Progress bar for scene loading (#71)

studio-ui/src/lib/progress.element.scss

@@ -0,0 +1,15 @@
+:host {
+	display: block;
+	height: 0.5rem;
+	background: #713837;
+	overflow: hidden;
+}
+
+.fill {
+	height: 100%;
+	background: #E66462;
+}
+
+.animated {
+	// TODO
+}

studio-ui/src/lib/progress.element.ts

@@ -0,0 +1,51 @@
+import { LitElement, type PropertyValues, html, unsafeCSS } from "lit";
+import { customElement, property } from "lit/decorators.js";
+import { styleMap } from "lit/directives/style-map.js";
+
+import styles from "./progress.element.scss?inline";
+
+@customElement("sts-progress")
+export class ProgressElement extends LitElement {
+	static override styles = unsafeCSS(styles);
+
+	@property() override role = "progressbar";
+
+	@property({ type: Number }) min = 0;
+	@property({ type: Number }) max = 100;
+	@property({ type: Number }) value = 0;
+	@property({ type: Boolean }) indeterminate = false;
+
+	protected override willUpdate(changes: PropertyValues<this>): void {
+		if (this.min === this.max)
+			this.indeterminate = true;
+
+		if (this.indeterminate) {
+			this.removeAttribute("aria-valuenow");
+			this.removeAttribute("aria-valuemin");
+			this.removeAttribute("aria-valuemax");
+		} else {
+			this.setAttribute("aria-valuenow", this.value.toString());
+
+			if (this.min !== 0)
+				this.setAttribute("aria-valuemin", this.min.toString());
+
+			if (this.max !== 100)
+				this.setAttribute("aria-valuemax", this.max.toString());
+		}
+
+		super.willUpdate(changes);
+	}
+
+	protected override render = () => html`
+		${this.indeterminate ? html`
+			<div class="animated" part="animated"></div>
+		` : html`
+			<div class="fill"
+				part="fill"
+				style=${styleMap({
+					width: `${(this.value / (this.max - this.min)) * 100}%`
+				})}
+			></div>
+		`}
+	`;
+}