While fixing the previous commit I noticed that window titles don't
actually _work_ properly if you change the terminal character set,
because the text accumulated in the OSC string buffer is sent to the
TermWin as raw bytes, with no indication of what character set it
should interpret them as. You might get lucky if you happened to
choose the right charset (in particular, UTF-8 is a common default),
but if you change the charset half way through a run, then there's
certainly no way the frontend will know to interpret two window titles
sent before and after the change in two different charsets.
So, now win_set_title() and win_set_icon_title() both include a
codepage parameter along with the byte string, and it's up to them to
translate the provided window title from that encoding to whatever the
local window system expects to receive.
On Windows, that's wide-string Unicode, so we can just use the
existing dup_mb_to_wc utility function. But in GTK, it's UTF-8, so I
had to write an extra utility function to encode a wide string as
UTF-8.
When the terminal is in UTF-8 mode, we accumulate UTF-8 text normally
in the OSC string buffer - but the byte 0x9C is interpreted as the C1
control character String Terminator, which terminates the OSC
sequence. That's not really what you want in UTF-8 mode, because 0x9C
is also a perfectly normal UTF-8 continuation character. For example,
you'd expect this to set the window title to "FÜNF":
echo -ne '\033]0;FÜNF\007'
but in fact, by the sheer chance that Ü is encoded with an 0x9C byte,
you get a window title consisting of "F" followed by an illegal-
encoding marker, and the OSC sequence is terminated abruptly so that
the trailing 'NF' is printed normally to the terminal and then the BEL
generates a beep.
Now, in UTF-8 mode, we only support the C1 control for ST if it
appears in the form of the proper UTF-8 encoding of U+009C. So that
example now 'works', at least in the sense that the terminal considers
the OSC sequence to terminate where the sender expected it to
terminate.
Another case where we interpret 0x9C inappropriately as ST is if the
terminal is in a single-byte character set in which that character is
a printing one. In CP437, for example, you can't set a window title
containing a pound sign, because its encoding is 0x9C.
This commit by itself doesn't make those window titles _work_, in the
sense of coming out looking right. They just mean that the OSC
sequence is not terminated at the wrong place. The actual title
rendering will be fixed in the next commit.
The input length field is now a size_t rather than an int, on general
principles. The return value is now void (we weren't using the
previous return value at all). And we now require the client to have
previously allocated a BidiContext, which will allow allocated storage
to be reused between runs, saving a lot of churn on malloc.
(However, the current BidiContext doesn't contain anything
interesting. I could have moved the existing mallocs into it, but
there's no point, since I'm about to rewrite the whole thing anyway.)
This contains terminal.c, bidi.c (formerly minibidi.c), and
terminal.h. I'm about to make a couple more bidi-related source files,
so it seems worth starting by making a place to put them that won't be
cluttering up the top level.
