Automatically reflow wrapped lines when a pane is resized, requested by

many over the years and finally implemented by Richard Woodbury.

grid.c

@@ -460,3 +460,44 @@ grid_duplicate_lines(
 		dy++;
 	}
 }
+
+/*
+ * Reflow lines from src grid into dst grid based on width sx. Returns number
+ * of lines fewer in the visible area, or zero.
+ */
+u_int
+grid_reflow(struct grid *dst, const struct grid *src, u_int sx)
+{
+	u_int			 px, py, line, cell;
+	int			 previous_wrapped;
+	struct grid_line	*gl;
+
+	px = py = 0;
+	previous_wrapped = 1;
+	for (line = 0; line < src->sy + src->hsize; line++) {
+		gl = src->linedata + line;
+		if (!previous_wrapped) {
+			px = 0;
+			py++;
+			if (py >= dst->hsize + dst->sy)
+				grid_scroll_history(dst);
+		}
+		for (cell = 0; cell < gl->cellsize; cell++) {
+			if (px == sx) {
+				dst->linedata[py].flags |= GRID_LINE_WRAPPED;
+				px = 0;
+				py++;
+				if (py >= dst->hsize + dst->sy)
+					grid_scroll_history(dst);
+			}
+			grid_set_cell(dst, px, py, gl->celldata + cell);
+			px++;
+		}
+		previous_wrapped = gl->flags & GRID_LINE_WRAPPED;
+	}
+	py++; /* account for final line, which never wraps */
+
+	if (py > src->sy)
+		return (0);
+	return (src->sy - py);
+}

screen.c

@@ -120,7 +120,7 @@ screen_set_title(struct screen *s, const char *title)
 
 /* Resize screen. */
 void
-screen_resize(struct screen *s, u_int sx, u_int sy)
+screen_resize(struct screen *s, u_int sx, u_int sy, int reflow)
 {
 	if (sx < 1)
 		sx = 1;
@@ -140,6 +140,9 @@ screen_resize(struct screen *s, u_int sx, u_int sy)
 
 	if (sy != screen_size_y(s))
 		screen_resize_y(s, sy);
+
+	if (reflow)
+		screen_reflow(s, sx);
 }
 
 void
@@ -356,3 +359,18 @@ screen_check_selection(struct screen *s, u_int px, u_int py)
 
 	return (1);
 }
+
+/* Reflow wrapped lines. */
+void
+screen_reflow(struct screen *s, u_int sx)
+{
+	struct grid	*old, *new;
+
+	old = s->grid;
+	new = grid_create(old->sx, old->sy, old->hlimit);
+
+	s->cy -= grid_reflow(new, old, sx);
+	s->grid = new;
+
+	grid_destroy(old);
+}

tmux.h

@@ -1964,6 +1964,7 @@ void	 grid_move_cells(struct grid *, u_int, u_int, u_int, u_int);
 char	*grid_string_cells(struct grid *, u_int, u_int, u_int);
 void	 grid_duplicate_lines(
 	     struct grid *, u_int, struct grid *, u_int, u_int);
+u_int	 grid_reflow(struct grid *, const struct grid *, u_int);
 
 /* grid-cell.c */
 u_int	 grid_cell_width(const struct grid_cell *);
@@ -2057,11 +2058,12 @@ void	 screen_reset_tabs(struct screen *);
 void	 screen_set_cursor_style(struct screen *, u_int);
 void	 screen_set_cursor_colour(struct screen *, const char *);
 void	 screen_set_title(struct screen *, const char *);
-void	 screen_resize(struct screen *, u_int, u_int);
+void	 screen_resize(struct screen *, u_int, u_int, int);
 void	 screen_set_selection(struct screen *,
 	     u_int, u_int, u_int, u_int, u_int, struct grid_cell *);
 void	 screen_clear_selection(struct screen *);
 int	 screen_check_selection(struct screen *, u_int, u_int);
+void	 screen_reflow(struct screen *, u_int);
 
 /* window.c */
 extern struct windows windows;

window-choose.c

@@ -203,7 +203,7 @@ window_choose_resize(struct window_pane *wp, u_int sx, u_int sy)
 	if (data->selected > sy - 1)
 		data->top = data->selected - (sy - 1);
 
-	screen_resize(s, sx, sy);
+	screen_resize(s, sx, sy, 0);
 	window_choose_redraw_screen(wp);
 }
 

window-clock.c

@@ -79,7 +79,7 @@ window_clock_resize(struct window_pane *wp, u_int sx, u_int sy)
 	struct window_clock_mode_data	*data = wp->modedata;
 	struct screen			*s = &data->screen;
 
-	screen_resize(s, sx, sy);
+	screen_resize(s, sx, sy, 0);
 	window_clock_draw_screen(wp);
 }
 

window-copy.c

@@ -335,9 +335,9 @@ window_copy_resize(struct window_pane *wp, u_int sx, u_int sy)
 	struct screen			*s = &data->screen;
 	struct screen_write_ctx	 	 ctx;
 
-	screen_resize(s, sx, sy);
+	screen_resize(s, sx, sy, 0);
 	if (data->backing != &wp->base)
-		screen_resize(data->backing, sx, sy);
+		screen_resize(data->backing, sx, sy, 0);
 
 	if (data->cy > sy - 1)
 		data->cy = sy - 1;

window.c

@@ -853,7 +853,7 @@ window_pane_resize(struct window_pane *wp, u_int sx, u_int sy)
 	ws.ws_col = sx;
 	ws.ws_row = sy;
 
-	screen_resize(&wp->base, sx, sy);
+	screen_resize(&wp->base, sx, sy, wp->saved_grid == NULL);
 	if (wp->mode != NULL)
 		wp->mode->resize(wp, sx, sy);
 
@@ -914,7 +914,7 @@ window_pane_alternate_off(struct window_pane *wp, struct grid_cell *gc,
 	 * before copying back.
 	 */
 	if (sy > wp->saved_grid->sy)
-		screen_resize(s, sx, wp->saved_grid->sy);
+		screen_resize(s, sx, wp->saved_grid->sy, 1);
 
 	/* Restore the grid, cursor position and cell. */
 	grid_duplicate_lines(s->grid, screen_hsize(s), wp->saved_grid, 0, sy);
@@ -933,8 +933,8 @@ window_pane_alternate_off(struct window_pane *wp, struct grid_cell *gc,
 	 * the current size.
 	 */
 	wp->base.grid->flags |= GRID_HISTORY;
-	if (sy > wp->saved_grid->sy)
-		screen_resize(s, sx, sy);
+	if (sy > wp->saved_grid->sy || sx != wp->saved_grid->sx)
+		screen_resize(s, sx, sy, 1);
 
 	grid_destroy(wp->saved_grid);
 	wp->saved_grid = NULL;