Re: Font related crash?

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 5 Nov 2015 00:45:51 -0800
> From: Yuan MEI <yuan.mei.list@gmail.com>
> Cc: Eli Zaretskii <eliz@gnu.org>, emacs-devel <emacs-devel@gnu.org>
> 
> Program received signal SIGFPE, Arithmetic exception.
> 0x0000000000413a88 in required_matrix_width (w=w@entry=0x21db2f8)
> at dispnew.c:1727
> 1727 / ch_width) * w->ncols_scale_factor
> (gdb) p ch_width
> $1 = 0
> (gdb) p w->ncols_scale_factor
> $2 = 1
> (gdb) p WINDOW_PIXEL_WIDTH (w)
> $3 = 96
> (gdb) 

Martin, this probably means the code in font_open_entity, which AFAICS
is the only place where we set FRAME_SMALLEST_CHAR_WIDTH, was not yet
called for this frame, or maybe it was called, but the logic there
that assigns a value to the above is flawed.

Such a small pixel width probably means the former, in which case I
think we need some simple protection in required_matrix_width against
FRAME_SMALLEST_CHAR_WIDTH being zero (and a similar protection in
required_matrix_height, to be called next).

Or maybe when we create a frame we should simply initialize
FRAME_SMALLEST_CHAR_WIDTH to 1 (and similarly with
FRAME_SMALLEST_FONT_HEIGHT).