Key echo in Python in separate thread doesn't display first key stroke

Question

I would try to post a minimal working example, but unfortunately this problem just requires a lot of pieces so I have stripped it down best I can.

First of all, I'm using a simple script that simulates pressing keys through a function call. This is tweaked from here.

import ctypes

SendInput = ctypes.windll.user32.SendInput

PUL = ctypes.POINTER(ctypes.c_ulong)

class KeyBdInput(ctypes.Structure):
    _fields_ = [("wVk", ctypes.c_ushort),
                ("wScan", ctypes.c_ushort),
                ("dwFlags", ctypes.c_ulong),
                ("time", ctypes.c_ulong),
                ("dwExtraInfo", PUL)]

class HardwareInput(ctypes.Structure):
    _fields_ = [("uMsg", ctypes.c_ulong),
                ("wParamL", ctypes.c_short),
                ("wParamH", ctypes.c_ushort)]

class MouseInput(ctypes.Structure):
    _fields_ = [("dx", ctypes.c_long),
                ("dy", ctypes.c_long),
                ("mouseData", ctypes.c_ulong),
                ("dwFlags", ctypes.c_ulong),
                ("time",ctypes.c_ulong),
                ("dwExtraInfo", PUL)]

class Input_I(ctypes.Union):
    _fields_ = [("ki", KeyBdInput),
                 ("mi", MouseInput),
                 ("hi", HardwareInput)]

class Input(ctypes.Structure):
    _fields_ = [("type", ctypes.c_ulong),
                ("ii", Input_I)]

def getKeyCode(unicodeKey):
    k = unicodeKey
    curKeyCode = 0
    if k == "up": curKeyCode = 0x26
    elif k == "down": curKeyCode = 0x28
    elif k == "left": curKeyCode = 0x25
    elif k == "right": curKeyCode = 0x27
    elif k == "home": curKeyCode = 0x24
    elif k == "end": curKeyCode = 0x23
    elif k == "insert": curKeyCode = 0x2D
    elif k == "pgup": curKeyCode = 0x21
    elif k == "pgdn": curKeyCode = 0x22
    elif k == "delete": curKeyCode = 0x2E
    elif k == "\n": curKeyCode = 0x0D

    if curKeyCode == 0:
        return 0, int(unicodeKey.encode("hex"), 16), 0x0004
    else:
        return curKeyCode, 0, 0

def PressKey(unicodeKey):
    key, unikey, uniflag = getKeyCode(unicodeKey)

    extra = ctypes.c_ulong(0)
    ii_ = Input_I()
    ii_.ki = KeyBdInput( key, unikey, uniflag, 0, ctypes.pointer(extra) )
    x = Input( ctypes.c_ulong(1), ii_ )
    ctypes.windll.user32.SendInput(1, ctypes.pointer(x), ctypes.sizeof(x))

def ReleaseKey(unicodeKey):
    key, unikey, uniflag = getKeyCode(unicodeKey)
    extra = ctypes.c_ulong(0)
    ii_ = Input_I()
    ii_.ki = KeyBdInput( key, unikey, uniflag + 0x0002, 0, ctypes.pointer(extra) )
    x = Input( ctypes.c_ulong(1), ii_ )
    ctypes.windll.user32.SendInput(1, ctypes.pointer(x), ctypes.sizeof(x))

I stored this in a file named keyPress.py.

Using this, I wanted to make a simple program that could detect what the user was typing while they were typing it in the python shell. The idea was that I would use msvcrt.getch() to get the key pressed, then the script above to make it seem like it was still pressed (and "echo" the key press in a sense")

Here is the code:

import keyPress
import msvcrt        
import threading

def getKey():

    k = msvcrt.getch()

    # Escaped Key: 224 is on the keyboard, 0 is on the numpad
    if int(k.encode("hex"), 16) == 224 or int(k.encode("hex"), 16) == 0:
        k = msvcrt.getch()
        if k == "H": k = "up"
        elif k == "P": k = "down"
        elif k == "K": k = "left"
        elif k == "M": k = "right"
        elif k == "G": k = "home"
        elif k == "O": k = "end"
        elif k == "R": k = "insert"
        elif k == "I": k = "pgup"
        elif k == "Q": k = "pgdn"
        elif k == "S": k = "delete"

    # Fix weird linebreak
    if k == "\r":
        k = "\n"

    return k


def actualGetKeys():
    while True:
        k = getKey()
        keyPress.PressKey(k)
        keyPress.ReleaseKey(k)

def getKeys():
    p = threading.Thread(target=actualGetKeys)
    p.daemon = True
    p.start()   

I stored this in a file named keyGet.py.

