How do I correctly handle newlines?

[mainrs]

I shaped the following input using the alltools-shape cli

Hello,
world!

and got the following as output. The newline character \n is shaped as well. I would have expected that it does not get processed separately as a GlyphInfo but gets included by advancing vertically after the , character. Is that not the case?

script is set to LATN and lang is set to ENG, if that matters. I use the LibreBaskerville font.

900,0 (0, 0) Info {
    glyph: RawGlyph {
        unicodes: [
            'H',
        ],
        glyph_index: 30,
        liga_component_pos: 0,
        glyph_origin: Char(
            'H',
        ),
        small_caps: false,
        multi_subst_dup: false,
        is_vert_alt: false,
        fake_bold: false,
        fake_italic: false,
        variation: Some(
            VS15,
        ),
        extra_data: (),
    },
    kerning: -25,
    placement: None,
    is_mark: false,
}
573,0 (0, 0) Info {
    glyph: RawGlyph {
        unicodes: [
            'e',
        ],
        glyph_index: 17,
        liga_component_pos: 0,
        glyph_origin: Char(
            'e',
        ),
        small_caps: false,
        multi_subst_dup: false,
        is_vert_alt: false,
        fake_bold: false,
        fake_italic: false,
        variation: Some(
            VS15,
        ),
        extra_data: (),
    },
    kerning: 0,
    placement: None,
    is_mark: false,
}
325,0 (0, 0) Info {
    glyph: RawGlyph {
        unicodes: [
            'l',
        ],
        glyph_index: 7,
        liga_component_pos: 0,
        glyph_origin: Char(
            'l',
        ),
        small_caps: false,
        multi_subst_dup: false,
        is_vert_alt: false,
        fake_bold: false,
        fake_italic: false,
        variation: Some(
            VS15,
        ),
        extra_data: (),
    },
    kerning: 0,
    placement: None,
    is_mark: false,
}
325,0 (0, 0) Info {
    glyph: RawGlyph {
        unicodes: [
            'l',
        ],
        glyph_index: 7,
        liga_component_pos: 0,
        glyph_origin: Char(
            'l',
        ),
        small_caps: false,
        multi_subst_dup: false,
        is_vert_alt: false,
        fake_bold: false,
        fake_italic: false,
        variation: Some(
            VS15,
        ),
        extra_data: (),
    },
    kerning: 0,
    placement: None,
    is_mark: false,
}
654,0 (0, 0) Info {
    glyph: RawGlyph {
        unicodes: [
            'o',
        ],
        glyph_index: 10,
        liga_component_pos: 0,
        glyph_origin: Char(
            'o',
        ),
        small_caps: false,
        multi_subst_dup: false,
        is_vert_alt: false,
        fake_bold: false,
        fake_italic: false,
        variation: Some(
            VS15,
        ),
        extra_data: (),
    },
    kerning: 0,
    placement: None,
    is_mark: false,
}
273,0 (0, 0) Info {
    glyph: RawGlyph {
        unicodes: [
            ',',
        ],
        glyph_index: 284,
        liga_component_pos: 0,
        glyph_origin: Char(
            ',',
        ),
        small_caps: false,
        multi_subst_dup: false,
        is_vert_alt: false,
        fake_bold: false,
        fake_italic: false,
        variation: Some(
            VS15,
        ),
        extra_data: (),
    },
    kerning: 0,
    placement: None,
    is_mark: false,
}
756,0 (0, 0) Info {
    glyph: RawGlyph {
        unicodes: [
            '\n',
        ],
        glyph_index: 0,
        liga_component_pos: 0,
        glyph_origin: Char(
            '\n',
        ),
        small_caps: false,
        multi_subst_dup: false,
        is_vert_alt: false,
        fake_bold: false,
        fake_italic: false,
        variation: Some(
            VS15,
        ),
        extra_data: (),
    },
    kerning: 0,
    placement: None,
    is_mark: false,
}
835,0 (0, 0) Info {
