鼠标点击操作

(一)MFC 鼠标双击响应单击事件:
https://blog.csdn.net/qq_26669845/article/details/46472827

(二)鼠标点击事件:
https://bbs.csdn.net/topics/360232427

检查一下CXXXDlg头文件的消息响应函数声明
    //{{AFX_MSG(CXXXDlg)
    afx_msg void OnLButtonDown(UINT nFlags, CPoint point);//声明
    //}}AFX_MSG
    再检查下源文件中的消息映射
    BEGIN_MESSAGE_MAP(CXXXDlg, CDialog)
    //{{AFX_MSG_MAP(CXXXDlg)
    ON_WM_LBUTTONDOWN()     //消息映射
    //}}AFX_MSG_MAP
    END_MESSAGE_MAP()
    如果都正确的话应该可以响应的

(三)消息映射宏 ON_WM_LBUTTONDOWN(),如何将 消息 与 响应函数 关联起来的呢?
```
BEGIN_MESSAGE_MAP(CDrawView, CView)
    //{{AFX_MSG_MAP(CDrawView)
    ON_WM_LBUTTONDOWN()
    ON_WM_KEYDOWN()
    //}}AFX_MSG_MAP
    // Standard printing commands
    ON_COMMAND(ID_FILE_PRINT, CView::OnFilePrint)
    ON_COMMAND(ID_FILE_PRINT_DIRECT, CView::OnFilePrint)
    ON_COMMAND(ID_FILE_PRINT_PREVIEW, CView::OnFilePrintPreview)
END_MESSAGE_MAP()
```
以上代码, 消息映射宏
`ON_WM_LBUTTONDOWN()  ON_WM_KEYDOWN()`
如何将 `消息`与 `映射函数 `关联起来的呢?
答案:  
ON_WM_LBUTTONDOWN()添加一个条目到CDrawView得消息列表里，它是一个数组，这个条目其中有一项为OnLButton()，即该消息处理函数的地址

所有的CWnd类的WindowProc都会被替换成AfxWndProcBase或AfxWndProc，有消息来时，AfxWndProc首先被调用，继而，要调用到一个叫做OnWndMsg的函数，这个函数查上述的消息列表，查到WM_LBUTTONDOWN后，调用OnLButton。

(四)【VC6.0】直线的橡皮筋绘图技术(貌似只能画点):
```
CPoint m_ptTarget;
bool m_MouseIsButtonDown;
CPoint m_ptOrigin;

void CImage_ProcessingView::OnLButtonDown(UINT nFlags, CPoint point)
{
	//CString s;
	//s.Format(L"%d", point.x);
	////MessageBox(s);
	////MessageBox(L"按下了鼠标!!!!!!");

m_ptOrigin = point;
	m_ptTarget = point;
	m_MouseIsButtonDown = 1;

CWnd::OnLButtonDown(nFlags, point);
}

void CImage_ProcessingView::OnLButtonUp(UINT nFlags, CPoint point)
{
	if (!m_MouseIsButtonDown)
		return;//如果鼠标左键没有被按下，则不响应直接返回

CClientDC   ClientDC(this);
	ClientDC.SelectStockObject(NULL_BRUSH);//SelectStockObject 选择的是系统预定义的GDI对象

//SelectObject 选择你自己自定义的的GDI对象

CPen pen, *oldPen;
	pen.CreatePen(PS_SOLID, 10, RGB(255, 0, 0));
	oldPen = ClientDC.SelectObject(&pen);
	ClientDC.SetROP2(R2_NOTXORPEN);

ClientDC.MoveTo(m_ptOrigin.x, m_ptOrigin.y);
	ClientDC.LineTo(m_ptTarget.x, m_ptTarget.y);

m_ptTarget = point;
	ClientDC.MoveTo(m_ptOrigin.x, m_ptOrigin.y);  //这两句画本次鼠标移动事件的直线因为有异或操作
	ClientDC.LineTo(m_ptTarget.x, m_ptTarget.y);
	ClientDC.SelectObject(oldPen);

CWnd::OnLButtonUp(nFlags, point); //调用下基类的
}

void CImage_ProcessingView::OnMouseMove(UINT nFlags, CPoint point)
{
	if (!m_MouseIsButtonDown)
		return;//如果鼠标左键没有被按下，则不响应直接返回

m_MouseIsButtonDown = false;

CClientDC   ClientDC(this);
	ClientDC.SelectStockObject(NULL_BRUSH);

CPen pen, *oldPen;
	pen.CreatePen(PS_SOLID, 10, RGB(255, 255, 0));

oldPen = ClientDC.SelectObject(&pen);
	ClientDC.SetROP2(R2_COPYPEN); //
	ClientDC.MoveTo(m_ptOrigin.x, m_ptOrigin.y);
	ClientDC.LineTo(m_ptTarget.x, m_ptTarget.y);
	ClientDC.SelectObject(oldPen);//

CWnd::OnMouseMove(nFlags, point);
}

