Event: Events

In termr: Modern Reactive Terminal Applications with Data Workflows

Events

Description

Everything that happens in a termr application is an event: key presses, terminal resizes, focus changes, widgets being mounted, and messages that widgets send (such as "button.pressed").

Events are delivered to their target widget and, if they bubble, to each ancestor in turn and finally to the App. Any handler can call event$stop() to stop propagation.

Event types and their classes:

• "key": KeyEvent with fields key, char, ctrl, alt, shift;

• "resize": ResizeEvent with width and height;

• "paste": PasteEvent with the pasted text (bracketed paste);

• "focus" / "blur": FocusEvent / BlurEvent (do not bubble);

• "mount" / "unmount": MountEvent / UnmountEvent (do not bubble);

• any other name: MessageEvent, created by widget$post_message().

Public fields

type

Event type, e.g. "key" or "button.pressed".

sender

The widget that created the event (or NULL).

target

The widget the event is delivered to first.

current

The widget currently handling the event.

data

A list of event-specific values.

bubbles

Is the event passed on to ancestors?

time

Creation time (seconds, monotonic).

Active bindings

stopped

Has propagation been stopped?

default_prevented

Was prevent_default() called?

Methods

Public methods

• Event$new()

• Event$stop()

• Event$prevent_default()

• Event$format()

• Event$print()

• Event$clone()

---

Event$new()

Create an event.

Usage

Event$new(type, sender = NULL, data = list(), bubbles = TRUE)

Arguments

type

Event type.

sender

Sending widget.

data

List of values.

bubbles

Does the event bubble?

---

Event$stop()

Stop the event from reaching further handlers.

Usage

Event$stop()

---

Event$prevent_default()

Ask the sender not to perform its default behaviour.

Usage

Event$prevent_default()

---

Event$format()

One-line description.

Usage

Event$format(...)

Arguments

...

Ignored.

---

Event$print()

Print the event.

Usage

Event$print(...)

Arguments

...

Ignored.

---

Event$clone()

The objects of this class are cloneable with this method.

Usage

Event$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Super class

Event -> KeyEvent

Public fields

key

Canonical key name, e.g. "a", "enter", "ctrl+c".

char

The printable character, or "".

ctrl, alt, shift

Modifier flags.

Methods

Public methods

• KeyEvent$new()

• KeyEvent$is_printable()

• KeyEvent$clone()

Inherited methods

• Event$format()
• Event$prevent_default()
• Event$print()
• Event$stop()

---

KeyEvent$new()

Create a key event.

Usage

KeyEvent$new(key, char = NULL)

Arguments

key

Key name (normalised).

char

Printable character, if any.

---

KeyEvent$is_printable()

Is this a printable character without ctrl/alt?

Usage

KeyEvent$is_printable()

---

KeyEvent$clone()

The objects of this class are cloneable with this method.

Usage

KeyEvent$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Super class

Event -> ResizeEvent

Public fields

width, height

New terminal size.

Methods

Public methods

• ResizeEvent$new()

• ResizeEvent$clone()

Inherited methods

• Event$format()
• Event$prevent_default()
• Event$print()
• Event$stop()

---

ResizeEvent$new()

Create a resize event.

Usage

ResizeEvent$new(width, height)

Arguments

width, height

Terminal size.

---

ResizeEvent$clone()

The objects of this class are cloneable with this method.

Usage

ResizeEvent$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Super class

Event -> PasteEvent

Public fields

text

The pasted text, normalised: line breaks are LF, tabs are kept and other control characters are removed.

Methods

Public methods

• PasteEvent$new()

• PasteEvent$clone()

Inherited methods

• Event$format()
• Event$prevent_default()
• Event$print()
• Event$stop()

---

PasteEvent$new()

Create a paste event.

Usage

PasteEvent$new(text)

Arguments

text

Pasted text.

---

PasteEvent$clone()

The objects of this class are cloneable with this method.

