Sending WM_COPYDATA with Python 3

Question

I'm trying to write a python script that will interface with my copy of stickies. I'm having trouble with how Python interacts with the WM_COPYDATA struct, and unfortunately I haven't been able to find many examples online.

Using the code:

import struct
import win32con
import win32gui

import struct, array
int_buffer = array.array("L", [0])
char_buffer = array.array('b', 'do new sticky')
int_buffer_address = int_buffer.buffer_info()[0]
char_buffer_address, char_buffer_size = char_buffer.buffer_info

copy_struct = struct.pack("pLp",
int_buffer_address,
char_buffer_size, char_buffer_address)

hwnd = win32gui.FindWindow("ZhornSoftwareStickiesMain", None)

win32gui.SendMessage(w, WM_COPYDATA, hwnd, copy_struct)

I get the following error:

C:\Users\%userprofile%\Desktop>python sender.py
Traceback (most recent call last):
  File "sender.py", line 7, in <module>
    char_buffer = array.array('b', 'do new sticky')
TypeError: an integer is required

I can't seem to figure out why I'm getting such an error. Any ideas?

Edit: Some partially working code

import struct
import win32con
import win32gui
import struct, array


int_buffer = array.array("L", [0])
char_buffer = array.array('b', b"do manage open")
int_buffer_address = int_buffer.buffer_info()[0]

# Add () to buffer_info to call it.
char_buffer_address, char_buffer_size = char_buffer.buffer_info()

# Need P  type for the addresses.
copy_struct = struct.pack("PLP",int_buffer_address,char_buffer_size, char_buffer_address)

hwnd = win32gui.FindWindow(None, "ZhornSoftwareStickiesMain")
win32gui.SendMessage(hwnd, win32con.WM_COPYDATA, None, copy_struct)

Mark Tolonen · Accepted Answer · 2013-11-17T23:02:31.747

5

In Python 3, strings are Unicode. Try using a byte string:

>>> import array
>>> array.array('b',b'do new sticky')
array('b', [100, 111, 32, 110, 101, 119, 32, 115, 116, 105, 99, 107, 121])

There are a few other changes as well:

import struct, array
int_buffer = array.array("L", [0])
char_buffer = array.array('b', b'do new sticky')
int_buffer_address = int_buffer.buffer_info()[0]

# Add () to buffer_info to call it.
char_buffer_address, char_buffer_size = char_buffer.buffer_info()

# Need P  type for the addresses.
copy_struct = struct.pack("PLP",int_buffer_address,char_buffer_size, char_buffer_address)

I didn't install the software, but I think the next lines should be:

hwnd = win32gui.FindWindow(None, "ZhornSoftwareStickiesMain")
win32gui.SendMessage(hwnd, win32con.WM_COPYDATA, None, copy_struct)

Edit

I installed the software. Initially I couldn't get any commands to work, but the trick that wasn't clear from the API documentation is that each string must start with api:

import struct
import win32con
import win32gui
import array

char_buffer = array.array('B', b'api do new sticky hello, world')
char_buffer_address, char_buffer_size = char_buffer.buffer_info()
copy_struct = struct.pack("PLP", 12345, char_buffer_size, char_buffer_address)
hwnd = win32gui.FindWindow(None, "ZhornSoftwareStickiesMain")
win32gui.SendMessage(hwnd, win32con.WM_COPYDATA, None, copy_struct)

Stickies sample

edited Nov 17 '13 at 23:02

answered Nov 17 '13 at 20:39

Mark Tolonen

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Wow, my code is just screwy all over the place. I caught the last edit about the hwnd variable being off. This does give me a message, and run without an error. The only problem I have is that no matter what command I stick in char_buffer, it always creates a new sticky. Could there be a problem with Stickies not liking a Unicode string? – Jacobm001 Nov 17 '13 at 21:13
1

