Beginner 4 sections ~15 min C++17/20

Flags

Flags are named boolean properties on every component. Use system flags to enable built-in behaviors, and custom manifest flags to track your own component state.

Introduction

What Are Flags?

Flags are named boolean properties on every ml::Core object. Two kinds exist: system flags (ml::Flag) managed automatically by the framework, and custom flags declared in your manifest. Both use the same five-method API.

ml::Flag — System Flags
Available on every ml::Core always
Set and cleared automatically by framework dispatchers
Control built-in behavior like dragging and focus
Example: ml::Flag::HOVERED, DRAGGABLE

Custom Flags — from Manifest

Declared in your manifest's Flag enum
Set and read by your application code
Great for: selected, disabled, highlighted, active
Example: MyManifest::Flag::Selected

1Core Concepts

System Flags — ml::Flag

Framework subsystems read and write these flags automatically. You can read them in draw() to adjust visual appearance, or write them to enable built-in behaviors.

Flag	Set by	Meaning
`ml::Flag::HOVERED`	HoverableDispatcher	Mouse cursor is currently over this component
`ml::Flag::CLICKED`	ClickableDispatcher	Mouse button is held down over this component
`ml::Flag::FOCUSED`	ClickableDispatcher	Component has keyboard focus
`ml::Flag::DRAGGING`	DraggableDispatcher	A drag gesture is currently in progress
`ml::Flag::DRAGGABLE`	User code	Enables mouse-drag handling — set this to allow dragging
`ml::Flag::HIDDEN`	User code	Conventionally marks a component as not visible
`ml::Flag::ENABLED`	User code	Marks a component as active and interactive
`ml::Flag::VERTICAL`	User code	Layout/scroll axis hint

    Reading system flags in draw()
    cpp
  

void MyWidget::draw(sf::RenderTarget& t, sf::RenderStates s) const
{
    // Highlight border on hover (HOVERED set automatically by framework)
    if (checkFlag(ml::Flag::HOVERED))
        _body.setOutlineColor(sf::Color(255, 255, 255, 100));
    else
        _body.setOutlineColor(sf::Color::Transparent);

    // Teal glow while dragging
    if (checkFlag(ml::Flag::DRAGGING))
        _body.setOutlineColor(sf::Color(93, 202, 165, 180));

    t.draw(_body, s);
}

// Enabling drag
myRect.setFlag(ml::Flag::DRAGGABLE);  // or: enableFlag(ml::Flag::DRAGGABLE)

2Core Concepts

Custom Flags — From Your Manifest

Declare a Flag enum in your manifest and every component that inherits ComponentWith<M> automatically gets a dedicated flag store for those values.

    Manifest with custom flags
    cpp
  

class CardManifest : public ml::Manifest
{
public:
    enum class Flag { Selected, Highlighted, Completed, Disabled };
    enum class State { Idle, Active, Done };
};

    Using custom flags in a component
    cpp
  

class TaskCard : public ml::ComponentWith
{
public:
    void select()
    {
        enableFlag(Flag::Selected);
        disableFlag(Flag::Highlighted);
    }

    void complete()
    {
        enableFlag(Flag::Completed);
        disableFlag(Flag::Selected);
        // Fade to 80% when done
        setFillOpacity(0.8f);
    }

    void draw(sf::RenderTarget& target, sf::RenderStates states) const override
    {
        // Custom flags drive visual appearance
        if (checkFlag(Flag::Selected))
            _body.setOutlineColor(sf::Color(124, 106, 247, 200));  // purple
        else if (checkFlag(Flag::Highlighted))
            _body.setOutlineColor(sf::Color(255, 255, 255, 60));   // white dim
        else
            _body.setOutlineColor(sf::Color::Transparent);

        // Grey out disabled components
        auto c = _body.getFillColor();
        c.a = checkFlag(Flag::Disabled) ? 80 : 255;
        _body.setFillColor(c);

        target.draw(_body, states);
    }
};

3Core Concepts

Flag API Reference

All five flag methods work identically for both system flags (ml::Flag) and custom manifest flags. The overload set automatically dispatches to the correct flag store.

Method	Description
`enableFlag(flag)`	Set this flag to `true`
`disableFlag(flag)`	Set this flag to `false`
`setFlag(flag, bool)`	Set to an explicit `true` or `false`
`toggleFlag(flag)`	Flip between `true` and `false`
`checkFlag(flag)`	Return `true` if set, `false` otherwise

    All flag operations
    cpp
  

// System flag
myCard.enableFlag(ml::Flag::DRAGGABLE);
myCard.setFlag(ml::Flag::HIDDEN, false);

// Custom flag
myCard.enableFlag(CardManifest::Flag::Selected);
myCard.disableFlag(CardManifest::Flag::Highlighted);
myCard.toggleFlag(CardManifest::Flag::Completed);

bool hovered  = myCard.checkFlag(ml::Flag::HOVERED);
bool selected = myCard.checkFlag(CardManifest::Flag::Selected);

Flags default to false — a flag that has never been set returns false from checkFlag(). You never need to initialize them.