DirectWrite Programming Guide

DirectWrite is a powerful API for high-quality text rendering on Windows. It provides advanced typography features, including Unicode support, font management, text layout, and anti-aliased rendering.

Introduction to DirectWrite

DirectWrite is designed to provide developers with a comprehensive solution for rendering text that is both visually appealing and performant. It works in conjunction with Direct2D for advanced graphics rendering, allowing for seamless integration of text into your applications.

Whether you're building a modern UI, a game, or a document editing application, DirectWrite offers the tools to achieve superior text display across a wide range of languages and scripts.

Key Features

• High-Quality Typography: Advanced font selection, glyph substitution, and OpenType feature support.
• Unicode Support: Comprehensive handling of Unicode characters and international text.
• Text Layout and Shaping: Complex script support for languages like Arabic, Hebrew, and Indic scripts.
• Anti-aliased Rendering: Smooth, crisp text rendering for improved readability.
• Font Management: Access to system fonts, font enumeration, and font metrics.
• Text Hit Testing: Accurate determination of character positions for interactive text.
• Direct2D Integration: Seamlessly render DirectWrite text using Direct2D's powerful graphics pipeline.

Getting Started

To begin using DirectWrite, you'll need to include the necessary headers and link against the DirectWrite library.

Here's a basic example of how to create a DirectWrite factory object:

#include <dwrite.h>

// ...

IDWriteFactory* pFactory = NULL;
HRESULT hr = DWriteCreateFactory(
    DWRITE_FACTORY_TYPE_SHARED,
    __uuidof(IDWriteFactory),
    reinterpret_cast<IUnknown**>(&pFactory)
);

if (SUCCEEDED(hr)) {
    // Use the factory object
    // ...

    // Release the factory when done
    pFactory->Release();
}
            

The DWriteCreateFactory function initializes the DirectWrite factory, which is the entry point for all DirectWrite operations. The DWRITE_FACTORY_TYPE_SHARED option provides a shared factory instance that can be used across multiple threads.

Core Concepts

Text Layout

DirectWrite's text layout engine is responsible for arranging text according to typographic rules. This includes breaking lines, handling justification, and applying complex script shaping.

You'll typically use the IDWriteTextLayout interface to represent a block of text with its associated properties, such as font, size, color, and paragraph formatting.

Font Rendering

DirectWrite provides fine-grained control over font rendering. You can select specific fonts, choose font styles, and access detailed font metrics like ascent, descent, and advance width.

The IDWriteTextFormat interface is used to specify font properties for text layout.

Text Analysis

DirectWrite can analyze text to identify properties such as script, language, and breaking opportunities. This is crucial for implementing features like bidirectional text support and word wrapping.

Interfaces like IDWriteTextAnalyzer can be used for these purposes.

API Reference

For detailed information on each DirectWrite interface and function, please refer to the official DirectWrite API documentation.

Sample Code

Explore the DirectX samples repository for practical examples of using DirectWrite in various scenarios.

These samples demonstrate common tasks such as drawing formatted text, handling font selection, and implementing advanced text effects.