[HarfBuzz] HarfBuzz rewrite

[Behdad Esfahbod]

On Wed, 2007-01-03 at 09:16 -0500, Simon Hausmann wrote:
> On Wednesday 03 January 2007 10:41, Behdad Esfahbod wrote:
> > On Wed, 2007-01-03 at 03:02 -0500, Lars Knoll wrote:
> > > This is a little problematic, as the compiler is free to add paddings
> > > inside
> > > the structs (actually it's dependent on the ABI you have on the OS).
> > > It
> > > should work fine on x86, but you might run into problems on risk
> > > architectures. gcc has a workaround for this (the packed attribute).
> > > This is
> > > something we'll need to look into for other compilers (which we
> > > support with
> > > Qt).
> >
> > Thanks Lars.  I already faced such problems as padding and alignment and
> > have solved some, and have plans to solve the rest.  The neat thing is,
> > it's a single place (the DEFINE_INT_TYPE macro) you need to tweak for
> > that.  You can use an array of chars for example, etc etc.  I'll get to
> > that when the rest is done.
> 
> Lars and I just had a look at it and we're afraid that it may not be possible
> to get the padding/alignment working portably for all compilers :-(

Even if the only basic type I use in my structs is char?  I did my Tag
type as a char[4] and that fixed the alignment problem on gcc.  I can
replace all other type definitions with things like "char a,b,c,d".  Do
you have any examples that that doesn't work?

> Maybe it'd be easier to just have (initially generate) little wrapper classes
> with member functions. For example:
> 
> struct OpenTypeFontFace
> {
>     enum Offsets {
>         Tag_Offset = 0,
>         SFntVersion_Offset = 4,
>         NumTables_Offset = 8,
>         SearchRange_Offset = 12,
>         ...
>     };
>     OpenTypeFontFace(const char *_data) : data(_data) {}
> 
>     uint32 tag() const { return fromBE32<uint32>(data + Tag_Offset); }
>     uint32 sfntVersion() const { return fromBE32<uint32>(data + SFntVersion_Offset); }
>     uint32 numTables() const { return fromBE32<uint32>(data + NumTables_Offset); }
>     ...
> 
> private:
>     const char *data;
> };
> 
> That keeps the code using it still very readable/maintainable and should work
> nicely for all platforms.

That works too.  But needs some more work.  But do you have to use a
wrapper at all?  Can't you do the same thing using "this"?

> Simon
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-- 
behdad
http://behdad.org/

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