Determine text boundary box with Direct2D/DirectWr

问题:

ID2D1RenderTarget::DrawGlyphRun takes the following params:

D2D1_POINT_2F baselineOrigin,
__in CONST DWRITE_GLYPH_RUN *glyphRun,
__in ID2D1Brush *foregroundBrush,
DWRITE_MEASURING_MODE measuringMode /*= DWRITE_MEASURING_MODE_NATURAL */

Where DWRITE_GLYPH_RUN is

struct DWRITE_GLYPH_RUN
{
    __notnull IDWriteFontFace* fontFace;
    FLOAT fontEmSize;
    UINT32 glyphCount;
    __field_ecount(glyphCount) UINT16 const* glyphIndices;
    __field_ecount_opt(glyphCount) FLOAT const* glyphAdvances;
    __field_ecount_opt(glyphCount) DWRITE_GLYPH_OFFSET const* glyphOffsets;
    BOOL isSideways;
    UINT32 bidiLevel;
};

I am trying to find out the smallest rect that contains the output glyphs.

This is all data I have. Note that I have 1 point which is baselineOrigin and I can potentially calculate the width using glyphAdvances and glyphOffsets from the DWRITE_GLYPH_RUN. The question is how to determine the height?

Thanks.

回答1:

I use an alternative way to do this before:

1. Create a path geometry
2. Open the path geometry to get the geometry sink
3. Call GetGlyphRunOutline to convert to text to geometry
4. Call GetBounds of the converted geometry to get the boundary rectangle

After converting the text to geometry, you can translate/rotate/scaling it, and do everything what a geometry can do. you can also just drop the geometry after getting the boundary rectangle and drawing with your own method.

Some codes for your references

// Create path geometry
hr = pD2DFactory->CreatePathGeometry(&pPathGeometry);
if(FAILED(hr))
{
        MessageBox(NULL, L"Create path geometry failed!", L"Error", 0);
        return;
}

// Open sink
hr = pPathGeometry->Open(&pGeometrySink);
if(FAILED(hr))
{
        MessageBox(NULL, L"Open geometry sink failed!", L"Error", 0);
        return;
}

// Get glyph run outline
hr = pFontFace->GetGlyphRunOutline(
        fontSize_,                              // font size
        pGlyphIndices,
        NULL,
        NULL,
        textLength,
        FALSE,
        FALSE,
        pGeometrySink
        );
if(FAILED(hr))
{
        MessageBox(NULL, L"Get glyph run outline failed!", L"Error", 0);
        return;
}

// Close sink
pGeometrySink->Close();