Attempt to solve bug #17497 by minimizing cursor motion during TTY menu updates.

 src/term.c (tty_menu_display): Don't position cursor here.  Instead,
 pass the cursor coordinates to update_frame_with_menu.
 (tty_menu_activate): Send the hide cursor command only once in an
 iteration through the outer 'while' loop.
 src/dispnew.c (update_frame_1): Accept an additional argument
 SET_CURSOR_P, and position the cursor at the end of the frame
 update only if that argument is non-zero.  All callers changed to
 provide the additional argument as non-zero, except for
 update_frame_with_menu.
 (update_frame_with_menu): Accept 2 additional arguments ROW and
 COL; if they are non-negative, instruct update_frame_1 not to
 position the cursor, and instead position it according to ROW and
 COL.
 src/dispextern.h (update_frame_with_menu): Update prototype.

4 files changed, 50 insertions, 18 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 5759d155580..16e3328a735 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,23 @@
+2014-06-04  Eli Zaretskii  <eliz@gnu.org>
+
+        Minimize cursor motion during TTY menu updates.
+        * term.c (tty_menu_display): Don't position cursor here.  Instead,
+        pass the cursor coordinates to update_frame_with_menu.
+        (tty_menu_activate): Send the hide cursor command only once in an
+        iteration through the outer 'while' loop.
+
+        * dispnew.c (update_frame_1): Accept an additional argument
+        SET_CURSOR_P, and position the cursor at the end of the frame
+        update only if that argument is non-zero.  All callers changed to
+        provide the additional argument as non-zero, except for
+        update_frame_with_menu.
+        (update_frame_with_menu): Accept 2 additional arguments ROW and
+        COL; if they are non-negative, instruct update_frame_1 not to
+        position the cursor, and instead position it according to ROW and
+        COL.
+
+        * dispextern.h (update_frame_with_menu): Update prototype.
+
 2014-06-02  Stefan Monnier  <monnier@iro.umontreal.ca>
 
         * callproc.c (call_process): Don't check read-only if we don't insert
diff --git a/src/dispextern.h b/src/dispextern.h
index 9ecd4ecdf7e..8ccc3d35d8c 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -3454,7 +3454,7 @@ extern Lisp_Object marginal_area_string (struct window *, enum window_part,
                                          int *, int *, int *, int *);
 extern void redraw_frame (struct frame *);
 extern bool update_frame (struct frame *, bool, bool);
-extern void update_frame_with_menu (struct frame *);
+extern void update_frame_with_menu (struct frame *, int, int);
 extern void bitch_at_user (void);
 extern void adjust_frame_glyphs (struct frame *);
 void free_glyphs (struct frame *);
diff --git a/src/dispnew.c b/src/dispnew.c
index 1a9eefc5cfc..163780952a6 100644
--- a/src/dispnew.c
+++ b/src/dispnew.c
@@ -92,7 +92,7 @@ static void check_matrix_pointers (struct glyph_matrix *,
 static void mirror_line_dance (struct window *, int, int, int *, char *);
 static bool update_window_tree (struct window *, bool);
 static bool update_window (struct window *, bool);
-static bool update_frame_1 (struct frame *, bool, bool);
+static bool update_frame_1 (struct frame *, bool, bool, bool);
 static bool scrolling (struct frame *);
 static void set_window_cursor_after_update (struct window *);
 static void adjust_frame_glyphs_for_window_redisplay (struct frame *);
@@ -3070,7 +3070,7 @@ update_frame (struct frame *f, bool force_p, bool inhibit_hairy_id_p)
 
       /* Update the display  */
       update_begin (f);
-      paused_p = update_frame_1 (f, force_p, inhibit_hairy_id_p);
+      paused_p = update_frame_1 (f, force_p, inhibit_hairy_id_p, 1);
       update_end (f);
 
       if (FRAME_TERMCAP_P (f) || FRAME_MSDOS_P (f))
@@ -3100,12 +3100,17 @@ update_frame (struct frame *f, bool force_p, bool inhibit_hairy_id_p)
    glyphs.  This is like the second part of update_frame, but it
    doesn't call build_frame_matrix, because we already have the
    desired matrix prepared, and don't want it to be overwritten by the
-   text of the normal display.  */
+   text of the normal display.
+
+   ROW and COL, if non-negative, are the row and column of the TTY
+   frame where to position the cursor after the frame update is
+   complete.  Negative values mean ask update_frame_1 to position the
+   cursor "normally", i.e. at point in the selected window.  */
 void
-update_frame_with_menu (struct frame *f)
+update_frame_with_menu (struct frame *f, int row, int col)
 {
   struct window *root_window = XWINDOW (f->root_window);
-  bool paused_p;
+  bool paused_p, cursor_at_point_p;
 
   eassert (FRAME_TERMCAP_P (f));
 