```

(五)VC真正的橡皮筋技术(经测试,正确!)
```
CPoint OriginPos;    // 绘图的起始点
CPoint TargetPos;   // 绘图的目标点
bool m_bDrawing;    // 是否在绘图状态

void CImage_ProcessingView::OnLButtonDown(UINT nFlags, CPoint point)
{
	m_bDrawing = true;
	OriginPos = point;
	TargetPos = point;

CWnd::OnLButtonDown(nFlags, point);
}

void CImage_ProcessingView::OnLButtonUp(UINT nFlags, CPoint point)
{
	
	if (!m_bDrawing)
		return;

m_bDrawing = false;

CClientDC   ClientDC(this);
	ClientDC.DPtoLP(&point);
	ClientDC.SelectStockObject(NULL_BRUSH);

CPen pen, *oldPen;
	pen.CreatePen(PS_SOLID, 1, RGB(255, 0, 0));
	oldPen = ClientDC.SelectObject(&pen);
	ClientDC.SetROP2(R2_COPYPEN);
	ClientDC.MoveTo(OriginPos.x, OriginPos.y);
	ClientDC.LineTo(TargetPos.x, TargetPos.y);
	ClientDC.SelectObject(oldPen);
	CView::OnLButtonUp(nFlags, point);

CWnd::OnLButtonUp(nFlags, point); //调用下基类的
}

void CImage_ProcessingView::OnMouseMove(UINT nFlags, CPoint point)
{
	if (!m_bDrawing)
		return;

CClientDC   ClientDC(this);
	ClientDC.DPtoLP(&point);
	ClientDC.SelectStockObject(NULL_BRUSH);

CPen pen, *oldPen;
	pen.CreatePen(PS_SOLID, 1, RGB(255, 0, 0));
	oldPen = ClientDC.SelectObject(&pen);
	ClientDC.SetROP2(R2_NOT);
	ClientDC.MoveTo(OriginPos.x, OriginPos.y);
	ClientDC.LineTo(TargetPos.x, TargetPos.y);
	TargetPos = point;
	ClientDC.MoveTo(OriginPos.x, OriginPos.y);
	ClientDC.LineTo(TargetPos.x, TargetPos.y);
	ClientDC.SelectObject(oldPen);

CWnd::OnMouseMove(nFlags, point);
}

```
(六)MFC移动画矩形:

https://blog.csdn.net/chenjie863/article/details/17531339

(七)获取当前鼠标的位置,以及messagebox显示位置
```
	CPoint   point;
	GetCursorPos(&point);
	CRect rect_ctr;
	this->GetWindowRect(&rect_ctr);   //获取主窗口相对屏幕左上角的坐标，/存储到rect_ctr中
	point.x += rect_ctr.left;        //在屏幕上的绝对坐标
	point.y += rect_ctr.top;

SetCursorPos(100, 200);//移动到某点坐标

GetCursorPos(&point);  //获取当前光标位置
	  
	int  i= 2;
	float f = 1.8f;
	CString s;
	s.Format(L"%d", point.x);  //显示变量point.x
	MessageBox(s);

s.Format(L"%.1f", f);//显示变量f
	MessageBox(s);

SetCursorPos(400, 200);//移动到某点坐标
	GetCursorPos(&point);
	
```

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