feuerwerk/src/ui/widgets/Label.ts

import { CanvasTextMetrics, Text } from 'pixi.js';
import { centreY } from '../math';
import { Theme, textStyle, type TextStyleToken } from '../Theme';
import { type Size, Widget } from '../Widget';

export interface LabelOptions {
  style?: TextStyleToken;
  align?: 'left' | 'center' | 'right';
  /** Horizontal padding inside the label bounds. */
  padding?: number;
}

/** Single-line text that truncates with an ellipsis when narrower than its content. */
export class Label extends Widget {
  private readonly textNode: Text;
  private fullText: string;
  private readonly align: NonNullable<LabelOptions['align']>;
  private readonly padding: number;

  constructor(text = '', options: LabelOptions = {}) {
    super();
    this.eventMode = 'none';
    this.fullText = text;
    this.align = options.align ?? 'left';
    this.padding = options.padding ?? 0;
    this.textNode = new Text({ text, style: textStyle(options.style ?? 'body') });
    this.addChild(this.textNode);
    this.minHeight = Theme.rowHeight;
  }

  /** The full text, not the truncated version on screen. */
  get text(): string {
    return this.fullText;
  }

  setText(text: string): void {
    if (text === this.fullText) return;
    this.fullText = text;
    this.invalidate();
  }

  /** Repaints only; the measured size may change, so the parent must relayout when that matters. */
  setStyle(token: TextStyleToken): void {
    this.textNode.style = textStyle(token);
    this.invalidate();
  }

  override measure(): Size {
    const metrics = CanvasTextMetrics.measureText(this.fullText, this.textNode.style);
    return {
      w: Math.max(this.minWidth, Math.ceil(metrics.width) + this.padding * 2),
      h: Math.max(this.minHeight, Math.ceil(metrics.height)),
    };
  }

  override redraw(): void {
    const available = this.w - this.padding * 2;
    this.textNode.text = truncate(this.fullText, this.textNode.style, available);
    const tw = this.textNode.width;
    let x = this.padding;
    if (this.align === 'center') x = (this.w - tw) / 2;
    else if (this.align === 'right') x = this.w - this.padding - tw;
    this.textNode.position.set(Math.round(x), centreY(this.h, this.textNode.height));
  }
}

/** Cuts `text` to fit `maxWidth` in the given style, appending "…" when shortened. */
export function truncate(text: string, style: Text['style'], maxWidth: number): string {
  if (maxWidth <= 0) return '';
  if (CanvasTextMetrics.measureText(text, style).width <= maxWidth) return text;
  let lo = 0;
  let hi = text.length;
  while (lo < hi) {
    const mid = Math.ceil((lo + hi) / 2);
    if (CanvasTextMetrics.measureText(text.slice(0, mid) + '…', style).width <= maxWidth) lo = mid;
    else hi = mid - 1;
  }
  return lo === 0 ? '' : text.slice(0, lo) + '…';
}