Re: 32-bit characters in Java string literals
According to Roedy Green <see_website@mindprod.com.invalid>:
Is any OS, JVM, utility, browser etc. capable of rendering a code
point above 0xffff?
Oh yes, plenty.
Well, at least on my system (Linux with Ubuntu 9.10). For instance,
if I write this HTML file:
<html>
<body>
<p>🂓</p>
</body>
</html>
then both Firefox and Chromium display the "DOMINO TILE VERTICAL-06-06"
as they should. Now if I write this Java code:
public class Foo {
public static void main(String[] args)
{
StringBuilder sb = new StringBuilder();
sb.appendCodePoint(0x1F093);
System.out.println(sb.toString());
}
}
and run it in a standard terminal (GNOME Terminal 2.28.1 on that
system), then the domino tile is displayed. If I redirect the output in
a file, I can edit it just fine with the vim text editor; the domino
tile is being handled as a single character, just like it is supposed to
be.
Internally, C programs which wish to handle the full Unicode on Linux
use the 'wide character' type (wchar_t) which, on Linux, is defined to
be a 32-bit integer. Therefore there is nothing special with the 0xFFFF
limit. In practice, Unicode display trouble usually stem from limited
availability of fonts with exotic characters (although Linux has a fair
share of such fonts), double-width characters in monospace fonts, and
right-to-left scripts, all of which being orthogonal to the 16/32-bit
issue.
The same is not true in Windows, which switched to Unicode earlier, when
code points were 16-bit only; on Windows, wchar_t and the "wide string
literals" use 16-bit characters, and recent versions of Windows have to
resort to UTF-16 to process higher planes, just like Java. I have been
told that the OS is plainly able to process and display all of the
Unicode planes, but it can be expected that some applications are not up
to it yet.
C# is a late-comer (2001) but uses a 16-bit char type. This may be an
artefact of Java imitation. This may also be an attempt to ease
conversion of C or C++ code for Windows into C# code.
--Thomas Pornin