Use wh_cbt hook to display the non-modal dialog box as the Modal Dialog Box

Keywords: Non-modal, modal,Hook,Wh_cbt,CBTProc,

 

1, Intention

Sometimes we want to display a non-modal window as a modal window. For exampleIESelect "print" under the "file" menu, and the "print" dialog box is non-modal (maybe we do not knowMicrosoftIn general, the "print" dialog box here should be modal ). In this case, how does one display the "print" dialog box as a modal mode?Black Box)?

 

2, Simple implementation

Simply put, when a modal window is displayed, its parent window isDisableSo the modal window is displayed as "Modal", so you only need to display the parent window before the non-modal windowDisableThis can be achieved as follows:

 

......

Afxgetmainwnd ()-> enablewindow (false );//Set the Main WindowDisableThe displayed non-modal window becomes modal.

Showmodelesswindow ();

......

 

The problem is that the non-modal window is returned immediately after it is displayed.EnableOfCodeWhere is it? The stupid way is to use the clock to constantly check whether the displayed non-modal window is closed. If it is closed, the parent window isEnable.

Of course, a better approach is needed.

 

3,Wh_cbt hook

Wh_cbt For more information about hooks, see Msdn All we need to know is that the system will call Wh_cbt Hook function, which is exactly what we need. Specifically, before the non-modal window is displayed Wh_cbt After the hook processing function, the handle created in the non-modal window can be stored in Ncode Is Hcbt_createwnd (create window) Hour from Wparam Obtain the parameters, save them, and Ncode Is Hcbt_destroywnd (destruction window) Time and Wparam Parameters are compared. If they match, Enable Status.

 

2, Implementation

1)First, define two variables, which are global static variables.

 

Static hhook g_hhook = NULL;

Static hwnd g_hwnddialog = NULL;//Used to save the window handle

 

2)Add another functionCbtprocBecause it is a callback function, be sure to declare itStatic.

 

Static lresult callbackCbtproc(INT ncode, wparam, lparam );

 

3)Hook

Suppose the following is a function that calls the "print" dialog box in a browser.

Void CMyhtmlView: onfileprint ()

{

Afxgetmainwnd ()-> enablewindow (false );

G_hwnddialog = 0;//It may be called multiple times. You need to reset the variable that saves the window handle.

G_hhook = setwindowshookex (wh_cbt, cbtproc, null, getcurrentthreadid ());

If (! G_hhook)

{

Afxgetmainwnd ()-> enablewindow (true );

Return;

}

Call the "print" dialog box

}

 

Lresult callback CMyhtmlView: cbtproc (INT ncode, wparam, lparam)

{

Switch (ncode)

{

Case hcbt_createwnd:

{

Hwnd = (hwnd) wparam;

Lpcbt_createwnd pcbt = (lpcbt_createwnd) lparam;

Lpcreatestruct PCs = pcbt-> lpcs;

If (DWORD) PCs-> lpszclass = 0x00008002) // #32770, "Print" dialog box Class Name

{

If (g_hwnddialog = 0)

G_hwnddialog = hwnd;//Save the "print" window handle only once

}

Break;

}

 

Case hcbt_destroywnd:

{

Hwnd = (hwnd) wparam;

If (hwnd = g_hwnddialog)

{

Afxgetmainwnd ()-> enablewindow (true );//Restore window status

Unhookwindowshookex (g_hhook );//Remove hook

}

Break;

}

}

Return callnexthookex (g_hhook, ncode, wparam, lparam );

}

 

It's easy. More importantly, this method works.

 

References:

Msdn:Cbtproc

 

Reference address: Use wh_cbt hook to display the non-modal dialog box as the Modal Dialog Box