C++ Direct2D径向渐变画笔

你好我正在使用Direct2D，而我正在使用径向渐变画笔，但我被困在一个地方。C++ Direct2D径向渐变画笔

我的径向渐变画笔代码

结构SampleWindow：DesktopWindow

{ 
    //FOr Radial Gradient Brush 

    ComPtr<ID2D1RadialGradientBrush> radialBrush; 

    void CrateDeviceResources() 
    { 
     D2D1_GRADIENT_STOP stops[] = 
     { 
      {0.0f, COLOR_WHITE}, 
      {1.0f, COLOR_BLUE} 
     }; 

     ComPtr<ID2D1GradientStopCollection> collection; 
     m_target->CreateGradientStopCollection(stops, _countof(stops),collection.ReleaseAndGetAddressOf()); 

     D2D1_RADIAL_GRADIENT_BRUSH_PROPERTIES props = {}; 
     m_target->CreateRadialGradientBrush(props,collection.Get(),radialBrush.ReleaseAndGetAddressOf()); 
    } 

    void Draw() 
    { 
     auto size = m_target->GetSize(); 
     radialBrush -> SetCenter(Point2F(size.width/2.0f, size.height/2.0f)); 
     radialBrush -> SetRadiusX(size.width/2.0f); 
     radialBrush -> SetRadiusY(size.height/2.0f); 

     auto rect = RectF(0.0f, 0.0f, size.width, size.height); 
     m_target -> FillRectangle(rect,radialBrush.Get()); 
    } 

    void MouseMoved(int x, int y, WPARAM) 
    { 
     auto centere = radialBrush->GetCenter(); 
     radialBrush->SetGradientOriginOffset(Point2F(x - centere.x, y - centere.y)); 
     Invalidate(); 
    } 
}

在功能鼠标移动时，我用这条线

auto centere = radialBrush->GetCenter();

我的计划打破它告诉我，

Access violation Exception

的DesktopWindow类代码是：

BEGIN_MSG_MAP() 
     MESSAGE_HANDLER(WM_PAINT, PaintHandler) 
     MESSAGE_HANDLER(WM_DESTROY, DestroyHandler) 
     MESSAGE_HANDLER(WM_SIZE, SizeHandler) 
     MESSAGE_HANDLER(WM_DISPLAYCHANGE, DisplayChangeHandler) 
     MESSAGE_HANDLER(WM_MOUSEMOVE, MouseMovedHandler) 
    END_MSG_MAP() 

LRESULT MouseMovedHandler(UINT, WPARAM wParam, LPARAM lParam,BOOL &) 
    { 
     MouseMoved(GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam),wParam); 
     return 0; 
    } 

    virtual void MouseMoved(int x, int y, WPARAM) 
    { 

    }

我做的mouseMoved功能虚拟的，这样我就可以在ovverride我的其他类此功能。我无法理解我在哪里做错了请纠正我在哪里应该在我的代码中进行更正。

来源

2012-12-26 Haseeb Khan

这个问题的答案是，鼠标移动功能来渲染目标初始化之前所以要避免这种失败使用这种方法

LRESULT MouseMovedHandler(UINT, WPARAM wParam, LPARAM lParam,BOOL &) 
    { 
     if (m_target) 
     { 
      MouseMoved(GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam),wParam); 
     } 
     return 0; 
    }

现在的代码将运行良好

来源

2012-12-26 15:16:55

C++ Direct2D径向渐变画笔

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