Mark to Mark placement

[solomancode]

Does allsorts support mark to mark placement ?

I was able to find MarkAnchor Mark to base anchor, But couldn't find mkmk placement.
https://docs.rs/allsorts/latest/allsorts/gpos/enum.Placement.html#variant.MarkAnchor

Is overlapping anchors enough to apply mark to base, I didn't use the base_glyph_index property.

MarkAnchor(uszie, Anchor, Anchor)

[wezm]

Yes this is supported

allsorts/src/gpos.rs

Line 313 in ebd05d9

fn gpos_lookup_markmarkpos(

[solomancode]

@wezm Thank you,

Where can I find an example on how to use this fn. to implement mark to mark positioning ?

[wezm]

It's not a public function so you would not use it directly. If you're trying to position glyphs then you could shape your text then feed that result into GlyphLayout to retrieve their positions.

[solomancode]

@wezm I appreciate your response, Below my implementation. I'm not sure if my configuration is correct, please feel free to point out if there is something that I'm missing.

pub fn word_glyphs(font_data: Vec<u8>, word: &str) -> WordGlyphs {
    let scope = ReadScope::new(&font_data);
    let font_file = scope.read::<FontData<'_>>().expect("corrupt font data");
    let provider = font_file.table_provider(0).expect("error: table provider");
    let mut font = Font::new(provider).unwrap().expect("cmap missing");

    let glyphs = font.map_glyphs(word, tag::ARAB, MatchingPresentation::NotRequired);

    let script = tag::from_string("arab").unwrap();
    let lang = tag::from_string("ara").unwrap();

    let features = FeatureMask::CCMP
        | FeatureMask::RLIG
        | FeatureMask::CLIG
        | FeatureMask::LIGA
        | FeatureMask::LOCL
        | FeatureMask::CALT;

    let shaped_glyphs = font
        .shape(glyphs, script, Some(lang), &Features::Mask(features), true)
        .map_err(|(err, _infos)| err)
        .expect("Failed to shape");

    let mut layout = GlyphLayout::new(&mut font, &shaped_glyphs, TextDirection::RightToLeft, false);
    let positions = layout
        .glyph_positions()
        .expect("Failed to get layout positions");

    let layout_glyphs = shaped_glyphs.iter().zip(&positions).collect::<Vec<_>>();

    let mut outlines = WordGlyphs::new();

    if font.glyph_table_flags.contains(GlyphTableFlags::CFF) {
        let cff_data = font
            .font_table_provider
            .read_table_data(tag::CFF)
            .expect("Unable to read table");

        let mut builder = ReadScope::new(&cff_data)
            .read::<CFF<'_>>()
            .expect("Error: CFF");

        visit(layout_glyphs, &mut builder, &mut outlines);
    } else if font.glyph_table_flags.contains(GlyphTableFlags::GLYF) {
        let loca_data = font
            .font_table_provider
            .read_table_data(tag::LOCA)
            .expect("Error: LOCA");

        let loca = ReadScope::new(&loca_data)
            .read_dep::<LocaTable<'_>>((
                usize::from(font.maxp_table.num_glyphs),
                font.head_table()
                    .unwrap()
                    .ok_or("missing head table")
                    .unwrap()
                    .index_to_loc_format,
            ))
            .expect("Error: LocaTable");

        let glyf_data = font
            .font_table_provider
            .read_table_data(tag::GLYF)
            .expect("Error: GlyfTable");

        let mut builder = ReadScope::new(&glyf_data)
            .read_dep::<GlyfTable<'_>>(&loca)
            .expect("Error Glyph Scope");

        visit(layout_glyphs, &mut builder, &mut outlines);
    } else {
        panic!("no glyf or CFF table");
    }
    outlines
}

Here is the rendered glyphs on the right and the correct rendering on the left, I'm the second mark should be on top of the the first one.

[solomancode]

@wezm Thank you, I did it.

[wezm]

Glad you worked it out.