这是一个绘制直线的简单绘图程序，能过实现动态轨迹画线，在拖动时产生临时线来表示可能画出的直线效果。
首先：建立一个单文档程序，名称为Demo
然后：在视图类的声明文件里面加入数据成员
class CDemoView : public CView
{
//········
protected:
int m_Dragging;
HCURSOR m_HCross;
CPoint m_PointOld;
CPoint m_PointOrigin;
//········
};
{
//········
protected:
int m_Dragging;
HCURSOR m_HCross;
CPoint m_PointOld;
CPoint m_PointOrigin;
//········
};
接着：在视图类的构造函数里面
CDemoView::CDemoView()
{
// TODO: add construction code here
m_Dragging=0;
m_HCross=AfxGetApp()->LoadStandardCursor(IDC_CROSS);//载入标准的十字光标
}
{
// TODO: add construction code here
m_Dragging=0;
m_HCross=AfxGetApp()->LoadStandardCursor(IDC_CROSS);//载入标准的十字光标
}
接着：为视图类添加鼠标左键，鼠标移动，鼠标左键释放消息
void CDemoView::OnLButtonDown(UINT nFlags, CPoint point)
{
// TODO: Add your message handler code here and/or call default
::SetCursor(m_HCross);//这一句能防止左键单击的时候，保持鼠标样式不变
m_PointOrigin=point;
m_PointOld=point;
SetCapture();//捕获鼠标，充分控制鼠标
m_Dragging=1;
RECT Rect;
GetClientRect(&Rect);//取得窗口当前显示坐标
ClientToScreen(&Rect);//转换为屏幕坐标
::ClipCursor(&Rect);//限定光标在指定矩形了吗
CView::OnLButtonDown(nFlags, point);
}
{
// TODO: Add your message handler code here and/or call default
::SetCursor(m_HCross);//这一句能防止左键单击的时候，保持鼠标样式不变
m_PointOrigin=point;
m_PointOld=point;
SetCapture();//捕获鼠标，充分控制鼠标
m_Dragging=1;
RECT Rect;
GetClientRect(&Rect);//取得窗口当前显示坐标
ClientToScreen(&Rect);//转换为屏幕坐标
::ClipCursor(&Rect);//限定光标在指定矩形了吗
CView::OnLButtonDown(nFlags, point);
}
void CDemoView::OnMouseMove(UINT nFlags, CPoint point)
{
// TODO: Add your message handler code here and/or call default
::SetCursor(m_HCross);
if (m_Dragging)
{
CClientDC ClientDC(this);
ClientDC.SetROP2(R2_NOT);//逆转当前屏幕颜色来画线的绘图方式
ClientDC.MoveTo(m_PointOrigin);//
ClientDC.LineTo(m_PointOld); //擦去上一次的线
ClientDC.MoveTo(m_PointOrigin);
ClientDC.LineTo(point);//绘制这一次的临时线
m_PointOld=point;
}
CView::OnMouseMove(nFlags, point);
}
{
// TODO: Add your message handler code here and/or call default
::SetCursor(m_HCross);
if (m_Dragging)
{
CClientDC ClientDC(this);
ClientDC.SetROP2(R2_NOT);//逆转当前屏幕颜色来画线的绘图方式
ClientDC.MoveTo(m_PointOrigin);//
ClientDC.LineTo(m_PointOld); //擦去上一次的线
ClientDC.MoveTo(m_PointOrigin);
ClientDC.LineTo(point);//绘制这一次的临时线
m_PointOld=point;
}
CView::OnMouseMove(nFlags, point);
}
void CDemoView::OnLButtonUp(UINT nFlags, CPoint point)
{
// TODO: Add your message handler code here and/or call default
if (m_Dragging)
{
m_Dragging=0;
::ReleaseCapture();//结束捕获鼠标
::ClipCursor(NULL);//解锁鼠标
CClientDC ClientDC(this);
ClientDC.SetROP2(R2_NOT);
ClientDC.MoveTo(m_PointOrigin);
ClientDC.LineTo(m_PointOld);//擦去上一次的临时线
ClientDC.SetROP2(R2_COPYPEN);//缺省绘图模式，像素为画笔颜色
ClientDC.MoveTo(m_PointOrigin);
ClientDC.LineTo(point);//绘制固定线
}
CView::OnLButtonUp(nFlags, point);
}
{
// TODO: Add your message handler code here and/or call default
if (m_Dragging)
{
m_Dragging=0;
::ReleaseCapture();//结束捕获鼠标
::ClipCursor(NULL);//解锁鼠标
CClientDC ClientDC(this);
ClientDC.SetROP2(R2_NOT);
ClientDC.MoveTo(m_PointOrigin);
ClientDC.LineTo(m_PointOld);//擦去上一次的临时线
ClientDC.SetROP2(R2_COPYPEN);//缺省绘图模式，像素为画笔颜色
ClientDC.MoveTo(m_PointOrigin);
ClientDC.LineTo(point);//绘制固定线
}
CView::OnLButtonUp(nFlags, point);
}