Hi
The issue is with the following code that tries to use the Widget
library. The slots of the widget are actually not necessary to see the problem.
(widget-create 'integer
:help-echo "Enter an integer..."
:notify (lambda (w1 &rest ws)
(ignore ws)
(message "WIFT: IF: %s"
(widget-value w1)
))
:size 4
)
If you set up a widget buffer, the field will appear as expected with a 0 as initial value. The problem starts if you try to clear the field and then enter a new value, say by hitting C-k, and the problem is in the :value-to-external functions in the in sexp and restricted-sexp widgets (the number, float and natnum widgets must also be fixed).
The library :value-to-external functions eventually do a (read value) where value is the widget value; alas, value can be "" if you edit the field in a pretty standard way, as, as I said above, if you had tried to kill the field line (C-k); this causes the traditional minor demons to fly out of the nose, as a 'End of file during parsing' error gets signaled. After that, the buffer with the widgets is pretty much in a random state.
Specializing the widget with a hack like the function below fixes the problem, but a
good solution may need some more work to get all the corner cases. Note that setting a "widget buffer" in overwrite mode goes a long way to mitigate these problems: maybe having widget-setup switch to it would be another good thing to do.
:value-to-external
(lambda (widget value)
;; Lifted, and fixed, from `:value-to-external' in
;; `restricted-sexp'.
(unless (stringp value)
(display-warning
'widget-bad-default-value
(format-message
"\nA widget of type %S has a bad default value.
value: %S
match function: %S
match-alternatives: %S"
(widget-type widget)
value
(widget-get widget :match)
(widget-get widget :match-alternatives))
:warning))
(if (and (stringp value) (string-equal "" value))
;; Oooops, we cannot just `read'.
(widget-get widget :default-value)
(read value))
)
Note: this goes back, at least, to 25.x.
Thanks for the attention
Marco Antoniotti
In GNU Emacs 28.2 (build 2, x86_64-w64-mingw32)
of 2022-09-13 built on AVALON
Windowing system distributor 'Microsoft Corp.', version 10.0.22621
System Description: Microsoft Windows 10 Pro (v10.0.2009.22621.1778)
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Memory information:
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--
Marco Antoniotti
Somewhere over the Rainbow