Re: A bug in tetris

[Leo <sdl.web@gmail.com>]

On 2007-08-23 13:17 +0100, Kenichi Handa wrote:
> In article <E1INSWq-0003IU-BH@etlken.m17n.org>, Kenichi Handa <handa@m17n.org> writes:
>
>> I don't have a strong objection to it.  Anyway, I found that
>> the current problem is in the different place.  gamegrid.el
>> has this function.
>
>> (defun gamegrid-setup-default-font ()
>>   (setq gamegrid-face
>> 	(copy-face 'default
>> 		   (intern (concat "gamegrid-face-" (buffer-name)))))
>>   (when (eq gamegrid-display-mode 'glyph)
>>     (let ((max-height nil))
>>       (loop for c from 0 to 255 do
>> 	    (let ((glyph (aref gamegrid-display-table c)))
>> 	      (when (and (listp glyph) (eq (car  glyph) 'image))
>> 		(let ((height (cdr (image-size glyph))))
>> 		  (if (or (null max-height)
>> 			  (< max-height height))
>> 		      (setq max-height height))))))
>>       (when (and max-height (< max-height 1))
>> 	(set-face-attribute gamegrid-face nil :height max-height)))))
>
>> It tries to make a face height shorter than the grid-glyph
>> height.  I confirmed that when I change the last line to:
>
>> 	(set-face-attribute gamegrid-face nil :height (- max-height 0.1))))))
>
>> the resulting face is good and doesn't produce 1-dot
>> horizontal gap in the play field.   I'm now investigating
>> why the original code isn't good enough.
>
> The source of the problem is the rounding off done while
> converting a point size to pixel size.  In my environment,
> resolution of the screen is 96dpi, grid-glyph height is
> 16dots, canonical char height is 20dots, the default font
> height is 12.1pt, thus the requested height of the font is
> 9.6pt (== 12.1 * (16 / 20)).  The corresponding pixel size
> is 12.75 (== 96 * (9.6 / 72.27)).  So, it's rounded off to 13,
> but what we want here is a font of 12 pixel size.
>
> So, I've just installed the attached change.  It may be
> possible to add a special face attribute to tell not to
> choose a font that is larger than the requested size, but
> that require many C code changes.  In addition, I think such
> a case (need a font equal to or smaller than a requested
> size) is rare.
[...]

Thanks. The patch works great.

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

         Gnus is one component of the Emacs operating system.