Interact workflow

Interact workflow

In MuseScore 3, most of the interactions between the user and the model are done through commands. There is a list of shortcuts, actions are created from them (QActions), the action contains a command, when the action is triggered, the command pass to the main window (MuseScore), some commands are processed here, then pass to the current view (ScoreView), some commands are processed into the view, then pass to the model (libmscore), and there the rest of the teams are being processed.

In MuseScore 4, the main window (AppShell) defines only the UI structure of the application and does not contain any action handlers. Another feature, in MuseScore 4 there may be a model object (notation/libmscore), but the notation (score) view may not be loaded, for example, if we are working in the sequencer mode now, so the notation (score) cannot process actions, or several handlers of the same action may appear in different places, which leads to complexity and code duplication. For these reasons, in MuseScore 4, another workflow interaction

This architecture is very similar to Flux architecture

Example of sending and processing actions

Submit action

void NotationToolBarModel::click(const QString& action)
{
    dispatcher()->dispatch(actions::namefromQString(action));
}

Register handlers

NotationActionController::NotationActionController()
{
    dispatcher()->reg("note-input", this, &NotationActionController::toggleNoteInput);
    dispatcher()->reg("pad-note-4", [this]() { padNote(Pad::NOTE4); });
    ...
}

Handlers

void NotationActionController::toggleNoteInput()
{
    auto notation = currentNotation();
    if (!notation) {
        return;
    }

    if (notation->inputState()->isNoteEnterMode()) {
        notation->endNoteEntry();
    } else {
        notation->startNoteEntry();
    }
}

void NotationActionController::padNote(const Pad& pad)
{
    auto notation = currentNotation();
    if (!notation) {
        return;
    }

    notation->padNote(pad);
}

Send notifications

void Notation::startNoteEntry()
{
    ...
    m_inputStateChanged.notify();
}

void Notation::endNoteEntry()
{
    ...
    m_inputStateChanged.notify();
}

void Notation::padNote(const Pad& pad)
{
    ...
    m_inputStateChanged.notify();
}

Subscription and notification processing

void NotationToolBarModel::onNotationChanged()
{
    std::shared_ptr<INotation> notation = globalContext()->currentNotation();

    //! NOTE Unsubscribe from previous notation, if it was
    m_notationChanged.resetOnNotify(this);
    m_inputStateChanged.resetOnNotify(this);

    if (notation) {
        m_inputStateChanged = notation->inputStateChanged();
        m_inputStateChanged.onNotify(this, [this]() {
            updateState();
        });
    }

    updateState();
}

void NotationPaintView::open()
{
    ...
    m_notation->inputStateChanged().onNotify(this, [this]() {
        onInputStateChanged();
    });
}