Samiksha Jaiswal (Editor)

DirectWrite

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DirectWrite is a text layout and glyph rendering API by Microsoft. It was designed to replace GDI/GDI+ and Uniscribe for screen-oriented rendering and was shipped with Windows 7 and Windows Server 2008 R2, as well as Windows Vista and Windows Server 2008 (with Platform Update installed). DirectWrite is hardware-accelerated (using the GPU) when running on top of Direct2D, but can really render on the CPU to any target, including a GDI bitmap.

Contents

Features

  • Comprehensive support for Unicode, with over 20 scripts providing layout and rendering of every language supported in Windows. DirectWrite supports measuring, drawing, and hit-testing of multi-format text. Supported Unicode features include BIDI, line breaking, surrogates, UVS, language-guided script itemization, number substitution, and glyph shaping.
  • Sub-pixel ClearType text rendering with bi-directional antialiasing which can interoperate with GDI/GDI+, Direct2D/Direct3D and any application-specific technology. When using with Direct2D, text rendering can be hardware-accelerated or can use WARP software rasterizer when hardware acceleration is not available.
  • Supports advanced typographic features of OpenType, such as stylistic alternates and swashes, which were never supported in GDI and WinForms. These features were demoed at DirectWrite's launch (at PDC2008) using the Gabriola font, itself also introduced with Windows 7.
  • Provides a low-level glyph rendering API for those who employ proprietary text layout and Unicode-to-glyph processing.

    • In Windows 8.1, DirectWrite gained support for color fonts.

    Uses

    The XPS viewer in Windows 7 uses DirectWrite, but it renders the output on a GDI+ surface.

    Internet Explorer 9 and later versions use DirectWrite layered over Direct2D for improved visual quality and performance. Firefox 4 also added DirectWrite support, but rendering in the DirectWrite specific style was made non-default for some fonts in Firefox 7 due to user complaints about the rendering quality.

    Microsoft Office 2013 supports either Direct2D/DirectWrite or GDI/Uniscribe for display rendering and typography.

    Google Chrome in Windows supports DirectWrite starting from version 37.

    References

    DirectWrite Wikipedia
    (Text) CC BY-SA