AttributedGlyphLine.hpp

// Copyright 2020 Pokitec
// All rights reserved.
 
#pragma once
 
#include "TTauri/Text/AttributedGlyph.hpp"
#include <vector>
#include <optional>
 
namespace tt {
 
struct AttributedGlyphLine {
    using vector_type = std::vector<AttributedGlyph>;
    using iterator = vector_type::iterator;
    using const_iterator = vector_type::const_iterator;
    using value_type = vector_type::value_type;
 
    vector_type line;
    float width;
    float ascender;
    float descender;
    float lineGap;
    float capHeight;
    float xHeight;
    float y;
 
    AttributedGlyphLine(iterator first, iterator last) noexcept :
        line(), width(0.0f), ascender(0.0f), descender(0.0f), lineGap(0.0f), capHeight(0.0f), xHeight(0.0f)
    {
        tt_assume(std::distance(first, last) > 0);
 
        line.reserve(std::distance(first, last));
        std::move(first, last, std::back_inserter(line));
        calculateLineMetrics();
    }
 
    [[nodiscard]] bool shouldWrap(float maximum_width) noexcept {
        tt_assume(ssize(line) >= 1);
        return
            width > maximum_width &&
            ssize(line) >= (line.back().isParagraphSeparator() ? 3 : 2);
    }
 
    [[nodiscard]] AttributedGlyphLine wrap(float maximum_width) noexcept {
        tt_assume(shouldWrap(maximum_width));
 
        auto word_end = line.begin();
        auto line_width = 0.0f;
        auto line_valid_width = 0.0f;
 
        auto i = line.begin();
        for (; i != line.end(); ++i) {
            line_width += i->metrics.advance.x();
            if (i->isVisible()) {
                line_valid_width = line_width;
            }
 
            if (line_valid_width > maximum_width) {
                // Found position where to wrap.
                break;
 
            } else if (i->isWhiteSpace()) {
                // Include the whitespace in the word, as it should belong at the end of the line.
                word_end = i + 1;
            }
        }
 
        auto split_position =
            (word_end != line.begin()) ? word_end : // Wrap at word boundary
            (i != line.begin()) ? i : // Wrap at character boundary
            i + 1; // Include at least one character.
 
        auto reset_of_line = AttributedGlyphLine(split_position, line.end());
        line.erase(split_position, line.cend());
        calculateLineMetrics();
        return reset_of_line;
    }
 
    [[nodiscard]] aarect boundingBox() const noexcept {
        tt_assume(ssize(line) >= 1);
 
        ttlet p0 = vec::point(
            line.front().position.x(),
            line.front().position.y() - descender
        );
 
        ttlet p3 = vec::point(
            line.back().position.x() + line.back().metrics.advance.x(),
            line.back().position.y() + ascender
        );
 
        return aarect::p0p3(p0, p3);
    }
 
    [[nodiscard]] bool contains(vec coordinate) const noexcept {
        return boundingBox().contains(coordinate);            
    }
 
    [[nodiscard]] const_iterator find(vec coordinate) const noexcept {
        auto bbox = boundingBox();
 
        if (coordinate.y() < bbox.y() || coordinate.y() > bbox.p3().y()) {
            return cend();
        }
 
        if (coordinate.x() < bbox.x()) {
            return cbegin();
        }
 
        if (coordinate.x() > bbox.p3().x()) {
            return cend() - 1;
        }
 
        return std::lower_bound(cbegin(), cend(), coordinate.x(), [](ttlet &a, ttlet &b) {
            return (a.position.x() + a.metrics.advance.x()) < b;
        });
    }
 
    [[nodiscard]] size_t size() const noexcept { return line.size(); }
 
    [[nodiscard]] iterator begin() noexcept { return line.begin(); }
    [[nodiscard]] const_iterator begin() const noexcept { return line.cbegin(); }
    [[nodiscard]] const_iterator cbegin() const noexcept { return line.cbegin(); }
 
    [[nodiscard]] iterator end() noexcept { return line.end(); }
    [[nodiscard]] const_iterator end() const noexcept { return line.cend(); }
    [[nodiscard]] const_iterator cend() const noexcept { return line.cend(); }
 
    void positionGlyphs(vec position) noexcept {
        tt_assume(position.is_point());
        y = position.y();
        for (auto &&g: line) {
            g.position = position;
            position += g.metrics.advance;
        }
    }
 
private:
    void calculateLineMetrics() noexcept {
        ascender = 0.0f;
        descender = 0.0f;
        lineGap = 0.0f;
        capHeight = 0.0f;
        xHeight = 0.0f;
 
        auto totalWidth = 0.0f;
        auto validWidth = 0.0f;
        for (ttlet &g: line) {
            totalWidth += g.metrics.advance.x();
            ascender = std::max(ascender, g.metrics.ascender);
            descender = std::max(descender, g.metrics.descender);
            lineGap = std::max(lineGap, g.metrics.lineGap);
            capHeight += g.metrics.capHeight;
            xHeight += g.metrics.xHeight;
 
            if (g.isVisible()) {
                // Don't include trailing whitespace in the width.
                validWidth = totalWidth;
            }
        }
        capHeight /= numeric_cast<float>(ssize(line));
        xHeight /= numeric_cast<float>(ssize(line));
 
        width = validWidth;
    }
 
};
 
}