Question

Let’s say I’ve got a window for which I want to simulate a mouse click
at a specific x, y coordinate. I already have the hwnd but I’m not sure
how to construct the lParam. I’ve used SendMessage in the past to click
on buttons, etc., but I knew their hwnds.
Any help would be greatly appreciated. I also can’t help but wonder if
I’m going about this the right way. My end goal is clicking on a certain
user on skype main window (for example). I used EnumChildWindows
to find all the main window’s children, but couldn’t find the right one. So
figured I would try to ‘click’ on it using coordinates.

Answer 1

You can use the low level windows api thanks to ctypes. See an example below (adapted from something i didn’t test it but it should be ok)

import ctypes
MOUSEEVENTF_MOVE = 0x0001 # mouse move
MOUSEEVENTF_ABSOLUTE = 0x8000 # absolute move
MOUSEEVENTF_MOVEABS = MOUSEEVENTF_MOVE + MOUSEEVENTF_ABSOLUTE

MOUSEEVENTF_LEFTDOWN = 0x0002 # left button down 
MOUSEEVENTF_LEFTUP = 0x0004 # left button up 
MOUSEEVENTF_CLICK = MOUSEEVENTF_LEFTDOWN + MOUSEEVENTF_LEFTUP

def click(x, y):
    #move first
    x = 65536L * x / ctypes.windll.user32.GetSystemMetrics(0) + 1
    y = 65536L * y / ctypes.windll.user32.GetSystemMetrics(1) + 1
    ctypes.windll.user32.mouse_event(MOUSEEVENTF_MOVEABS, x, y, 0, 0)

    #then click
    ctypes.windll.user32.mouse_event(MOUSEEVENTF_CLICK, 0, 0, 0, 0)

Update:
I didn’t test the code below but I think that it should help you to write something to get the child position. Then you can try to click at the correct position.

CHILD= None

def the_callback(child_hwnd, regex):
    '''Pass to win32gui.EnumWindows() to check all the opened windows'''
    if re.match(regex, win32gui.GetWindowText(child_hwnd)):
        CHILD= child_hwnd

win32gui.EnumChildWindows(hwnd, the_callback, regex)


if CHILD:
    (x_tl, y_tl, x_br, y_br) = win32gui.GetWindowRect(CHILD)