Passing a string into SendInput() (C++)

Question

Due To The Inconvenience, I've moved to C# for this project, no further comments needed

I've encountered an issue during the development of a C++ tidbit, which sends keystrokes based on user input.

Upon trying to send the actual keystrokes, I am greeted with an error.

<error-type> message

I have posted a code snippet down below. Any help is very much appreciated.

/*Code snippet from program that handles actual keypresses*/
string message;
getline(cin, message);

SendInput(message);

@FredLarson Thank you for the answer, but I get another error in return. In this case, "too few arguments in function call" — Koi, Mar 27 '18 at 02:07
You'll need to read [the docs](https://msdn.microsoft.com/en-us/library/windows/desktop/ms646310(v=vs.85).aspx). It's not that simple, I'm afraid. — Fred Larson, Mar 27 '18 at 02:11
Is that a compiler error or is it what gets displayed when you mouse over message? — user253751, Mar 27 '18 at 02:41

Barmak Shemirani · Answer 1 · 2018-05-25T04:23:48.010

4

Look at documentation for SendInput

You have to setup the INPUT structure, then pass array of INPUT.

#include <iostream>
#include <string>
#include <vector>
#include <Windows.h>

int main()
{
    std::wstring msg = L"ΨΦΩ, ελη, ABC, abc, 123";
    //or std::string msg = "ABCD - abcd - 1234";

    std::vector<INPUT> vec;
    for(auto ch : msg)
    {
        INPUT input = { 0 };
        input.type = INPUT_KEYBOARD;
        input.ki.dwFlags = KEYEVENTF_UNICODE;
        input.ki.wScan = ch;
        vec.push_back(input);

        input.ki.dwFlags |= KEYEVENTF_KEYUP;
        vec.push_back(input);
    }

    //Find a notepad window or another window for send
    HWND hwnd = FindWindow("Notepad", 0);
    if (hwnd)
        SetForegroundWindow(hwnd);
    else
        std::cout << "no window!\n";

    SendInput(vec.size(), vec.data(), sizeof(INPUT));
    return 0;
}

Note that ANSI is deprecated in Windows. This code with std::string works only for ASCII characters. For UNICODE compatibility use std::wstring

edited May 25 '18 at 04:23

answered Mar 27 '18 at 02:59

Barmak Shemirani

30,904
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1

Note that `KEYEVENTF_UNICODE` expects UTF-16 input, and separate `INPUT` down/up pairs for UTF-16 surrogate pairs. If you need to send non-ASCII strings, you need to convert them to this format. – Remy Lebeau Mar 27 '18 at 03:57
@RemyLebeau I got ASCII and ANSI confused again. I think the answer is corrected now. – Barmak Shemirani Mar 27 '18 at 04:20
Thank you for your response. However, I now get the following errors: "'input' was not declared in this scope' and 'ch' does not name a type" – Koi Mar 27 '18 at 04:30
1

@Koi are you using C++11 or later? If not, then change the [range-based `for` loop](http://en.cppreference.com/w/cpp/language/range-for) into a normal `for` loop: `for(size_t i = 0; i < msg.size(); ++i) { ... input.ki.wScan = (WORD) msg[i]; ... }` – Remy Lebeau Mar 27 '18 at 05:23

score 0 · Answer 2 · answered Mar 27 '18 at 02:45

0

Check this out: SendInput() Keyboard letters C/C++

You can't really just pass a entire string to it.

answered Mar 27 '18 at 02:45

Yu Hua Guo

36
4

That's correct but the examples send one `INPUT` at a time, it's supposed to send an array. – Barmak Shemirani Mar 27 '18 at 02:59

Passing a string into SendInput() (C++)

2 Answers2

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