primitive.go

package tview

import "github.com/gdamore/tcell/v2"

// Primitive is the top-most interface for all graphical primitives.
type Primitive interface {
	// Draw draws this primitive onto the screen. Implementers can call the
	// screen's ShowCursor() function but should only do so when they have focus.
	// (They will need to keep track of this themselves.)
	Draw(screen tcell.Screen)

	// GetRect returns the current position of the primitive, x, y, width, and
	// height.
	GetRect() (int, int, int, int)

	// SetRect sets a new position of the primitive.
	SetRect(x, y, width, height int)

	// InputHandler returns a handler which receives key events when it has focus.
	// It is called by the Application class.
	//
	// A value of nil may also be returned, in which case this primitive cannot
	// receive focus and will not process any key events.
	//
	// The handler will receive the key event and a function that allows it to
	// set the focus to a different primitive, so that future key events are sent
	// to that primitive.
	//
	// The Application's Draw() function will be called automatically after the
	// handler returns.
	//
	// The Box class provides functionality to intercept keyboard input. If you
	// subclass from Box, it is recommended that you wrap your handler using
	// Box.WrapInputHandler() so you inherit that functionality.
	InputHandler() func(event *tcell.EventKey, setFocus func(p Primitive))

	// Focus is called by the application when the primitive receives focus.
	// Implementers may call delegate() to pass the focus on to another
	// primitive which is usually a child primitive. This is not called on
	// parents of the primitive that receives focus.
	Focus(delegate func(p Primitive))

	// HasFocus determines if the primitive (or any of its child primitives) has
	// focus.
	HasFocus() bool

	// Blur is called by the application when the primitive loses focus. This is
	// not called on parents of the primitive that loses focus.
	Blur()

	// MouseHandler returns a handler which receives mouse events.
	// It is called by the Application class.
	//
	// A value of nil may also be returned to stop the downward propagation of
	// mouse events.
	//
	// The Box class provides functionality to intercept mouse events. If you
	// subclass from Box, it is recommended that you wrap your handler using
	// Box.WrapMouseHandler() so you inherit that functionality.
	MouseHandler() func(action MouseAction, event *tcell.EventMouse, setFocus func(p Primitive)) (consumed bool, capture Primitive)

	// PasteHandler returns a handler which receives pasted text.
	// It is called by the Application class.
	//
	// A value of nil may also be returned to stop the downward propagation of
	// paste events.
	//
	// The Box class may provide functionality to intercept paste events in the
	// future. If you subclass from [Box], it is recommended that you wrap your
	// handler using Box.WrapPasteHandler() so you inherit that functionality.
	PasteHandler() func(text string, setFocus func(p Primitive))

	// focusChain adds the chain of primitives that have focus to the given
	// slice, starting with the bottom-most primitive that has focus and ending
	// with this box. If this box or none of its descendents has focus, the
	// slice is not modified. If chain is nil, no chain is added. Returns
	// whether or not this box or one of its descendents has focus.
	focusChain(chain *[]Primitive) bool

	// focused is called when the current input focus changes. It is called on
	// the primitive which newly received focus as well as on all of its
	// ancestors (in no defined order). The default implementation in [Box]
	// invokes the callback set with [Box.SetFocusFunc]. This can also happen
	// when the focus is set to the primitive that already has focus.
	focused()

	// blurred is called when the current input focus changes. It is called on
	// the primitive which lost focus as well as on all of its ancestors (in no
	// defined order). The default implementation in [Box] invokes the callback
	// set with [Box.SetBlurFunc]. This can also happen when the focus is set to
	// the primitive that already has focus.
	blurred()
}