Hi Chris, thanks for your comments.

Chris Bore wrote:
>  > So why are you keen to retain the current behaviour? 
>
> The logical behavior of left-right and up-down mirroring is useful in
> applications such as back projection, head-up displays and two-sided
> see-through displays, as well as potentially in other reflected displays.

Can you give a more concrete example, e.g. some pseudo-code, showing 
how such an application would use the invalid rectangle returned by 
GetStringExtents?

> If you delete a behavior like this, on which some applications rely, then it
> would cause many problems in some domains.

Well, if this were to be included in some future release of DirectFB 
then it would be mentioned in the release notes and the authors of such 
applications would have the opportunity to change their code.  It's 
like any non-backward-compatible API change.  I believe that it would 
simplify the code in all the cases that I can think of.

> I don't think it is safe to delete a feature on the assumption that it is
> not used.

I would like to think that I'm "fixing" it, rather than "deleting" it, 
and the reason for my post was to establish whether or not it is used 
so that I don't have to assume anything.

> I have no evidence that the current behavior is broken.

OK, here's a sketch:

CreateFont( user-specified font )
GetStringExtents( logical_rect )
FillRectangle or Blit or similar ( logical_rect )

This sort of thing must be common.  At present, this works only for 
left-to-right fonts.  If the user selects a right-to-left font the 
application will crash when it uses the rectangle.  With my proposed 
change, this sort of code will work correctly for all fonts.

> If it is in some
> implementations then those should either be fixed or should return
> DFB_UNSUPPORTED or some other informative error that would let the
> application know not to use these features.

Are you suggesting that GetStringExtents() above should return 
UNSUPPORTED if the font is right-to-left?


Regards,

Phil.





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