bug#68452: w32-use-native-image-API makes weird behavior

[Eli Zaretskii]

> Date: Mon, 15 Jan 2024 10:30:26 +0800
> Cc: 68452@debbugs.gnu.org
> From: Jinsong Zhao <jszhao@yeah.net>
> 
> On 2024/1/15 0:34, Eli Zaretskii wrote:
> >> Date: Sun, 14 Jan 2024 21:52:00 +0800
> >> From: Jinsong Zhao <jszhao@yeah.net>
> >>
> >> I am not a skilled Emacs user. I mainly use Emacs as a front end for 
> >> Maxima with the help of
> >> imaxima. imaxima converts Maxima output into PNG image, which are then 
> >> displayed in Emacs. I am
> >> using Windows 10.
> >>
> >> It works fine on Emacs 28.2, when I type an expression, e.g. q^2 = 1; and 
> >> return, Emacs 28.2
> >> immediately displays the resulting PNG image.
> >>
> >> If I use Emacs 29.1, however, all I get after returning is an empty 
> >> square. And if I type another
> >> expression and return, a blank square appears. At the same time, the first 
> >> empty square was
> >> replaced by a PNG image of the first expression. That's weird.
> >>
> >> I saw the following messages in the *Messages* buffer:
> >>
> >> Processing Maxima output...done
> >> Unable to load image (image :type png :file 
> >> c:/Users/Jinso/AppData/Local/Temp/imaximatU5Y9B/1 :
> >> scale 1.001595744680851 :ascent center :mask (heuristic (color-values 
> >> imaxima-bg-color)) :
> >> transform-smoothing t) [35 times]
> >> Process imaxima finished
> >>
> >> After (setq w32-use-native-image-API nil), imaxima has the same behaviour 
> >> on Emacs 28.2 and
> >> 29.1.
> > 
> > Thanks, but we'd need an example of such a PNG image to investigate.
> > Can you send one such image, which works with w32-use-native-image-API
> > nil, but not when it is non-nil?
> > 
> > In any case, it is perfectly okay to reset w32-use-native-image-API to
> > nil if the native image APIs fail to process an image you want to see.
> > That's why we support both modes.
> 
> Thanks for the reply.
> 
> The PNG image is created on the fly by imaxima, a front end for Maxima. 
> I think it's a normal PNG image file, actually converted from a ps file 
> by ghostscript. I also tried to use JPEG, it's the same.

Well, we cannot do anything with this bug report unless we have an
example of an image to work with.  So please find a way to ask imaxima
to save the image on a file, and then send it.