emscripten_request_pointerlock() returns EMSCRIPTEN_RESULT_UNKNOWN_TARGET

I have made an example (I have attached it) that calls `emscripten_request_pointerlock("screen", false);` by mouse click:

void mousePressEvent(QMouseEvent *event) override
{
    EMSCRIPTEN_RESULT result = emscripten_request_pointerlock("screen", false);
    qDebug() << result;
}

It prints -4 to the console that means `EMSCRIPTEN_RESULT_UNKNOWN_TARGET`. I use `screen` because Qt's generated .html file has this element `<div id="screen"></div>`.

I have tried to use `EMSCRIPTEN_EVENT_TARGET_DOCUMENT` instead of `screen` but it returns -1 (it means `EMSCRIPTEN_RESULT_NOT_SUPPORTED`):

EMSCRIPTEN_RESULT result = emscripten_request_pointerlock(
            EMSCRIPTEN_EVENT_TARGET_DOCUMENT, false);
qDebug() << result;

Topic: https://forum.qt.io/topic/157324/emscripten_request_pointerlock-returns-emscripten_result_unknown_target