Rudimentary change list (accessible via g; and g,)

7 files changed, 70 insertions, 3 deletions

diff --git a/README b/README
index 9874fbe..45d5045 100644
--- a/README
+++ b/README
@@ -480,8 +480,9 @@ and their current support in vis.
  Jump list and change list
  -------------------------
 
-  A per window, fixed size, file local jump list is implemented.
-  The change list is currently not supported.
+  A per window, file local jump list (navigate with CTRL+O and CTRL+I)
+  and change list (navigate with g; and g,) is supported. The jump
+  list is implemented as a fixed sized ring buffer.
 
  Mouse support
  -------------
diff --git a/config.def.h b/config.def.h
index 655671f..db41216 100644
--- a/config.def.h
+++ b/config.def.h
@@ -384,6 +384,8 @@ static KeyBinding vis_mode_normal[] = {
 	{ { CONTROL('Y')            }, wslide,         { .i = +1                   } },
 	{ { CONTROL('O')            }, jumplist,       { .i = -1                   } },
 	{ { CONTROL('I')            }, jumplist,       { .i = +1                   } },
+	{ { NONE('g'), NONE(';')    }, changelist,     { .i = -1                   } },
+	{ { NONE('g'), NONE(',')    }, changelist,     { .i = +1                   } },
 	{ { NONE('a')               }, insertmode,     { .i = MOVE_CHAR_NEXT       } },
 	{ { NONE('A')               }, insertmode,     { .i = MOVE_LINE_END        } },
 	{ { NONE('C')               }, change,         { .i = MOVE_LINE_END        } },
diff --git a/editor.c b/editor.c
index ef59242..e472351 100644
--- a/editor.c
+++ b/editor.c
@@ -172,6 +172,34 @@ void editor_window_jumplist_invalidate(EditorWin *win) {
 	ringbuf_invalidate(win->jumplist);
 }
 
+size_t editor_window_changelist_prev(EditorWin *win) {
+	size_t pos = window_cursor_get(win->win);
+	if (pos != win->changelist.pos)
+		win->changelist.index = 0;
+	else
+		win->changelist.index++;
+	size_t newpos = text_history_get(win->text, win->changelist.index);
+	if (newpos == EPOS)
+		win->changelist.index--;
+	else
+		win->changelist.pos = newpos;
+	return win->changelist.pos;
+}
+
+size_t editor_window_changelist_next(EditorWin *win) {
+	size_t pos = window_cursor_get(win->win);
+	if (pos != win->changelist.pos)
+		win->changelist.index = 0;
+	else if (win->changelist.index > 0)
+		win->changelist.index--;
+	size_t newpos = text_history_get(win->text, win->changelist.index);
+	if (newpos == EPOS)
+		win->changelist.index++;
+	else
+		win->changelist.pos = newpos;
+	return win->changelist.pos;
+}
+
 void editor_resize(Editor *ed, int width, int height) {
 	ed->width = width;
 	ed->height = height;
diff --git a/editor.h b/editor.h
index 2cc097f..2be3fa6 100644
--- a/editor.h
+++ b/editor.h
@@ -13,11 +13,17 @@
 typedef struct Editor Editor;
 typedef struct EditorWin EditorWin;
 
+typedef struct {
+	size_t index;           /* #number of changes */
+	size_t pos;             /* where the current change occured */
+} ChangeList;
+
 struct EditorWin {
 	Editor *editor;         /* editor instance to which this window belongs */
 	Text *text;             /* underlying text management */
 	Win *win;               /* window for the text area  */
 	RingBuffer *jumplist;   /* LRU jump management */
+	ChangeList changelist;  /* state for iterating through least recently changes */
 	WINDOW *statuswin;      /* curses window for the statusbar */
 	int width, height;      /* window size including the statusbar */
 	EditorWin *prev, *next; /* neighbouring windows */
@@ -158,6 +164,9 @@ void editor_window_jumplist_add(EditorWin*, size_t pos);
 size_t editor_window_jumplist_prev(EditorWin*);
 size_t editor_window_jumplist_next(EditorWin*);
 void editor_window_jumplist_invalidate(EditorWin*);
+
+size_t editor_window_changelist_prev(EditorWin*);
+size_t editor_window_changelist_next(EditorWin*);
 /* rearrange all windows either vertically or horizontally */
 void editor_windows_arrange_vertical(Editor*);
 void editor_windows_arrange_horizontal(Editor*);
diff --git a/text.c b/text.c
index 7d17bbf..9afab01 100644
--- a/text.c
+++ b/text.c
@@ -1177,6 +1177,18 @@ void text_mark_intern_clear_all(Text *txt) {
 		text_mark_intern_clear(txt, mark);
 }
 
+size_t text_history_get(Text *txt, size_t index) {
+	for (Action *a = txt->current_action ? txt->current_action : txt->undo; a; a = a->next) {
+		if (index-- == 0) {
+			Change *c = a->change;
+			while (c && c->next)
+				c = c->next;
+			return c ? c->pos : EPOS;
+		}
+	}
+	return EPOS;
+}
+
 int text_fd_get(Text *txt) {
 	return txt->fd;
 }
diff --git a/text.h b/text.h
index 5156d84..faa340c 100644
--- a/text.h
+++ b/text.h
@@ -83,6 +83,9 @@ size_t text_mark_intern_get(Text*, MarkIntern);
 void text_mark_intern_clear(Text*, MarkIntern);
 void text_mark_intern_clear_all(Text*);
 
+/* get position of change denoted by index, where 0 indicates the most recent */
+size_t text_history_get(Text*, size_t index);
+
 size_t text_size(Text*);
 bool text_modified(Text*);
 /* test whether the underlying file uses UNIX style \n or Windows style \r\n newlines */
diff --git a/vis.c b/vis.c
index c0da6ac..aa37cb8 100644
--- a/vis.c
+++ b/vis.c
@@ -385,8 +385,10 @@ static TextObject *moves_linewise[] = {
 };
 
 /** functions to be called from keybindings */
-/* navigate jumplist either in forward (arg->i>0) or backward (arg->i<0) direction */
+/* navigate jump list either in forward (arg->i>0) or backward (arg->i<0) direction */
 static void jumplist(const Arg *arg);
+/* navigate change list either in forward (arg->i>0) or backward (arg->i<0) direction */
+static void changelist(const Arg *arg);
 static void macro_record(const Arg *arg);
 static void macro_replay(const Arg *arg);
 /* temporarily suspend the editor and return to the shell, type 'fg' to get back */
@@ -810,6 +812,16 @@ static void jumplist(const Arg *arg) {
 		window_cursor_to(vis->win->win, pos);
 }
 
+static void changelist(const Arg *arg) {
+	size_t pos;
+	if (arg->i > 0)
+		pos = editor_window_changelist_next(vis->win);
+	else
+		pos = editor_window_changelist_prev(vis->win);
+	if (pos != EPOS)
+		window_cursor_to(vis->win->win, pos);
+}
+
 static Macro *key2macro(const Arg *arg) {
 	if (arg->i)
 		return &vis->macros[arg->i];