Subject: bug#77429: 31.0.50; Image map and display slice on mode/header/tab line

From: David Ponce <[email-masked]>
Date: Tue, 1 Apr 2025 21:31:39 +0200

On 2025-04-01 20:53, Eli Zaretskii wrote:
>> Date: Tue, 1 Apr 2025 19:57:14 +0200
>> Cc: [email-masked]
>> From: David Ponce <[email-masked]>
>>
>> It seems the bug is only partially fixed.  The image map behaves as
>> expected for the help-echo and pointer properties, but doesn't report
>> the correct hot spot ID.  The updated recipe below illustrates this:
> 
> Sorry, I don't understand what that means.
> 
> Would you please accompany the code with some minimal description of
> how to produce the wrong result (and explanation why you think it's
> wrong)?  The previous example was already somewhat of a riddle, but at
> least with the wrong help-echo shown it was relatively easy to guess
> what was expected.  This time I'm completely stomped: what is "hot
> spot ID" and how do I see it?
> 
> Thanks.

Sorry for not being precise enough.

The hot spot ID is documented in the Elisp manual:

‘:map MAP’
      This associates an image map of “hot spots” with this image.

      An image map is an alist where each element has the format ‘(AREA
      ID PLIST)’.  An AREA is specified as either a rectangle, a circle,
      or a polygon.

      [...]
  
      When you click the mouse when the mouse pointer is over a hot-spot,
      an event is composed by combining the ID of the hot-spot with the
      mouse event; for instance, ‘[area4 mouse-1]’ if the hot-spot's ID
      is ‘area4’.

In my example, each colored rectangle RED, GREEN, BLUE corresponds to
a `rect' hot spot with the respective IDs: r, g, b.  And Each <ID
mouse-1> key is associated to a command that displays the color name
of the rectangle you click on.

So, when you click on the red rectangle you should see "Red" is the
echo area, "Green" when you click on the green rectangle, and "Blue"
when you click on the blue rectangle.

But on the sliced image which is on the left side on the header line,
showing a green and blue rectangle, a click on the green rectangle
displays "Red" instead of "Green" and click on the blue rectangle
displays "Green" instead of "Blue".  This is the issue.

Hope I am clear enough.