How to Send Multiple Characters Using SendInput: Addressing Parameter and Unicode Handling Issues?

Addressing the Use of SendInput for Sending Multiple Characters

SendInput is a function used to simulate keyboard input. However, in the given example, there is a crucial misunderstanding.

The first parameter of SendInput specifies the number of INPUT structures being passed in. In the original code, only one INPUT structure is defined, yet the function is being called with the parameter set to 2. This incorrect parameter count prevents any input from being sent.

Correcting the Approach

To send multiple characters using SendInput, you will need to create an array of INPUT structures. For each character, you will require two sets of structures, one for the keydown event and one for the keyup event. Therefore, to send two characters, you will need a total of four INPUT structures.

Alternatively, you can use the KEYEVENTF_UNICODE flag to send Unicode characters directly. However, be aware that for UTF-16 surrogate pairs, you will need to use two sets of keydown/keyup events to send the code units.

Example:

Here is a snippet that demonstrates how to send a string of Unicode characters using the KEYEVENTF_UNICODE flag:

<code class="cpp">#include <vector>
#include <string>

void SendUnicodeString(const std::wstring &str) {
    int length = str.length();
    std::vector<INPUT> input(length * 2);
    int index = 0;
    for (int i = 0; i < length; ++i) {
        WORD character = static_cast<WORD>(str[i]);
        input[index].type = INPUT_KEYBOARD;
        input[index].ki.wScan = character;
        input[index].ki.dwFlags = KEYEVENTF_UNICODE;
        ++index;
        input[index] = input[index - 1];
        input[index].ki.dwFlags |= KEYEVENTF_KEYUP;
        ++index;
    }
    SendInput(input.size(), &input[0], sizeof(INPUT));
}</code>

This code will send the specified Unicode string as keyboard input, taking into account UTF-16 surrogate pairs if necessary.

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