How to Create a CDC class from HDC?

How to Create a CDC class from HDC?

Sometimes Windows API will give you a DC handle, and you can create a CDC class through it. For example, drop-down list, combo box, And button. With HDC, you will receive the draw message. The following describes how to convert HDC to a more familiar CDC.Program. You can also use this technique to convert any other MFC class and Windows handle.

Void mydlist: drawitem (lpdrawitemstruct lpdrawitem)
{
CDC mydc;
Mydc. Attach (lpdrawitem-> HDC );
// Insert other requiredCode.

// If you do not separate the handle, it will be deleted, leading to problems.
Mydc. Detach ();
}
Another method is to call the fromhandle method of the CDC class:
CDC * PDC = CDC: fromhandle (lpdrawitem-> HDC );

It is not clear which method is better-fromhandle () may have fewer errors, because it does not require you to detach the handle.