Support limiting search to region

[yuki-tsubaki]

This is a fairly simple idea that I think would be quite useful but I have been unable to figure out a clean way to implement this given the current functions available in Avy.

The idea is that this could be easily used to limit Avy's context to make selection quicker. E.g. one could select within a specific symbolic expression in Lisp, within a paragraph, or within any other construct that can be selected using Emacs and available packages or functions.

This would make Avy more flexible.

I have tried a few things to implement this, but haven't figured out how to do this yet. Ideally a clean way to add in this functionality could be added that doesn't break the compatibility with existing code (e.g. an additional conditional branch somewhere that is controlled by a new variable which people can then let bind to create "region bound" versions of Avy commands.

If anyone has suggestions or ideas on how this could be done (short of rewriting everything) it would be much appreciated.

[ZelphirKaltstahl]

I don't know the details of the implementation of avy, but could such a thing be achieved by simply using save-restriction in a custom procedure wrapping what avy provides?

save-restriction is a special-form in ‘C source code’.

(save-restriction &rest BODY)

Execute BODY, saving and restoring current buffer’s restrictions.
The buffer’s restrictions make parts of the beginning and end invisible.
(They are set up with ‘narrow-to-region’ and eliminated with ‘widen’.)
This special form, ‘save-restriction’, saves the current buffer’s
restrictions, including those that were set by ‘with-restriction’ with a
label argument, when it is entered, and restores them when it is exited.
So any ‘narrow-to-region’ within BODY lasts only until the end of the form.
The old restrictions settings are restored even in case of abnormal exit
(throw or error).

The value returned is the value of the last form in BODY.

Note: if you are using both ‘save-excursion’ and ‘save-restriction’,
use ‘save-excursion’ outermost:
    (save-excursion (save-restriction ...))

  Probably introduced at or before Emacs version 21.1.
  This function has a ‘byte-compile’ property
    ‘byte-compile-save-restriction’.  See the manual for details.

Note, that this only works, if the implementation of avy does not circumvent it, for example by looking up the file that a buffer is visiting and then retrieves the full content of the file, escaping the narrowing of save-restriction.

[yuki-tsubaki]

Thanks for that idea and sorry for the late response.

I tested and as long as I bind avy-all-windows to nil using a restriction via with-restriction (which the previous one can be saved via the form that you discussed) does limit the scope of an avy search, but it also visibly narrows the buffer while it is active. I.e. it isn't just narrowing the range of for avy, it is narrowing the range of the buffer for everything. This breaks some things (I get some Jinx timer errors when running these blocks) and also obviously is a bit less clean than other versions.

The main inspiration for this question was the Lispy avy integrations from the lispy-ace- series of functions. I can't remember exactly what problems I was running into, but I wanted to make an avy-goto-char-timer version of that.

My hope was that there is some cleaner way to implement this (than picking the current one apart and building in the timer function myself).

So far it looks like there's not. Thanks anyway though.