Advanced MFC Programming

Chapter 7. Common Dialog Boxes
……
m_pColorDlg->m_cc.lCustData=(LONG)m_pColorDlg;
m_pColorDlg->m_cc.Flags|=CC_ENABLETEMPLATE | CC_FULLOPEN;
m_pColorDlg->m_cc.hwndOwner=m_pColorDmDlg->GetSafeHwnd();
m_pColorDlg->m_cc.lpTemplateName="CHOOSECUSCOLOR";
m_pColorDlg->m_cc.hInstance=(HWND)AfxGetInstanceHandle();
The address of m_pColorDlg is stored as custom data, which will be sent to the hook function. The
dummy window is designated as the parent window of the color dialog box and its handle is assigned to
member hwndOwner of structure CHOOSECOLOR. A global COLORREF type array rgbColors is declared, which
will be used to initialize the custom colors in the color dialog box. Also, custom dialog template
"CHOOSECUSCOLOR" is used, which will allow the user to choose color from only custom colors.
The address of default hook procedure (which is contained in member lpfnHook of structure
CHOOSECOLOR after the constructor of class CColorDlg is called) is stored in global variable lpColorfn, and
the new hook procedure address is assigned to lpfnHook. Finally, API function ::ChooseColor(…) is called
to invoke the color dialog box:
……
}
lpColorfn=m_pColorDlg->m_cc.lpfnHook;
m_pColorDlg->m_cc.lpfnHook=ColorHook;
::ChooseColor(&m_pColorDlg->m_cc);
In the hook procedure, after receiving message WM_INITDIALOG, we can obtain the value of
m_pColorDlg from LPARAM parameter and attach the color dialog box’s window handle to it:
UINT CALLBACK ColorHook(HWND hDlg, UINT iMsg, UINT wParam, LONG lParam)
{
switch(iMsg)
{
case WM_INITDIALOG:
{
CColorDialog *pDlg;
}
pDlg=(CColorDialog *)((LPCHOOSECOLOR)lParam)->lCustData;
pDlg->Attach(hDlg);
break;
}
}
return lpColorfn(hDlg, iMsg, wParam, lParam);
However, there are still some problems left to be solved. Since the dialog box is modeless now, we can
execute command Color Dialog Box | Modeless again when the dialog box is being used. Also, in the new
situation, the user is able to exit the application without closing the dialog box first.
To avoid the dummy dialog box and the color dialog box from being created again while they are
active, we have to check m_pColorDlg and m_pColorDmDlg variables. First, if they are NULL, it means the
variables have not been initialized, we need to allocate buffers and create the window. If they are not
NULL, there are two possibilities: 1) The dialog box is currently active. 2) The dialog box is closed.
Obviously we don’t need to do anything for the first case. For the second case, we need to reinitialize the
two variables and create the window again. Since the window handle is attached to the variable in the hook
procedure, we need to detach it before releasing the allocated buffers. For the above reasons, the following
is added to the beginning of function CCDBDoc::OnColordialogboxModeless():
void CCDBDoc::OnColordialogboxModeless()
{
if(m_pColorDlg != NULL)
{
if(::IsWindow(m_pColorDlg->GetSafeHwnd()) == TRUE)return;
if(m_pColorDlg->GetSafeHwnd() != NULL)m_pColorDlg->Detach();
delete m_pColorDlg;
if(m_pColorDmDlg != NULL)delete m_pColorDmDlg;
m_pColorDmDlg=NULL;
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