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Initial revision
This commit is contained in:
Jim Blandy
parent
d1682c8933
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c6953be16f
1 changed files with 322 additions and 0 deletions
322
src/undo.c
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322
src/undo.c
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/* undo handling for GNU Emacs.
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Copyright (C) 1990 Free Software Foundation, Inc.
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This file is part of GNU Emacs.
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GNU Emacs is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY. No author or distributor
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accepts responsibility to anyone for the consequences of using it
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or for whether it serves any particular purpose or works at all,
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unless he says so in writing. Refer to the GNU Emacs General Public
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License for full details.
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Everyone is granted permission to copy, modify and redistribute
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GNU Emacs, but only under the conditions described in the
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GNU Emacs General Public License. A copy of this license is
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supposed to have been given to you along with GNU Emacs so you
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can know your rights and responsibilities. It should be in a
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file named COPYING. Among other things, the copyright notice
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and this notice must be preserved on all copies. */
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#include "config.h"
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#include "lisp.h"
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#include "buffer.h"
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/* Last buffer for which undo information was recorded. */
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Lisp_Object last_undo_buffer;
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/* Record an insertion that just happened or is about to happen,
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for LENGTH characters at position BEG.
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(It is possible to record an insertion before or after the fact
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because we don't need to record the contents.) */
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record_insert (beg, length)
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Lisp_Object beg, length;
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{
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Lisp_Object lbeg, lend;
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if (current_buffer != XBUFFER (last_undo_buffer))
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Fundo_boundary ();
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XSET (last_undo_buffer, Lisp_Buffer, current_buffer);
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if (EQ (current_buffer->undo_list, Qt))
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return;
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if (MODIFF <= current_buffer->save_modified)
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record_first_change ();
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/* If this is following another insertion and consecutive with it
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in the buffer, combine the two. */
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if (XTYPE (current_buffer->undo_list) == Lisp_Cons)
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{
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Lisp_Object elt;
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elt = XCONS (current_buffer->undo_list)->car;
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if (XTYPE (elt) == Lisp_Cons
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&& XTYPE (XCONS (elt)->car) == Lisp_Int
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&& XTYPE (XCONS (elt)->cdr) == Lisp_Int
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&& XINT (XCONS (elt)->cdr) == beg)
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{
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XSETINT (XCONS (elt)->cdr, beg + length);
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return;
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}
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}
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XFASTINT (lbeg) = beg;
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XFASTINT (lend) = beg + length;
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current_buffer->undo_list = Fcons (Fcons (lbeg, lend), current_buffer->undo_list);
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}
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/* Record that a deletion is about to take place,
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for LENGTH characters at location BEG. */
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record_delete (beg, length)
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int beg, length;
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{
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Lisp_Object lbeg, lend, sbeg;
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if (current_buffer != XBUFFER (last_undo_buffer))
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Fundo_boundary ();
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XSET (last_undo_buffer, Lisp_Buffer, current_buffer);
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if (EQ (current_buffer->undo_list, Qt))
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return;
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if (MODIFF <= current_buffer->save_modified)
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record_first_change ();
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if (point == beg + length)
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XSET (sbeg, Lisp_Int, -beg);
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else
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XFASTINT (sbeg) = beg;
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XFASTINT (lbeg) = beg;
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XFASTINT (lend) = beg + length;
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current_buffer->undo_list
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= Fcons (Fcons (Fbuffer_substring (lbeg, lend), sbeg),
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current_buffer->undo_list);
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}
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/* Record that a replacement is about to take place,
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for LENGTH characters at location BEG.
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The replacement does not change the number of characters. */
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record_change (beg, length)
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int beg, length;
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{
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record_delete (beg, length);
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record_insert (beg, length);
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}
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/* Record that an unmodified buffer is about to be changed.
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Record the file modification date so that when undoing this entry
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we can tell whether it is obsolete because the file was saved again. */
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record_first_change ()
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{
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Lisp_Object high, low;
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XFASTINT (high) = (current_buffer->modtime >> 16) & 0xffff;
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XFASTINT (low) = current_buffer->modtime & 0xffff;
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current_buffer->undo_list = Fcons (Fcons (Qt, Fcons (high, low)), current_buffer->undo_list);
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}
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DEFUN ("undo-boundary", Fundo_boundary, Sundo_boundary, 0, 0, 0,
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"Mark a boundary between units of undo.\n\
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An undo command will stop at this point,\n\
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but another undo command will undo to the previous boundary.")
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()
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{
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Lisp_Object tem;
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if (EQ (current_buffer->undo_list, Qt))
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return Qnil;
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tem = Fcar (current_buffer->undo_list);
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if (!NULL (tem))
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current_buffer->undo_list = Fcons (Qnil, current_buffer->undo_list);
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return Qnil;
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}
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/* At garbage collection time, make an undo list shorter at the end,
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returning the truncated list.
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MINSIZE and MAXSIZE are the limits on size allowed, as described below.
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In practice, these are the values of undo-threshold and
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undo-high-threshold. */
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Lisp_Object
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truncate_undo_list (list, minsize, maxsize)
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Lisp_Object list;
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int minsize, maxsize;
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{
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Lisp_Object prev, next, last_boundary;
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int size_so_far = 0;
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prev = Qnil;
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next = list;
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last_boundary = Qnil;
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/* Always preserve at least the most recent undo record.
