/mnt/nas/libepaper/include/epaper/graphics/font.hpp

Bitmap font wrapper.

Bitmap font wrapper.Encapsulates raw font data and provides access to character bitmaps. Supports fixed-width bitmap fonts in Waveshare format.

Design:

• Value type: Cheap to copy (just pointer + dimensions)
• Non-owning: Font data must outlive Font instance (typically static)
• Thread-safe: Immutable after construction (const methods only)

Character Addressing:

• ASCII printable range: 0x20 (space) to 0x7E (~) = 95 characters
• Invalid characters (< 0x20 or > 0x7E) return empty span
• Offset calculation: (ascii_code - 0x20) × bytes_per_char()

Factory Methods:

• font8(), font12(), font16(), font20(), font24(): Built-in fonts
• Return const references to static instances (zero allocation)
• Thread-safe initialization (C++11 static local guarantee)

// Using built-in font
const Font& font = Font::font16();
std::cout << "Font size: " << font.width() << "x" << font.height() << std::endl;
 
// Accessing character bitmap
auto bitmap = font.char_data('A');
std::cout << "'A' bitmap size: " << bitmap.size() << " bytes" << std::endl;
 
// Custom font from external data
extern const std::uint8_t custom_font_table[];
Font custom{custom_font_table, 12, 16};

See also

FontMetrics, Graphics::draw_text()

#pragma once
 
#include <cstddef>
#include <cstdint>
#include <span>
 
namespace epaper {
 
struct FontMetrics {
  std::uint16_t width;
  std::uint16_t height;
};
 
class Font {
public:
  constexpr Font(const std::uint8_t *table, std::uint16_t width, std::uint16_t height)
      : table_(table), width_(width), height_(height) {}
 
  [[nodiscard]] constexpr auto metrics() const noexcept -> FontMetrics { return {.width = width_, .height = height_}; }
 
  [[nodiscard]] constexpr auto width() const noexcept -> std::uint16_t { return width_; }
 
  [[nodiscard]] constexpr auto height() const noexcept -> std::uint16_t { return height_; }
 
  [[nodiscard]] auto char_data(char c) const -> std::span<const std::uint8_t>;
 
  [[nodiscard]] constexpr auto bytes_per_char() const noexcept -> std::size_t {
    const auto width_bytes = static_cast<std::size_t>((width_ % 8 == 0) ? (width_ / 8) : ((width_ / 8) + 1));
    return width_bytes * static_cast<std::size_t>(height_);
  }
 
  // Factory methods for built-in fonts
  static auto font8() -> const Font &;
 
  static auto font12() -> const Font &;
 
  static auto font16() -> const Font &;
 
  static auto font20() -> const Font &;
 
  static auto font24() -> const Font &;
 
private:
  const std::uint8_t *table_;
  std::uint16_t width_;
  std::uint16_t height_;
};
 
} // namespace epaper