ID2D1EffectImpl::PrepareForRender method (d2d1effectauthor.h)

Article
02/22/2024

Prepares an effect for the rendering process.

Syntax

HRESULT PrepareForRender(
  D2D1_CHANGE_TYPE changeType
);

Parameters

changeType

Type: D2D1_CHANGE_TYPE

Indicates the type of change the effect should expect.

Return value

Type: HRESULT

If the method succeeds, it returns S_OK. If it fails, it returns an HRESULT error code.

Remarks

This method is called by the renderer when the effect is within an effect graph that is drawn.

The method will be called:

If the effect has been initialized but has not previously been drawn.
If an effect property has been set since the last draw call.
If the context state has changed since the effect was last drawn.

The method will not otherwise be called. The transforms created by the effect will be called to handle their input and output rectangles for every draw call.

Most effects defer creating any resources or specifying a topology until this call is made. They store their properties and map them to a concrete set of rendering techniques when first drawn.

Examples

An effect normally waits until it is rendered before snapping its current state and applying it to any transforms it has encapsulated.

class CMyTransform : public ID2D1DrawTransform
{
public:

    // Transform methods omitted.
    
    HRESULT PrepareForRender(FLOAT radius);
};

class CEffectImplementation : public ID2D1EffectImpl
{
public:

    void SetRadius(FLOAT radius) { _radius = radius; }

    IFACEMETHODIMP PrepareForRender(D2D1_CHANGE_TYPE /*type*/)
    {
        // Send the radius to the transform and ask it to render.
        return _pMyTransform->PrepareForRender(_radius);
    }

private:

    CMyTransform *_pMyTransform;
    FLOAT _radius;
};

Requirements

Requirement	Value
Minimum supported client	Windows 8 and Platform Update for Windows 7 [desktop apps \| UWP apps]
Minimum supported server	Windows Server 2012 and Platform Update for Windows Server 2008 R2 [desktop apps \| UWP apps]
Target Platform	Windows
Header	d2d1effectauthor.h
Library	D2D1.lib

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