Re: Emacs Lisp manual issues regarding overlays, display properties, margins, etc.

[Joe Wells]

Johan Bockgård <bojohan+news@dd.chalmers.se> writes:
>Joe Wells <jbw@macs.hw.ac.uk> writes:
>
>> Issue 1:  The “height” display specification seems not to work at
>> all.  For example, in the following the B is not larger:
>>
>>   (test-overlays
>>    (insert "ABC")
>>    (let ((o (make-overlay 2 3)))
>>      (overlay-put o 'display '(height 2))))
>
> This worked for me.

For me, running all of the above in a fresh “emacs -Q”, all three
characters (A, B, and C) get displayed with font
“-Misc-Fixed-Medium-R-SemiCondensed--13-120-75-75-C-60-ISO8859-1”.  I
used “C-u C-x =” to find out what font is used.

By the way, I have no font settings for Emacs in my X resources.

Have you tried the example in a fresh “emacs -Q”?  If so, what fonts
do the 3 characters get displayed with?  Can you try it also with no X
resource font settings for Emacs?

>> Issue 6:  The “Overlay Properties” manual node says this on
>> overlay priorities: [...]
>
>> So what is the relative priority of an overlay which has a
>> nonnegative integer value of its priority property, and one which
>> has no priority property at all?  It seems that nil is below 0:
>>
>>   (test-overlays
>>    (insert "ABC")
>>    (let ((o1 (make-overlay 2 3))
>>          (o2 (make-overlay 2 3)))
>>      (overlay-put o1 'display "123")
>>      (overlay-put o2 'priority 0)
>>      (overlay-put o2 'display "abc")))
>
> Both overlays have priority 0. o2 takes precedence because it is on top
> (you get the same result without the second last line).

Can this please be documented?  Both that no “priority” property (or a
value of nil) is equivalent to a value of 0, and how priority works
for overlays with the same priority.

-- 
Joe

P.S.  Here is the test-overlays macro again:

  (defmacro test-overlays (&rest body)
    `(let ((buf (get-buffer-create "xyzzy")))
      (with-current-buffer buf
        (display-buffer buf)
        (erase-buffer)
        (dolist (o (overlays-in (point-min) (point-max)))
          (delete-overlay o))
        ,@body)))