Re: Buttons in help buffer that displays contents of variables

[Stephen Berman]

On Sat, 22 Jul 2023 21:24:39 +0000 Heime <heimeborgia@protonmail.com> wrote:

> ------- Original Message -------
> On Sunday, July 23rd, 2023 at 8:48 AM, Stephen Berman 
> <stephen.berman@gmx.net> wrote:
>
>
>> On Sat, 22 Jul 2023 20:24:16 +0000 Heime heimeborgia@protonmail.com wrote:
>> 
>> > ------- Original Message -------
>> > On Sunday, July 23rd, 2023 at 8:14 AM, Stephen Berman
>> > stephen.berman@gmx.net wrote:
>> > 
>> > > On Sat, 22 Jul 2023 19:18:03 +0000 Heime heimeborgia@protonmail.com 
>> > > wrote:
>> > > 
>> > > > ------- Original Message -------
>> > > > On Sunday, July 23rd, 2023 at 2:40 AM, Heime
>> > > > heimeborgia@protonmail.com wrote:
>> > > > 
>> > > > > I want to use a button to display the contents of a variable inside
>> > > > > a help buffer, but the following gives
>> > > > > 
>> > > > > (wrong-number-of-arguments ((t) nil "Function to be executed when
>> > > > > the button
>> > > > > is clicked..." (interactive) (message "Button clicked!")) 1)
>> > > > > my-action(#<overlay from 1 to 8 in Help>)
>> > > > 
>> > > > Why does pressing the button give me such error ?
>> > > > 
>> > > > > (defconst myvar "Text of Front A")
>> > > > > 
>> > > > > (defun my-action ()
>> > > > > "Function to be executed when the button is clicked."
>> > > > > (interactive)
>> > > > > (message "%s" myvar))
>> > > > > 
>> > > > > (defun qrh ()
>> > > > > "Some description."
>> > > > > 
>> > > > > (interactive)
>> > > > > 
>> > > > > (with-help-window (help-buffer)
>> > > > > (insert-button "Front A" 'action 'my-action 'follow-link t)))
>> > > 
>> > > The error says the function my-action expects one argument, but you
>> > > defined it with an empty argument list. If you don't want to use the
>> > > argument, you can use `' as a placeholder for the required argument,
>> > > which will be ignored by the byte compiler:
>> > > 
>> > > (defun my-action ()
>> > > "Function to be executed when the button is clicked."
>> > > (interactive)
>> > > (message "%s" myvar))
>> > > 
>> > > Steve Berman
>> > 
>> > I do not understand the reason it expects an argument.
>> 
>> 
>> In the Emacs Lisp info manual there is the node `(elisp) Buttons', whose
>> first subnode is` (elisp) Button Properties', whose first entry is the
>> `action' property:
>> 
>> ‘action’
>> The function to call when the user invokes the button, which is
>> passed the single argument BUTTON. By default this is ‘ignore’,
>> which does nothing.
>> 
>> > Would there be
>> > a more suitable way to print some text after pressing the button ?
>> 
>> 
>> If you want to use a button, then I guess not, since it needs an action
>> (or mouse-action) property to do something on pressing the button.
>> 
>> Steve Berman
>
> In other words, insert-button needs a function with a single argument so it 
> can
> pass ignore.  Yes ?

No.  `ignore' is the function that is the default value of the `action'
property of `insert-button', so if you want pressing the button to do
nothing you can just evaluate e.g. `(insert-button "Front A")'.  But if
you want pressing the button to do something, you have to pass the
`action' property to `insert-button' with a suitable function of one
argument as its value.

Steve Berman