Re: [RFC] Change (gui-get-selection) to default to UTF8_STRING

[Max Nikulin]

On 17/03/2025 11:58, Po Lu wrote:
> Max Nikulin writes:
>
> > I am trying to convince you that other packages needs a public
> > function similar to `gui--selection-value-internal' and I have
> > provided 2 examples. x-win.el calls this private function as well.
> >
> > Why wisdom collected in `gui--selection-value-internal' has to sealed
> > in a private function? Why developers of other package must be aware
> > that Po Lu made a commit b47d36f189 and they have to update their
> > wrappers for `gui-get-selection'?
> But they don't.  They could continue requesting selection contents as
> they always have, and we would endeavor to maintain compatibility in any
> ports we introduce.
Sorry, but you proposal is not clear to me.

- x-win.el: using an internal function here is not ideal, but acceptable 
since it resides withing the same repository and almost certainly will 
be updated if necessary.
- 
https://raw.githubusercontent.com/emacs-evil/evil/refs/heads/master/evil-common.el
directly calls `gui--selection-value-internal' and it is fragile. The 
function may be renamed any time in the emacs repository or, even worse, 
calling convention may be changed breaking evil-mode.
- org-compat.el:
> (defun org-get-x-clipboard (value)
>   "Get the value of the X or Windows clipboard."
>   (cond ((and (eq window-system 'x)
>               (fboundp 'gui-get-selection)) ;Silence byte-compiler.
>          (org-no-properties
>           (ignore-errors
>             (or (gui-get-selection value 'UTF8_STRING)
>                 (gui-get-selection value 'COMPOUND_TEXT)
>                 (gui-get-selection value 'STRING)
>                 (gui-get-selection value 'TEXT)))))
>         ((and (eq window-system 'w32) (fboundp 'w32-get-clipboard-data))
>          (w32-get-clipboard-data))))
I feel smell of bugs and user confusion due to subtle difference in 
behavior comparing it to select.el:
> (defun gui--selection-value-internal (type)
>   "Get a selection value of type TYPE.
> Call `gui-get-selection' with an appropriate DATA-TYPE argument
> decided by `x-select-request-type'.  The return value is already
> decoded.  If `gui-get-selection' signals an error, return nil."
>   ;; The doc string of `interprogram-paste-function' says to return
>   ;; nil if no other program has provided text to paste.
>   (unless (and gui-last-cut-in-clipboard
>                ;; `gui-backend-selection-owner-p' might be unreliable on
>                ;; some other window systems.
>                (memq window-system '(x haiku))
>                (eq type 'CLIPBOARD)
>                ;; Should we unify this with 
> gui--clipboard-selection-unchanged-p?
>                (gui-backend-selection-owner-p type))
>     (let ((request-type (if (memq window-system '(x pgtk haiku))
>                             (or x-select-request-type
>                                 '(UTF8_STRING COMPOUND_TEXT STRING 
> text/plain\;charset=utf-8))
>                           'STRING))
>           text)
>       (with-demoted-errors "gui-get-selection: %S"
>         (if (consp request-type)
>             (while (and request-type (not text))
>               (setq text (gui-get-selection type (car request-type)))
>               (setq request-type (cdr request-type)))
>           (setq text (gui-get-selection type request-type))))
>       (if text
>           (remove-text-properties 0 (length text) '(foreign-selection nil) 
> text))
>       text)))
Lists of targets are not identical, lists of `window-system' variants 
have been diverged as well.
My impression from GitHub search results is that more users would like 
to have a reliable way to just get selection text.
> > Non-private (but not documented in elisp reference)
> > `gui-get-primary-selection' and `gui-selection-value' are not building
> > blocks for other functions, they are wrappers for
> > `gui--selection-value-internal' for specific actions: middle click and
> > for yank from clipboard.
> Why are they (particularly the former)?  Here is the doc string of
> gui-get-primary-selection:
>
>    Return the PRIMARY selection, or the best emulation thereof.
It does not allow to get CLIPBOARD contents, it is not even mentioned in 
(info "elisp").
I have no idea if it is relevant, but I use both PRIMARY and CLIPBOARD 
and I found it convenient that they may have different contents.