCallback() {
 		this._container_sheet ??= new CSSStyleSheet();
 		this._container_sheet.replaceSync(CSS);
+		this._title_sheet ??= new CSSStyleSheet();
 		this._shadowRoot ??= this.attachShadow({ mode: "open" });
-		this._shadowRoot.adoptedStyleSheets = [this._container_sheet];
+		this._shadowRoot.adoptedStyleSheets = [
+			this._container_sheet,
+			this._title_sheet,
+		];
 		this._shadowRoot.innerHTML = HTML_TEMPLATE;
 		this._layout = this.parentElement as RegularLayout;
 		this._header = this._shadowRoot.children[0] as HTMLElement;
@@ -106,6 +134,10 @@ export class RegularLayoutFrame extends HTMLElement {
 	}
 
 	private onPointerDown = (event: PointerEvent): void => {
+		if (event.button !== 0) {
+			return;
+		}
+
 		const elem = event.target as RegularLayoutTab;
 		if (elem.part.contains("tab")) {
 			const path = this._layout.calculateIntersect(event);
@@ -184,5 +216,28 @@ export class RegularLayoutFrame extends HTMLElement {
 		for (let j = this._header.children.length - 1; j >= last_index; j--) {
 			this._header.removeChild(this._header.children[j]);
 		}
+
+		this.drawTitles(attr, new_tab_panel.tabs);
+	};
+
+	/**
+	 * Regenerates this frame's title stylesheet, mapping each tab (by its slot
+	 * `name`) to its label. The label is rendered via the title's `::before`
+	 * `content`, reading the slot's `--regular-layout-<slot>--title` override
+	 * variable with the slot name as the fallback - so a consumer can relabel a
+	 * tab purely in CSS and the change applies reactively.
+	 *
+	 * @param attr - The child name attribute (`CHILD_ATTRIBUTE_NAME`).
+	 * @param tabs - The slot names rendered in this frame's titlebar.
+	 */
+	private drawTitles = (attr: string, tabs: string[]) => {
+		const css = tabs
+			.map(
+				(slot) =>
+					`regular-layout-tab[${attr}="${slot}"] [part~="title"]::before{content:var(${title_variable(slot)}, ${css_string(slot)})}`,
+			)
+			.join("\n");
+
+		this._title_sheet.replaceSync(css);
 	};
 }

src/regular-layout-tab.ts

@@ -34,6 +34,14 @@ export class RegularLayoutTab extends HTMLElement {
 	 * @param index - The index of this tab within the tab panel.
 	 */
 	populate = (layout: RegularLayout, tab_panel: TabLayout, index: number) => {
+		// Stamp the slot onto the tab so its title can be styled by name (see
+		// `RegularLayoutFrame#drawTitles`). Tag-qualified selectors keep this
+		// distinct from the panel `name` on `<regular-layout-frame>`.
+		this.setAttribute(
+			layout.savePhysics().CHILD_ATTRIBUTE_NAME,
+			tab_panel.tabs[index],
+		);
+
 		if (this._tab_panel) {
 			const tab_changed =
 				(index === tab_panel.selected) !==
@@ -44,9 +52,6 @@ export class RegularLayoutTab extends HTMLElement {
 
 			if (index_changed) {
 				const selected = tab_panel.selected === index;
-				const slot = tab_panel.tabs[index];
-				this.children[0].textContent = slot;
-
 				if (selected) {
 					this.children[1].part.add("active-close");
 					this.part.add("active-tab");
@@ -56,7 +61,6 @@ export class RegularLayoutTab extends HTMLElement {
 				}
 			}
 		} else {
-			const slot = tab_panel.tabs[index];
 			const selected = tab_panel.selected === index;
 			const parts = selected ? "active-close close" : "close";
 			this.innerHTML = `<div part="title"></div><button part="${parts}"></button>`;
@@ -67,7 +71,6 @@ export class RegularLayoutTab extends HTMLElement {
 			}
 
 			this.addEventListener("pointerdown", this.onTabClick);
-			this.children[0].textContent = slot;
 			this.children[1].addEventListener("pointerdown", this.onTabClose);
 		}
 
@@ -76,28 +79,23 @@ export class RegularLayoutTab extends HTMLElement {
 		this._index = index;
 	};
 
-	private onTabClose = (_: Event) => {
+	private onTabClose = (event: Event) => {
+		if (event instanceof PointerEvent && event?.button !== 0) {
+			return;
+		}
+
 		if (this._tab_panel !== undefined && this._index !== undefined) {
 			this._layout?.removePanel(this._tab_panel.tabs[this._index]);
 		}
 	};
 
-	private onTabClick = (_: PointerEvent) => {
-		if (
-			this._tab_panel !== undefined &&
-			this._index !== undefined &&
-			this._index !== this._tab_panel.selected
-		) {
-			const new_layout = this._layout?.save();
-			const new_tab_panel = this._layout?.getPanel(
-				this._tab_panel.tabs[this._index],
-				new_layout,
-			);
+	private onTabClick = (event: PointerEvent) => {
+		if (event.button !== 0) {
+			return;
+		}
 
