how to use sendinput function C++

Question

I have no idea about what parameters are inputted even though I saw the sendinput function from msdn.

UINT WINAPI SendInput(
_In_ UINT nInputs,
_In_ LPINPUT          


        

Answer 1

UINT is an unsigned integer type. _In_ means the parameter is an input parameter that you send into the function. This is opposed to an output parameter, which would be something you send in, and the function would fill in.

The LPINPUT structure is defined as follows:

typedef struct tagINPUT {
    DWORD   type;

    union
    {
        MOUSEINPUT      mi;
        KEYBDINPUT      ki;
        HARDWAREINPUT   hi;
    };
} INPUT, *PINPUT, FAR* LPINPUT;

So it looks like a DWORD coupled with a union of some other structures. Refer to WinUser.h for more.

DWORD is a 32-bit unsigned integer (source):

A DWORD is a 32-bit unsigned integer (range: 0 through 4294967295 decimal). Because a DWORD is unsigned, its first bit (Most Significant Bit (MSB)) is not reserved for signing. This type is declared as follows: typedef unsigned long DWORD, *PDWORD, *LPDWORD;

MOUSEINPUT

typedef struct tagMOUSEINPUT {
    LONG    dx;
    LONG    dy;
    DWORD   mouseData;
    DWORD   dwFlags;
    DWORD   time;
    ULONG_PTR dwExtraInfo;
} MOUSEINPUT, *PMOUSEINPUT, FAR* LPMOUSEINPUT;

KEYBDINPUT

typedef struct tagKEYBDINPUT {
    WORD    wVk;
    WORD    wScan;
    DWORD   dwFlags;
    DWORD   time;
    ULONG_PTR dwExtraInfo;
} KEYBDINPUT, *PKEYBDINPUT, FAR* LPKEYBDINPUT;

HARDWAREINPUT

typedef struct tagHARDWAREINPUT {
    DWORD   uMsg;
    WORD    wParamL;
    WORD    wParamH;
} HARDWAREINPUT, *PHARDWAREINPUT, FAR* LPHARDWAREINPUT;

WORD, LONG, ULONG, and ULONG_PTR are all well-defined on the MSDN page (See the column on the right)

Here's an example of using SendInput that can be easily found via Googling (Source):

//
// keystroke.c - Pauses, then simulates a key press
// and release of the "A" key.
//
// Written by Ted Burke - last updated 17-4-2012
//
// To compile with MinGW:
//
//      gcc -o keystroke.exe keystroke.c
//
// To run the program:
//
//      keystroke.exe
//
// ...then switch to e.g. a Notepad window and wait
// 5 seconds for the A key to be magically pressed.
//

// Because the SendInput function is only supported in
// Windows 2000 and later, WINVER needs to be set as
// follows so that SendInput gets defined when windows.h
// is included below.
#define WINVER 0x0500
#include <windows.h>

int main()
{
    // This structure will be used to create the keyboard
    // input event.
    INPUT ip;

    // Pause for 5 seconds.
    Sleep(5000);

    // Set up a generic keyboard event.
    ip.type = INPUT_KEYBOARD;
    ip.ki.wScan = 0; // hardware scan code for key
    ip.ki.time = 0;
    ip.ki.dwExtraInfo = 0;

    // Press the "A" key
    ip.ki.wVk = 0x41; // virtual-key code for the "a" key
    ip.ki.dwFlags = 0; // 0 for key press
    SendInput(1, &ip, sizeof(INPUT));

    // Release the "A" key
    ip.ki.dwFlags = KEYEVENTF_KEYUP; // KEYEVENTF_KEYUP for key release
    SendInput(1, &ip, sizeof(INPUT));

    // Exit normally
    return 0;
}

The other part of your question:

Also, type, ki.wScan, ki.time, ki.dwExtraInfo, ki.wVk, ki.dwFlags What do objects above mean

I believe you're referring to this code from the MSDN page:

// IMPORTANT: Current keyboard layout 0xf0010413 (Netherland with USA kbd)!!!!!!!
WORD vkCode = 0x36; // '6'
INPUT keyEvent = {0};
keyEvent.type = INPUT_KEYBOARD;
keyEvent.ki.wVk = vkCode;
keyEvent.ki.wScan = MapVirtualKeyEx(vkCode, 0, (HKL)0xf0010413);
SendInput(1, &keyEvent, sizeof(keyEvent));

That code was posted by another use on the page; it's not part of the documentation. The user simply created an LPINPUT structure named keyEvent, and then accessed the KEYBDEVENT part of the structure:

KEYBDINPUT      ki;