True Type Instructions
gcdart_squeak at rediffmail.com
Tue May 16 11:48:11 UTC 2006
On Tue, 16 May 2006 Boris Gaertner wrote :
>"Noname Myname" <gcdart_squeak at rediffmail.com> wrote:
> > I believe that True Type Font Support in Already there in SQUEAK.
>Yes, some support for True Type Fonts is available, but it is
> > After seeing the Open Type specifications by microsoft and adobe ,
> > I think that to extended Support to Open Type fonts , is it just
> > nessacary to extract the extra tables present in the Open Type
> > font ( not CFF format ).
>Right. However, the extraction of the more advanced tables
>I find the specification for the tables GSUB, GPOS and GDEF quite
>difficult to follow. For indian scripts, you will certainly need full
>support for GSUB. In the "OpenTypeViewer" that you can
>download from SqueakMap you will find incomplete support for
>the GSUB table, but the subtables for contextual substitution
>are not read - the application is still incomplete.
> > There was one Open Type font reader implemented, which
> > failed to work on Indian Languages ( mangal.ttf , latha.ttf
> > provided by microsoft ). Wat Xactly is the problem ?
> > More Over , Even if i extract all the tables how xacty
> > shud i implement the script shaping ?
> > that is wer shud i implement it ?
>For several reasons this is the hard part of the exercise:
>1. The Open Type Format is very flexible and allows for
>a considerable difference in script shaping. You may not
>assume that two different TTF fonts for, say, Devanagari,
>will contain the same or similar glyph substitution rules.
>2. For script shaping support, you will have to rewrite
>most of the text formatting and display machinery.
>For text formatting and display the following classes
>cooperate (always with subclasses included):
> Text, DisplayText, Paragraph, NewParagraph,
>CharacterScanner, AbstractFont, TextStyle, TextLine,
>3. I think that for script shaping you will have to implement
>a structure that maintains both a string of stored codepoints
>and a string that maintains the indices of the shaped glyphs
>to display. The mapping between these two strings is not a
>one-to-one mapping; due to script shaping several
>codepoints may merge into one display glyph, a ligature.
> Greetings, Boris
One more Question , shud the true type instructions in the Open Type files definitely be executed ?
Or are they supported currently in SQUEAK ? Well if they are ... then wud'nt the display of characters be terribly slow ?
Becuz you have to create an intrepreter inside another interpreter("SQUEAK") to understand the instructions and execute them.
how does SQUEAK Handle the text display so efficiently or am i missing something very basic .... ?
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