bug#49253: 27.2; Emacs non-responsive when pasting into terminal-mode

[Matt Bisson <bisson.m@gmail.com>]

I definitely want to give the feedback here that this was an
outstanding explanation of what's going on inside Emacs, and thanks
very much for taking the time to write it.  I didn't even know of the
existence of some of these maps, and I now know not only that, but
their intended purpose.  Again, thanks a lot for this!

On Mon, Dec 11, 2023 at 5:13 PM Jared Finder <jared@finder.org> wrote:
>
> On 2023-12-11 08:10, Matt Bisson wrote:
> > TL;DR: It works!
>
> Thank you for the testing!
>
> Eli, I think the fully correct definition for term--xterm-paste is the
> following, which has additional error checking:
>
> (defun term--xterm-paste (event)
>    "Insert the text pasted in an XTerm bracketed paste operation."
>    (interactive "e")
>    (unless (eq (car-safe event) 'xterm-paste)
>      (error "term--xterm-paste must be found to xterm-paste event"))
>    (let ((str (nth 1 event)))
>      (unless (stringp str)
>        (error "term--xterm-paste provided event does not contain paste
> text"))
>      (term-send-raw-string str)))
>
> >> I don't think this is the right approach.
> >
> > Totally! :)  The patch was definitely not a serious suggestion of what
> > should be submitted, but just a demonstration that the interplay
> > between the two functions is causing the issue, and it can be solved
> > by touching only that.  I haven't built up the knowledge of how these
> > events function like you have, and was hoping you'd teach me a bit in
> > response, and you did!
>
> No worries!  I hope I didn't come across as judgemental here. :)  If you
> want a bit more detail around the architecture here, read on (Eli,
> please correct if I get anything wrong):
>
> In Emacs, in addition to the local and global keymaps, there are also
> translation keymaps.
> (https://www.gnu.org/software/emacs/manual/html_node/elisp/Translation-Keymaps.html)
>   The docs are accurate but a bit hard to understand without concrete
> examples.  So let me provide an example for each of the translation
> keymaps.  There are three of them:
>
> 1. input-decode-map.  This exists to translate terminal escape sequences
> into the their proper events.  That can be for keys (like the PF1 key
> mentioned in the docs) but it also an be for mouse clicks or the xterm
> paste operation.
>
> EXAMPLE:
> This bug!  In this bug, input-decode-map is what translates the
> character sequence "ESC [ 2 0 0 ~ PASTED TEXT HERE ESC [ 2 0 1 ~"  into
> a single <xterm-paste> event, (xterm-paste "PASTED TEXT HERE").  It does
> this by mapping "ESC [ 2 0 0 ~" to a function that reads until
> encountering the "ESC [ 2 0 1 ~" sequence and returns that new event.
>
> 2. (local-)function-key-map.  This exists to rename keys to more
> preferred names that allow keybindings to be shared.  The docs say "the
> remapping only applies if the original key sequence would otherwise not
> have any binding", this is to allow you to use the native keynames on
> your keyboard if you do want to distinguish.
>
> EXAMPLE:
> Many keyboards have a separate keypad number area.  These keys get their
> own events, e.g. "<kp-0>" for the zero character on the keypad.  Emacs
> uses function-key-map to translate "<kp-0>" into "0", so pressing the
> keypad 0 acts the same as the number row 0.  If you wanted to map the
> keypad numbers to a different set of commands, you can still do so with
> the original "<kp-0>" key.  If you do so, that also implicitly overrides
> this translation.
>
> 3. key-translation-map.  I've never actually used this directly so I'm
> not entirely clear on its intent.  The docs make it sound like it is
> intended for changing keyboard layouts.  Which explains why I have never
> used it -- I generally use OSes that allow keyboard layout translating
> natively.
>
> EXAMPLE:
> Based on my guess above, key-translation-map would let me map between
> QWERTY and Dvorak inside Emacs.  This would be nice if I was running
> directly in a Linux terminal and did not have permission to run "sudo
> loadkeys".
>
> As a final note, notice that all three of these examples involve
> changing a key into a different key.  None of them are for binding
> commands.  Commands being bound to a key always is the job of the local
> and global keymaps.
>
> I hope these examples help you understand the setup here!
>
>    -- MJF