/// <summary>
/// Combines multiple emoji with a zero-width-joiner to (potentially) create a new symbol
/// </summary>
/// <param name="emoji"></param>
/// <returns></returns>
public static string Combine(IEnumerable <SingleEmoji> emoji)
{
#if !NET20
return(string.Join(ZeroWidthJoiner.AsString(), emoji));
#else
return(string.Join(ZeroWidthJoiner.AsString(), emoji.Select(e => e.ToString()).ToArray()));
#endif
}
/// <summary>
/// Determines whether a string is comprised solely of emoji, optionally with a maximum number of drawn symbols.
/// Can be used to determine whether a message consists of ≦ x emoji for purposes such as displaying at a larger size. Since one emoji symbol can be formed
/// from many separate emoji "characters" combined with zero-width joiners or even non-emoji characters followed by a "use emoji representation" marker, this
/// cannot be determined solely from the codepoints.
/// </summary>
/// <param name="message"></param>
/// <param name="maxSymbolCount"></param>
/// <returns></returns>
public static bool IsEmoji(string message, int maxSymbolCount = int.MaxValue)
{
var codepoints = message.Codepoints();
bool nextMustBeVS = false;
string zwj = ZeroWidthJoiner.AsString();
string variationSelector = VariationSelector.AsString();
bool ignoreNext = false;
int count = 0;
foreach (var cp in codepoints)
{
//we used to have message = message.trim() previously. This avoids the extra allocation, hepful in case of long messages.
//this was not premature optimization, it came out of necessity.
if (cp == "\n" || cp == "\r" || cp == "\t" || cp == " ")
{
continue;
}
if (nextMustBeVS)
{
nextMustBeVS = false;
if (cp != variationSelector)
{
//a non-emoji codepoint was found and this (the codepoint after it) is not the variation selector
return(false);
}
}
if (cp.In(SkinTones.All))
{
//don't count as part of the length
continue;
}
if (cp == zwj)
{
ignoreNext = true;
continue;
}
if (cp == variationSelector)
{
continue;
}
if (cp == Codepoints.ObjectReplacementCharacter)
{
//this is explicitly blacklisted for UI purposes
return(false);
}
if (cp == Keycap)
{
//this is not in the UTR, but is used to box symbols in an icon
//do not consider it part of the length
continue;
}
if (!ignoreNext)
{
++count;
if (count > maxSymbolCount)
{
return(false);
}
//by default, the UTR lists numbers, the asterisk, and the number sign as emoji, but we won't consider them as such unless they are followed by a VS
if (Languages.ArabicNumerals.Contains(cp) || cp == "#" || cp == "*")
{
nextMustBeVS = true;
continue;
}
else if (Languages.Emoji.Contains(cp))
{
continue;
}
else
{
//we've either encountered a non-emoji character OR a non-emoji codepoint that should be treated as an emoji if followed by the variation selector codepoint
nextMustBeVS = true;
continue;
}
}
ignoreNext = false;
}
if (nextMustBeVS)
{
return(false);
}
return(count > 0 && count <= maxSymbolCount);
}
/// <summary>
/// Combines multiple emoji with a zero-width-joiner to (potentially) create a new symbol
/// </summary>
/// <param name="emoji"></param>
/// <returns></returns>
public static string Combine(IEnumerable <SingleEmoji> emoji)
{
//does not work on .NET 2.0
//return string.Join(ZeroWidthJoiner.AsString(), emoji);
return(string.Join(ZeroWidthJoiner.AsString(), emoji.Select(e => e.ToString()).ToArray()));
}