font.hpp File Reference

Bitmap font rendering for e-paper displays. More...

#include <cstddef>
#include <cstdint>
#include <span>

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Classes
struct	epaper::FontMetrics
	Font dimension metrics. More...
class	epaper::Font

Namespaces
namespace	epaper

Detailed Description

Bitmap font rendering for e-paper displays.

Provides fixed-width bitmap font support using Waveshare font format. Fonts are stored as packed bitmap arrays with MSB-first encoding.

Font Format Specification:

Waveshare Bitmap Font Format
├─ Fixed-width: All characters same dimensions (width × height)
├─ ASCII Range: 0x20 (space) to 0x7E (tilde) = 95 printable characters
├─ Bitmap Layout: Row-major, MSB-first bit packing
└─ No Kerning: Characters placed at fixed intervals

Bitmap Encoding:

Character 'A' (8×12 font):
Row 0: [76543210]  ← MSB is leftmost pixel
Row 1: [76543210]
...
Row 11: [76543210]
 
Total bytes = ceil(width/8) × height
Example: 8×12 → 1 byte/row × 12 rows = 12 bytes
         12×16 → 2 bytes/row × 16 rows = 32 bytes

Memory Layout:

Font table array:
[Char_0x20][Char_0x21][Char_0x22]...[Char_0x7E]
   ↓          ↓          ↓              ↓
 Space       '!'        '"'           '~'
 
Each character occupies bytes_per_char() bytes sequentially.

Built-in Fonts:

• font8(): 8×8 pixels - Small, compact (terminals, labels)
• font12(): 12×12 pixels - Medium (body text)
• font16(): 16×16 pixels - Large (headers, important text)
• font20(): 20×20 pixels - Extra large (titles)
• font24(): 24×24 pixels - Display headers

Usage Patterns:

// Using built-in fonts
const Font& f = Font::font16();
display.draw(display.text("Hello").at({10,10}).font(&f).build());
 
// Custom font from external data
extern const uint8_t my_font_data[];
Font custom_font{my_font_data, 16, 20};  // 16px wide, 20px tall

Text Rendering Process:

1. TextCommand specifies string and font
2. Graphics::draw_text() iterates characters
3. Font::char_data() retrieves bitmap for each char
4. Bitmap bits decoded MSB-first, drawn as pixels

Limitations:

• No variable-width fonts (monospaced only)
• No Unicode support (ASCII 0x20-0x7E only)
• No anti-aliasing (1-bit bitmaps)
• No font scaling (use different size fonts)

See also

Graphics::draw_text(), TextCommand, FontMetrics