fontforge-users

[Fontforge-users] New AddAnchorClass syntax.

[<pa...@um...>]

Hello,

I recently upgraded to the latest version of FontForge. I noticed that  
a lot of my scripts no longer work due to the changes to the syntax of  
the AddAnchorClass command. Moreover, I cannot figure out what the  
appropriate syntax might be.

The old syntax

    AddAnchorClass(name,type,script-lang,tag,flags,merge-with)

has been replaced with

    AddAnchorClass(name,type,lookup-subtable-name)

An example of my old code is:

    AddAnchorClass("sub","default","deva{dflt}","blwm",-1,"")
    AddAnchorClass("top","default","deva{dflt}","abvm",-1,"")

Could someone kindly please advise me of the valid options for  
lookup-subtable-name?

Thank you.

Regards,
Anshuman

Re: [Fontforge-users] New AddAnchorClass syntax.

[George W. <gw...@si...>]

On Wed, 2008-05-21 at 20:42, pa...@um... wrote:
> The old syntax
> 
>     AddAnchorClass(name,type,script-lang,tag,flags,merge-with)
> 
> has been replaced with
> 
>     AddAnchorClass(name,type,lookup-subtable-name)
> 
> An example of my old code is:
> 
>     AddAnchorClass("sub","default","deva{dflt}","blwm",-1,"")
>     AddAnchorClass("top","default","deva{dflt}","abvm",-1,"")
> 
> Could someone kindly please advise me of the valid options for  
> lookup-subtable-name?
ff's internal representation of GPOS/GSUB moved from a feature based
system to a lookup based system about a year and a half ago.

It used to be that an anchor class was attached to a feature ("blwm" and
script "deva{dflt}")
Now anchor classes live in lookup subtables which live in lookups which
are attached to features.

In other words ff now represents things the same way GPOS does.

So if you are starting with a blank font then the first thing you must
do is create a lookup
   AddLookup("belowbaseline","gpos_mark2base",0,
        [["blwm",[["deva",["dflt"]]]]])
then in that lookup you need to create (at least one) subtable
   AddLookupSubtable("belowbaseline", "belowbasesub")
then in that subtable you create your anchor class
   AddAnchorClass("sub","default","belowbasesub")
If you have more than one anchor class in the "blwm" feature it can live
in the same lookup subtable.

But your anchor class "top" is in a different feature, and it needs its
own lookup and lookup-subtable.

I'm sorry this is so complicated. But that's the way OpenType works. I
tried to hide some of the complexity when I first did things, but came
to realize the complexity was needed and had to scrap the earlier
methodology.

Re: [Fontforge-users] New AddAnchorClass syntax.

[Anshuman P. <pa...@um...>]

Dear George,

On Thu, 21 May 2008, George Williams wrote:

> So if you are starting with a blank font then the first thing you must
> do is create a lookup
>   AddLookup("belowbaseline","gpos_mark2base",0,
>        [["blwm",[["deva",["dflt"]]]]])
> then in that lookup you need to create (at least one) subtable
>   AddLookupSubtable("belowbaseline", "belowbasesub")
> then in that subtable you create your anchor class
>   AddAnchorClass("sub","default","belowbasesub")
> If you have more than one anchor class in the "blwm" feature it can live
> in the same lookup subtable.

Ok. This makes sense. I set up the lookup subtables in my script and 
everything works as expected.

> I'm sorry this is so complicated. But that's the way OpenType works. I
> tried to hide some of the complexity when I first did things, but came
> to realize the complexity was needed and had to scrap the earlier
> methodology.

Ah, it's bound to end up this way! :) Thanks for the prompt advice on how 
to set up the lookup subtable and declaring anchor classes. I will look 
into the OpenType specification later. I'm trying to create TrueType fonts 
from TeX bitmaps that supplement new Indic scripts that I've proposed for 
inclusion in Unicode.

Now, I'm struggling with the AddPosSub syntax that replaced AddATT.

Regards,
Anshuman

[Fontforge-users] AddPosSub (old AddATT) syntax

[<pa...@um...>]

In several of my scripts I used the deprecated AddATT command:

   AddATT("Ligature","deva{dflt}","abvs",-1,"glyph_a glyph_b")

ff reports that AddATT has been replaced by AddPosSub:

   AddPosSub(subtable-name,variant-glyph-name(s))
   AddPosSub(subtable-name,dx,dy,dadv_x,dadv_y)
   AddPosSub(subtable-name,other-glyph-name,dx1,dy1,
             dadv_x1,dadv_y1,dx2,dy2,dadv_x2,dadv_y2)

I am not quite sure how to go about migrating the AddATT command to  
the new AddPosSub. I appreciate any advice regarding this matter.

Regards,
Anshuman

Re: [Fontforge-users] AddPosSub (old AddATT) syntax

[George W. <gw...@si...>]

On Thu, 2008-05-22 at 00:02, pa...@um... wrote:
> In several of my scripts I used the deprecated AddATT command:
> 
>    AddATT("Ligature","deva{dflt}","abvs",-1,"glyph_a glyph_b")
> 
> ff reports that AddATT has been replaced by AddPosSub:
> 
>    AddPosSub(subtable-name,variant-glyph-name(s))
>    AddPosSub(subtable-name,dx,dy,dadv_x,dadv_y)
>    AddPosSub(subtable-name,other-glyph-name,dx1,dy1,
>              dadv_x1,dadv_y1,dx2,dy2,dadv_x2,dadv_y2)
> 
> I am not quite sure how to go about migrating the AddATT command to  
> the new AddPosSub. I appreciate any advice regarding this matter.
Er... The answer is pretty much the same as the one I gave you
yesterday. If that didn't make it clear I'm not sure what I could say to
improve matters.
  Perhaps it would help to look at
    http://fontforge.sf.net/fontinfo.html#Lookups
    http://fontforge.sf.net/lookups.html
these describe the basic philosophy behind lookups.

Once again you will need to create a lookup and then a subtable with in
it.
   AddLookup("above-ligs","gsub_ligature",0,
        [["abvs",[["deva",["dflt"]]]]])
   AddLookupSubtable("above-ligs", "above-ligs-sub")
   AddPosSub("above-ligs-sub","glyph_a glyph_b")