You're doing better than me. I went ahead and installed the app but can't get a message to display. The SendMessage is failing. Perhaps share what is working for you? – Mark Tolonen Nov 17 '13 at 21:36
Added my code to the edit. No matter what I do, I get a new sticky. No text added to it if supplied, just a new sticky. – Jacobm001 Nov 17 '13 at 21:54
I get nothing. Not sure what is different about my system. I was also playing with `ctypes` as @DavidHeffernan as posted. Not sure what is wrong with my installation. Spy++ shows Stickies isn't receiving the WM_COPYDATA also, but we're running the same code. – Mark Tolonen Nov 17 '13 at 21:58
I'm running Python 3.3x64, and I assume you have the latest version of stickies(x32 as it is the only option). Might the builds need to match? – Jacobm001 Nov 17 '13 at 22:08
32/64 no problem. Windows marshals the struct across process – David Heffernan Nov 17 '13 at 22:17
@MarkTolonen: Thank you for all the effort you put into this question, I know it was a big one. **Edit:** I'll give you the bounty in 4 hours (it won't let me do it now). – Jacobm001 Nov 18 '13 at 16:25
Give Mark the bounty, but switch to using ctypes because it is way easier to use and much better suited to this task. – David Heffernan Nov 18 '13 at 16:31
You're welcome! I recommend switching to ctypes to format the structure as well. – Mark Tolonen Nov 18 '13 at 16:41
@DavidHeffernan, MarkTolonen: I will switch to ctypes, it is a much cleaner code base. Now to actually wrap all this in a useable framework :) – Jacobm001 Nov 18 '13 at 16:51

David Heffernan · Answer 2 · 2013-11-17T22:29:27.087

This is much easier to do with ctypes. This code has been tested with a simple Delphi application that receives and displays the string that is sent via WM_COPYDATA.

import win32con
import ctypes
import ctypes.wintypes

FindWindow = ctypes.windll.user32.FindWindowW
SendMessage = ctypes.windll.user32.SendMessageW

class COPYDATASTRUCT(ctypes.Structure):
    _fields_ = [
        ('dwData', ctypes.wintypes.LPARAM),
        ('cbData', ctypes.wintypes.DWORD),
        ('lpData', ctypes.c_wchar_p) 
        #formally lpData is c_void_p, but we do it this way for convenience
    ]

hwnd = FindWindow('TheNameOfMyWindowClass', None)
cds = COPYDATASTRUCT()
cds.dwData = 0
str = 'boo'
cds.cbData = ctypes.sizeof(ctypes.create_unicode_buffer(str))
cds.lpData = ctypes.c_wchar_p(str)

SendMessage(hwnd, win32con.WM_COPYDATA, 0, ctypes.byref(cds))

This assumes that the recipient expects a UTF-16 encoded payload. If the recipient is expecting ANSI encoded payload then you need to use this variant.

import win32con
import ctypes
import ctypes.wintypes

FindWindow = ctypes.windll.user32.FindWindowW
SendMessage = ctypes.windll.user32.SendMessageW

class COPYDATASTRUCT(ctypes.Structure):
    _fields_ = [
        ('dwData', ctypes.wintypes.LPARAM),
        ('cbData', ctypes.wintypes.DWORD),
        ('lpData', ctypes.c_char_p)
        #formally lpData is c_void_p, but we do it this way for convenience
]

hwnd = FindWindow('TheNameOfMyWindowClass', None)
cds = COPYDATASTRUCT()
cds.dwData = 0
str = b'boo'
cds.cbData = ctypes.sizeof(ctypes.create_string_buffer(str))
cds.lpData = ctypes.c_char_p(str)

SendMessage(hwnd, win32con.WM_COPYDATA, 0, ctypes.byref(cds))

Now, looking at the Stickies link that you posted, you need to use the ANSI variant. If you want to receive notification, you'll need to pass a window handle in you SendMessage call instead of 0 as above.

If done so, SendMessage throws a TypeError: WPARAM must be a Unicode, int, or buffer object (got CArgObject). Yes, wParam. — user508402, Mar 27 '20 at 20:54
(can't edit above) What's needed is something like lParam = PCOPYDATASTRUCT.from_address(ctypes.addressof(cds)) where PCOPYDATASTRUCT = ctypes.POINTER(COPYDATASTRUCT) — user508402, Mar 27 '20 at 21:02

Argimko · Answer 3 · 2021-12-24T13:00:02.300

The next variant supports unicode input string without using ctypes lib:

import array, struct, win32con, win32gui

def copy_data(hwnd, message, dwData = 0):
    buffer = array.array('u', message + '\x00')
    buffer_address, buffer_length = buffer.buffer_info()

    copy_struct = struct.pack('PLP', dwData, buffer_length * buffer.itemsize, buffer_address)

    return win32gui.SendMessage(hwnd, win32con.WM_COPYDATA, None, copy_struct)

hwnd = win32gui.FindWindow(None, 'ZhornSoftwareStickiesMain')
copy_data(hwnd, 'Hello ')

Sending WM_COPYDATA with Python 3

3 Answers3

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