bug#20628: 25.0.50; Incorrect line height for some fonts

[Clément Pit--Claudel]

On 05/22/2015 02:15 PM, Eli Zaretskii wrote:
>> From: Oleh Krehel <ohwoeowho@gmail.com>
>> Cc: clement.pitclaudel@live.com,  20628@debbugs.gnu.org
>> Date: Fri, 22 May 2015 18:33:43 +0200
>>
>>> Math fonts are notorious for requesting huge ascent and descent
>>> values.  I always disable them using fontsets.
>>
> 
> It would be nice if someone could look at gedit sources and describe
> what it does to avoid the problem.  Finding such a solution is what
> this discussion is all about, no?

I don't know much about gedit's source code, nor how fonts are handled. 
However, I'm not sure if gedit can really give us much information: indeed, 
Emacs is the only application that behaves this way on my system. LibreOffice 
and Thunderbird, for example, display these characters fine.

Here is an hypothesis. When I open Latin Modern in FontForge, I see two types 
of ascent and descent values: the ones in the "General" tab are 806 and 194, 
and the ones in the OS/2 tab, in particular Win Ascent and Win Descent, are 
3560 and 3060. Such a discrepancy does not seem to exist in the few 
well-behaved fonts that I checked.

Could it be that most applications use the first set of values, but Emacs 
relies on the second?

Clément.