tree d37b8158a6075b57e3a7a44862d87961f2a3bfaa
parent ccc6745afaa68ce7497a6cd02ce85986d3c863d0
author Behdad Esfahbod <behdad@behdad.org> 1301943009 -0400
committer Behdad Esfahbod <behdad@behdad.org> 1301943009 -0400

[hb-view] Rewrite --features parsing, with range support

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