LIGATURES_PATCH breaks BOXDRAW_PATCH when applied together

[AlexKurisu]

LIGATURES_PATCH for some reason completely breaks rendering of BOXDRAW_PATCH. LukeSmithxyz/st works fine. Here's screenshot:

[avih]

That's probably because ligature originally has a very slightly different patch if it's used together with boxdraw: Basic: https://st.suckless.org/patches/ligatures/0.8.3/st-ligatures-20200430-0.8.3.diff With boxdraw: https://st.suckless.org/patches/ligatures/0.8.3/st-ligatures-boxdraw-20200430-0.8.3.diff

The only difference is that without boxdraw hbtransform at hb.c has this code towards the end:

    /* Apply the transformation to glyph specs. */
    for (int i = 0, specidx = 0; i < len; i++) {
        if (glyphs[i].mode & ATTR_WDUMMY)
            continue;

        if (codepoints[i] != specs[specidx].glyph)
            ((Glyph *)glyphs)[i].mode |= ATTR_LIGA;

        specs[specidx++].glyph = codepoints[i];
    }

While with boxdraw it has one more check:

    /* Apply the transformation to glyph specs. */
    for (int i = 0, specidx = 0; i < len; i++) {
        if (glyphs[i].mode & ATTR_WDUMMY)
            continue;
        if (glyphs[i].mode & ATTR_BOXDRAW) {
            specidx++;
            continue;
        }

        if (codepoints[i] != specs[specidx].glyph)
            ((Glyph *)glyphs)[i].mode |= ATTR_LIGA;

        specs[specidx++].glyph = codepoints[i];
    }

So the fix is probably to change it to be like so:

    /* Apply the transformation to glyph specs. */
    for (int i = 0, specidx = 0; i < len; i++) {
        if (glyphs[i].mode & ATTR_WDUMMY)
            continue;
#if BOXDRAW_PATCH 
        if (glyphs[i].mode & ATTR_BOXDRAW) {
            specidx++;
            continue;
        }
#endif

        if (codepoints[i] != specs[specidx].glyph)
            ((Glyph *)glyphs)[i].mode |= ATTR_LIGA;

        specs[specidx++].glyph = codepoints[i];
    }

[bakkeby]

Thanks @avih.

@AlexKurisu can you try with the above change? Also for reference how do you reproduce this issue?

[AlexKurisu]

Yep, above change fixed the issue. To reproduce it you could:

1. enable BOXDRAW_PATCH and LIGATURES_PATCH
2. set const int boxdraw = 1 in config.h
3. launch any program that uses box drawing characters ({n,}vim, mc, elinks, etc…)

[bakkeby]

Thanks @AlexKurisu, yes mc looks interesting without the change.

Thanks for reporting, much appreciated.

[avih]

@bakkeby the ligature page has also different patches when combined with scrollback and/or alpha - https://st.suckless.org/patches/ligatures/

I didn't check how they differ, but you probably should.

[bakkeby]

Just checked, the alpha variant doesn't have any actual code changes (just different line number references), and the scrollback patch just adds an if statement. These should be fine.

[avih]

Nice.