Hi, Eli,

Many many thinks, your suggestion is really very very great.
Now we can get the frame font width no matter it is default, remapped or 
rescaled.

I updated the patch as you suggested, other changes also include in 
attachment:
1, remove "default_font_width" global variable, get font width from 
FRAME_PTR as you sugguested.
2, pass FRAME_PTR to every xftfont_info structure, we can use it anywhere.
3, add a feild "is_cjk" to "xftfont_info" structure, initialize it when 
xftfont_open, avoid call "is_cjk_font" many times when draw and extents 
calculation.

Now, it works very well with font remapping, rescaling.



于 2012年04月12日 22:27, Eli Zaretskii 写道:
>> Date: Thu, 12 Apr 2012 19:18:39 +0800
>> From: 黄建忠<jianzhong.huang@i-soft.com.cn>
>> CC: kanru@kanru.info, emacs-devel@gnu.org
>>
>>>> Can anybody provide a clue how to catch the new width of default font
>>>> via FRAME_PTR when scale happened?
>>> I don't think there is a way to do that, if all you have is the frame
>>> pointer.  text-scale-mode does not modify the frame's default font, it
>>> remaps the 'default' face to another face which specifies a larger or
>>> a smaller font.  So the way to find the width of the font after
>>> scaling is to get hold of the font itself, or of the face to which
>>> 'default' was remapped.  Then you can use FONT_WIDTH, I think (but I
>>> didn't test this).
>> I can get the default font(the first font loaded when frame be
>> initialized) via FRAME_FONT, it's great that it can not be changed after
>> first font loaded.
>> But I still can not get the current width after scale, since the props
>> of FRAME_FONT also not be changed.
>> [...]
>> I noticed there were some global Lisp_Object such as
>> "f_Vface_font_rescale_alist"/"f_Vface_remapping_alist"/"f_Vface_new_frame_defaults",
>> maybe I can use them, Hope so.
> This will retrieve the numerical ID of the default face on frame F:
>
>    int id = lookup_basic_face (F, DEFAULT_FACE_ID);
>
> lookup_basic_face consults f_Vface_remapping_alist.  If the value of
> id above is different from DEFAULT_FACE_ID, that means the default
> face was remapped.  Then you can get the remapped face like this:
>
>    struct face *face = FACE_FROM_ID (F, id);
>
> Now the font of the face is available as
>
>    struct font *font = face->font;
>
> And I think FONT_WIDTH (font) will give you the width you want to use
> instead of FRAME_COLUMN_WIDTH.
>
> Again, this is 100% untested.  Good luck!
>
>