Add new logical linewise movements

The column position is currently not correctly preserved when
there are lines with multibyte characters involved spanning
multiple screen lines.

In general this might still be a bit fragile.

text-motions.c

@@ -154,6 +154,15 @@ size_t text_line_next(Text *txt, size_t pos) {
 	return it.pos;
 }
 
+size_t text_line_offset(Text *txt, size_t pos, size_t off) {
+	char c;
+	size_t bol = text_line_begin(txt, pos);
+	Iterator it = text_iterator_get(txt, bol);
+	while (off-- > 0 && text_iterator_byte_get(&it, &c) && c != '\r' && c != '\n')
+		text_iterator_byte_next(&it, NULL);
+	return it.pos;
+}
+
 static size_t text_customword_start_next(Text *txt, size_t pos, int (*isboundry)(int)) {
 	char c;
 	Iterator it = text_iterator_get(txt, pos);

text-motions.h

@@ -34,6 +34,7 @@ size_t text_line_finish(Text*, size_t pos);
 size_t text_line_lastchar(Text*, size_t pos);
 size_t text_line_end(Text*, size_t pos);
 size_t text_line_next(Text*, size_t pos);
+size_t text_line_offset(Text*, size_t pos, size_t off);
 /*
  * A longword consists of a sequence of non-blank characters, separated with
  * white space. TODO?: An empty line is also considered to be a word.

vis.c

@@ -202,6 +202,8 @@ static Operator ops[] = {
 
 /* these can be passed as int argument to movement(&(const Arg){ .i = MOVE_* }) */
 enum {
+	MOVE_LINE_DOWN,
+	MOVE_LINE_UP,
 	MOVE_SCREEN_LINE_UP,
 	MOVE_SCREEN_LINE_DOWN,
 	MOVE_SCREEN_LINE_BEGIN,
@@ -281,6 +283,8 @@ static size_t window_lines_middle(const Arg *arg);
 static size_t window_lines_bottom(const Arg *arg);
 
 static Movement moves[] = {
+	[MOVE_LINE_UP]             = { .win = window_line_up                                       },
+	[MOVE_LINE_DOWN]           = { .win = window_line_down                                     },
 	[MOVE_SCREEN_LINE_UP]      = { .win = window_screenline_up                                 },
 	[MOVE_SCREEN_LINE_DOWN]    = { .win = window_screenline_down                               },
 	[MOVE_SCREEN_LINE_BEGIN]   = { .win = window_screenline_begin,  .type = CHARWISE           },
@@ -380,6 +384,8 @@ static TextObject textobjs[] = {
 
 /* if some movements are forced to be linewise, they are translated to text objects */
 static TextObject *moves_linewise[] = {
+	[MOVE_LINE_UP]          = &textobjs[TEXT_OBJ_LINE_UP],
+	[MOVE_LINE_DOWN]        = &textobjs[TEXT_OBJ_LINE_DOWN],
 	[MOVE_SCREEN_LINE_UP]   = &textobjs[TEXT_OBJ_LINE_UP],
 	[MOVE_SCREEN_LINE_DOWN] = &textobjs[TEXT_OBJ_LINE_DOWN],
 };

window.c

@@ -788,6 +788,30 @@ size_t window_scroll_down(Win *win, int lines) {
 	return cursor->pos;
 }
 
+size_t window_line_up(Win *win) {
+	Cursor *cursor = &win->cursor;
+	if (cursor->line->prev && cursor->line->prev->prev &&
+	    cursor->line->lineno != cursor->line->prev->lineno &&
+	    cursor->line->prev->lineno != cursor->line->prev->prev->lineno)
+		return window_screenline_up(win);
+	size_t bol = text_line_begin(win->text, cursor->pos);
+	size_t prev = text_line_prev(win->text, bol);
+	size_t pos = text_line_offset(win->text, prev, cursor->pos - bol);
+	window_cursor_to(win, pos);
+	return cursor->pos;
+}
+
+size_t window_line_down(Win *win) {
+	Cursor *cursor = &win->cursor;
+	if (!cursor->line->next || cursor->line->next->lineno != cursor->line->lineno)
+		return window_screenline_down(win);
+	size_t bol = text_line_begin(win->text, cursor->pos);
+	size_t next = text_line_next(win->text, bol);
+	size_t pos = text_line_offset(win->text, next, cursor->pos - bol);
+	window_cursor_to(win, pos);
+	return cursor->pos;
+}
+
 size_t window_screenline_up(Win *win) {
 	Cursor *cursor = &win->cursor;
 	if (!cursor->line->prev)

window.h

@@ -36,6 +36,8 @@ void window_tabwidth_set(Win*, int tabwidth);
  * they return new cursor postion */
 size_t window_char_next(Win*);
 size_t window_char_prev(Win*);
+size_t window_line_down(Win*);
+size_t window_line_up(Win*);
 size_t window_screenline_down(Win*);
 size_t window_screenline_up(Win*);
 size_t window_screenline_begin(Win*);