ProceduralFont.h

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// SPDX-FileCopyrightText: 2026 Valentin Eloy
// SPDX-License-Identifier: GPL-3.0-or-later
 
#pragma once
 
#include <cstddef>
#include <cstdint>
#include <filesystem>
#include <optional>
#include <string>
#include <string_view>
#include <unordered_map>
#include <vector>
 
#include "HMI/Graphics/AssetContract.h"  // hmi::AssetValidation

 
namespace hmi {

struct GlyphMetrics {
    int x = 0;
    int y = 0;
    int width = 0;
    int height = 0;
    int advance = 0;
};

struct FontMetrics {
    int lineHeight = 0;
    char32_t replacementCodePoint = U'?';
    std::unordered_map<char32_t, GlyphMetrics> glyphs;

    [[nodiscard]] const GlyphMetrics* glyph(char32_t codePoint) const;
};

struct TextExtent {
    float width = 0.0f;
    float height = 0.0f;
};

[[nodiscard]] char32_t nextUtf8CodePoint(std::string_view text, std::size_t& index) noexcept;

[[nodiscard]] TextExtent measureText(const FontMetrics& metrics, std::string_view text,
                                     float scale = 1.0f) noexcept;

struct ProceduralFontImage {
    int width = 0;
    int height = 0;
    std::vector<std::uint32_t> pixels;
};

struct ProceduralFont {
    ProceduralFontImage image;
    FontMetrics metrics;
};

[[nodiscard]] ProceduralFont buildProceduralFont();

inline constexpr int FONT_METRICS_FORMAT_VERSION = 1;

enum class FontMetricsError {
    None,                
    FileNotFound,        
    ParseError,          
    UnsupportedVersion,  
    MalformedStructure,  
};

struct FontMetricsResult {
    std::optional<FontMetrics> metrics;
    std::string error;
    FontMetricsError errorCode = FontMetricsError::None;

    [[nodiscard]] bool ok() const noexcept {
        return metrics.has_value();
    }
};

[[nodiscard]] FontMetricsResult loadFontMetricsFromString(std::string_view json);

[[nodiscard]] FontMetricsResult loadFontMetricsFromFile(const std::filesystem::path& path);

[[nodiscard]] AssetValidation validateFontMetricsAgainstTexture(const FontMetrics& metrics,
                                                                const std::string& fileName,
                                                                int textureWidth,
                                                                int textureHeight);
 
}  // namespace hmi