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From: Luc Moulinier on 28 Jun 2010 10:34
Hello,

While exercising with fonts using the Tk C API , I noted something I
don't understand :

tkmafonte = Tk_GetFont(interp, tkwin, "-adobe-courier-bold-r-
normal--24-240-75-75-m-150-iso10646-1");
Tk_GetFontMetrics(tkmafonte,&fm);
wdt = Tk_TextWidth(tkmafonte,"X",1);
printf("Tk : ascent ascent %d descent %d width %d
\n",fm.ascent,fm.descent, wdt);
Tk_FreeFont(tkmafonte);

XFontStruct *maSfonte;
maSfonte = XLoadQueryFont(Tk_Display(tkwin),"-adobe-courier-bold-r-
normal--24-240-75-75-m-150-iso10646-1");
wdt = XTextWidth(maSfonte,"X",1);
printf("xlib : ascent ascent %d descent %d width %d\n",maSfonte-
>ascent,maSfonte->descent, wdt);

gives (the font is Courier 24 bold):

Tk : ascent ascent 22 descent 6 width 15
xlib : ascent ascent 19 descent 5 width 15

Can someone explain me the observed differences in ascent and
descent ? I found nothing in the man pages about that...

Many thanks !

Luc
From: Luc Moulinier on 29 Jun 2010 07:34
To precise : working with Tcl/Tk 8.5.8 under Linux (redhat)


Luc
From: Eric Boudaillier on 29 Jun 2010 13:51
Hello Luc,

The difference is probably due to the use of XFT in Tk 8.5.
XLoadFont is not used in this case. XFT add antialiasing, and explain
the size difference.

-eric

On 28 juin, 16:34, Luc Moulinier <luc.moulin...(a)igbmc.fr> wrote:
>   Hello,
>
>   While exercising with fonts using the Tk C API , I noted something I
> don't understand :
>
>   tkmafonte = Tk_GetFont(interp, tkwin, "-adobe-courier-bold-r-
> normal--24-240-75-75-m-150-iso10646-1");
>   Tk_GetFontMetrics(tkmafonte,&fm);
>   wdt = Tk_TextWidth(tkmafonte,"X",1);
>   printf("Tk : ascent ascent %d descent %d width %d
> \n",fm.ascent,fm.descent, wdt);
>   Tk_FreeFont(tkmafonte);
>
>   XFontStruct *maSfonte;
>   maSfonte = XLoadQueryFont(Tk_Display(tkwin),"-adobe-courier-bold-r-
> normal--24-240-75-75-m-150-iso10646-1");
>   wdt = XTextWidth(maSfonte,"X",1);
>   printf("xlib : ascent ascent %d descent %d width %d\n",maSfonte-
>
> >ascent,maSfonte->descent, wdt);
>
>   gives (the font is Courier 24 bold):
>
> Tk : ascent ascent 22 descent 6 width 15
> xlib : ascent ascent 19 descent 5 width 15
>
> Can someone explain me the observed differences in ascent and
> descent ? I found nothing in the man pages about that...
>
> Many thanks !
>
> Luc

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