On This Page

• Overview
• Architecture
• Usage
• Font Tables
• Limitations
• vs Bitmap Fonts

TrueType Font Support

guideXOS now includes experimental support for loading and rendering TrueType (.ttf) and OpenType (.otf) fonts, enabling scalable text rendering without pre-generated bitmap fonts.

Overview

TrueType fonts are the industry standard for scalable font rendering. Unlike bitmap fonts (which store pre-rendered pixel grids), TrueType fonts store mathematical outlines of each character that can be scaled to any size without loss of quality.

Why TrueType?

• Resolution Independence: Text looks sharp at any size
• Smaller Files: One TTF file vs hundreds of bitmap PNG files
• Unicode Support: Access to thousands of characters
• Professional Typography: Kerning, ligatures, hinting (future)
• Industry Standard: Use any .ttf/.otf font

Architecture

TrueTypeFont Class

The main font loader in Kernel\Misc\TrueTypeFont.cs handles:

• Parsing TTF/OTF binary format
• Reading font tables (cmap, glyf, head, hhea, hmtx, maxp, loca)
• Character-to-glyph mapping via cmap
• Glyph metrics (advance width, bounding boxes)
• Rasterizing glyphs to bitmaps

Font Loading Pipeline

Usage

1. Loading a TrueType Font

using guideXOS.Misc;
using guideXOS.FS;

// Load font from file at 16pt
byte[] fontData = File.ReadAllBytes("fonts/DejaVuSans.ttf");
TrueTypeFont font = new TrueTypeFont(fontData, 16);

2. Rendering Text

// Draw string with white color
font.DrawString(Framebuffer.Graphics, 100, 100, "Hello World!", 0xFFFFFFFF);

// Measure string width
int width = font.MeasureString("Hello World!");

// Get advance width for single character
int charWidth = font.GetAdvanceWidth('A');

3. Rendering Individual Characters

// Render character to bitmap
Image glyph = font.RenderChar('A');

// Draw glyph manually
Graphics.DrawImage(glyph, x, y);

// Dispose when done
glyph.Dispose();

Font Tables Parsed

Current Limitations

Future Enhancements

• ? Full glyph contour parsing and rasterization
• ? Quadratic Bézier curve rendering
• ? Scanline rasterization with anti-aliasing
• ? Glyph caching for performance
• ? Kerning table (kern) support
• ? Vertical metrics (vhea/vmtx)

Bitmap Fonts vs TrueType Fonts

Technical Details

TrueType File Structure

TTF File:
??? Offset Table (signature, table count)
??? Table Directory (table tags and offsets)
??? Font Tables:
?   ??? cmap (character mapping)
?   ??? glyf (glyph outlines)
?   ??? head (font header)
?   ??? hhea (horizontal header)
?   ??? hmtx (horizontal metrics)
?   ??? loca (glyph locations)
?   ??? maxp (maximum profile)
?   ??? ... (optional tables)

Coordinate System

TrueType fonts use a coordinate system called "Font Units per EM" (typically 1024, 2048, or 4096). All glyph coordinates are in this space and must be scaled to the desired pixel size:

pixelSize = (fontUnits / unitsPerEm) * fontSize

Example: 16pt font with 2048 units per EM:
  scale = 16 / 2048 = 0.0078125
  If glyph width = 1000 units ? pixel width = 7.8125 ? 8 pixels

Recommended Fonts