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import {
BOUND_TEXT_PADDING,
DEFAULT_FONT_SIZE,
DEFAULT_FONT_FAMILY,
} from "../constants";
import { getFontString, isTestEnv, normalizeEOL } from "../utils";
import type { FontString, ExcalidrawTextElement } from "./types";
export const measureText = (
text: string,
font: FontString,
lineHeight: ExcalidrawTextElement["lineHeight"],
) => {
const _text = text
.split("\n")
// replace empty lines with single space because leading/trailing empty
// lines would be stripped from computation
.map((x) => x || " ")
.join("\n");
const fontSize = parseFloat(font);
const height = getTextHeight(_text, fontSize, lineHeight);
const width = getTextWidth(_text, font);
return { width, height };
};
const DUMMY_TEXT = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".toLocaleUpperCase();
// FIXME rename to getApproxMinContainerWidth
export const getApproxMinLineWidth = (
font: FontString,
lineHeight: ExcalidrawTextElement["lineHeight"],
) => {
const maxCharWidth = getMaxCharWidth(font);
if (maxCharWidth === 0) {
return (
measureText(DUMMY_TEXT.split("").join("\n"), font, lineHeight).width +
BOUND_TEXT_PADDING * 2
);
}
return maxCharWidth + BOUND_TEXT_PADDING * 2;
};
export const getMinTextElementWidth = (
font: FontString,
lineHeight: ExcalidrawTextElement["lineHeight"],
) => {
return measureText("", font, lineHeight).width + BOUND_TEXT_PADDING * 2;
};
export const isMeasureTextSupported = () => {
const width = getTextWidth(
DUMMY_TEXT,
getFontString({
fontSize: DEFAULT_FONT_SIZE,
fontFamily: DEFAULT_FONT_FAMILY,
}),
);
return width > 0;
};
export const normalizeText = (text: string) => {
return (
normalizeEOL(text)
// replace tabs with spaces so they render and measure correctly
.replace(/\t/g, " ")
);
};
const splitIntoLines = (text: string) => {
return normalizeText(text).split("\n");
};
/**
* To get unitless line-height (if unknown) we can calculate it by dividing
* height-per-line by fontSize.
*/
export const detectLineHeight = (textElement: ExcalidrawTextElement) => {
const lineCount = splitIntoLines(textElement.text).length;
return (textElement.height /
lineCount /
textElement.fontSize) as ExcalidrawTextElement["lineHeight"];
};
/**
* We calculate the line height from the font size and the unitless line height,
* aligning with the W3C spec.
*/
export const getLineHeightInPx = (
fontSize: ExcalidrawTextElement["fontSize"],
lineHeight: ExcalidrawTextElement["lineHeight"],
) => {
return fontSize * lineHeight;
};
// FIXME rename to getApproxMinContainerHeight
export const getApproxMinLineHeight = (
fontSize: ExcalidrawTextElement["fontSize"],
lineHeight: ExcalidrawTextElement["lineHeight"],
) => {
return getLineHeightInPx(fontSize, lineHeight) + BOUND_TEXT_PADDING * 2;
};
let textMetricsProvider: TextMetricsProvider | undefined;
/**
* Set a custom text metrics provider.
*
* Useful for overriding the width calculation algorithm where canvas API is not available / desired.
*/
export const setCustomTextMetricsProvider = (provider: TextMetricsProvider) => {
textMetricsProvider = provider;
};
export interface TextMetricsProvider {
getLineWidth(text: string, fontString: FontString): number;
}
class CanvasTextMetricsProvider implements TextMetricsProvider {
private canvas: HTMLCanvasElement;
constructor() {
this.canvas = document.createElement("canvas");
}
/**
* We need to use the advance width as that's the closest thing to the browser wrapping algo, hence using it for:
* - text wrapping
* - wysiwyg editor (+padding)
*
* > The advance width is the distance between the glyph's initial pen position and the next glyph's initial pen position.
*/
public getLineWidth(text: string, fontString: FontString): number {
const context = this.canvas.getContext("2d")!;
context.font = fontString;
const metrics = context.measureText(text);
const advanceWidth = metrics.width;
// since in test env the canvas measureText algo
// doesn't measure text and instead just returns number of
// characters hence we assume that each letteris 10px
if (isTestEnv()) {
return advanceWidth * 10;
}
return advanceWidth;
}
}
export const getLineWidth = (text: string, font: FontString) => {
if (!textMetricsProvider) {
textMetricsProvider = new CanvasTextMetricsProvider();
}
return textMetricsProvider.getLineWidth(text, font);
};
export const getTextWidth = (text: string, font: FontString) => {
const lines = splitIntoLines(text);
let width = 0;
lines.forEach((line) => {
width = Math.max(width, getLineWidth(line, font));
});
return width;
};
export const getTextHeight = (
text: string,
fontSize: number,
lineHeight: ExcalidrawTextElement["lineHeight"],
) => {
const lineCount = splitIntoLines(text).length;
return getLineHeightInPx(fontSize, lineHeight) * lineCount;
};
export const charWidth = (() => {
const cachedCharWidth: { [key: FontString]: Array<number> } = {};
const calculate = (char: string, font: FontString) => {
const unicode = char.charCodeAt(0);
if (!cachedCharWidth[font]) {
cachedCharWidth[font] = [];
}
if (!cachedCharWidth[font][unicode]) {
const width = getLineWidth(char, font);
cachedCharWidth[font][unicode] = width;
}
return cachedCharWidth[font][unicode];
};
const getCache = (font: FontString) => {
return cachedCharWidth[font];
};
const clearCache = (font: FontString) => {
cachedCharWidth[font] = [];
};
return {
calculate,
getCache,
clearCache,
};
})();
export const getMinCharWidth = (font: FontString) => {
const cache = charWidth.getCache(font);
if (!cache) {
return 0;
}
const cacheWithOutEmpty = cache.filter((val) => val !== undefined);
return Math.min(...cacheWithOutEmpty);
};
export const getMaxCharWidth = (font: FontString) => {
const cache = charWidth.getCache(font);
if (!cache) {
return 0;
}
const cacheWithOutEmpty = cache.filter((val) => val !== undefined);
return Math.max(...cacheWithOutEmpty);
};
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