Windows support class-CAxDialogImpl

CAxDialogImpl

CAxDialogImpl implements a dialog box that hosts ActiveX Controls. This statement might trigger in the first go, but we will understand it in-depth in this section. 

Dialog boxes are the pop-ups used to interact with the user. Dialog boxes also help in taking input from the user. 

For example: When you leave the website or application, it asks you one more time whether you want to leave or not. 

Now, there are two types of Dialog Boxes: Modal and Modeless. 

Modal and Modeless Dialog Box

A modal dialog prevents you from accessing the rest of the application until it is closed. When a modal dialogue box is open, it is always active and prevents opening any other dialogue boxes or windows until it is closed.

While the modeless dialogue is open, you can use the rest of the application. Other application windows may hide it.

CAxDialoglmpl implements both types of DialogBox: Modal and Modeless. 

Dialog Box hosts ActiveX controls. But what are ActiveX Controls? Let us explore: 

ActiveX Controls

ActiveX is a set of tools created by Microsoft that allows Windows applications to have more functionality in networked environments. An ActiveX control is a program embedded in a Web site to improve the user's interaction with other applications running on the site. Customized applications for data collection, viewing specific types of files, and displaying animation. ActiveX controls are commonly used in command buttons, list boxes, and dialogue boxes.

Let us quickly see the Syntax of CAxDialoglmpl class: 

Syntax 

template <class T, class TBase = CWindow>
class ATL_NO_VTABLE CAxDialogImpl : public CDialogImplBaseT<TBase>

Parameters

• T = It is your class that is derived from CAxDialogImpl.
• TBase = It is the base class of your new class. Although, the default base class is CWindow. 

Hierarchy 

CAxDialogImpl is derived from CDialogImplBaseT, which is derived from TBase (CWindow by default) and CMessageMap.

An IDD member containing the dialogue template resource ID must be defined in your class. When you add an ATL Dialog object to your class using the Add Class dialogue box, the following line is automatically added:

enum { IDD = IDD_MYDLG };

Members 

Member contains public and protected methods. Let us see them all:

Public Methods  

Name	Description
CAxDialogImpl::AdviseSinkMap	Call this method to advise or unadvise all entries in the sink map event map of the object.
CAxDialogImpl::Create	To create a modeless dialog box, use this method.
CAxDialogImpl::DestroyWindow	To destroy a modeless dialog box, use this method.
CAxDialogImpl::DoModal	Use this method to create a modal dialog box.
CAxDialogImpl::EndDialog	Use this method to destroy a modal dialog box.
CAxDialogImpl::GetDialogProc	Use this method to get a pointer to the DialogProc callback function.
CAxDialogImpl::GetIDD	To collect the dialog template resource ID, use this method.
CAxDialogImpl::IsDialogMessage	Call this method to see if a message is intended for this dialogue box and, if so, to process it.

 

Protected Methods

Name	Description
CAxDialogImpl::m_bModal	It only exists in debug builds and is set to true if the dialogue box is modal.

 

Let us now discuss the syntax of each method and their return value: 
 

1.CAxDialogImpl::AdviseSinkMap

Syntax 

HRESULT AdviseSinkMap(bool bAdvise);

Parameters	Return Value
bAdvise: If all sink entries are to be advised, set this to true; otherwise, set this to false.	On Success: S_OK, On Failure: HRESULT

 

2. CAxDialogImpl::Create

Syntax 

HWND Create(HWND hWndParent, LPARAM dwInitParam = NULL);
HWND Create(HWND hWndParent, RECT&, LPARAM dwInitParam = NULL);

Parameters	Return Value
hWndParent: The handle to the owner window. dwInitParam: It specifies the value to pass to the dialog box in the lParam parameter of the WM_INITDIALOG message.	It returns the handle to the newly created dialog box.

 

3. CAxDialogImpl::DestroyWindow

Syntax

BOOL DestroyWindow();

Return Value: If the window was successfully destroyed, TRUE; otherwise, FALSE.

 

4. CAxDialogImpl::DoModal

Syntax 

INT_PTR DoModal(
    HWND hWndParent = ::GetActiveWindow(),
    LPARAM dwInitParam = NULL);

Return Value: If successful, the nRetCode parameter specified in the EndDialog call; otherwise, -1.

 

5. CAxDialogImpl::EndDialog

Syntax 

BOOL EndDialog(int nRetCode);

Parameters	Return Value
nRetCode: The value to be returned by DoModal.	If the dialogue box is destroyed, TRUE; otherwise, FALSE.

 

6. CAxDialogImpl::GetDialogProc

Syntax 

virtual DLGPROC GetDialogProc();

Return Value: This function returns a pointer to the DialogProc callback function.

 

7. CAxDialogImpl::GetIDD

Syntax

int GetIDD();

Return Value: The dialogue template resource ID is returned.

 

8. CAxDialogImpl::IsDialogMessage

Syntax

BOOL IsDialogMessage(LPMSG pMsg);

Parameters	Return Value
pMsg: A pointer to an MSG structure containing the message to be validated.	If the message has been processed, it returns TRUE; otherwise, it returns FALSE.

 

9. CAxDialogImpl::m_bModal

Syntax 

bool m_bModal;

Frequently Asked Questions

What is ATL?

ATL stands for Active Template Library. Its library contains numerous classes that can be used to manipulate and develop Windows.

What are the ways to add a dialog box?

There are two ways to add a dialog box to the ATL project. These are - using ATL Dialog Wizard and manually adding it.

What are dialog boxes?

Dialog boxes are the pop-ups used to interact with the user. Dialog boxes also help in taking input from the user. 

Which ATL libraries help in implementing dialog boxes?

Three ATL libraries help in dialog box implementation. These are -  CDialogImpl, CAxDialogImpl, and CSimpleDialog.

Conclusion

In this article, we have discussed Windows support class-CAxDialogImpl in ATL. We have also discussed the types of Dialog Boxes: Modal and Modeless. At last, we have discussed the data members of CAxDialoglmpl class in ATL. 

Do not stop learning! We recommend you read these articles -. 

1. Debugging tips for ATL
2. ATL Control Containment
3. ATL Services
4. ATL COM property pages
    

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