[Dev-luatex] Request for bugfix - rule nodes (subtypes: 1 = box, 2 = image, 3 = empty, 4 = user) in DVI mode

24 Jan 2020

      Three things to be fixed for the rule nodes with subtypes 1 to 4 in DVi mode.
(Function dvi_place_rule from dvigen.c file)

void dvi_place_rule(PDF pdf, halfword q, scaledpos size)
{
    synch_dvi_with_pos(pdf->posstruct->pos);
    if ((subtype(q) >= box_rule) && (subtype(q) <= user_rule)) {
        /*tex place nothing, only take space */
        if (textdir_is_L(pdf->posstruct->dir))
            dvi.h += size.h;
    } else {
        /*tex normal_rule or >= 100 being a leader rule */
        if (textdir_is_L(pdf->posstruct->dir)) {
            /*tex movement optimization for |dir_*L*| */
            dvi_out(set_rule);
            dvi.h += size.h;
        } else
            dvi_out(put_rule);
    }
    dvi_four(size.v);
    dvi_four(size.h);
}

Problem 1. Bad dvi file due the arguments output without dvi command (misplaced the two last lines in the code).

Possible fix:

void dvi_place_rule(PDF pdf, halfword q, scaledpos size)
{
    synch_dvi_with_pos(pdf->posstruct->pos);
    if ((subtype(q) >= box_rule) && (subtype(q) <= user_rule)) {
        /*tex place nothing, only take space */
        if (textdir_is_L(pdf->posstruct->dir))
            dvi.h += size.h;
    } else {
        /*tex normal_rule or >= 100 being a leader rule */
        if (textdir_is_L(pdf->posstruct->dir)) {
            /*tex movement optimization for |dir_*L*| */
            dvi_out(set_rule);
            dvi.h += size.h;
        } else
            dvi_out(put_rule);
        dvi_four(size.v);
        dvi_four(size.h);
    }
}

Problem 2. Not reserved space for the rule in the output.

Possible fix:

void dvi_place_rule(PDF pdf, halfword q, scaledpos size)
{
    synch_dvi_with_pos(pdf->posstruct->pos);
    if ((subtype(q) >= box_rule) && (subtype(q) <= user_rule)) {
        /*tex place nothing, only take space */
        if (textdir_is_L(pdf->posstruct->dir))
            dvi.h += size.h;
        movement(size.h, right1);
    } else {
        /*tex normal_rule or >= 100 being a leader rule */
        if (textdir_is_L(pdf->posstruct->dir)) {
            /*tex movement optimization for |dir_*L*| */
            dvi_out(set_rule);
            dvi.h += size.h;
        } else
            dvi_out(put_rule);
        dvi_four(size.v);
        dvi_four(size.h);
    }
}

Problem 3. Broken consistency with PDF mode as process_rule callback is missing in DVI mode.

Possible fix:

void dvi_place_rule(PDF pdf, halfword q, scaledpos size, int callback_id)
{
    synch_dvi_with_pos(pdf->posstruct->pos);
    if ((subtype(q) >= box_rule) && (subtype(q) <= user_rule)) {
        /*tex place nothing, only take space */
        if (textdir_is_L(pdf->posstruct->dir))
            dvi.h += size.h;
        if (subtype(q) == user_rule && callback_id != 0) {
            run_callback(callback_id, “Ndd->”, q, size.h, size.v);
        }
        movement(size.h, right1);
    } else {
        /*tex normal_rule or >= 100 being a leader rule */
        if (textdir_is_L(pdf->posstruct->dir)) {
            /*tex movement optimization for |dir_*L*| */
            dvi_out(set_rule);
            dvi.h += size.h;
        } else
            dvi_out(put_rule);
        dvi_four(size.v);
        dvi_four(size.h);
    }
}

and fix in dvigen.h

< extern void dvi_place_rule(PDF pdf, halfword q, scaledpos size);
...
extern void dvi_place_rule(PDF pdf, halfword q, scaledpos size, int callback_id);
Regards,
Sigitas

P.S. Some point for the discussion. For the wider usabillity maybe the rules with zero dimensions (width, height+depth) can be allowed in the output.

[Dev-luatex] Request for bugfix - rule nodes (subtypes: 1 = box, 2 = image, 3 = empty, 4 = user) in DVI mode

Sigitas Tolusis