lay_out()

LayoutResult MayaFlux::Portal::Text::lay_out	(	std::string_view	text,
		GlyphAtlas &	atlas,
		float	pen_x = 0.F,
		float	pen_y = 0.F,
		uint32_t	wrap_w = 0
	)

Lay out a UTF-8 string into a sequence of screen-space quads.

Handles
(advance pen_y by atlas.line_height(), reset pen_x to the initial value) and \r (consumed silently). All other control codepoints with no glyph in the face are skipped without advancing the pen.

Bidirectional reordering and shaping are not performed. HarfBuzz slots in before the glyph index step when needed; the quad assembly loop and GlyphAtlas remain unchanged.

Parameters

text	UTF-8 encoded input string.
atlas	GlyphAtlas to query and populate. May be modified (dirty flag set) if new glyphs are rasterized.
pen_x	Starting horizontal pen position in pixels.
pen_y	Starting vertical pen position in pixels (baseline).

Returns

LayoutResult containing quads and final pen position.

Definition at line 9 of file TypeSetter.cpp.

{
    if (text.empty()) {
        return { .quads = {}, .final_pen_x = pen_x, .final_pen_y = pen_y };
    }
 
    LayoutResult out;
    out.quads.reserve(text.size());
 
    const float origin_x = 0.F;
 
    const auto* bytes = reinterpret_cast<const utf8proc_uint8_t*>(text.data());
    auto remaining = static_cast<utf8proc_ssize_t>(text.size());
    utf8proc_ssize_t offset = 0;
 
    while (offset < remaining) {
        utf8proc_int32_t codepoint = 0;
        const utf8proc_ssize_t n = utf8proc_iterate(bytes + offset, remaining - offset, &codepoint);
 
        if (n <= 0) {
            MF_WARN(Journal::Component::Portal, Journal::Context::API,
                "TypeSetter: invalid UTF-8 sequence at byte offset {}, skipping byte",
                static_cast<size_t>(offset));
            offset += 1;
            continue;
        }
 
        offset += n;
 
        if (codepoint < 0) {
            continue;
        }
 
        if (codepoint == '\n') {
            pen_x = origin_x;
            pen_y += static_cast<float>(atlas.line_height());
            continue;
        }
 
        if (codepoint == '\r') {
            continue;
        }
 
        const GlyphMetrics* m = atlas.get_or_rasterize(static_cast<FT_ULong>(codepoint));
        if (!m) {
            continue;
        }
 
        if (m->width > 0 && m->height > 0) {
            GlyphQuad q {};
            q.x0 = pen_x + static_cast<float>(m->bearing_x);
            q.y0 = pen_y - static_cast<float>(m->bearing_y);
            q.x1 = q.x0 + static_cast<float>(m->width);
            q.y1 = q.y0 + static_cast<float>(m->height);
            q.uv_x0 = m->uv_x0;
            q.uv_y0 = m->uv_y0;
            q.uv_x1 = m->uv_x1;
            q.codepoint = static_cast<uint32_t>(codepoint);
            q.uv_y1 = m->uv_y1;
            out.quads.push_back(q);
        }
 
        pen_x += static_cast<float>(m->advance_x);
 
        if (wrap_w > 0 && static_cast<uint32_t>(std::ceil(pen_x)) > wrap_w) {
            pen_x = 0.F;
            pen_y += static_cast<float>(atlas.line_height());
        }
    }
 
    out.final_pen_x = pen_x;
    out.final_pen_y = pen_y;
    return out;
}

References MayaFlux::Portal::Text::GlyphMetrics::advance_x, MayaFlux::Journal::API, MayaFlux::Portal::Text::GlyphMetrics::bearing_x, MayaFlux::Portal::Text::GlyphMetrics::bearing_y, MayaFlux::Portal::Text::LayoutResult::final_pen_x, MayaFlux::Portal::Text::LayoutResult::final_pen_y, MayaFlux::Portal::Text::GlyphAtlas::get_or_rasterize(), MayaFlux::Portal::Text::GlyphMetrics::height, MayaFlux::Portal::Text::GlyphAtlas::line_height(), MF_WARN, MayaFlux::Journal::Portal, q, MayaFlux::Portal::Text::LayoutResult::quads, MayaFlux::Portal::Text::GlyphMetrics::uv_x0, MayaFlux::Portal::Text::GlyphMetrics::uv_x1, MayaFlux::Portal::Text::GlyphMetrics::uv_y0, MayaFlux::Portal::Text::GlyphMetrics::uv_y1, MayaFlux::Portal::Text::GlyphMetrics::width, and MayaFlux::Portal::Text::GlyphQuad::x0.

Referenced by create_layout(), and impress().

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