text_layout.hpp

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#pragma once
 
#include <pulp/canvas/canvas.hpp>
#include <string>
#include <vector>
 
namespace pulp::canvas {

struct FontSpec {
    std::string family = "Inter";
    float size = 14.0f;
    int weight = 400;      
    bool italic = false;
    float letter_spacing = 0.0f;
};

struct TextRun {
    std::string text;
    FontSpec font;
    Color color;
    size_t start = 0;  
    size_t length = 0; 
};

struct GlyphPosition {
    float x = 0, y = 0;         
    float advance = 0;          
    uint32_t codepoint = 0;     
    size_t text_index = 0;      
};

struct TextLine {
    std::vector<GlyphPosition> glyphs;
    float width = 0;       
    float ascent = 0;      
    float descent = 0;     
    float leading = 0;     
    float baseline_y = 0;  
};

class GlyphArrangement {
public:
    GlyphArrangement() = default;

    void add_line(TextLine line) { lines_.push_back(std::move(line)); }

    const std::vector<TextLine>& lines() const { return lines_; }
    int line_count() const { return static_cast<int>(lines_.size()); }

    float total_width() const {
        float w = 0;
        for (auto& line : lines_) w = std::max(w, line.width);
        return w;
    }
 
    float total_height() const {
        if (lines_.empty()) return 0;
        auto& last = lines_.back();
        return last.baseline_y + last.descent;
    }

    size_t hit_test(float x, float y) const;

    float position_for_index(size_t index) const;

    void clear() { lines_.clear(); }
 
private:
    std::vector<TextLine> lines_;
};

GlyphArrangement layout_paragraph(const std::string& text,
                                    const FontSpec& font,
                                    float max_width = 0,
                                    Color color = Color::rgba(1.0f, 1.0f, 1.0f));

struct Parallelogram {
    float x0 = 0, y0 = 0;   
    float x1 = 0, y1 = 0;   
    float x2 = 0, y2 = 0;   
    float x3 = 0, y3 = 0;   

    static Parallelogram from_rect_shear(float x, float y, float w, float h, float shear) {
        return {x + shear, y,  x + w + shear, y,  x + w, y + h,  x, y + h};
    }

    bool contains(float px, float py) const {
        // Cross product method for convex quad
        auto cross = [](float ax, float ay, float bx, float by) { return ax * by - ay * bx; };
        float d1 = cross(x1 - x0, y1 - y0, px - x0, py - y0);
        float d2 = cross(x2 - x1, y2 - y1, px - x1, py - y1);
        float d3 = cross(x3 - x2, y3 - y2, px - x2, py - y2);
        float d4 = cross(x0 - x3, y0 - y3, px - x3, py - y3);
        return (d1 >= 0 && d2 >= 0 && d3 >= 0 && d4 >= 0) ||
               (d1 <= 0 && d2 <= 0 && d3 <= 0 && d4 <= 0);
    }
};
 
} // namespace pulp::canvas