[Cairo] Re: [xsvg] cairo_text_extents ?

[Christof Petig]

John Ellson schrieb:
> Carl Worth wrote:
> 
>> Several similar names do show up for the term known as "left
>> sidebearing", "LSB", "sideBearing", etc. But, couldn't we just omit
>> this field? Unless I'm missing something, it seems trivial to compute
>> this term given the current point and the bounding box.
>>
>> Or would it help avoid confusion to include left_bearing,
>> right_bearing even if redundant?
>>  
>>
> It is true that the left_side_bearing, right_side_bearing, ascent,
> and descent describe a bounding box.  However the terms are
> clearly with reference to the origin of the (first) character.
> x,y,width,height kind of looses that for me.

it does not have to ...

> There is no fixed relationship between the origin of the first character
> of the string and the left-side-bearing.  i.e. left_side_bearing
> is not, in general, redundant. (It is clearly non-redundant
> for vertical text.)
> 
> Also, the advance_x not the same as the right-side-bearing.
> 
> I recommend the diagrams in the freetype tutorial for understanding the
> different measures:

IIRC the tuple  x,y,w,h,advancex,advancey clearly covers all information 
needed for a glyph (advancex/advancey might depend on the next character 
  (kerning)).

x/y should equal bearingX/Y (x and y might be negative)

FT only defines five values for a glyph (bearingX+Y, width, height, 
advance).

    Christof