Using Owner-Drawn Buttons

The parent window of an owner-drawn button typically responds to at least three messages for the button: WM_INITDIALOG, WM_COMMAND, and WM_DRAWITEM. It is not necessary to process the WM_MEASUREITEM message for owner-drawn buttons.

When you must paint an owner-drawn button, the system sends the parent window a WM_DRAWITEM message whose lParam points to a DRAWITEMSTRUCT structure. Use this structure with all owner-drawn controls to provide the application with the information it requires to paint the control. The itemAction and itemState members of the DRAWITEMSTRUCT structure define how to paint an owner-drawn button.

The following example shows how to process WM_INITDIALOG, WM_DRAWITEM, and WM_COMMAND messages for owner-drawn buttons. This example demonstrates how to draw one of two bitmaps for a control, depending on whether the control is selected. You would typically use the wParam parameter of the WM_DRAWITEM message to identify the control; in this example, only one control is assumed.

BOOL CALLBACK OwnDrawProc(HWND hDlg, UINT message, WPARAM wParam, 
                          LPARAM lParam) 
{ 
    HDC hdcMem; 
    LPDRAWITEMSTRUCT lpdis; 
 
    switch (message) 
    { 
        case WM_INITDIALOG: 
 
            // hinst, hbm1 and hbm2 are defined globally. 
            hbm1 = LoadBitmap((HANDLE) hinst, "OwnBit1"); 
            hbm2 = LoadBitmap((HANDLE) hinst, "OwnBit2"); 
            return TRUE; 
 
        case WM_DRAWITEM: 
            lpdis = (LPDRAWITEMSTRUCT) lParam; 
            hdcMem = CreateCompatibleDC(lpdis->hDC); 
 
            if (lpdis->itemState & ODS_SELECTED)  // if selected 
                SelectObject(hdcMem, hbm2); 
            else 
                SelectObject(hdcMem, hbm1); 
 
            // Destination 
            StretchBlt( 
                lpdis->hDC,         // destination DC 
                lpdis->rcItem.left, // x upper left 
                lpdis->rcItem.top,  // y upper left 
 
                // The next two lines specify the width and 
                // height. 
                lpdis->rcItem.right - lpdis->rcItem.left, 
                lpdis->rcItem.bottom - lpdis->rcItem.top, 
                hdcMem,    // source device context 
                0, 0,      // x and y upper left 
                32,        // source bitmap width 
                32,        // source bitmap height 
                SRCCOPY);  // raster operation 
 
            DeleteDC(hdcMem); 
            return TRUE; 
 
        case WM_COMMAND: 
            if (wParam == IDOK 
                || wParam == IDCANCEL) 
            { 
                EndDialog(hDlg, TRUE); 
                return TRUE; 
            } 
            if (HIWORD(wParam) == BN_CLICKED) 
            { 
                switch (LOWORD(wParam)) 
                { 
                    case IDC_OWNERDRAW: 
 
                        // application-defined processing 
 
                        break; 
                } 
            } 
            break; 
 
        case WM_DESTROY: 
            DeleteObject(hbm1);  // delete bitmaps 
            DeleteObject(hbm2); 
 
            break; 
 
    } 
    return FALSE; 
        UNREFERENCED_PARAMETER(lParam); 
}