Re: [ft] putting text in a box

[Dave Calkins]

>    
> > It seems like the bounding box calculation is always correct.  The
> > problem is that the descender I'm querying is for the font face in
> > general which I assume accounts for every glyph in the font.
> >      
> If you have a negative value in the bbox, this is the amount below the
> baseline.
>
>    
I'm not getting negative values in the bounding box.  I'm getting a 
positive overall width and height for the text string in question 
(although I should say I'm calling the FreeTypeGL bounding box method, 
so I suppose I need to see which FreeType calls thats using).  And I can 
verify that this bounding box is correct.  If I render and check the 
bounding box, I can, in MSPaint for example, line it up with a box that 
size and it does exactly enclose all the text.  So the bounding box 
looks great.

The problem is that I need to know where to render the text.  When I set 
the output position, this positions the baseline of the text.  So the 
only way to put the text exactly in that box (I think) is to know the 
descender values for the individual chars in the specific string I'm 
rendering.

I can get a descender value for the font face overall, but this ends up 
being too large (for some fonts) and if I use this to position the 
string the string is too high since the specific string doesn't actually 
have descender values that large.


> > Any suggestions on computing the descenders for individual glyphs?
> >      
> Calculate the bbox for individual glyphs.  In most cases, a cbox
> should be sufficient, BTW.
>
>    
I'll look again today, but I don't recall seeing a descender value for a 
glyph.  The example code I looked at computed a bounding box, telling me 
what box would enclose the char, but I need the distance the char 
extends below the baseline.  I could just have overlooked something though.
> > I took a look at the glyph metrics from FreeType, but these didn't
> > seem to help.  For example, I found a case where "E" seemed to
> > report a descender (comparing height and vertBearingY).
> >      
> It's easily possible that the glyph `E' descends slightly (due to
> serifs, for example).
>
>    
In that case, the descent was definitely not from a serif.  It was a 
value much larger than you'd expect.  I drew the "E", then drew a 
cross-hair at the output positionn and there was really no descent.