How does ATL implement contained windows?

CContainedWindowT

This class creates a window that is encapsulated by another object.

The members of this class and this class cannot be used in Windows Runtime apps.

A subset of CContainedWindowT is CContainedWindow. Use CContainedWindowT directly to alter the base class or characteristics.

The window class that uses CContainedWindowT::WindowProc and is based on an existing class is registered first by the Create method. Create then creates a window based on this new window class. Each instance of CContainedWindowT can superclass a separate window class. Call CContainedWindowT:: Create after that.

You don't have to supply a Windows class name to subclass an existing window; pass NULL to the constructor. Pass the handle to the window being subclassed when calling the CContainedWindowT::SubclassWindow function.

In a container class, enclosed windows are often used as data members. The container must be a descendant of CMessageMap, but it need not be a window.

A confined window can use alternative message maps to manage its messages. You should define multiple alternate message mappings, each corresponding to a different enclosed window if you have more than one contained window.

Syntax:

template <class TBase = CWindow, class TWinTraits = CControlWinTraits>
class CContainedWindowT : public TBase

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Parameters

*1CWindow is the default class.

*2CControlWinTraits is the default trait class

CMessageMap

The message maps of an object can be accessed by other objects thanks to this class.

The members of this class and this class cannot be used in Windows Runtime applications.

The message maps of one object can be accessed by another object using the abstract base class CMessageMap. A class must inherit from CMessageMap for an object to disclose its message maps.

How does ATL implement contained windows?

Following is an example of a container class with two contained windows:

class CMyContainer : public CMessageMap
{
public:
   CContainedWindow m_wndEdit;
   CContainedWindow m_wndList;
   CMyContainer() : m_wndEdit(_T("Edit"), this, 1), 
                    m_wndList(_T("List"), this, 2)
   {
   }
   BEGIN_MSG_MAP(CMyContainer)
   ALT_MSG_MAP(1)
   ALT_MSG_MAP(2)
   END_MSG_MAP()
};

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Frequently Asked Questions

What are the C++ standard library files?

A few standard libraries are the Diagnostics Library, General Utilities Library, and Standard String Templates.

What is the purpose of C++?

C++ is used to create browsers, operating systems, and apps, as well as in-game programming, software engineering, data structures, and other applications.

Do people still use the component object model?

Even though it's regarded as the. NET Framework's former version, COM, is nevertheless widely used today. Many technologies used today are still built on and rely on COM.

What is the purpose of ATL?

Microsoft created a collection of template-based C++ classes called the Active Template Library (ATL) to make designing Component Object Model (COM) objects easier. Developers may construct different COM objects, OLE Automation servers, and ActiveX controls thanks to the COM functionality in Microsoft Visual C++.

Conclusion

In this blog, we discuss how ATL implements contained windows. We will also be looking in through CContainedWindowT.If you think this blog has helped you enhance your knowledge of the above question or want to learn more, check out our articles. Visit our website to read more such blogs. 

• Introduction To C++
• Data Types in C++
• Containers In C++ STL
• STL containers in C++

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