setEmojiPresentationWidth function
Sets the display width used for emoji presentation characters.
Values outside {1,2} are ignored.
Implementation
void setEmojiPresentationWidth(int width) {
if (width != 1 && width != 2) return;
if (_emojiPresentationWidth == width) return;
_emojiPresentationWidth = width;
_unicodeStringWidthCache.clear();
}