This is all working very well, except that whenever the user presses enter, the first key isn't displayed on the screen. The console still knows that you typed it, it just doesn't show up there. Something like this:

What is happening? I've tried many many things and I can't seem to get this behavior to change.

I am now able to get this essentially working, as in it can capture key input asynchronously while a script is running, and execute with the text of each command you type into a command prompt (so you could, say, store these to an array). The only problem I am running into is something like this:

I know this is due to essentially having to have a robot retype their input after they type it, I'm just wondering if there is a way to do this that prevents that input from actually being displayed when the robot types it, so it acts just like the user would expect.

Answer 1

Here is the resulting code, basically written by eryksun's comments because somehow he knows all.

This is called readcmd.py

# Some if this is from http://nullege.com/codes/show/src@e@i@einstein-HEAD@Python25Einstein@[email protected]/380/win32api.GetStdHandle
# and
# http://nullege.com/codes/show/src@v@i@VistA-HEAD@Python@[email protected]/901/win32console.GetStdHandle.PeekConsoleInput

from ctypes import *
import time
import threading

from win32api import STD_INPUT_HANDLE, STD_OUTPUT_HANDLE

from win32console import GetStdHandle, KEY_EVENT, ENABLE_WINDOW_INPUT, ENABLE_MOUSE_INPUT, ENABLE_ECHO_INPUT, ENABLE_LINE_INPUT, ENABLE_PROCESSED_INPUT

import keyPress


class CaptureLines():
    def __init__(self):
        self.stopLock = threading.Lock()

        self.isCapturingInputLines = False

        self.inputLinesHookCallback = CFUNCTYPE(c_int)(self.inputLinesHook)
        self.pyosInputHookPointer = c_void_p.in_dll(pythonapi, "PyOS_InputHook")
        self.originalPyOsInputHookPointerValue = self.pyosInputHookPointer.value

        self.readHandle = GetStdHandle(STD_INPUT_HANDLE)
        self.readHandle.SetConsoleMode(ENABLE_LINE_INPUT|ENABLE_ECHO_INPUT|ENABLE_PROCESSED_INPUT)

    def inputLinesHook(self):

        self.readHandle.SetConsoleMode(ENABLE_LINE_INPUT|ENABLE_ECHO_INPUT|ENABLE_PROCESSED_INPUT)
        inputChars = self.readHandle.ReadConsole(10000000)
        self.readHandle.SetConsoleMode(ENABLE_LINE_INPUT|ENABLE_PROCESSED_INPUT)

        if inputChars == "\r\n":
            keyPress.KeyPress("\n")
            return 0

        inputChars = inputChars[:-2]

        inputChars += "\n"

        for c in inputChars:
            keyPress.KeyPress(c)

        self.inputCallback(inputChars)

        return 0


    def startCapture(self, inputCallback):
        self.stopLock.acquire()

        try:
            if self.isCapturingInputLines:
                raise Exception("Already capturing keystrokes")

            self.isCapturingInputLines = True
            self.inputCallback = inputCallback

            self.pyosInputHookPointer.value = cast(self.inputLinesHookCallback, c_void_p).value
        except Exception as e:
            self.stopLock.release()
            raise

        self.stopLock.release()

    def stopCapture(self):
        self.stopLock.acquire()

        try:
            if not self.isCapturingInputLines:
                raise Exception("Keystrokes already aren't being captured")

            self.readHandle.SetConsoleMode(ENABLE_LINE_INPUT|ENABLE_ECHO_INPUT|ENABLE_PROCESSED_INPUT)

            self.isCapturingInputLines = False
            self.pyosInputHookPointer.value = self.originalPyOsInputHookPointerValue

        except Exception as e:
            self.stopLock.release()
            raise

        self.stopLock.release()

