keyemitter.cpp

#include "keyemitter.h"

#include <vector>
#include <windows.h>

KeyEmitter::KeyEmitter(QObject *parent)
    : QObject(parent) {}

void KeyEmitter::reset() {
    lastText.clear();
}

void KeyEmitter::applyText(const QString &text) {
    if (text == lastText)
        return;

    int prefix = 0;
    const int minLen = qMin(text.size(), lastText.size());
    while (prefix < minLen && text.at(prefix) == lastText.at(prefix))
        ++prefix;

    const int toDelete = lastText.size() - prefix;
    if (toDelete > 0)
        sendBackspace(toDelete);

    const QString toAdd = text.mid(prefix);
    if (!toAdd.isEmpty())
        sendUnicodeText(toAdd);

    lastText = text;
}

void KeyEmitter::appendText(const QString &text) {
    if (text.isEmpty())
        return;

    sendUnicodeText(text);
    lastText += text;
}

void KeyEmitter::sendBackspace(int count) {
    if (count <= 0)
        return;

    // Batch all backspace key events into a single SendInput call
    std::vector<INPUT> inputs(static_cast<size_t>(count) * 2, INPUT{});
    for (int i = 0; i < count; ++i) {
        const size_t idx = static_cast<size_t>(i) * 2;
        inputs[idx].type = INPUT_KEYBOARD;
        inputs[idx].ki.wVk = VK_BACK;
        inputs[idx + 1].type = INPUT_KEYBOARD;
        inputs[idx + 1].ki.wVk = VK_BACK;
        inputs[idx + 1].ki.dwFlags = KEYEVENTF_KEYUP;
    }
    SendInput(static_cast<UINT>(inputs.size()), inputs.data(), sizeof(INPUT));
}

void KeyEmitter::sendUnicodeText(const QString &text) {
    if (text.isEmpty())
        return;

    // Batch all character key events into a single SendInput call
    std::vector<INPUT> inputs(static_cast<size_t>(text.size()) * 2, INPUT{});
    for (int i = 0; i < text.size(); ++i) {
        const size_t idx = static_cast<size_t>(i) * 2;
        const ushort unicode = text.at(i).unicode();
        inputs[idx].type = INPUT_KEYBOARD;
        inputs[idx].ki.wScan = unicode;
        inputs[idx].ki.dwFlags = KEYEVENTF_UNICODE;
        inputs[idx + 1].type = INPUT_KEYBOARD;
        inputs[idx + 1].ki.wScan = unicode;
        inputs[idx + 1].ki.dwFlags = KEYEVENTF_UNICODE | KEYEVENTF_KEYUP;
    }
    SendInput(static_cast<UINT>(inputs.size()), inputs.data(), sizeof(INPUT));
}