Function hasBuiltInDarkTheme

src/inject/detector.ts:7–80

()

const COLOR_SCHEME_META_SELECTOR = 'meta[name="color-scheme"]';

function hasBuiltInDarkTheme() {
    const rootStyle = getComputedStyle(document.documentElement);
    if (rootStyle.filter.includes('invert(1)') || rootStyle.colorScheme === 'dark') {
        return true;
    }

    const CELL_SIZE = 256;
    const MAX_ROW_COUNT = 4;
    const winWidth = innerWidth;
    const winHeight = innerHeight;
    const stepX = Math.floor(winWidth / Math.min(MAX_ROW_COUNT, Math.ceil(winWidth / CELL_SIZE)));
    const stepY = Math.floor(winHeight / Math.min(MAX_ROW_COUNT, Math.ceil(winHeight / CELL_SIZE)));

    const processedElements = new Set<Element>();

    for (let y = Math.floor(stepY / 2); y < winHeight; y += stepY) {
        for (let x = Math.floor(stepX / 2); x < winWidth; x += stepX) {
            const element = document.elementFromPoint(x, y);
            if (!element || processedElements.has(element) || element.tagName.toLocaleLowerCase() === 'img') {
                continue;
            }
            processedElements.add(element);
            const style = element === document.documentElement ? rootStyle : getComputedStyle(element);
            const bgColor = parseColorWithCache(style.backgroundColor);
            if (!bgColor) {
                return false;
            }
            if (bgColor.r === 24 && bgColor.g === 26 && bgColor.b === 27) {
                // For some websites changes to CSSStyleSheet.disabled and HTMLStyleElement.textContent
                // are not being applied synchronously. For example https://zorin.com/
                // Probably a browser bug. Treat as not having a dark theme.
                return false;
            }
            if (bgColor.a === 1) {
                const bgLightness = getSRGBLightness(bgColor.r, bgColor.g, bgColor.b);
                if (bgLightness > 0.6) {
                    return false;
                }
            } else {
                const textColor = parseColorWithCache(style.color);
                if (!textColor) {
                    return false;
                }
                const textLightness = getSRGBLightness(textColor.r, textColor.g, textColor.b);
                if (textLightness < 0.4) {
                    return false;
                }
            }
        }
    }

    const rootColor = parseColorWithCache(rootStyle.backgroundColor);
    if (!rootColor) {
        return false;
    }

    const bodyColor = document.body ? parseColorWithCache(getComputedStyle(document.body).backgroundColor) : {r: 0, g: 0, b: 0, a: 0};
    if (!bodyColor) {