[xemacs-hg @ 2003-02-13 09:57:04 by ben] profile updates profile.c: Major reworking. Keep track of new information -- total function timing (includes descendants), GC usage, total GC usage (includes descendants). New functions to be called appropriately from eval.c, alloc.c to keep track of this information. Keep track of when we're actually in a function vs. in its profile, for more accurate timing counts. Track profile overhead separately. Create new mechanism for specifying "internal sections" that are tracked just like regular Lisp functions and even appear in the backtrace if `backtrace-with-internal-sections' is non-nil (t by default for error-checking builds). Add some KKCC information for the straight (non-Elisp) hash table used by profile, which contains Lisp objects in its keys -- but not used yet. Remove old ad-hoc methods for tracking garbage collection, redisplay (which was incorrect anyway when Lisp was called within these sections). Don't record any tick info when blocking under MS Windows, since the timer there is in real time rather than in process time. Make `start-profiling', `stop-profiling' interactive. Be consistent wrt. recursive functions and functions currently on the stack when starting or stopping -- together these make implementing the `total' values extremely difficult. When we start profiling, we act as if we just entered all the functions currently on the stack. Likewise when exiting. Create vars in_profile for tracking time spent inside of profiling, and profiling_lock for setting exclusive access to the main hash table when reading from it or modifying it. (protects against getting screwed up by the signal handle going off at the same time. profile.h: New file. Create macros for declaring internal profiling sections. lisp.h: Move profile-related stuff to profile.h. alloc.c: Keep track of total consing, for profile. Tell profile when we are consing. Use new profile-section method for noting garbage-collection. alloc.c: Abort if we attempt to call the allocator reentrantly. backtrace.h, eval.c: Add info for use by profile in the backtrace frame and transfer PUSH_BACKTRACE/POP_BACKTRACE from eval.c, for use with profile. elhash.c: Author comment. eval.c, lisp.h: New Lisp var `backtrace-with-internal-sections'. Set to t when error-checking is on. eval.c: When unwinding, eval.c: Report to profile when we are about-to-call and just-called wrt. a function. alloc.c, eval.c: Allow for "fake" backtrace frames, for internal sections (used by profile and `backtrace-with-internal-sections'. event-Xt.c, event-gtk.c, event-msw.c, event-tty.c: Record when we are actually blocking on an event, for profile's sake. event-stream.c: Record internal profiling sections for getting, dispatching events. extents.c: Record internal profiling sections for map_extents. hash.c, hash.h: Add pregrow_hash_table_if_necessary(). (Used in profile code since the signal handler is the main grower but can't allow a realloc(). We make sure, at critical points, that the table is large enough.) lread.c: Create internal profiling sections for `load' (which may be triggered internally by autoload, etc.). redisplay.c: Remove old profile_redisplay_flag. Use new macros to declare internal profiling section for redisplay. text.c: Use new macros to declare internal profiling sections for char-byte conversion and internal-external conversion. SEMI-UNRELATED CHANGES: ----------------------- text.c: Update the long comments.

@node Undo, Minibuffer, Basic, Top
@chapter Undoing Changes
@cindex undo
@cindex mistakes, correcting

  Emacs allows you to undo all changes you make to the text of a buffer,
up to a certain amount of change (8000 characters).  Each buffer records
changes individually, and the undo command always applies to the
current buffer.  Usually each editing command makes a separate entry
in the undo records, but some commands such as @code{query-replace}
make many entries, and very simple commands such as self-inserting
characters are often grouped to make undoing less tedious.

@table @kbd
@item C-x u
Undo one batch of changes (usually, one command's worth) (@code{undo}).
@item C-_
The same.
@end table

@kindex C-x u
@kindex C-_
@findex undo
  The command @kbd{C-x u} or @kbd{C-_} allows you to undo changes.  The
first time you give this command, it undoes the last change.  Point
moves to the text affected by the undo, so you can see what was undone.

  Consecutive repetitions of the @kbd{C-_} or @kbd{C-x u} commands undo
earlier and earlier changes, back to the limit of what has been
recorded.  If all recorded changes have already been undone, the undo
command prints an error message and does nothing.

  Any command other than an undo command breaks the sequence of undo
commands.  Starting at this moment, the previous undo commands are
considered ordinary changes that can themselves be undone.  Thus, you can
redo changes you have undone by typing @kbd{C-f} or any other command
that have no important effect, and then using more undo commands.

  If you notice that a buffer has been modified accidentally, the
easiest way to recover is to type @kbd{C-_} repeatedly until the stars
disappear from the front of the mode line.  When that happens, all the
modifications you made have been canceled.  If you do not remember
whether you changed the buffer deliberately, type @kbd{C-_} once. When
you see Emacs undo the last change you made, you probably remember why you
made it.  If the change was an accident, leave it undone.  If it was
deliberate, redo the change as described in the preceding paragraph.

  Whenever an undo command makes the stars disappear from the mode line,
the buffer contents is the same as it was when the file was last read in
or saved.

  Not all buffers record undo information.  Buffers whose names start with
spaces don't; these buffers are used internally by Emacs and its extensions
to hold text that users don't normally look at or edit.  Minibuffers,
help buffers, and documentation buffers also don't record undo information.

  Emacs can remember at most 8000 or so characters of deleted or
modified text in any one buffer for reinsertion by the undo command.
There is also a limit on the number of individual insert, delete, or
change actions that Emacs can remember.

  There are two keys to run the @code{undo} command, @kbd{C-x u} and
@kbd{C-_}, because on some keyboards, it is not obvious how to type
@kbd{C-_}. @kbd{C-x u} is an alternative you can type in the same
fashion on any terminal.