Usage

PasteEvent$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Super class

Event -> FocusEvent

Methods

Public methods

• FocusEvent$new()

• FocusEvent$clone()

Inherited methods

• Event$format()
• Event$prevent_default()
• Event$print()
• Event$stop()

---

FocusEvent$new()

Create a focus event.

Usage

FocusEvent$new(widget)

Arguments

widget

The widget that received focus.

---

FocusEvent$clone()

The objects of this class are cloneable with this method.

Usage

FocusEvent$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Super class

Event -> BlurEvent

Methods

Public methods

• BlurEvent$new()

• BlurEvent$clone()

Inherited methods

• Event$format()
• Event$prevent_default()
• Event$print()
• Event$stop()

---

BlurEvent$new()

Create a blur event.

Usage

BlurEvent$new(widget)

Arguments

widget

The widget that lost focus.

---

BlurEvent$clone()

The objects of this class are cloneable with this method.

Usage

BlurEvent$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Super class

Event -> MountEvent

Methods

Public methods

• MountEvent$new()

• MountEvent$clone()

Inherited methods

• Event$format()
• Event$prevent_default()
• Event$print()
• Event$stop()

---

MountEvent$new()

Create a mount event.

Usage

MountEvent$new(widget)

Arguments

widget

The mounted widget.

---

MountEvent$clone()

The objects of this class are cloneable with this method.

Usage

MountEvent$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Super class

Event -> UnmountEvent

Methods

Public methods

• UnmountEvent$new()

• UnmountEvent$clone()

Inherited methods

• Event$format()
• Event$prevent_default()
• Event$print()
• Event$stop()

---

UnmountEvent$new()

Create an unmount event.

Usage

UnmountEvent$new(widget)

Arguments

widget

The removed widget.

---

UnmountEvent$clone()

The objects of this class are cloneable with this method.

Usage

UnmountEvent$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Super class

Event -> MessageEvent

Methods

Public methods

• MessageEvent$new()

• MessageEvent$clone()

Inherited methods

• Event$format()
• Event$prevent_default()
• Event$print()
• Event$stop()

---

MessageEvent$new()

Create a custom message.

Usage

MessageEvent$new(type, sender = NULL, data = list(), bubbles = TRUE)

Arguments

type

Message name, e.g. "counter.changed".

sender

Sending widget.

data

List of values.

bubbles

Does the message bubble?

---

MessageEvent$clone()

The objects of this class are cloneable with this method.

Usage

MessageEvent$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Super class

Event -> MouseEvent

Public fields

action

"down", "up", "move", "scroll" or "click".

button

"left", "middle", "right" or "none".

direction

Wheel direction for scroll events, else NA.

screen_x, screen_y

Pointer position on the screen (1-based).

x, y

Pointer position inside the target widget (1-based, relative to the widget's region).

origin_x, origin_y

Where the button went down (screen coordinates) for ⁠drag.*⁠ events, else NA.

shift, ctrl, alt

Modifier flags.

Methods

Public methods

• MouseEvent$new()

• MouseEvent$offset_in()

• MouseEvent$clone()

Inherited methods

• Event$format()
• Event$prevent_default()
• Event$print()
• Event$stop()

---

MouseEvent$new()

Create a mouse event.

Usage

MouseEvent$new(
  action,
  screen_x,
  screen_y,
  button = "none",
  direction = NA_character_,
  shift = FALSE,
  ctrl = FALSE,
  alt = FALSE
)

Arguments

action

Event action.

screen_x, screen_y

Screen position.

button

Button name.

direction

Wheel direction (scroll events).

shift, ctrl, alt

Modifiers.

---

MouseEvent$offset_in()

The pointer position relative to another widget.

Usage

MouseEvent$offset_in(widget)

Arguments

widget

A widget with a region.

Returns

c(x =, y =), 1-based; may be outside the widget.

---

MouseEvent$clone()

The objects of this class are cloneable with this method.

Usage

MouseEvent$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

termr documentation built on Oct. 21, 2026, 5:13 p.m.