Re: [emacs-unicode-2] Segmentation fault 0x081b3df2 in xftfont_draw

[Leo]

Dear Kenichi,

----- Kenichi Handa (2007-04-14) wrote:-----

>> It happens usually when there are many links in a buffer such as in ERC
>> or W3M. I can move around mouse in a w3m buffer with tons of links (such
>> as www.6park.com) to catch a crash, which usually happens within a few
>> minutes. I just catch one with 'emacs -Q'. Unfortunately I don't know
>> the exact recipe to trigger a crash.
>
> I've just installed w3m and emacs-w3m, visited
> www.6park.com, moved mouse-cursor and normal cursor onto
> various links, but couldn't trigger a crash.

I will try a font that cause flickering and see if I can catch a bug.

>
>> The following can help you see the bug although it won't crash Emacs:
>
>>          o  emacs -Q --enable-font-backend -fn SOMEFONT
>>          o  C-u 3 2 M-x hanoi
>
>> You should see the frame flickering like TV disturbed by static.
>
> I can confirm the flickering with some fonts of some size.
> For instance, this cause flickering:
>
> emacs-unicode --enable-font-backend -fn 'dejavu sans mono:pixelsize=16'
>
> but these don't cause flickering:
>
> emacs-unicode --enable-font-backend -fn 'dejavu sans mono:pixelsize=24'
> emacs-unicode --enable-font-backend -fn 'lucidatypewriter:pixelsize=16'
>
> I think the reason is that font-height of "dejavu sans
> mono:pixelsize=16" is somehow shorter than the glyph '|' in
> that font.  So, every time Emacs redraw '|', the upper and
> lower lines are also redrawn which leads to the whole buffer
> redrawing.  For instance, when I replace all occurence of
> "?\|" in lisp/play/hanoi.el with "?i", even this:
>
> emacs-unicode --enable-font-backend -fn 'dejavu sans mono:pixelsize=16'
>
> stops flickering.

I can confirm this. Do you think that's a bug in dejavu sans mono?

>
> Perhaps we must do something like this:
>
> o When we open a font for a frame, check the ascents and
>   descents of ASCII characters (perhaps checking only "\|/"
>   is ok), and set font's ascent and descent to the maximum
>   of them if the font's data is shorter than glyphs' data.

regards,
-- 
Leo <sdl.web AT gmail.com>                         (GPG Key: 9283AA3F)