Window Finder OLE Control

Visual C++ 4.0 Project

Window Finder is an ActiveX control similar to Spy++’s Window Finder
control. The user can drag the circle over a window (a border will
be drawn around the window) to select it, and your program can figure out
what the handle of the window is.

To use the Window Finder ActiveX control, you will first need to register
it using regsvr32 (type regsvr32 winfinder.ocx at the
command line). In the Insert Control dialog, the control will be named
“WinFinder Control”.

Changes From 1.0 to 2.0


  • No global callback function needed, a WM_USER + 100 message is sent to
    parent window when selection changes
  • Demo project changes
  • Minor bugfixes

In the demo project, “targetWindow” is shown in the static control, it
is updated in the callback function.

Note: The variable type for the catagory targetWindow is “long” because
it seems that I could only use certain varible types, and HWND was not
one of them.

Notification Message

When the window selection changes, the WinFinder control sends a
WM_CHAR + 100 message to it’s parent window (usually a dialog).
The LPARAM parameter contains the new selected window handle.

This replaces the callback function, but for compatability the callback
function can still be used (see the next section). If you need more
flexibility, use the callback function.

Callback Function

To set a callback function that is called when the selected window c
changes, you have to send a WM_USER + 100 message to the WinFinder
control. LPARAM should be the address to a structure that looks like
this:


typedef int (*WINFINDERCALLBACK)(HWND);

typedef struct
{
WINFINDERCALLBACK pfn;
} *LPWINFINDERCALLBACKSTRUCT;

‘pfn’ should point to the address of the callback function. The WPARAM
parameter to the message should be zero if you want the callback function
set to the one specified in the LPARAM structure, or zero if you don’t
wan’t to set it. The return value of the message handler is always the
address of the callback function, so setting WPARAM to a non-zero value
can be used to retrive the address to the function.

The callback function should return a value of “0” to allow the window
to be selected, or “1” to ignore the window (this is ueful for ignoring
the dialog that the control is in, like Spy++ does). The declaration
of the callback function should be similar to:


int WindowFinderSelected(HWND hWnd);

‘hWnd’ is the handle of the currently selected window, which can also be
retreived by the “targetWindow” property.

The default callback function allows all windows to be selected.

The sample project displays the the window handle of the window that is
selected by the Window Finder Control. The callback function sets
the caption of the window handle to the window handle of the selected
window.

Conclusion

The WinFinder control isn’t very useful for many applications, but
sometimes it may be just what you need.

Downloads

Download OCX – 11 Kb
Download demo project – 16 Kb
Download source – 33 Kb

More by Author

Must Read