IDWriteTextRenderer::DrawUnderline method

IDWriteTextLayout::Draw calls this function to instruct the client to draw an underline.

Syntax

virtual HRESULT DrawUnderline(
             void             * clientDrawingContext,
             FLOAT             baselineOriginX,
             FLOAT             baselineOriginY,
  [in] const DWRITE_UNDERLINE * underline,
             IUnknown         * clientDrawingEffect
) = 0;

Parameters

clientDrawingContext

Type: void*

The application-defined drawing context passed to IDWriteTextLayout::Draw.

baselineOriginX

Type: FLOAT

The pixel location (X-coordinate) at the baseline origin of the run where underline applies.

baselineOriginY

Type: FLOAT

The pixel location (Y-coordinate) at the baseline origin of the run where underline applies.

underline [in]

Type: const DWRITE_UNDERLINE*

Pointer to a structure containing underline logical information.

clientDrawingEffect

Type: IUnknown*

Application-defined effect to apply to the underline. Usually this argument represents effects such as the foreground brush filling the interior of a line.

Return value

Type: HRESULT

If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

Remarks

A single underline can be broken into multiple calls, depending on how the formatting changes attributes. If font sizes/styles change within an underline, the thickness and offset will be averaged weighted according to characters. To get an appropriate starting pixel position, add underline::offset to the baseline. Otherwise there will be no spacing between the text. The x coordinate will always be passed as the left side, regardless of text directionality. This simplifies drawing and reduces the problem of round-off that could potentially cause gaps or a double stamped alpha blend. To avoid alpha overlap, round the end points to the nearest device pixel.

Requirements

See also

IDWriteTextRenderer