Restore cursor position after an undo/redo

4 files changed, 33 insertions, 16 deletions

diff --git a/editor.c b/editor.c
index 455f3ae..ad3da53 100644
--- a/editor.c
+++ b/editor.c
@@ -484,7 +484,8 @@ static void editor_prompt_update(Prompt *prompt) {
 
 static void editor_prompt_clear(Prompt *prompt) {
 	Text *text = prompt->win->text;
-	while (text_undo(text));
+	while (text_undo(text) != (size_t)-1);
+	window_cursor_to(prompt->win->win, 0);
 }
 
 void editor_prompt_hide(Editor *ed) {
diff --git a/text.c b/text.c
index 92a0644..b68d707 100644
--- a/text.c
+++ b/text.c
@@ -84,7 +84,8 @@ typedef struct Change Change;
 struct Change {
 	Span old;               /* all pieces which are being modified/swapped out by the change */
 	Span new;               /* all pieces which are introduced/swapped in by the change */
-	Change *next;
+	size_t pos;             /* absolute position at which the change occured */
+	Change *next;           /* next change which is part of the same action */
 };
 
 /* An Action is a list of Changes which are used to undo/redo all modifications
@@ -144,7 +145,7 @@ static Location piece_get_extern(Text *txt, size_t pos);
 static void span_init(Span *span, Piece *start, Piece *end);
 static void span_swap(Text *txt, Span *old, Span *new);
 /* change management */
-static Change *change_alloc(Text *txt);
+static Change *change_alloc(Text *txt, size_t pos);
 static void change_free(Change *c);
 /* action management */
 static Action *action_alloc(Text *txt);
@@ -439,7 +440,7 @@ static Location piece_get_extern(Text *txt, size_t pos) {
 
 /* allocate a new change, associate it with current action or a newly
  * allocated one if none exists. */
-static Change *change_alloc(Text *txt) {
+static Change *change_alloc(Text *txt, size_t pos) {
 	Action *a = txt->current_action;
 	if (!a) {
 		a = action_alloc(txt);
@@ -449,6 +450,7 @@ static Change *change_alloc(Text *txt) {
 	Change *c = calloc(1, sizeof(Change));
 	if (!c)
 		return NULL;
+	c->pos = pos;
 	c->next = a->change;
 	a->change = c;
 	return c;
@@ -501,7 +503,7 @@ bool text_insert_raw(Text *txt, size_t pos, const char *data, size_t len) {
 	if (cache_insert(txt, p, off, data, len))
 		return true;
 
-	Change *c = change_alloc(txt);
+	Change *c = change_alloc(txt, pos);
 	if (!c)
 		return false;
 
@@ -547,31 +549,35 @@ bool text_insert(Text *txt, size_t pos, const char *data) {
 }
 
 /* undo all changes of the last action, return whether changes existed */
-bool text_undo(Text *txt) {
+size_t text_undo(Text *txt) {
+	size_t pos = -1;
 	Action *a = action_pop(&txt->undo);
 	if (!a)
-		return false;
+		return pos;
 	for (Change *c = a->change; c; c = c->next) {
 		span_swap(txt, &c->new, &c->old);
+		pos = c->pos;
 	}
 
 	action_push(&txt->redo, a);
 	lineno_cache_invalidate(&txt->lines);
-	return true;
+	return pos;
 }
 
 /* redo all changes of the last action, return whether changes existed */
-bool text_redo(Text *txt) {
+size_t text_redo(Text *txt) {
+	size_t pos = -1;
 	Action *a = action_pop(&txt->redo);
 	if (!a)
-		return false;
+		return pos;
 	for (Change *c = a->change; c; c = c->next) {
 		span_swap(txt, &c->old, &c->new);
+		pos = c->pos;
 	}
 
 	action_push(&txt->undo, a);
 	lineno_cache_invalidate(&txt->lines);
-	return true;
+	return pos;
 }
 
 /* save current content to given filename. the data is first saved to
@@ -706,7 +712,7 @@ bool text_delete(Text *txt, size_t pos, size_t len) {
 		return true;
 	size_t cur; // how much has already been deleted
 	bool midway_start = false, midway_end = false;
-	Change *c = change_alloc(txt);
+	Change *c = change_alloc(txt, pos);
 	if (!c)
 		return false;
 	Piece *before, *after; // unmodified pieces before / after deletion point
diff --git a/text.h b/text.h
index bedd16b..2cec7b1 100644
--- a/text.h
+++ b/text.h
@@ -33,8 +33,10 @@ bool text_insert(Text*, size_t pos, const char *data);
 bool text_insert_raw(Text*, size_t pos, const char *data, size_t len);
 bool text_delete(Text*, size_t pos, size_t len);
 void text_snapshot(Text*);
-bool text_undo(Text*);
-bool text_redo(Text*);
+/* undo/redos to the last snapshoted state. returns the position where
+ * the change occured or (size_t)-1 if nothing could be undo/redo. */
+size_t text_undo(Text*);
+size_t text_redo(Text*);
 
 size_t text_pos_by_lineno(Text*, size_t lineno);
 size_t text_lineno_by_pos(Text*, size_t pos);
diff --git a/vis.c b/vis.c
index 88cefd2..b2559d7 100644
--- a/vis.c
+++ b/vis.c
@@ -593,13 +593,21 @@ static void mark_line(const Arg *arg) {
 }
 
 static void undo(const Arg *arg) {
-	if (text_undo(vis->win->text))
+	size_t pos = text_undo(vis->win->text);
+	if (pos != (size_t)-1) {
+		window_cursor_to(vis->win->win, pos);
+		/* redraw all windows in case some display the same file */
 		editor_draw(vis);
+	}
 }
 
 static void redo(const Arg *arg) {
-	if (text_redo(vis->win->text))
+	size_t pos = text_redo(vis->win->text);
+	if (pos != (size_t)-1) {
+		window_cursor_to(vis->win->win, pos);
+		/* redraw all windows in case some display the same file */
 		editor_draw(vis);
+	}
 }
 
 static void zero(const Arg *arg) {