MFC：如何启用通过鼠标滚轮换页打印预览？

Question

In print preview dialog, I would like to enable page change via mouse wheeling. As I am still a beginner for MFC programming, I don't have code to start with. The closest question I've found is this one (for C#) but no clear answer yet: https://www.codeproject.com/Questions/555242/5bc-23-5dplusprintpreviewdialogplusandplusmousewhe .

Answer 1

If you are using MFC's CPreviewView class, then you can derive a custom class from that, in which you can override the OnMouseWheel member. In your override, you would call the OnVScroll handler to shift up or down, as though you had clicked on the up/down arrows of the scrollbar:

BOOL MyPreviewView::OnMouseWheel(UINT /*flags*/, short delta, CPoint /*point*/)
{
    OnVScroll(UINT((delta < 0) ? SB_LINEDOWN : SB_LINEUP), 0, nullptr);
    return TRUE;
}

Also, you need to add ON_WM_MOUSEWHEEL() to your derived class' message-map:

BEGIN_MESSAGE_MAP(MyPreviewView, CPreviewView)
    //...
    ON_WM_MOUSEWHEEL()
    //...
END_MESSAGE_MAP()

Feel free to ask for further clarification and/or explanation.

Answer 2

It is an addition to the existing answer of Adrian Mole's Answer

If you are not using custom class already, this is the complete implementation of the class:

MyPreviewViewEx.h

// CMyPreviewViewEx view

class CMyPreviewViewEx : public CPreviewViewEx
{
    DECLARE_DYNCREATE(CMyPreviewViewEx)

protected:
    CMyPreviewViewEx()              {}           // protected constructor used by dynamic creation
    virtual ~CMyPreviewViewEx()     {}

    DECLARE_MESSAGE_MAP()
public:
    afx_msg BOOL OnMouseWheel(UINT nFlags, short zDelta, CPoint pt);
    static void MyPrintPreview(CView* pView);
};

MyPreviewViewEx.cpp

// CMyPreviewViewEx
IMPLEMENT_DYNCREATE(CMyPreviewViewEx, CPreviewViewEx)

BEGIN_MESSAGE_MAP(CMyPreviewViewEx, CPreviewViewEx)
    ON_WM_MOUSEWHEEL()
END_MESSAGE_MAP()


// CMyPreviewViewEx message handlers

BOOL CMyPreviewViewEx::OnMouseWheel(UINT nFlags, short zDelta, CPoint pt)
{
    OnVScroll(UINT((zDelta < 0) ? SB_LINEDOWN : SB_LINEUP), 0, nullptr);
    return TRUE;
}

// Override AFXPrintPreview
void CMyPreviewViewEx::MyPrintPreview(CView* pView)
{
    ASSERT_VALID(pView);

    CPrintPreviewState *pState= new CPrintPreviewState;

    if (!pView->DoPrintPreview(IDD_AFXBAR_RES_PRINT_PREVIEW, pView, RUNTIME_CLASS(CMyPreviewViewEx), pState))
    {
        TRACE0("Error: OnFilePrintPreview failed.\n");
        AfxMessageBox(AFX_IDP_COMMAND_FAILURE);
        delete pState;      // preview failed to initialize, delete State now
    }
}

In the view class, change as applicable

// AFXPrintPreview(pView);
CMyPreviewViewEx::MyPrintPreview(pView);