src/vs/editor/common/viewModel/monospaceLineBreaksComputer.ts/computeCharWidth
function computeCharWidth(charCode: number, visibleColumn: number, tabSize: number, columnsForFullWidthChar: number): number {
	if (charCode === CharCode.Tab) {
		return (tabSize - (visibleColumn % tabSize));
	}
	if (strings.isFullWidthCharacter(charCode)) {
		return columnsForFullWidthChar;
	}
	if (charCode < 32) {
		// when using `editor.renderControlCharacters`, the substitutions are often wide
		return columnsForFullWidthChar;
	}
	return 1;
}