Subclassing a Windows Control

Subclassing an existing windows universal control can reduce a lot of work. The new control can inherit many capabilities of the subclass control, such as drawing and responding to the mouse. When you create a project using MFC ActiveX Control wizard, you can select subclass A Windows Control to generate some necessaryCode. You can also manually add the code to an existing ActiveX project:

I,Overload colecontrol: issubclassedcontrol, precreatewindow

Bool cdemosubclassctrl: precreatewindow (createstruct & CS)
{
CS. lpszclass = _ T ("button"); // identifies the subclass from a button container
Return colecontrol: precreatewindow (CS );
}

Bool cdemosubclassctrl: issubclassedcontrol ()
{
Return true;
}

II,Modify the ondraw function.

Void cdemosubclassctrl: ondraw (CDC * PDC, const crect & rcbounds, const crect & rcinvalid)
{
Dosuperclasspaint (PDC, rcbounds );
}

III,Process Reflected container messages

Windows controls generally communicate with the parent window by sending messages to the parent window and receiving reflected messages from the parent window. The reflect message mainly aims to give the control the opportunity to control its own features, such as wm_ctlcolor and wm_drawitem.

However, the communication between ActiveX Control and Its package container is not the same. ActiveX controls send events to the container and read the ambient attribute of the container to interact with the container. Although ActiveX control is also a container, it does not need to send any messages to the parent window. Events are similar to messages on the surface, but their internal mechanisms are completely different. The event is based on the connection point, while message processing in MFC relies on a message chain from the subclass to the parent class. (For details, refer to Hou Jie's in-depth introduction to MFC)

However, when an ActiveX control subclass has a Windows Control, it automatically sends a message to its parent window, such as bn_clicked. Try to prevent it from sending messages to the package container. To this end, colecontrol generates an additional parent window named "reflector" for this type of ActiveX control, with the same size and position as the control. After receiving the message from the control, it will send a reflector message to the control to tell the control what kind of message it just sent, in this way, the control can be processed accordingly, such as sending an event to the package container.

Message sent by the Control	Message reflected to the control
Wm_command	Ocm_command
Wm_ctlcolorbtn	Ocm_ctlcolorbtn
Wm_ctlcoloredit	Ocm_ctlcoloredit
Wm_ctlcolordlg	Ocm_ctlcolordlg
Wm_ctlcolorlistbox	Ocm_ctlcolorlistbox
Wm_ctlcolorscrollbar	Ocm_ctlcolorscrollbar
Wm_ctlcolorstatic	Ocm_ctlcolorstatic
Wm_ctlcolor	Ocm_ctlcolor
Wm_drawitem	Ocm_drawitem
Wm_measureitem	Ocm_measureitem
Wm_deleteitem	Ocm_deleteitem
Wm_vkeytoitem	Ocm_vkeytoitem
Wm_chartoitem	Ocm_chartoitem
Wm_compareitem	Ocm_compareitem
Wm_hscroll	Ocm_hscroll
Wm_vscroll	Ocm_vscroll
Wm_parentnotify	Ocm_parentnotify
Wm_notify	Ocm_policy

You need to manually add the reflected message processing:

 (1) Class cdemosubclassctrl: Public colecontrol {protected: lresult onocmcommand (wparam, lparam );....}; (2) begin_message_map (cursor, colecontrol) on_message (ocm_command, onocmcommand) end_message_map () (3) lresult Syntax: onocmcommand (wparam, lparam) {# ifdef _ win32word wnotifycode = hiword (wparam); # elseword wnotifycode = hiword (lparam); # endifswitch (W Policycode) {Case bn_clicked: fireclick ();  // generally, events are sent to the package container. You can also do other things  break;} return 0;} in the same way. You can also process messages such as ocm_ctlcolorbtn or ocm_drawitem to change the appearance of the button.