IDWriteGlyphRunAnalysis interface (dwrite.h)

Article
02/22/2024

Contains low-level information used to render a glyph run.

Inheritance

The IDWriteGlyphRunAnalysis interface inherits from the IUnknown interface. IDWriteGlyphRunAnalysis also has these types of members:

Methods

The IDWriteGlyphRunAnalysis interface has these methods.


IDWriteGlyphRunAnalysis::CreateAlphaTexture Creates an alpha texture of the specified type for glyphs within a specified bounding rectangle.
IDWriteGlyphRunAnalysis::GetAlphaBlendParams Gets alpha blending properties required for ClearType blending.
IDWriteGlyphRunAnalysis::GetAlphaTextureBounds Gets the bounding rectangle of the physical pixels affected by the glyph run.

Remarks

The alpha texture can be a bi-level alpha texture or a ClearType alpha texture.

A bi-level alpha texture contains one byte per pixel, therefore the size of the buffer for a bi-level texture will be the area of the texture bounds, in bytes. Each byte in a bi-level alpha texture created by CreateAlphaTexture is either set to DWRITE_ALPHA_MAX (that is, 255) or zero.

A ClearType alpha texture contains three bytes per pixel, therefore the size of the buffer for a ClearType alpha texture is three times the area of the texture bounds, in bytes.

Examples

The following code example shows how to create a glyph run analysis object. In this example, an empty glyph run is being used.

HRESULT CreateGlyphRunAnalysis(IDWriteFontFace *pFontFace, IDWriteGlyphRunAnalysis **ppGlyphRunAnalysis)
{
    HRESULT hr = S_OK;
    IDWriteFactory* pDWriteFactory = NULL;

    // Create the DirectWrite factory.
    hr = DWriteCreateFactory(
            DWRITE_FACTORY_TYPE_SHARED,
            __uuidof(IDWriteFactory),
            reinterpret_cast<IUnknown**>(&pDWriteFactory)
            );

    DWRITE_GLYPH_RUN emptyGlyphRun = { 0 };
    UINT16 glyphIndex = 0;
    
    emptyGlyphRun.fontFace = pFontFace;
    emptyGlyphRun.glyphIndices = &glyphIndex;
    emptyGlyphRun.glyphCount = 0;
   
    emptyGlyphRun.fontEmSize = 12;

    IDWriteGlyphRunAnalysis* pGlyphRunAnalysis = NULL;

    if (SUCCEEDED(hr))
    {
        hr = pDWriteFactory->CreateGlyphRunAnalysis(
            &emptyGlyphRun,
            1.0f, // pixelsPerDip,
            NULL, // transform,
            DWRITE_RENDERING_MODE_CLEARTYPE_GDI_CLASSIC,
            DWRITE_MEASURING_MODE_GDI_CLASSIC,
            0.0f, // baselineOriginX,
            0.0f, // baselineOriginY,
            &pGlyphRunAnalysis);
    }
    
    *ppGlyphRunAnalysis = pGlyphRunAnalysis;

    SafeRelease(&pDWriteFactory);

    return S_OK;
}

Requirements

Requirement	Value
Minimum supported client	Windows 7, Windows Vista with SP2 and Platform Update for Windows Vista [desktop apps \| UWP apps]
Minimum supported server	Windows Server 2008 R2, Windows Server 2008 with SP2 and Platform Update for Windows Server 2008 [desktop apps \| UWP apps]
Target Platform	Windows
Header	dwrite.h

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