60 lines
2.2 KiB
JavaScript
60 lines
2.2 KiB
JavaScript
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"use strict";
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Object.defineProperty(exports, "__esModule", { value: true });
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exports.nextFontError = exports.calculateFallbackFontValues = void 0;
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const DEFAULT_SANS_SERIF_FONT = {
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name: 'Arial',
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azAvgWidth: 934.5116279069767,
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unitsPerEm: 2048,
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};
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const DEFAULT_SERIF_FONT = {
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name: 'Times New Roman',
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azAvgWidth: 854.3953488372093,
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unitsPerEm: 2048,
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};
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function calcAverageWidth(font) {
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try {
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const avgCharacters = 'aaabcdeeeefghiijklmnnoopqrrssttuvwxyz ';
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const hasAllChars = font
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.glyphsForString(avgCharacters)
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.flatMap((glyph) => glyph.codePoints)
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.every((codePoint) => font.hasGlyphForCodePoint(codePoint));
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if (!hasAllChars)
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return undefined;
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const widths = font
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.glyphsForString(avgCharacters)
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.map((glyph) => glyph.advanceWidth);
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const totalWidth = widths.reduce((sum, width) => sum + width, 0);
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return totalWidth / widths.length;
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}
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catch {
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// Could not calculate average width from the font file, skip size-adjust
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return undefined;
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}
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}
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function formatOverrideValue(val) {
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return Math.abs(val * 100).toFixed(2) + '%';
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}
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function calculateFallbackFontValues(font, category = 'serif') {
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const fallbackFont = category === 'serif' ? DEFAULT_SERIF_FONT : DEFAULT_SANS_SERIF_FONT;
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const azAvgWidth = calcAverageWidth(font);
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const { ascent, descent, lineGap, unitsPerEm } = font;
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const fallbackFontAvgWidth = fallbackFont.azAvgWidth / fallbackFont.unitsPerEm;
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let sizeAdjust = azAvgWidth
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? azAvgWidth / unitsPerEm / fallbackFontAvgWidth
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: 1;
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return {
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ascentOverride: formatOverrideValue(ascent / (unitsPerEm * sizeAdjust)),
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descentOverride: formatOverrideValue(descent / (unitsPerEm * sizeAdjust)),
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lineGapOverride: formatOverrideValue(lineGap / (unitsPerEm * sizeAdjust)),
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fallbackFont: fallbackFont.name,
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sizeAdjust: formatOverrideValue(sizeAdjust),
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};
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}
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exports.calculateFallbackFontValues = calculateFallbackFontValues;
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function nextFontError(message) {
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const err = new Error(message);
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err.name = 'NextFontError';
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throw err;
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}
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exports.nextFontError = nextFontError;
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