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; Two updates of etc/TODO

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* etc/TODO: Remove the redesign-overlays item (already done in
Emacs 29.1).  Add an item about supporting external indentation
rules.
This commit is contained in:
Eli Zaretskii 2023-09-08 16:31:14 +03:00
parent 0ab2823f51
commit 82af484ec1
1 changed files with 14 additions and 35 deletions
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49
etc/TODO
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@ -419,41 +419,6 @@ modify them. Also, when properties are looked up during redisplay, we
generally can't run Elisp code, whereas we generally can do that when
properties are added.
*** Move overlays to intervals.c
Currently overlays are implemented as (two) sorted singly linked lists (one
for overlays_before some position and one for overlay_after that
position, for some quirky definition of "before" and "after").
The function 'overlay-recenter' changes the position used for the split
(and is called internally in various situations).
Each overlay is itself implemented with two markers (which keep track of
the overlay-start and overlay-end). Markers are implemented as
a non-sorted singly linked list of markers. So every text
insertion/deletion requires O(N) time, where N is the number of markers
since we have to go down that list to update those markers that are
affected by the modification.
You can start in src/buffer.[ch], maybe grepping for overlays_before for
a starting point.
Text-properties, OTOH, are implemented with a (mostly) balanced binary
tree. This is implemented in src/intervals.[ch].
So we'd like to change overlays so that they don't use markers (and we
don't keep them in two sorted singly-linked lists) any more. Instead,
we'll store them inside the balanced binary tree used for
text-properties. I think we can use the "augmented tree" approach
described in https://en.wikipedia.org/wiki/Interval_tree.
To ease up debugging during development, I'd guess the implementation
would first add the new stuff, keeping the old stuff (i.e. add to
Lisp_Overlay whichever fields are needed for the new code, while keeping
the old ones, add needed overlay fields to the intervals tree, but keep
the old fields, the overlays_before etc...). This way, you can add
consistency checks that make sure the new code computes the same results
as the old code. And once that works well, we can remove the old code
and old fields.
** Implement Unicode-compliant display of "default-ignorable" characters
See the "Characters Ignored for Display" section of paragraph 5.21 in
the Unicode Standard for the details.
@ -473,6 +438,20 @@ wrapping of long lines under 'visual-line-mode'. The algorithm for
selecting the wrap point may also need be changed to break at the soft
hyphen.
** Support external rules for indentation
This should teach Emacs to read indentation rules from a file and use
them in preference to the user customizations and the built-in
defaults. An example of such rule files is '.clang-format', see
https://clang.llvm.org/docs/ClangFormatStyleOptions.html
As a minimum, there should be a command, a variant of indent-region,
which could be told to use the rules from such a file, and should then
reformat the region of source code according to the rules.
The next step is to use these rules during editing of files residing
in a directory that has such an indentation-rules spec in it.
** FFI (foreign function interface)
See eg https://lists.gnu.org/r/emacs-devel/2013-10/msg00246.html