[openbeos] Re: Right-to-left writing

  • From: "Niklas Nisbeth" <noisetonepause@xxxxxxxxx>
  • To: openbeos@xxxxxxxxxxxxx
  • Date: Mon, 6 Nov 2006 20:53:15 +0000

Hey Stephan.

Don't worry. The only OS to my knowledge the get right-to-left scripts
right is OS X, because it's absolutely anal about text rendering - and
even on 10.3 it was a bit dodgy. I appriciate that it's difficult,
and, let's face it, a bit of a niche for computers.

I'm not really sure where to go from here (except for apple.com:S) as
I know bugger all about text rendering on a computer, I just know how
it needs to look when it's done.

There's a GPL'd GTK editor called Katoob which is supposedly good for
Arabic but I've not tried it. I'm going to try and look at the BFont
headers and dig further into the Be Book and try to find out what's
going on.

Can anyone explain to me exactly what an Input Method is, BTW? I know
that for Japanese writing, it takes more than one character to make
one glyph (so you push more than one button on your keyboard to get
one glyph on the screen) and that that's why you need something more
advanced to help input_server interpret the keystrokes, but that's
about it, and I'm not sure it applies to Perso-Arabic script..

-Niklas

On 11/7/06, Stephan Assmus <superstippi@xxxxxx> wrote:

Hello Niklas,

It could be that (the Haiku) TextView makes some unfortunate assumptions
about text direction, but actually that is a responsibility of BFont. IIRC,
there are methods in BFont, which tell you the direction. As far as Haiku
is concerned, the text rendering needs to be improved a lot. It only
supports one type of glyph spacing, while BFont knows about four or so
(B_BITMAP_SPACING, B_CHAR_SPACING...). I didn't bother at all with thinking
about right->left or bottom->top text rendering. I didn't know of a way to
test it, and I have basically no clue about it. I thought to myself, if
someone with the knowledge about proper text rendering is desperate enough,
then he should do it. :-)

That being said, if you can test this on Haiku and it doesn't work, I can
at least try to help you to get it work properly.

However, in pretty much any application, text rendering is done with the
BView::DrawString() method. It get's provided a "starting point" of the
text. In any of my own code, and virtually all code I came across from
other people, the point is calculated to be on the left side of the string.
So I would assume that even if we made the necessary changes in the Haiku
app_server, I'm afraid all applications would need to be adjusted. Or some
smart trick invented. Or, of course, I might be talking non-sense because I
just don't have enough of a clue. :-)

Best regards,
-Stephan

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