CODEWITHSUNDEEP
c++winapi
Moe
Moe

Reputation: 555

Sending Two or more chars using SendInput

To send a char, we can use SendInput. How can I use it to send more than one char?

I tried this code but it does not send anything:

INPUT in;
in.type=INPUT_KEYBOARD;
in.ki.wScan=0;
in.ki.time=0;
in.ki.dwExtraInfo=0;
in.ki.wVk=0x53+0x54;

SendInput(2,&in,sizeof(INPUT));

So, what is the right way?

Upvotes: 6

Views: 4281

Answers (3)

Remy Lebeau
Remy Lebeau

Reputation: 598349

The first parameter of SendInput() specifies how many INPUT structures you are passing in. You are only passing in 1, but you are telling SendInput() that you are passing in 2.

You cannot specify two separate virtual keys in a single INPUT. You need to declare an array of multiple INPUTs, 2 INPUTs for each virtual key - one for the keydown event, and one for the keyup event. So, in your example, you actually need 4 INPUTs to send 2 virtual keys, as shown in @user4581301's answer.

Now, regarding KEYEVENTF_UNICODE, you don't use virtual keys with it, you use actual Unicode codepoints instead, where they are specified using UTF-16 codeunits, one per INPUT. So that means if you want to send a Unicode codepoint that requires a UTF-16 surrogate pair, you need 2 sets of down/up INPUTs, one set for the high surrogate, and one set for the low surrogate. That caveat is NOT mentioned in the SendInput() documentation, but it is implied by the fact that the vScan field is a 16bit WORD, and that KEYEVENTF_UNICODE events generate WM_CHAR messages, which passes UTF-16 surrogate codeunits as separate messages.

So, to send a string of Unicode characters using KEYEVENTF_UNICODE, you can do something like this:

#include <vector>
#include <string>

void SendInputString(const std::wstring &str)
{
    int len = str.length();
    if (len == 0) return;

    std::vector<INPUT> in(len*2);
    ZeroMemory(&in[0], in.size()*sizeof(INPUT));

    int i = 0, idx = 0;
    while (i < len)
    {
        WORD ch = (WORD) str[i++];

        if ((ch < 0xD800) || (ch > 0xDFFF))
        {
            in[idx].type = INPUT_KEYBOARD;
            in[idx].ki.wScan = ch;
            in[idx].ki.dwFlags = KEYEVENTF_UNICODE;
            ++idx;

            in[idx] = in[idx-1];
            in[idx].ki.dwFlags |= KEYEVENTF_KEYUP;
            ++idx;
        }
        else
        {
            in[idx].type = INPUT_KEYBOARD;
            in[idx].ki.wScan = ch;
            in[idx].ki.dwFlags = KEYEVENTF_UNICODE;
            ++idx;

            in[idx].type = INPUT_KEYBOARD;
            in[idx].ki.wScan = (WORD) str[i++];
            in[idx].ki.dwFlags = KEYEVENTF_UNICODE;
            ++idx;

            in[idx] = in[idx-2];
            in[idx].ki.dwFlags |= KEYEVENTF_KEYUP;
            ++idx;

            in[idx] = in[idx-2];
            in[idx].ki.dwFlags |= KEYEVENTF_KEYUP;
            ++idx;
        }
    }

    SendInput(in.size(), &in[0], sizeof(INPUT));
}

Upvotes: 16

catalyst
catalyst

Reputation: 48

Other answer didn't seem to work in a DirectX game. I tested the following in TrackMania Nations and it worked correctly: (notepad etc work as well)

#define _WIN32_WINNT 0x0500
#include <windows.h>
#include <string>

void press_some_keys (std::string str) {
    INPUT input[2 * (int)str.size()] = {0};

    int cnt = 0;
    for (char ch: str) {
        input[cnt].type = INPUT_KEYBOARD;
        input[cnt].ki.dwFlags = KEYEVENTF_SCANCODE;
        input[cnt].ki.wScan = MapVirtualKey(LOBYTE(VkKeyScan(ch)), 0);
        cnt++;

        input[cnt] = input[cnt - 1];
        cnt++;
    }

    SendInput(2 * (int)str.size(), input, sizeof(INPUT));
    Sleep(10);

    for (cnt = 1; cnt < 2 * (int)str.size(); cnt += 2)
        input[cnt].ki.dwFlags |= KEYEVENTF_KEYUP;

    SendInput(2 * (int)str.size(), input, sizeof(INPUT));
}

I only tested lowercase alphabet characters (no arrows or others), but it was enough for me.

It was a pain to get it working since the closest thing I found was a single tap function in a Youtube video :-)

Upvotes: 0

user4581301
user4581301

Reputation: 33982

If I've got you right, you want something more along the lines of this:

INPUT in[4] = {0}; // four inputs

// first input 0x53
in[0].type=INPUT_KEYBOARD;
in[0].ki.wScan=0;
in[0].ki.dwFlags=0;
in[0].ki.time=0;
in[0].ki.dwExtraInfo=0;
in[0].ki.wVk=0x53;

in[1] = in[0];
in[1].ki.dwFlags |= KEYEVENTF_KEYUP;

// second input 0x54
in[2].type=INPUT_KEYBOARD;
in[2].ki.wScan=0;
in[2].ki.dwFlags=0;
in[2].ki.time=0;
in[2].ki.dwExtraInfo=0;
in[2].ki.wVk=0x54;

in[3] = in[2];
in[3].ki.dwFlags |= KEYEVENTF_KEYUP;

SendInput(4,in,sizeof(INPUT));

Probably want to wrap the grunt work setting up the INPUT structure into a function to reduce duplication.

Upvotes: 4

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