vpa - hpa

[Philippe Blain]

>From Philippe Blain, Bordeaux, France.
My computer: P133 - 8,4 Go - 32 Mo Red Hat Linux 7.0

Subject: Corrections for ncurses-5.3-20030823+

1-----------------------------------------------------------------------
File : ncurses/tty/lib_mvcur.c

Using vpa/hpa in the function relative_move(), is a nonsense:

Column_address (hpa) or row_address (vpa) must be OUTSIDE relative_move()
and considered as a case in itself (tactic#6).

The reason why is that they give VERY OFTEN (but not always) the best cost
comparing with parm_down/parm_up , cursor_right/cursor_left, ... hiding them
and then the tactics #2,#3,#4,#5 become nothing else than
(special_case)+vpa/hpa where (special_case) is mostly useless (except
increasing the cost) as we use the absolute cursor addressing capabilities
of the terminal.


Proof, for linux we have :
        hpa=\E[%i%p1%dG, vpa=\E[%i%p1%dd
        cub1=^H, cud1=^J, cuf1=\E[C, cuu1=\E[A
        ABSENT CAPS : cub, cud, cuf, cuu     [parm_xxx_cursor]
vpa/hpa is MOSTLY choosen by relative_move() (shortest sequence) except
when the new point is close to the old one or the edges of screen.
In these cases, relative_move() without vpa/hpa is sufficient.

Moving to x=0,y=12 gives in most cases : (padding=2 or 0.2 msec)

tactic#0   [ 1 3 ; 1 H                          (cup) real_cost: 14
tactic#1   [ 1 3 d  [ 1 G                 (vpa/hpa) real_cost: 18
tactic#2    [ 1 3 d ^[ [ 1 G         (cr + vpa/hpa) real_cost: 20
tactic#3   [ H  [ 1 3 d ^[ [ 1 G   (home + vpa/hpa) real_cost: 24
tactic#4  no capability                                 real_cost: 1000000
tactic#5  no capability                                 real_cost: 1000000

Useless to do an action (cr/home/...anything) before absolute addressing.
That's why I suggest to put vpa/hpa outside relative_move() and use them
as a tactic (like cup).


Something like that :
/* move via (vpa/hpa) only */
static int absolute_addressing (string_desc * target, int from_y, int
from_x,
                                int to_y, int to_x)
{
    string_desc save;
    int vcost = 0, hcost = 0;

    if (row_address && column_address) {
        _nc_str_copy (&save, target);

        if (to_y != from_y) {
            vcost = INFINITY;
            if (_nc_safe_strcat (target, tparm (row_address, to_y))) {
                vcost = SP->_vpa_cost;
            }
            if (vcost == INFINITY) return (INFINITY);
        }

        save = *target;  // same as _nc_str_copy (&save, target);

        if (to_x != from_x) {
            hcost = INFINITY;
            if (_nc_safe_strcat
                (_nc_str_copy (target, &save), tparm (column_address,
to_x))) {
                hcost = SP->_hpa_cost;
            }
            if (hcost == INFINITY) return (INFINITY);
        }
        return (vcost + hcost);
    }
    else return (INFINITY);
}

------------------------------------------------------------------------
- Philippe