@lightningtv/renderer/src/core/text-rendering/TrFontManager.ts

Lightning 3 Renderer

/*
 * If not stated otherwise in this file or this component's LICENSE file the
 * following copyright and licenses apply:
 *
 * Copyright 2023 Comcast Cable Communications Management, LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the License);
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import type { TrFontFace } from './font-face-types/TrFontFace.js';
import type { TextRendererMap, TrFontProps } from './renderers/TextRenderer.js';

const weightConversions: { [key: string]: number } = {
  normal: 400,
  bold: 700,
  bolder: 900,
  lighter: 100,
};

const fontWeightToNumber = (weight: string | number): number => {
  if (typeof weight === 'number') {
    return weight;
  }

  return weightConversions[weight] || 400;
};

function resolveFontToUse(
  familyMapsByPriority: FontFamilyMap[],
  family: string,
  weightIn: string | number,
  style: string,
  stretch: string,
): TrFontFace | undefined {
  let weight = fontWeightToNumber(weightIn);

  for (const fontFamiles of familyMapsByPriority) {
    const fontFaces = fontFamiles[family];

    if (!fontFaces) {
      continue;
    }

    if (fontFaces.size === 1) {
      // No Exact match found, find nearest weight match
      console.warn(
        `TrFontManager: Only one font face found for family: '${family}' - will be used for all weights and styles`,
      );

      return fontFaces.values().next().value as TrFontFace;
    }

    const weightMap = new Map<number, TrFontFace>();
    for (const fontFace of fontFaces) {
      const fontFamilyWeight = fontWeightToNumber(fontFace.descriptors.weight);
      if (
        fontFamilyWeight === weight &&
        fontFace.descriptors.style === style &&
        fontFace.descriptors.stretch === stretch
      ) {
        return fontFace;
      }

      weightMap.set(fontFamilyWeight, fontFace);
    }

    // No Exact match found, find nearest weight match
    const msg = `TrFontManager: No exact match: '${family} Weight: ${weight} Style: ${style} Stretch: ${stretch}'`;
    console.error(msg);

    // Follow the CSS font-weight algorithm to find the nearest weight match
    // https://www.w3.org/TR/2018/REC-css-fonts-3-20180920/#font-matching-algorithm

    if (weight === 400 && weightMap.has(500)) {
      return weightMap.get(500);
    }

    if (weight === 500 && weightMap.has(400)) {
      return weightMap.get(400);
    }

    if (weight < 400) {
      while (weight > 0) {
        if (weightMap.has(weight)) {
          return weightMap.get(weight);
        }
        weight -= 100;
      }
      // reset back for the next loop
      weight = 600;
    }

    while (weight < 1000) {
      if (weightMap.has(weight)) {
        return weightMap.get(weight);
      }
      weight += 100;
    }

    // finally check lower again
    weight = 500;
    while (weight > 0) {
      if (weightMap.has(weight)) {
        return weightMap.get(weight);
      }
      weight -= 100;
    }
  }

  return;
}

/**
 * Structure mapping font family names to a set of font faces.
 */
export interface FontFamilyMap {
  [familyName: string]: Set<TrFontFace>;
}

export class TrFontManager {
  private fontCache = new Map<string, TrFontFace>();

  constructor(private textRenderers: Partial<TextRendererMap>) {
    // Intentionally left blank
  }

  public addFontFace(font: TrFontFace): void {
    // All the font face to all of the text renderers that support it
    for (const trId in this.textRenderers) {
      const tr = this.textRenderers[trId as keyof TextRendererMap];
      if (tr && tr.isFontFaceSupported(font)) {
        tr.addFontFace(font);
      }
    }
  }

  /**
   * Utility method to resolve a single font face from a list of prioritized family maps based on
   * a set of font properties.
   *
   * @remarks
   * These are to be used by a text renderer to resolve a font face if needed.
   *
   * @param familyMapsByPriority
   * @param props
   * @returns
   */
  public resolveFontFace(
    familyMapsByPriority: FontFamilyMap[],
    props: TrFontProps,
    rendererType: 'canvas' | 'sdf',
  ): TrFontFace | undefined {
    const { fontFamily, fontWeight, fontStyle, fontStretch } = props;
    const fontCacheString = `${rendererType}_${fontFamily}_${fontStyle}_${fontWeight}_${fontStretch}`;

    if (this.fontCache.has(fontCacheString) === true) {
      return this.fontCache.get(fontCacheString);
    }

    const resolvedFont = resolveFontToUse(
      familyMapsByPriority,
      fontFamily,
      fontWeight,
      fontStyle,
      fontStretch,
    );
    if (resolvedFont !== undefined) {
      this.fontCache.set(fontCacheString, resolvedFont);
    }

    return resolvedFont;
  }
}