Re: Buttons in help buffer that displays contents of variables

[Heime]

------- Original Message -------
On Sunday, July 23rd, 2023 at 10:02 AM, Heime <heimeborgia@protonmail.com> 
wrote:


> ------- Original Message -------
> On Sunday, July 23rd, 2023 at 9:46 AM, Stephen Berman stephen.berman@gmx.net 
> wrote:
> 
> 
> 
> > 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
> > > > > 

Do you know what the single argument is used for ?
> > > > > 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
> 
> 
> That explains it.