bug#25863: 25.1; garbage display by small image

[ynyaaa]

Eli Zaretskii <eliz@gnu.org> writes:
>> Evaluating the form below, the lower part of 'g' shape
>> remains to be displayed.
>> 
>> (progn
>>   (switch-to-buffer (generate-new-buffer "temp"))
>>   (insert-image (create-image (concat "P4\n8 22\n" (make-string 22 127))
>>                               'pbm t))
>>   (insert ?g)
>>   (redisplay)
>>   (delete-char -1))
>
> Not reproducible here.

Reducing the height of the image or enlarging the font may show garbages.
Otherwise I have no idea.

With emacs -Q, the font used is
"-outline-Courier New-normal-normal-normal-mono-20-*-*-*-c-*-iso8859-1".
In this case, garbages are shown with images of height from 11 to 22.

Setting the font to
"-outline-Courier New-normal-normal-normal-mono-16-*-*-*-c-*-iso8859-1".
In this case, garbages are shown with images of height from 9 to 18.