And here is keyPress.py

# Modified from http://stackoverflow.com/a/13615802/2924421

import ctypes
from ctypes import wintypes
import time

user32 = ctypes.WinDLL('user32', use_last_error=True)

INPUT_MOUSE    = 0
INPUT_KEYBOARD = 1
INPUT_HARDWARE = 2

KEYEVENTF_EXTENDEDKEY = 0x0001
KEYEVENTF_KEYUP       = 0x0002
KEYEVENTF_UNICODE     = 0x0004
KEYEVENTF_SCANCODE    = 0x0008

MAPVK_VK_TO_VSC = 0

# C struct definitions
wintypes.ULONG_PTR = wintypes.WPARAM

SendInput = ctypes.windll.user32.SendInput

PUL = ctypes.POINTER(ctypes.c_ulong)

class KEYBDINPUT(ctypes.Structure):
    _fields_ = (("wVk",         wintypes.WORD),
                ("wScan",       wintypes.WORD),
                ("dwFlags",     wintypes.DWORD),
                ("time",        wintypes.DWORD),
                ("dwExtraInfo", wintypes.ULONG_PTR))

class MOUSEINPUT(ctypes.Structure):
    _fields_ = (("dx",          wintypes.LONG),
                ("dy",          wintypes.LONG),
                ("mouseData",   wintypes.DWORD),
                ("dwFlags",     wintypes.DWORD),
                ("time",        wintypes.DWORD),
                ("dwExtraInfo", wintypes.ULONG_PTR))

class HARDWAREINPUT(ctypes.Structure):
    _fields_ = (("uMsg",    wintypes.DWORD),
                ("wParamL", wintypes.WORD),
                ("wParamH", wintypes.WORD))

class INPUT(ctypes.Structure):
    class _INPUT(ctypes.Union):
        _fields_ = (("ki", KEYBDINPUT),
                    ("mi", MOUSEINPUT),
                    ("hi", HARDWAREINPUT))
    _anonymous_ = ("_input",)
    _fields_ = (("type",   wintypes.DWORD),
                ("_input", _INPUT))

LPINPUT = ctypes.POINTER(INPUT)

def _check_count(result, func, args):
    if result == 0:
        raise ctypes.WinError(ctypes.get_last_error())
    return args

user32.SendInput.errcheck = _check_count
user32.SendInput.argtypes = (wintypes.UINT, # nInputs
                             LPINPUT,       # pInputs
                             ctypes.c_int)  # cbSize

def KeyDown(unicodeKey):
    key, unikey, uniflag = GetKeyCode(unicodeKey)
    x = INPUT( type=INPUT_KEYBOARD, ki= KEYBDINPUT( key, unikey, uniflag, 0))
    user32.SendInput(1, ctypes.byref(x), ctypes.sizeof(x))

def KeyUp(unicodeKey):
    key, unikey, uniflag = GetKeyCode(unicodeKey)
    extra = ctypes.c_ulong(0)
    x = INPUT( type=INPUT_KEYBOARD, ki= KEYBDINPUT( key, unikey, uniflag | KEYEVENTF_KEYUP, 0))
    user32.SendInput(1, ctypes.byref(x), ctypes.sizeof(x))

def KeyPress(unicodeKey):
    time.sleep(0.0001)
    KeyDown(unicodeKey)
    time.sleep(0.0001)
    KeyUp(unicodeKey)
    time.sleep(0.0001)


def GetKeyCode(unicodeKey):
    k = unicodeKey
    curKeyCode = 0
    if k == "up": curKeyCode = 0x26
    elif k == "down": curKeyCode = 0x28
    elif k == "left": curKeyCode = 0x25
    elif k == "right": curKeyCode = 0x27
    elif k == "home": curKeyCode = 0x24
    elif k == "end": curKeyCode = 0x23
    elif k == "insert": curKeyCode = 0x2D
    elif k == "pgup": curKeyCode = 0x21
    elif k == "pgdn": curKeyCode = 0x22
    elif k == "delete": curKeyCode = 0x2E
    elif k == "\n": curKeyCode = 0x0D

    if curKeyCode == 0:
        return 0, int(unicodeKey.encode("hex"), 16), KEYEVENTF_UNICODE
    else:
        return curKeyCode, 0, 0