src/vs/editor/browser/viewParts/minimap/minimapCharSheet.ts/getCharIndex
export const getCharIndex = (chCode: number, fontScale: number) => {
	chCode -= Constants.START_CH_CODE;
	if (chCode < 0 || chCode > Constants.CHAR_COUNT) {
		if (fontScale <= 2) {
			// for smaller scales, we can get away with using any ASCII character...
			return (chCode + Constants.CHAR_COUNT) % Constants.CHAR_COUNT;
		}
		return Constants.CHAR_COUNT - 1; // unknown symbol
	}

	return chCode;
};