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If the first element is an undo boundary, skip past it. */
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if (XTYPE (next) == Lisp_Cons
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&& XCONS (next)->car == Qnil)
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{
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/* Add in the space occupied by this element and its chain link. */
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size_so_far += sizeof (struct Lisp_Cons);
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/* Advance to next element. */
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prev = next;
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next = XCONS (next)->cdr;
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}
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while (XTYPE (next) == Lisp_Cons
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&& XCONS (next)->car != Qnil)
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{
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Lisp_Object elt;
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elt = XCONS (next)->car;
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/* Add in the space occupied by this element and its chain link. */
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size_so_far += sizeof (struct Lisp_Cons);
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if (XTYPE (elt) == Lisp_Cons)
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{
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size_so_far += sizeof (struct Lisp_Cons);
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if (XTYPE (XCONS (elt)->car) == Lisp_String)
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size_so_far += (sizeof (struct Lisp_String) - 1
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+ XSTRING (XCONS (elt)->car)->size);
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}
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/* Advance to next element. */
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prev = next;
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next = XCONS (next)->cdr;
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}
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if (XTYPE (next) == Lisp_Cons)
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last_boundary = prev;
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while (XTYPE (next) == Lisp_Cons)
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{
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Lisp_Object elt;
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elt = XCONS (next)->car;
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/* When we get to a boundary, decide whether to truncate
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either before or after it. The lower threshold, MINSIZE,
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tells us to truncate after it. If its size pushes past
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the higher threshold MAXSIZE as well, we truncate before it. */
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if (NULL (elt))
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{
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if (size_so_far > maxsize)
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break;
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last_boundary = prev;
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if (size_so_far > minsize)
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break;
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}
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/* Add in the space occupied by this element and its chain link. */
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size_so_far += sizeof (struct Lisp_Cons);
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if (XTYPE (elt) == Lisp_Cons)
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{
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size_so_far += sizeof (struct Lisp_Cons);
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if (XTYPE (XCONS (elt)->car) == Lisp_String)
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size_so_far += (sizeof (struct Lisp_String) - 1
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+ XSTRING (XCONS (elt)->car)->size);
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}
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/* Advance to next element. */
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prev = next;
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next = XCONS (next)->cdr;
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}
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/* If we scanned the whole list, it is short enough; don't change it. */
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if (NULL (next))
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return list;
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/* Truncate at the boundary where we decided to truncate. */
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if (!NULL (last_boundary))
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{
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XCONS (last_boundary)->cdr = Qnil;
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return list;
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}
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else
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return Qnil;
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}
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DEFUN ("primitive-undo", Fprimitive_undo, Sprimitive_undo, 2, 2, 0,
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"Undo N records from the front of the list LIST.\n\
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Return what remains of the list.")
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(count, list)
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Lisp_Object count, list;
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{
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register int arg = XINT (count);
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#if 0 /* This is a good feature, but would make undo-start
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unable to do what is expected. */
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Lisp_Object tem;
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/* If the head of the list is a boundary, it is the boundary
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preceding this command. Get rid of it and don't count it. */
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tem = Fcar (list);
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if (NULL (tem))
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list = Fcdr (list);
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#endif
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while (arg > 0)
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{
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while (1)
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{
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Lisp_Object next, car, cdr;
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next = Fcar (list);
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list = Fcdr (list);
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if (NULL (next))
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break;
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car = Fcar (next);
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cdr = Fcdr (next);
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if (EQ (car, Qt))
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{
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Lisp_Object high, low;
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int mod_time;
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high = Fcar (cdr);
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low = Fcdr (cdr);
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mod_time = (high << 16) + low;
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/* If this records an obsolete save
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(not matching the actual disk file)
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then don't mark unmodified. */
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if (mod_time != current_buffer->modtime)
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break;
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#ifdef CLASH_DETECTION
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Funlock_buffer ();
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#endif /* CLASH_DETECTION */
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Fset_buffer_modified_p (Qnil);
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}
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else if (XTYPE (car) == Lisp_Int && XTYPE (cdr) == Lisp_Int)
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{
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Lisp_Object end;
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if (XINT (car) < BEGV
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|| XINT (cdr) > ZV)
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error ("Changes to be undone are outside visible portion of buffer");
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Fdelete_region (car, cdr);
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Fgoto_char (car);
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}
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else if (XTYPE (car) == Lisp_String && XTYPE (cdr) == Lisp_Int)
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{
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Lisp_Object membuf;
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int pos = XINT (cdr);
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membuf = car;
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if (pos < 0)
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{
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if (-pos < BEGV || -pos > ZV)
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error ("Changes to be undone are outside visible portion of buffer");
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SET_PT (-pos);
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Finsert (1, &membuf);
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}
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else
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{
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if (pos < BEGV || pos > ZV)
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error ("Changes to be undone are outside visible portion of buffer");
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SET_PT (pos);
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Finsert (1, &membuf);
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SET_PT (pos);
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}
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}
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}
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arg--;
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}
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return list;
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}
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syms_of_undo ()
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{
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defsubr (&Sprimitive_undo);
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defsubr (&Sundo_boundary);
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}
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