Button

Generated from engine/ui/button.h at 862e08b. The text under each declaration is the header's own comment, word for word. About the reference says how these pages are made.

Browse the ui module

#include "engine/ui/button.h" · namespace labrador

class Button

class Button

A widget, what activating it means, and whether it may be reached.

The visual is a loan - whatever the game already draws, a label or an image - and the button owns the callable the game supplies. That split is the whole design: the engine knows which widget the player is on and when they pressed the button, and it knows nothing at all about what pressing it does.

The action is stored once, when the page is built. It is not on the frame path: nothing here is called per frame, only on the frame a player activates something, so the indirection std::function costs is paid once per press rather than per widget per frame - which is what a string-keyed if-chain compared every frame would cost.

Action

using Action = std::function<void()>;

Button

Button() = default;

Button

explicit Button(UiWidget* visual, Action on_activate = nullptr);

A button with no action is legal and is not a mistake: pages use focusable rows that change a value on left/right and do nothing on A. activate() on one of those is a no-op, not a throw.

Button · operator=

Button(const Button& other);
Button& operator=(const Button& other);
Button(Button&&) noexcept = default;
Button& operator=(Button&&) noexcept = default;

Copies copy the stored std::function into independent action storage. Captures and reference-wrapped objects retain their own copying, sharing, or borrowing semantics.

visual · has_action

UiWidget* visual() const;
bool has_action() const;

activate

bool activate() const;

Runs the action if there is one. Returns whether anything ran, so a caller can tell "nothing is bound here" from "something happened" without asking twice. The stored action remains alive until it returns, even if it removes this button or reallocates its FocusGroup. Mutable captures persist between calls; activation does not copy the callable. Each invocation retains ownership until return or exception. If the button has gone, the last active invocation destroys the callable (PHILOSOPHY T11's bounded ownership exception).

It does not consult enabled(). Whether a disabled entry may be activated is a question about a cursor, and a Button has none; the answer lives one level up, in FocusGroup::activate.

enabled · set_enabled

bool enabled() const;
void set_enabled(bool enabled);

Whether a cursor may land here. True on construction, because a row a page went to the trouble of registering is one it means to offer.

A disabled entry is registered and unreachable, which is a different thing from either of the two states around it. Not registering it at all loses the press - there is no way to be on the row, so there is nothing to refuse and nothing to explain - and registering it live means the walk lands on it. This is the third state, and it is separate from on_activate_ being null on purpose: a row with no action is one the player may sit on where A means nothing, which is most option rows.

Related types

Named in the public declarations above: UiWidget.

In the samples and tests

No sample or test includes this header directly.