Re: Units and resolution independence for gtk+

[Alexander Larsson <alexl redhat com>]

On Thu, 2008-08-07 at 13:10 -0400, David Zeuthen wrote:

> Here's the revised proposal
> 
>  GTK_SIZE_EM
>    GTK_SIZE_ONE_TWELFTH_EM for convenience
> 
>  GTK_SIZE_POINT
>    cf. Behdad's proposal
> 
>  GTK_SIZE_MM
>    GTK_SIZE_INCH for convenience
> 
>  GTK_SIZE_PIXEL
> 
> The storage format is going to be like this
> 
>  bit 31: sign
>  bit 30, 29, 28: used for storing the unit type
> 
> giving us 7 different units (can't set all of bits 28, 29, 30 so it's 7
> instead of 8); thus we'll have some room for future expansion. Does this
> sound OK?

Is a physical size units even interesting? It just generally leads to
DPI style flamewars. For instance, a projector screen is really large,
but you don't want tiny fonts anyway, because you watch it from far
away. Something similar but reversed applies for the case of handhelds. 

What you really want to talk about is how large a pixel "looks" for a
viewer, and the actual unit here is something like steradians of the
viewers field of vision. However, this is a bit complex, and just using
some abstract point unit that does a device dependent scaling might be
better.