This includes HB_DIRECTION_INVALID and HB_SCRIPT_INVALID.
The INVALID will cause a "guess whatever from the text" in hb_shape().
While it's not ideal, it works better than the previous defaults at
least (HB_DIRECTION_LTR and HB_SCRIPT_COMMON).
The --features parsing handles errors now. More importantly, it
allos limiting individual features to specific byte ranges. The
format is Python-esque. Here is how it all works:
Syntax: Value: Start: End:
Setting value:
"kern" 1 0 ∞ # Turn feature on
"+kern" 1 0 ∞ # Turn feature off
"-kern" 0 0 ∞ # Turn feature off
"kern=0" 0 0 ∞ # Turn feature off
"kern=1" 1 0 ∞ # Turn feature on
"kern=2" 2 0 ∞ # Choose 2nd alternate
Setting index:
"kern[]" 1 0 ∞ # Turn feature on
"kern[:]" 1 0 ∞ # Turn feature on
"kern[5:]" 1 5 ∞ # Turn feature on, partial
"kern[:5]" 1 0 5 # Turn feature on, partial
"kern[3:5]" 1 3 5 # Turn feature on, range
"kern[3]" 1 3 3+1 # Turn feature on, single char
Mixing it all:
"kern[3:5]=0" 1 3 5 # Turn feature off for range
Accepts values like:
--features="-mkmk,aalt=2,calt=1,+cswh"
A minus sign means "=0", a plus sign means "=1". Default is "=1".
A minus sign overrides an explicit value.
Also adds --script support to hb-view.
If a script tag is not known to us, we pass the ISO 15924 tag around.
Right now, the OT layer ignores that, but we can fix it to blindly
convert that to an OT script tag.
- Rename HB_SCRIPT_INVALID_CODE to HB_SCRIPT_INVALID
- Add HB_DIRECTION_INVALID
- Make hb_script_get_horizontal_direction() public
- Make hb_shape() guess script from buffer text (first non-common
non-inherit script) if buffer script is set to HB_SCRIPT_INVALID (this
is NOT the default.)
- Make hb_shape() guess direction from buffer script if buffer direction
is set to HB_DIRECTION_INVALID (this is NOT the default.)
- Make hb-view.c set INVALID script and direction on the buffer.
The above changes are meant to make hb-view fairly useful for uni-script
uni-direction text. The guessing behavior however is NOT the default of
hb_shape() and must be asked for explicitly. This is intended, because
the guess is not a suitable substitute to full-fledged bidi and script
segmentation. It's just a testing tool.
Behdad Esfahbod
Ryan Lortie