    glyph: RawGlyph {
        unicodes: [
            'w',
        ],
        glyph_index: 24,
        liga_component_pos: 0,
        glyph_origin: Char(
            'w',
        ),
        small_caps: false,
        multi_subst_dup: false,
        is_vert_alt: false,
        fake_bold: false,
        fake_italic: false,
        variation: Some(
            VS15,
        ),
        extra_data: (),
    },
    kerning: -17,
    placement: None,
    is_mark: false,
}
654,0 (0, 0) Info {
    glyph: RawGlyph {
        unicodes: [
            'o',
        ],
        glyph_index: 10,
        liga_component_pos: 0,
        glyph_origin: Char(
            'o',
        ),
        small_caps: false,
        multi_subst_dup: false,
        is_vert_alt: false,
        fake_bold: false,
        fake_italic: false,
        variation: Some(
            VS15,
        ),
        extra_data: (),
    },
    kerning: 0,
    placement: None,
    is_mark: false,
}
477,0 (0, 0) Info {
    glyph: RawGlyph {
        unicodes: [
            'r',
        ],
        glyph_index: 8,
        liga_component_pos: 0,
        glyph_origin: Char(
            'r',
        ),
        small_caps: false,
        multi_subst_dup: false,
        is_vert_alt: false,
        fake_bold: false,
        fake_italic: false,
        variation: Some(
            VS15,
        ),
        extra_data: (),
    },
    kerning: 0,
    placement: None,
    is_mark: false,
}
325,0 (0, 0) Info {
    glyph: RawGlyph {
        unicodes: [
            'l',
        ],
        glyph_index: 7,
        liga_component_pos: 0,
        glyph_origin: Char(
            'l',
        ),
        small_caps: false,
        multi_subst_dup: false,
        is_vert_alt: false,
        fake_bold: false,
        fake_italic: false,
        variation: Some(
            VS15,
        ),
        extra_data: (),
    },
    kerning: 0,
    placement: None,
    is_mark: false,
}
675,0 (0, 0) Info {
    glyph: RawGlyph {
        unicodes: [
            'd',
        ],
        glyph_index: 12,
        liga_component_pos: 0,
        glyph_origin: Char(
            'd',
        ),
        small_caps: false,
        multi_subst_dup: false,
        is_vert_alt: false,
        fake_bold: false,
        fake_italic: false,
        variation: Some(
            VS15,
        ),
        extra_data: (),
    },
    kerning: 0,
    placement: None,
    is_mark: false,
}
308,0 (0, 0) Info {
    glyph: RawGlyph {
        unicodes: [
            '!',
        ],
        glyph_index: 324,
        liga_component_pos: 0,
        glyph_origin: Char(
            '!',
        ),
        small_caps: false,
        multi_subst_dup: false,
        is_vert_alt: false,
        fake_bold: false,
        fake_italic: false,
        variation: Some(
            VS15,
        ),
        extra_data: (),
    },
    kerning: 0,
    placement: None,
    is_mark: false,
}

[wezm]

The newline character \n is shaped as well. I would have expected that it does not get processed separately as a GlyphInfo but gets included by advancing vertically after the , character. Is that not the case?

Yes that is not the case. Line layout is a process separate from shaping. It needs to consider word-wrapping, hyphenation, etc. In a traditional open-source text rendering stack Fontconfig does font matching, Harfbuzz does the shaping, Pango does layout, freetype does rasterisation. Allsorts takes the place of Harfbuzz in this flow, so you still need something to do layout.

[mainrs]

Would that mean I have to manually search for newlines and offset each draw call by the height of my line plus some matching padding? Just to get a basic understanding of what allsorts does not do :)

[wezm]

Yes I believe so. There's an example of the segmentation and line layout in the azul project: https://github.com/fschutt/azul/blob/master/azul-text-layout/src/text_layout.rs