widgetapi

type EventMeta struct {
	// Focused asserts whether the widget's container is focused at the time of the event.
	// If the event itself changes focus, the value here reflects the state of
	// the focus after the change.
	Focused bool
}

type KeyScope int

type Meta struct {
	// Focused asserts whether the widget's container is focused.
	Focused bool
}

type MouseScope int

type Options struct {
	// Ratio allows a widget to request a canvas whose size will always have
	// the specified ratio of width:height (Ratio.X:Ratio.Y).
	// The zero value i.e. image.Point{0, 0} indicates that the widget accepts
	// canvas of any ratio.
	Ratio image.Point

	// MinimumSize allows a widget to specify the smallest allowed canvas size.
	// If the terminal size and/or splits cause the assigned canvas to be
	// smaller than this, the widget will be skipped. I.e. The Draw() method
	// won't be called until a resize above the specified minimum.
	MinimumSize image.Point

	// MaximumSize allows a widget to specify the largest allowed canvas size.
	// If the terminal size and/or splits cause the assigned canvas to be larger
	// than this, the widget will only receive a canvas of this size within its
	// container. Setting any of the two coordinates to zero indicates
	// unlimited.
	MaximumSize image.Point

	// WantKeyboard allows a widget to request keyboard events and specify
	// their desired scope. If set to KeyScopeNone, no keyboard events are
	// forwarded to the widget.
	WantKeyboard KeyScope

	// ExclusiveKeyboardOnFocus allows a widget to request exclusive access to
	// keyboard events when its container is focused. When set to true, no
	// other widgets will receive any keyboard events that happen while the
	// container of this widget is focused even if they registered for
	// KeyScopeGlobal.
	ExclusiveKeyboardOnFocus bool

	// WantMouse allows a widget to request mouse events and specify their
	// desired scope. If set to MouseScopeNone, no mouse events are forwarded
	// to the widget.
	// Note that the widget is only able to see the position of the mouse event
	// if it falls onto its canvas. See the documentation next to individual
	// MouseScope values for details.
	WantMouse MouseScope
}

type Widget interface {
	// When the infrastructure calls Draw(), the widget must block on the call
	// until it finishes drawing onto the provided canvas. When given the
	// canvas, the widget must first determine its size by calling
	// Canvas.Size(), then limit all its drawing to this area.
	//
	// The widget must not assume that the size of the canvas or its content
	// remains the same between calls.
	//
	// The argument meta is guaranteed to be valid (i.e. non-nil).
	Draw(cvs *canvas.Canvas, meta *Meta) error

	// Keyboard is called with every keyboard event whose scope the widget
	// registered for.
	//
	// The argument meta is guaranteed to be valid (i.e. non-nil).
	Keyboard(k *terminalapi.Keyboard, meta *EventMeta) error

	// Mouse is called with every mouse event whose scope the widget registered
	// for.
	//
	// The argument meta is guaranteed to be valid (i.e. non-nil).
	Mouse(m *terminalapi.Mouse, meta *EventMeta) error

	// Options returns registration options for the widget.
	// This is how the widget indicates to the infrastructure whether it is
	// interested in keyboard or mouse shortcuts, what is its minimum canvas
	// size, etc.
	//
	// Most widgets will return statically compiled options (minimum and
	// maximum size, etc.). If the returned options depend on the runtime state
	// of the widget (e.g. the user data provided to the widget), the widget
	// must protect against a case where the infrastructure calls the Draw
	// method with a canvas that doesn't meet the requested options. This is
	// because the data in the widget might change between calls to Options and
	// Draw.
	Options() Options
}