bug#71162:

[David McCracken <davidm@ixont.com>]

Sorry about my previous question about finding the source of 
tool-bar--image-expression. tool-bar.el.gz was easy to find. The 26.3 
and 27.1 versions are not identical but the differences are unrelated to 
either of the problems I have encountered. I am going to instrument the 
function to try to track down the problem but I suspect that Ubuntu is 
the cause. Replacing Emacs 27.1 with 26.3 without changing the OS would 
answer the question but I don't know how to do this. I always just used 
apt-get install emacs. How can I install a downrev?

On 2024-05-23 11:15 PM, Eli Zaretskii wrote:
>> Date: Thu, 23 May 2024 21:08:24 -0700
>> From: David McCracken <davidm@ixont.com>
>>
>> I have developed a library that includes a toolbar with custom icons. It
>> works in all versions of Emacs in Windows and in Emacs version 26.3
>> under Ubuntu-Mate 20.54 but the toolbar doesn't work in Emacs 27.1 under
>> Ubuntu-Mate 22.04. In my preferred configuration I put my icons under
>> the user home directory so that this doesn't change if Emacs is
>> updated. My library accesses this with e.g.
>> (tool-bar-add-item "~/icons/lxa-next"
>> to use my lxa-next.xpm icon. In Emacs 26.3 it also works to put my icon
>> in /usr/share/emacs/26.3/etc/images and refer to it as simply
>> "lxa-next". Emacs 27.1 shows nothing either way. My lxa-next.xpm appears
>> similar to the native lock-broken.xpm (4.7kB vs. 4.6kB) so I
>> experimented referring to that instead of mine and it worked. I also
>> tested left-arrow but instead of left-arrow.xpm or pbm, it showed a very
>> plain < image that doesn't exist in the images directory. It should be
>> noted that there is a lock-broken.pbm but the xpm version was
>> automatically selected. The icon selection mechanism of Emacs 26.3 is
>> usable but could be improved by accepting an explicit icon file
>> extension. That of 27.1 is unusable and, unless we can fix it, I will
>> have to advise users of my library to install an older version of Emacs.
> I tried to visit the XPM file you attached, and it displays okay with
> both Emacs 27.1 and the current development version, at least on
> MS-Windows.  So I don't see a reason why this would not work on a tool
> bar.  I suggest that you post some minimal Lisp code that displays
> these icons on the Emacs tool bar, starting from "emacs -Q", and then
> we could try the code and see if the problem can be reproduced and
> debugged.
>
> Btw, to clarify: you are saying that your XPM icons don't work in
> Emacs 27.1 both on MS-Windows and on Ubuntu?  Or only on Ubuntu?
>
> Thanks.