RE: [ft] putting text in a box

[David Bevan]

Werner, 

Is it also worth stating what a negative llx (xMin) value means, to facilitate 
understanding.

David %^>



> -----Original Message-----
> From: address@hidden [mailto:freetype-
> address@hidden On Behalf Of Werner LEMBERG
> Sent: 21 January 2010 07:42
> To: address@hidden
> Cc: address@hidden
> Subject: Re: [ft] putting text in a box
> 
> >> As I told you earlier: A negative bbox value descends below the
> >> baseline (which has y=0).
> >
> > How could a bounding box represent both the overall size of the
> > glyph and the descent at the same time?
> 
> Sorry for being imprecise.  A bbox consists of four values: The (x,y)
> values of the lower left (llx,lly) and the upper right (urx,ury)
> corner.  A box of a glyph with a descender looks like this:
> 
> 
>                        (urx,ury)
>            +----------+
>            |          |
>            |          |
>            |          |
>            |          |
>      ------+----------+------  baseline (y = 0)
>            |          |
>            +----------+
>   (llx,lly)
> 
> 
> If I say `a negative bbox value' I've meant that lly < 0; the
> descender is thus simply the value of lly.
> 
> > [...] let's say its height overall is 10 pixels (which completely
> > encloses top-to-bottom the glyph) and the descent is 3 pixels.  How
> > can both pieces of information be communicated through a box height?
> 
> Then you should have lly = -3 and ury = 7.
> 
> Hmm, I see that the description of FT_BBox doesn't mention the term
> `baseline'.  I've improved it now hopefully by adding this:
> 
>   /* <Note>
> */
>   /*    The bounding box is specified with the coordinates of the lower
> */
>   /*    left and the upper right corner.  In PostScript, those values are
> */
>   /*    often called (llx,lly) and (urx,ury), respectively.
> */
>   /*
> */
>   /*    If `yMin' is negative, this value gives the glyph's descender.
> */
>   /*    Otherwise, the glyph doesn't descend below the baseline.
> */
>   /*    Similarly, if `ymax' is positive, this value gives the glyph's
> */
>   /*    ascender.
> */
> 
> 
>     Werner
> 
> 
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