difficult to fix. Bugs with severity "minor" may be simpler, but this
is not always true.
-* Tentative plan for Emacs-24
+* Speed up Elisp execution
+** Speed up function calls
+Change src/bytecode.c so that calls from byte-code functions to byte-code
+functions don't go through Ffuncall/funcall_lambda/exec_byte_code but instead
+stay within exec_byte_code.
+
+** Add new `switch' byte-code
+This byte-code would take one argument from the stack (the object to test)
+and one argument from the constant-pool (a switch table, implemented as an
+eq-hashtable) and would jump to the "label" contained in the hashtable.
+
+Then add a `case' special-form that can be compiled to this byte-code.
+This would behave just like cl-case, but instead of expanding to cond+eq it
+would be its own special form and would be compiled specially.
+
+Then change pcase to use `case' when applicable.
+
+Then change the byte-compiler to recognize (cond ((eq x 'foo) bar) ...)
+and turn it into a `case' for more efficient execution.
+
+** Improve the byte-compiler to recognize immutable (lexical) bindings
+and get rid of them if they're used only once and/or they're bound to
+a constant expression.
+
+Such things aren't present in hand-written code, but macro expansion and
+defsubst can often end up generating things like
+(funcall (lambda (arg) (body)) actual) which then get optimized to
+(let ((arg actual)) (body)) but should additionally get optimized further
+when `actual' is a constant/copyable expression.
+
+** Add an "indirect goto" byte-code and use it for local lambda expressions.
+E.g. when you have code like
+
+ (let ((foo (lambda (x) bar)))
+ (dosomething
+ (funcall foo toto)
+ (blabla (funcall foo titi))))
+
+turn those `funcalls' into jumps and their return into indirect jumps back.
+
+** Compile efficiently local recursive functions
+
+Similar to the previous point, we should be able to handle something like
+
+ (letrec ((loop () (blabla) (if (toto) (loop))))
+ (loop))
+
+which ideally should generate the same byte-code as
+
+ (while (progn (blabla) (toto)))
+
+* Things that were planned for Emacs-24
** concurrency: including it as an "experimental" compile-time option
- sounds good. Of course there might still be big questions around
- "which form of concurrency" we'll want.
-** Overhaul of customize: sounds wonderful.
+ sounds good. Of course there might still be big questions around "which form
+ of concurrency" we'll want.
** better support for dynamic embedded graphics: I like this idea (my
mpc.el code could use it for the volume widget), though I wonder if the
resulting efficiency will be sufficient.
** Random things that cross my mind right now that I'd like to see (some of
them from my local hacks), but it's not obvious at all whether they'll
make it.
-*** multiple inheritance for keymaps (to get rid of the
- fix_submap_inheritance hack and to more cleanly express the
- relationship between minibuffer-local-*-map): I've had this locally
- for a long time, but the details of the semantics is somewhat ... delicate.
*** prog-mode could/should provide a better fill-paragraph default
that uses syntax-tables to recognize string/comment boundaries.
*** provide more completion-at-point-functions. Make existing
mechanism that suffices for the specific needs. That will be easy
for users to customize.
-** Compute the list of active keymaps *after* reading the first event.
-
** Distribute a bar cursor of width > 1 evenly between the two glyphs
on each side of the bar (what to do at the edges?).
It ought to be possible to omit text which is invisible (due to a
text-property, overlay, or selective display) from the kill-ring.
-** Change the way define-minor-mode handles autoloading.
- It should not generate :require. Or :require in defcustom
- should not be recorded in the user's custom-set-variables call.
-
** Feature to change cursor shape when Emacs is idle (for more than
a specified time).
http://lists.gnu.org/archive/html/emacs-pretest-bug/2005-12/msg00165.html,
and the rest of that discussion.
-** Height returned by frame-parameter ... and height given to
- make-frame does not mean the same thing. The former includes menu and
- tool bar lines, the latter don't. frame-parameter should return height
- without menu and tool bar lines.
-
** In Emacs Info, examples of using Customize should be clickable
and they should create Custom buffers.
processing. That is why we added text properties and variable
width fonts. However, more features are still needed to achieve this.
-** Extended text-properties (to make overlays "obsolete")
+** Extend text-properties and overlays
*** Several text-property planes
This would get us rid of font-lock-face property (and I'd be happy to
get rid of char-property-alias-alist as well) since font-lock would
simply use the `face' property in the `font-lock' plane.
-Each property would come with an Elisp merge-function. The merge
-would be performed in add-text-properties.
-*** zero-width text-properties.
+
+Basically `put-text-property' and friends would take an extra argument PLANE
+(maybe the best backward-compatible way to do that is to make it so that
+PROPERTY can be a cons cell (PLANE . PROP)). So font-lock would
+do (put-text-property start end '(font-lock . face) value).
+
+All the properties coming from the various planes would get merged via an Elisp
+function (so it can merge `face' differently than `keymap' or it could give
+different priorities to different planes (we could imagine enabling/disabling
+planes)). The merging would not happen lazily while looking up properties but
+instead it would take place eagerly in `add-text-properties'. This is based on
+the idea that it's much more frequent to lookup properties than to
+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.
+
** Having tabs above a window to switch buffers in it.
** "Perspectives" are named persistent window configurations. We have
* Other features we would like:
+** A more modern printing interface. One that pops up a dialog that lets
+you choose printer, page style, etc.
+Integration with the Gtk print dialog is apparently difficult. See eg:
+http://lists.gnu.org/archive/html/emacs-devel/2009-03/msg00501.html
+http://lists.gnu.org/archive/html/emacs-devel/2009-04/msg00034.html
+
** Allow frames(terminals) created by emacsclient to inherit their environment
from the emacsclient process.
** Save undo information in special temporary files, and reload it
when needed for undoing. This could extend undo capacity.
+ undo-tree, in ELPA, already does this; its saving code could be
+ integrated without requiring the use of undo-tree.
** Change the Windows NT menu code
so that it handles the deep_p argument and avoids
[Basic support added 2013/10:
http://lists.gnu.org/archive/html/emacs-devel/2013-10/msg00904.html ]
-** Eliminate the storm of warnings concerning char/unsigned char
- mismatches that we get with GCC 4.x and proprietary compilers on
- various systems. They make it difficult to spot the important warnings.
-
-** Fix anything necessary to use `long long' EMACS_INTs with GCC.
-
** Split out parts of lisp.h.
** Update the FAQ.
** Add definitions for symbol properties, for documentation purposes.
-** Add horizontal scroll bars.
+** Temporarily remove scroll bars when they are not needed, typically
+ when a buffer can be fully displayed in its window.
** Provide an optional feature which computes a scroll bar slider's
size and its position from lines instead of characters.
** Replace linum.el with nlinum.el
http://lists.gnu.org/archive/html/emacs-devel/2013-08/msg00379.html
-** Use pcomplete by default in shell-mode.
- This means to make it behave (by default) more like the current code.
- Use it also for read-shell-command, M-x compile, ...
-
** Merge sendmail.el and messages.el.
Probably not a complete merge, but at least arrange for messages.el to be
a derived mode of sendmail.el. Or arrange for messages.el to be split
** a two-char comment-starter whose two chars are symbol constituents will
not be noticed if it appears within a word.
-** Fix unexelf.c to handle the .data.rel and .data.rel.local
- sections made by GCC 3.4 on IRIX.
-
\f
This file is part of GNU Emacs.