-			if (new_tab_panel && new_layout) {
-				new_tab_panel.selected = this._index;
-				this._layout?.restore(new_layout);
-			}
+		if (this._tab_panel !== undefined && this._index !== undefined) {
+			this._layout?.select(this._tab_panel.tabs[this._index]);
 		}
 	};
 }

src/regular-layout.ts

@@ -17,7 +17,10 @@
  */
 
 import { EMPTY_PANEL } from "./core/types.ts";
-import { create_css_grid_layout } from "./layout/generate_grid.ts";
+import {
+	create_css_grid_layout,
+	create_css_maximize_layout,
+} from "./layout/generate_grid.ts";
 import type {
 	LayoutPath,
 	Layout,
@@ -106,6 +109,14 @@ export interface PointerEventCoordinates {
  * latter implementation would require synchronizing the light DOM
  * and shadow DOM slots/slotted children continuously.
  *
+ * Note that `::slotted()` only matches *directly* slotted nodes - it
+ * does not pierce a slotted `<slot>`. A consumer that wants to forward
+ * its own light-DOM content through `<regular-layout>` therefore cannot
+ * place a bare `<slot name="X">` as a layout child and expect it to be
+ * grid-positioned; instead, wrap the forwarding slot in a concrete
+ * `<regular-layout-frame name="X">` (which *is* directly slotted and so
+ * matched by the generated `::slotted([name="X"])` rules).
+ *
  */
 export class RegularLayout extends HTMLElement {
 	private _shadowRoot: ShadowRoot;
@@ -118,6 +129,7 @@ export class RegularLayout extends HTMLElement {
 	private _physics: Physics;
 	private _presizeQueue: PresizeQueue;
 	private _overlayController: OverlayController;
+	private _maximized?: string;
 
 	constructor() {
 		super();
@@ -253,6 +265,36 @@ export class RegularLayout extends HTMLElement {
 		await this.restore(remove_child(this._panel, name));
 	};
 
+	/**
+	 * Selects a panel by `name`, making it the front-most tab within its
+	 * containing stack, then dispatches a `<prefix>-select` event with
+	 * `detail: { name }`.
+	 *
+	 * The event fires whenever a tab is selected - including re-selecting the
+	 * already-active tab, or selecting the sole tab of a single-element stack -
+	 * so consumers can always map a tab interaction to an "active panel". When
+	 * the selection actually changes, a `<prefix>-update` event is dispatched
+	 * first (via {@link restore}).
+	 *
+	 * @param name - The name of the panel to select.
+	 */
+	select = async (name: string) => {
+		const layout = this.save();
+		const tab_panel = this.getPanel(name, layout);
+		if (!tab_panel) {
+			return;
+		}
+
+		const index = tab_panel.tabs.indexOf(name);
+		if (index !== -1 && tab_panel.selected !== index) {
+			tab_panel.selected = index;
+			await this.restore(layout);
+		}
+
+		const event_name = `${this._physics.CUSTOM_EVENT_NAME_PREFIX}-select`;
+		this.dispatchEvent(new CustomEvent(event_name, { detail: { name } }));
+	};
+
 	/**
 	 * Retrieves a panel by name from the layout tree.
 	 *
@@ -286,13 +328,50 @@ export class RegularLayout extends HTMLElement {
 		await this.restore(EMPTY_PANEL);
 	};
 
+	/**
+	 * Maximizes a panel by `name`, rendering it full-size and hiding every
+	 * other panel. This is transient display state - it is **not** persisted by
+	 * {@link save}, and any subsequent {@link restore} resets the layout to the
+	 * minimized (normal, multi-panel) view.
+	 *
+	 * Has no effect if `name` is not present in the current layout.
+	 *
+	 * @param name - The name of the panel to maximize.
+	 */
+	maximize = (name: string) => {
+		if (!this.getPanel(name)) {
+			return;
+		}
+
+		this._maximized = name;
+		this._stylesheet.replaceSync(
+			create_css_maximize_layout(name, this._physics),
+		);
+	};
+
+	/**
+	 * Restores the normal multi-panel view after a {@link maximize}, without
+	 * altering the layout tree. No-op if no panel is currently maximized.
+	 */
+	minimize = () => {
+		if (this._maximized === undefined) {
+			return;
+		}
+
+		this._maximized = undefined;
+		this._stylesheet.replaceSync(
+			create_css_grid_layout(this._panel, undefined, this._physics),
+		);
+	};
+
 	/**
 	 * Restores the layout from a saved state synchronously, without
 	 * dispatching the `regular-layout-before-resize` event.
 	 *
 	 * @param layout - The layout tree to restore
 	 */
 	restoreSync = (layout: Layout, _is_flattened: boolean = false) => {
+		this._maximized = undefined;
 		this._panel = !_is_flattened ? flatten(layout) : layout;
 		const css = create_css_grid_layout(this._panel, undefined, this._physics);
 		this._stylesheet.replaceSync(css);
@@ -320,13 +399,15 @@ export class RegularLayout extends HTMLElement {
 	restore = async (layout: Layout, _is_flattened: boolean = false) => {
 		const panel = !_is_flattened ? flatten(layout) : layout;
 		await this._presizeQueue.run(panel, () => {
+			this._maximized = undefined;
 			this._panel = panel;
 			const css = create_css_grid_layout(this._panel, undefined, this._physics);
 			this._stylesheet.replaceSync(css);
 			const event_name = `${this._physics.CUSTOM_EVENT_NAME_PREFIX}-update`;
 			const event = new CustomEvent<Layout>(event_name, {
 				detail: this._panel,
 			});
+
 			this.dispatchEvent(event);
 		});
 	};
@@ -528,6 +609,10 @@ export class RegularLayout extends HTMLElement {
 	};
 
 	private onPointerDown = (event: PointerEvent) => {
+		if (event.button !== 0) {
+			return;
+		}
+
 		if (!this._physics.GRID_DIVIDER_CHECK_TARGET || event.target === this) {
 			const [col, row, rect] = this.relativeCoordinates(event);
 			const size = this._physics.GRID_DIVIDER_SIZE;