Getting Started with DirectWrite

This guide will walk you through the initial steps of integrating DirectWrite into your Windows applications. DirectWrite is a high-performance, high-quality text layout and rendering API that provides advanced text manipulation features.

Prerequisites

Before you begin, ensure you have the following:

A C++ development environment (e.g., Visual Studio).
Basic understanding of Windows programming concepts.
Familiarity with graphics programming is helpful but not strictly required for basic usage.

Setting Up Your Project

DirectWrite is part of the Windows SDK. You can include its headers and link against its libraries during your project's build process.

Include DirectWrite Headers

Add the necessary include paths to your project settings. The primary header for DirectWrite is dwrite.h.

// In your project settings, ensure the Windows SDK include path is configured.
            // Typically, this is handled automatically by Visual Studio.
            #include <dwrite.h>

Linking the Library

You need to link your application against the DirectWrite library, dwrite.lib.

// In your project settings (Linker -> Input -> Additional Dependencies), add:
            // dwrite.lib

Core Components and Initialization

The central object in DirectWrite is the IDWriteFactory. You'll need to create an instance of this factory to access other DirectWrite objects and functionalities.

Creating the DirectWrite Factory

The DWriteCreateFactory function is used to create an IDWriteFactory object.

Example: Creating IDWriteFactory

#include <windows.h>
#include <dwrite.h>
#include <iostream>

// Function to create the DirectWrite factory
IDWriteFactory* CreateDWriteFactory() {
    IDWriteFactory* factory = nullptr;
    HRESULT hr = DWriteCreateFactory(
        DWRITE_FACTORY_TYPE_SHARED, // Or DWRITE_FACTORY_TYPE_ISOLATED
        __uuidof(IDWriteFactory),
        reinterpret_cast<IUnknown**>(&factory)
    );

    if (SUCCEEDED(hr)) {
        return factory;
    } else {
        std::cerr << "Failed to create DirectWrite factory. HRESULT: " << std::hex << hr << std::endl;
        return nullptr;
    }
}

// In your main application logic:
int main() {
    IDWriteFactory* dwriteFactory = CreateDWriteFactory();

    if (dwriteFactory) {
        std::cout << "DirectWrite factory created successfully." << std::endl;
        // ... use the factory ...

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

    return 0;
}

Understanding Factory Types

DWRITE_FACTORY_TYPE_SHARED: Creates a factory that can share resources with other DirectWrite objects. This is generally recommended for most applications.
DWRITE_FACTORY_TYPE_ISOLATED: Creates a factory that does not share resources. Use this if you need strict isolation.

Basic Text Rendering Workflow

Once you have the IDWriteFactory, you can proceed with creating text layout objects and rendering them.

1. Create an `IDWriteTextFormat`

This object defines the basic properties of the text, such as font family, font size, and style.

2. Create an `IDWriteTextLayout`

This object takes the text format and the actual text string to define how the text will be laid out.

3. Render the Text

Use the IDWriteTextLayout object in conjunction with a rendering context (e.g., GDI or Direct2D) to draw the text on the screen.

Note: For rendering text with DirectWrite, you'll typically integrate it with Direct2D for a modern graphics pipeline. While DirectWrite can technically work with GDI, its full power is realized when used with Direct2D.

Next Steps

Now that you have a basic understanding of setting up DirectWrite, you can explore more advanced topics: