Re: yank-media: allow users to limit image types that can be inserted

[Visuwesh <visuweshm@gmail.com>]

[வியாழன் அக்டோபர் 31, 2024] Eli Zaretskii wrote:

>> From: Visuwesh <visuweshm@gmail.com>
>> Cc: yantar92@posteo.net,  pinmacs@cas.cat,  rpluim@gmail.com,
>>   emacs-devel@gnu.org
>> Date: Thu, 31 Oct 2024 14:16:07 +0530
>> 
>> > This (and the patch you suggest) completes the full circle of this
>> > discussion: it started when I said that such a global preference makes
>> > very little sense to me, based on my experience with yanking different
>> > data types in other applications.  Users have no reason for such
>> > preferences, as they almost never have enough reasons to prefer one
>> > type over the others _globally_.  The preference only makes sense in
>> > each specific case, and then asking the user to choose is exactly TRT,
>> > which we already do.
>> 
>> At least for images, I see a value in having a global preference.  You
>> also seem to agree on this point.
>
> I agree with having an Emacs-wide preference rule, not with asking
> users to define those preferences.
>
>> > Major mode _does_ have a part: it registers only the handlers it wants
>> > to support.  So it determines, up front, which media types will be
>> > available, even if more of them are in the clipboard.
>> 
>> I agree but its participation could be improved.  When you copy a cell
>> from LibreOffice's Excel clone, it puts both image/png and a TSV data
>> type in your clipboard.  Taking the example of Org which has a handler
>> registered for image/png: if it registers a handler for the TSV data
>> type, the user would be asked to choose between image/png and TSV when
>> she copies a table cell.  The intent of registering image/png is a
>> hindrance here.  Having a separate command for yanking a table cell
>> would remove the convenience of having a single command that does TRT.
>
> The default yank-media (e.g., with an argument) should yank the TSV
> format, and only offer the PNG format as an option if the user for
> some reason wants that.
>
>> > Please tell me why on earth would you prefer PNG to JPEG when yanking,
>> > or vice versa.  The result is an image displayed in the buffer, which
>> > is neither PNG nor JPEG.  Why does it matter _for_you_personally_
>> > which intermediate format will Emacs use as part of the yanking
>> > process?
>> 
>> You answered the question yourself:
>> 
>>     For example, JPEG is generally inferior because it's lossy, so we
>>     could have that hypothetical variant of yank-media which doesn't ask
>>     questions to always prefer PNG to JPEG if both are possible.
>
> That is not something we should ask users to do, IMO.
>
>> > If we want to avoid the question when several image formats are
>> > available, we could teach Org, or Emacs in general, which formats to
>> > prefer.  For example, JPEG is generally inferior because it's lossy,
>> > so we could have that hypothetical variant of yank-media which doesn't
>> > ask questions to always prefer PNG to JPEG if both are possible.  This
>> > is IMO better than asking the users to decide that for Emacs.
>> 
>> I agree, but can we, at least, agree that it should be easy to override
>> it completely?
>
> Override how and for what purpose?  If we have a command which asks
> the user to select one format from a list of available ones, the
> general preference can always be overridden, just on a case by case
> basis.  Why do we also need to override it globally?
>
>> > Anyway, since with this message we've made a full circle, let me
>> > summarize my opinions on this:
>> >
>> >   . I think we should add to Emacs rules for preferring one media
>> >     format over the others when several are available and supported
>> >   . Such rules should be customized by major modes based on their
>> >     features and preferences (e.g., a mode that has no support for
>> >     faces might prefer plain text to other textual formats)
>> 
>> (1) and (2) would be best done with the help of user feedback.
>
> Feedback is always welcome, but I submit that we can formulate a very
> good approximation for the rules without any feedback.
>
>> IMO, coming up with such rules is a long game that requires user
>> feedback (like the one that started this whole thread).
>
> No, I think it is actually quite simple and will be quite close to the
> optimum the first time we come up with such rules.  It is possible
> that a major mode will want to override the rules, for its own
> reasons, but that should also be very obvious for each mode.
>
>> >   . I think we should have a variant of yank-media that yanks "the
>> >     best" of the available formats without asking, based on the above
>> >     rules
>> 
>> I like your idea of reusing C-u for this.
>> 
>> > If after all of this people still want a global "preference", I won't
>> > mount the barricades to fight that, although, as I explained, such a
>> > global preference makes little sense to me, and sounds like an
>> > inferior replacement for the missing built-in preference rules I think
>> > we should have.
>> 
>> The built-in preference rules is already a global "preference" from
>> where I stand.  Only that, the OP wanted control over these rules.
>
> And I'm saying that I don't understand why users would need such
> control, in addition to being able to select a format in each case.

OK, I think I finally understand your stance: we let yank-media pick the
best format out of all in the clipboard based on rules that a major-mode
can tweak.  Apart from this, we also have C-u or somesuch that asks the
user to select the data type instead of auto-selecting it.  Since the
C-u is good enough to override a case-by-case basis, you do not see
value in having a defcustom to let the user customise the selection
rules for the best data type, correct?