[Tkinter-discuss] How to handle any Windows message (eg. WM_GETOBJECT)?

[Aivar Annamaa]

Michael, thanks for the idea!

Unfortunately this does not work -- the callback is never called, even 
if the app is sent WM_GETOBJECT messages.

But I found another promising approach -- swapping Tk's message handler 
with my own handler:

    import tkinter as tk
    import win32gui
    import win32con

    root = tk.Tk()

    button = tk.Button(root, text="close", command=root.destroy)
    button.grid()


    hwnd = root.winfo_id()

    def new_wndproc(hWnd, msg, wParam, lParam):
         if msg == win32con.WM_GETOBJECT:
             print(hWnd, msg, wParam, lParam)

         # forward message to original (Tk) handler
         return win32gui.CallWindowProc(old_wndproc, hWnd, msg, wParam,
    lParam)

    # install new windows message handler
    old_wndproc = win32gui.SetWindowLong(hwnd, win32con.GWL_WNDPROC,
    new_wndproc)

    root.mainloop()

I'll see where this road takes me.

Best regards,
Aivar




On 10.12.2019 13:11, Michael Lange wrote:
> Hi,
>
> On Tue, 10 Dec 2019 12:49:27 +0200
> Aivar Annamaa <aivar.annamaa at gmail.com> wrote:
>
>> Hi!
>>
>> It looks like accessibility support in Tk won't happen
>> (https://core.tcl-lang.org/tk/tktview/deb6cddecf55c6921281f8f855b6b366aed6467e).
>> I'm wondering is it somehow possible to bolt on some accessibility
>> support at least on Windows.
>>
>> It looks like the starting point is that the app should be able to
>> provide customized responses to WM_GETOBJECT messages. I didn't find
>> such name in Tk source code. Does it mean Tk event loop simply drops
>> these? Is it somehow possible to install an extra WM event handler to
>> catch these?
> have you tried to do something like
>
> def test():
>      print('hello')
> root.wm_protocol('WM_GETOBJECT', test)
>
> I have no idea what WM_GETOBJECT does and if there is any chance that
> this will work, though :)
>
> Regards
>
> Michael
>
>
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