If you copy-paste a newline character where it's not interpreted, such
as in a level title, the print function wouldn't treat it any special.
font::print_wrap() would, but that's not used here.
However, now that bidi is involved, the newline is passed straight to
SheenBidi which interprets it as a new line (which would need a new
SBLine to be created, or maybe even a new SBParagraph if there's two).
All while we're still treating it as a single line. This means the text
would just stop being displayed after the first newline. This is now
fixed by treating all newlines as spaces.
Again, the RTL property controls whether textboxes will be
right-aligned, and that kind of stuff. It can't be font-bound, since
Space Station supports Hebrew characters and we want to be able to
support, say, a Hebrew translation or Hebrew levels in the future
without having to make a dedicated (or duplicated) font for it.
Therefore it's a property of both the language pack as well as custom
levels - like custom levels already had a <font> tag, they now also
have an <rtl> tag that sets this property.
Right now, we'll have to hardcode it so the menu option for the Arabic
font sets the <rtl> property to 1, and all the other options set it to
0. But it's future-proof in that we can later decide to split the
option for Space Station into an LTR option and an RTL option (so both
"english/..." and "עברית" would select Space Station, but one sets the
RTL property to 0 and the other sets it to 1).
This now returns true if any of the characters in the text belong to
the Arabic or Hebrew alphabet, or are one of the Unicode directional
formatting characters. This is just so the bidi machinery doesn't have
to run 100% of the time for 100% of the languages. I will also make it
so the Arabic language pack, as well as custom levels, have an RTL
attribute that always enables bidi (and does things like
right-alignment in textboxes and other design-flipping)
I'm now using SheenBidi to reorder RTL and bidirectional text properly
at text rendering time! For Arabic this is still missing reshaping, but
everything's looking really promising now!
The code changes are really non-invasive. The changes to Font.cpp are
absolutely minimal:
1305+ if (bidi_should_transform(text))
1306+ {
1307+ text = bidi_transform(text);
1308+ }
There's now a FontBidi.cpp, which implements these two functions,
notably bidi_transform(), which takes a UTF-8 encoded string and
returns another UTF-8 encoded string that has bidi reorderings and
reshapings applied.
In that function, SheenBidi gives us information about where in the
input string runs start and end, and on a basic level, all we need to
do there is to concatenate the parts together in the order that we're
given them, and to reverse the RTL runs (recognizable by odd levels).
As this is a proof-of-concept, bidi_should_transform() still always
returns true, applying the bidi algorithm to all languages and all
strings. I'm thinking of enabling bidi only when the language/font
metadata enables RTL (which could be for the interface or for a custom
level), or outside of that, at least when RTL characters are detected
(such as Arabic or Hebrew Unicode blocks).
