Catch CM_VISIBLECHANGED send by ANY control in the form?

[alogrep 0]

HI.

I don't know if I am on the right track.

After a lot ot research, I came up with this scheme.

I am stuck in get1Proc: I do not knoow how to get the handle

of the control taht sent the message.

 

mHook := SetWindowsHookEx(CM_VISIBLECHANGED ,@get1proc, hInstance, 0);


function get1Proc(nCode, wParam, lParam : integer) : integer; stdcall;

begin
  how do i get the handle of the control that sent this message
 to be used in Findcontrol()?
end;

 

[Remy Lebeau 1421]

1 hour ago, alogrep said:

I don't know if I am on the right track.

Sorry, but you are not on the right track, not even close.

 

You can't pass a message ID to SetWindowsHookEx() like you are doing.  The 1st parameter expects a hook type (one of the WH_... constants), not a message ID.  To hook window messages, you need to specify either the WH_GETMESSAGE or WH_CALLWNDPROC/RET hook type, and then look for your desired message ID inside of your hook callback function.

 

However, in this particular situation, CM_VISIBLECHANGED is a private message to the VCL only, it does not go through the Win32 messaging system at all, so a SetWindowsHookEx() hook will never see it.  The only way you can intercept CM_VISIBLECHANGED is to either:

 

• subclass the WindowProc property of every TControl you are interested in.
• derive your own UI classes that either override the virtual WndProc() or DefaultHandler() method, or define a 'message' handler for CM_VISIBECHANGED.
• use a detouring library, such as MSDetours, to hook into the non-virtual TControl.Perform() method directly (which is what the TControl.Visible property setter calls to send out CM_VISIBLECHANGED).

1 hour ago, alogrep said:

I am stuck in get1Proc: I do not knoow how to get the handle

of the control taht sent the message.

This won't help you in this particular situation, but in general to retrieve the relevant HWND in a SetWindowsHookEx() hook:

 

• for WH_GETMESSAGE, the lParam is a pointer to a MSG structure, which has an HWND member.
• for WH_CALLWNDPROC, the lParam is a pointer to a CWPSTRUCT structure, which has an HWND member.
• for WH_CALLWNDPROCRET, the lParam is a pointer to a CWPRETSTRUCT structure, which has an HWND member.

Edited December 6 by Remy Lebeau