@@ -3115,9 +3120,14 @@ update_frame_with_menu (struct frame *f)
 
   /* Update the display.  */
   update_begin (f);
+  cursor_at_point_p = !(row >= 0 && col >= 0);
   /* Force update_frame_1 not to stop due to pending input, and not
      try scrolling.  */
-  paused_p = update_frame_1 (f, 1, 1);
+  paused_p = update_frame_1 (f, 1, 1, cursor_at_point_p);
+  /* ROW and COL tell us where in the menu to position the cursor, so
+     that screen readers know the active region on the screen.  */
+  if (!cursor_at_point_p)
+    cursor_to (f, row, col);
   update_end (f);
 
   if (FRAME_TTY (f)->termscript)
@@ -4413,12 +4423,14 @@ scrolling_window (struct window *w, bool header_line_p)
 /* Update the desired frame matrix of frame F.
 
    FORCE_P means that the update should not be stopped by pending input.
-   INHIBIT_HAIRY_ID_P means that scrolling should not be tried.
+   INHIBIT_ID_P means that scrolling by insert/delete should not be tried.
+   SET_CURSOR_P false means do not set cursor at point in selected window.
 
    Value is true if update was stopped due to pending input.  */
 
 static bool
-update_frame_1 (struct frame *f, bool force_p, bool inhibit_id_p)
+update_frame_1 (struct frame *f, bool force_p, bool inhibit_id_p,
+                bool set_cursor_p)
 {
   /* Frame matrices to work on.  */
   struct glyph_matrix *current_matrix = f->current_matrix;
@@ -4490,7 +4502,7 @@ update_frame_1 (struct frame *f, bool force_p, bool inhibit_id_p)
   pause_p = 0 < i && i < FRAME_LINES (f) - 1;
 
   /* Now just clean up termcap drivers and set cursor, etc.  */
-  if (!pause_p)
+  if (!pause_p && set_cursor_p)
     {
       if ((cursor_in_echo_area
            /* If we are showing a message instead of the mini-buffer,
diff --git a/src/term.c b/src/term.c
index 12cd2ce8508..8661cba1160 100644
--- a/src/term.c
+++ b/src/term.c
@@ -2907,8 +2907,7 @@ tty_menu_display (tty_menu *menu, int x, int y, int pn, int *faces,
       display_tty_menu_item (menu->text[j], max_width, face, x, y + i,
                              menu->submenu[j] != NULL);
     }
-  update_frame_with_menu (sf);
-  cursor_to (sf, row, col);
+  update_frame_with_menu (sf, row, col);
 }
 
 /* --------------------------- X Menu emulation ---------------------- */
@@ -3079,7 +3078,7 @@ static void
 screen_update (struct frame *f, struct glyph_matrix *mtx)
 {
   restore_desired_matrix (f, mtx);
-  update_frame_with_menu (f);
+  update_frame_with_menu (f, -1, -1);
 }
 
 typedef enum {
@@ -3228,7 +3227,7 @@ tty_menu_activate (tty_menu *menu, int *pane, int *selidx,
 
   /* Force update of the current frame, so that the desired and the
      current matrices are identical.  */
-  update_frame_with_menu (sf);
+  update_frame_with_menu (sf, -1, -1);
   state[0].menu = menu;
   state[0].screen_behind = save_and_enable_current_matrix (sf);
 
@@ -3373,8 +3372,6 @@ tty_menu_activate (tty_menu *menu, int *pane, int *selidx,
                             state[statecount - 1].y,
                             state[statecount - 1].pane,
                             faces, x, y, first_item, 1);
-          tty_hide_cursor (tty);
-          fflush (tty->output);
           /* The call to display help-echo below will move the cursor,
              so remember its current position as computed by
              tty_menu_display.  */
@@ -3393,10 +3390,13 @@ tty_menu_activate (tty_menu *menu, int *pane, int *selidx,
              item, so that screen readers and other accessibility aids
              know where the active region is.  */
           cursor_to (sf, row, col);
-          tty_hide_cursor (tty);
-          fflush (tty->output);
           prev_menu_help_message = menu_help_message;
         }
+      /* Both tty_menu_display and help_callback invoke update_end,
+         which calls tty_show_cursor.  Re-hide it, so it doesn't show
+         through the menus.  */
+      tty_hide_cursor (tty);
+      fflush (tty->output);
     }
 
   sf->mouse_moved = 0;