CInputEvent class

• Download source demo project - 17 Kb

Introduction

The CInputEvent class manages mouse events. It updates a data structure which is available DrawItem or OnPaint methods to allow you to draw control at with the correct visual state.

Using the code

This class avoids the use of all the methods usually used to get the button state. The Button class doesn't need all the OnLButtonDown, OnMouseMove, etc. methods anymore Also, all the usual m_OverTracking, m_ButtonDown, TrackMouseEvent etc. are not necessary in the derived CWnd class (button, static, etc...).

The data structure is updated for each of these received messages. When the button needs to be drawn, say in the DrawItem() method, you just need to get the button status and then draw the corresponding bitmap or text or what ever you want.

To Use

Declare a pointer to a CInputEvent data :

CInputEvent* m_pInputEvent;

Init this data once the CWnd button is created, in the PreSubclassWindow.

void CMyButton::PreSubclassWindow() 
{
    //--------------------------------------------------
    // Init InputEvents
    //--------------------------------------------------
    m_pInputEvent = new CInputEvent(this);
    CButton::PreSubclassWindow();
}

Filter the Windows Message in PreTranslateMessage(MSG* pMsg). This will fill a data structure which updates the button state.

The CInputEvent class will filter the messages:

WM_MOUSEMOVE
WM_MOUSELEAVE
WM_LBUTTONDOWN
WM_LBUTTONUP
WM_LBUTTONDBLCLK

BOOL CMyButton::PreTranslateMessage(MSG* pMsg) 
{
    //--------------------------------------------------
    // Pass message to CInputEvent and relay it or not to mother class
    //--------------------------------------------------
    m_pInputEvent->RelayMsg(pMsg);
    return CButton::PreTranslateMessage(pMsg);
}

In the DrawItem method, get the InputStatus sructure. This structure contains the button state, the client rect (CRect), the mouse coords, the status of the ctrl and shift keys and other mouse buttons.

Here is the code used in the demo :

void CMyButton::DrawItem(LPDRAWITEMSTRUCT lpDrawItemStruct) 
{
    // Gets Button status
    CInputEvent::INPUTSTATUS ips;
    m_pInputEvent->GetStatus(&ips);
    CString    str;

    // Gets DC
    CDC* pDC=CDC::FromHandle(lpDrawItemStruct->hDC);

    // Button is disabled
    if (lpDrawItemStruct->itemState & ODS_DISABLED)
    {
        str="Disabled";
    }
    else
    {
        switch (ips.drawPosition)
        {
        case 1:     //CInputEvent::DRAW_NORMAL:
            str="Normal";
            break;
        case 2:     //CInputEvent::DRAW_OVER:
            str="Over";
            break;
        case 3:     //CInputEvent::DRAW_PUSHED:
            str="Pushed";
            break;
        }
    }
    
    pDC->FillSolidRect(&ips.rect, RGB(100,200,255));
    pDC->DrawText(str, &ips.rect, DT_CENTER|DT_VCENTER|DT_SINGLELINE);
}

Note that the disabled state is not managed since the button is disabled before receiving the WM_ENABLE message. So I use the DrawItem Structure to get this info. I could use WindowProc method but it receives messages from other controls.

Delete the CInputEvent data in the button destructor.

CMyButton::~CMyButton()
{
    // free memory
    delete m_pInputEvent;
}

Points of Interest

Using this class avoids to overload an Ownerdraw button class or a graphical static responding to mouse.

The other point is the windows message filtering. The class can manage any of the received messages. It becomes easy to add Wheel mouse, right click, keyboard input etc.. to manage the drawing of any control.