How to retrieve the selected text from the active window

Question

I am trying to create a simple open source utility for windows using Python that can perform user-defined actions on the selected text of the currently active window. The utility should be activated using a pre-defined keyboard shortcut.

Usage is partially outlined in the following example:

1. The user selects some text using the mouse or the keyboard (in any application window)
2. The user presses a pre-defined keyboard shortcut
3. The selected text is retrieved by our utility or copied to clipboard (both approaches should be fine)
4. The keyboard shortcut-dependent action is performed on the selected text

What puzzles me is step 3. How the selected text is retrieved from the active window. This should work with all applications.

I use the pywin32 module.

Thanks in advance for your answers and tips.

Update #1:

Turns out that there are two approaches to accomplish the task:

1. Find the active window, then send a message/keystroke (Ctrl-C) to it in order to copy the selected text to the clipboard. Then the utility can work on the text by accessing it using the clipboard-related functions.
2. Find the active Window, then retrieve the selected text directly (without copying it to clipboard). This seems more difficult than the 1st approach.

As starting points:

Get the active window ID as Anurag Uniyal has pointed out in his reply.

Or get the window object with the following code:

import win32ui
wnd = win32ui.GetForegroundWindow()
print wnd.GetWindowText()

Answer 1

the code below will work only on simple text boxes (just did it in VB6, and ported to python)

edit: it was tested only on python 2.6

from ctypes import *
import win32gui
import win32api
import win32con


user32 = windll.user32
kernel32 = windll.kernel32

class RECT(Structure):
 _fields_ = [
     ("left", c_ulong),
     ("top", c_ulong),
     ("right", c_ulong),
     ("bottom", c_ulong)
 ]

class GUITHREADINFO(Structure):
 _fields_ = [
     ("cbSize", c_ulong),
     ("flags", c_ulong),
     ("hwndActive", c_ulong),
     ("hwndFocus", c_ulong),
     ("hwndCapture", c_ulong),
     ("hwndMenuOwner", c_ulong),
     ("hwndMoveSize", c_ulong),
     ("hwndCaret", c_ulong),
     ("rcCaret", RECT)
 ]



def get_selected_text_from_front_window(): # As String
    ''' vb6 to python translation '''

    gui = GUITHREADINFO(cbSize=sizeof(GUITHREADINFO))
    txt=''
    ast_Clipboard_Obj=None
    Last_Clipboard_Temp = -1


    user32.GetGUIThreadInfo(0, byref(gui))

    txt = GetCaretWindowText(gui.hwndCaret, True)

    '''
    if Txt = "" Then
        LastClipboardClip = ""
        Last_Clipboard_Obj = GetClipboard
        Last_Clipboard_Temp = LastClipboardFormat
        SendKeys "^(c)"
        GetClipboard
        Txt = LastClipboardClip
        if LastClipboardClip <> "" Then Txt = LastClipboardClip
        RestoreClipboard Last_Clipboard_Obj, Last_Clipboard_Temp
        print "clbrd: " + Txt
    End If
    '''    
    return txt



def GetCaretWindowText(hWndCaret, Selected = False): # As String

    startpos =0
    endpos =0

    txt = ""

    if hWndCaret:

        buf_size = 1 + win32gui.SendMessage(hWndCaret, win32con.WM_GETTEXTLENGTH, 0, 0)
        if buf_size:
            buffer = win32gui.PyMakeBuffer(buf_size)
            win32gui.SendMessage(hWndCaret, win32con.WM_GETTEXT, buf_size, buffer)
            txt = buffer[:buf_size]

        if Selected and buf_size:
            selinfo  = win32gui.SendMessage(hWndCaret, win32con.EM_GETSEL, 0, 0)
            endpos   = win32api.HIWORD(selinfo)
            startpos = win32api.LOWORD(selinfo)
            return txt[startpos: endpos]

    return txt

if __name__ == '__main__':
    print get_selected_text_from_front_window()