Meziantou.Framework

Scripts

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Get the script of a character

UnicodeScripts gives the script of a code point (the Script property of the standard), the scripts a shared character is used with (Script_Extensions), and the names of the scripts:

Assert.Equal(UnicodeScript.Latin, UnicodeScripts.GetScript(new Rune('A')));
Assert.Equal(UnicodeScript.Cyrillic, UnicodeScripts.GetScript(new Rune(0x0410)));
Assert.Equal("Latn", UnicodeScripts.GetIso15924Code(UnicodeScript.Latin));

// Script_Extensions: the scripts a shared character is used with
Span<UnicodeScript> scripts = stackalloc UnicodeScript[UnicodeScripts.MaxScriptExtensionCount];
var count = UnicodeScripts.GetScriptExtensions(0x30FC, scripts);
Assert.Equal<UnicodeScript>([UnicodeScript.Hiragana, UnicodeScript.Katakana], scripts[..count]);
Assert.True(UnicodeScripts.HasScriptExtension(0x30FC, UnicodeScript.Katakana));

// The names of PropertyValueAliases.txt
Assert.True(UnicodeScripts.TryParseScript("Grek", out var script));
Assert.Equal(UnicodeScript.Greek, script);
  • Digits, punctuation and spaces are of the Common script, and combining marks of the Inherited script: they are used with many scripts. Script_Extensions narrows them down when the standard knows which scripts use them, such as the prolonged sound mark of Japanese, used with Hiragana and Katakana.
  • GetIso15924Code gives the four-letter code of ISO 15924 (Latn), and TryParseScript accepts these codes and the names of the standard (Greek).

Split a text into runs of one script

A font or a shaping engine works on runs of one script. Unicode.EnumerateScriptRuns splits a text into such runs, with the rules of UAX #24:

var text = "gamma (\u03B3) is";
var runs = new List<string>();
foreach (UnicodeScriptRun run in Unicode.EnumerateScriptRuns(text))
{
    runs.Add($"{text.Substring(run.Index, run.Length)}: {run.Script}");
}

Assert.Equal(["gamma (: Latin", "\u03B3: Greek", ") is: Latin"], runs);
  • Combining marks follow their base, and spaces and punctuation follow the text before them.
  • Script_Extensions are honored, and both brackets of a pair are in the same run.
  • Each UnicodeScriptRun has the Index and the Length of the run in the text, and its Script.

To find out whether a user name mixes scripts in a suspicious way, use Unicode.IsMixedScript: see Look-alike characters.