Virtual keyboard or onscreen keyboard for QtWidgets applications?

Question

I'm going to deploy the qtvirtualkeyboard in my widget-based application like so:

#include <QtWidgets>

int main(int argc, char *argv[]) {
    qputenv("QT_IM_MODULE", QByteArray("qtvirtualkeyboard"));
    QApplication app(argc, argv);
    QMainWindow window;
    QLineEdit input(&window);
    input.move(250, 250);
    window.show();
    return app.exec();
}

But the only issue is that the virtual keyboard input panel hides the underlying widgets and cover them!

How should I achieve this?

Is there any document or solution for widgets-based applications?

Answer 1

Finally got the solution!

You just need to call QGuiApplication::inputMethod() to get the application-wide Qt input method and then call QInputMethod::keyboardRectangle() and QInputMethod::isVisible() to get input method properties then remain a calculation based on your widget position and keyboard coordinate, here is a full-working sample to share:

lineedit.h:

class LineEdit :public QLineEdit {
    Q_OBJECT

public:
    LineEdit(QWidget *parent = nullptr);
    LineEdit(const QString&, QWidget *parent = nullptr);

protected:
    bool event(QEvent*) override;

private:
    bool _moved = false;
    int _lastDiff = 0;
};

lineedit.cpp:

LineEdit::LineEdit(QWidget *parent) :QLineEdit(parent) {
    setAttribute(Qt::WA_InputMethodEnabled, true);
    setInputMethodHints(inputMethodHints() | Qt::InputMethodHint::ImhDigitsOnly);
}

LineEdit::LineEdit(const QString& txt, QWidget *parent) : QLineEdit(txt, parent) {
    setAttribute(Qt::WA_InputMethodEnabled, true);
    setInputMethodHints(inputMethodHints() | Qt::InputMethodHint::ImhDigitsOnly);
}

bool LineEdit::event(QEvent* e) {
    const auto keyboard_rect = QGuiApplication::inputMethod()->keyboardRectangle();
    const auto keyboard_visible = QGuiApplication::inputMethod()->isVisible();
    const auto global_y = QWidget::mapToGlobal(rect().topLeft()).y() + height();
    const auto k_global_y = keyboard_rect.topLeft().y();
    const auto diff = k_global_y - global_y;
    const auto need_to_move = diff < 0;

    /* move main widget */
    if (keyboard_visible && !_moved && need_to_move) {
        _moved = true;
        _lastDiff = diff;
        const auto g = parentWidget()->frameGeometry();
        parentWidget()->move(g.x(), g.y() - qAbs(_lastDiff));
    }
    /* roll back */
    if (!keyboard_visible && _moved) {
        _moved = false;
        const auto g = parentWidget()->frameGeometry();
        parentWidget()->move(g.x(), g.y() + qAbs(_lastDiff));
    }
    return QLineEdit::event(e);
}

main.cpp:

#include <QtWidgets>

#define W 1024
#define H 768

int main(int argc, char *argv[]) {
    qputenv("QT_IM_MODULE", QByteArray("qtvirtualkeyboard"));
    QApplication app(argc, argv);

    QMainWindow window(nullptr, Qt::FramelessWindowHint);

    LineEdit lineedit1(&window);
    lineedit1.move(100, 450);

    LineEdit lineedit2(&window);
    lineedit2.move(100, 100);

    window.resize(W, H);
    window.show();
    return app.exec();
}

results: