Struct EventState 

pub struct EventState { /* private fields */ }

Event context state

This struct encapsulates window-specific event-handling state and handling. Most operations are only available via a EventCx handle, though some are available on this struct.

Besides event handling, this struct also configures widgets.

Some methods are intended only for usage by graphics and platform backends and are hidden from generated documentation unless the internal_doc feature is enabled. Event handling assumes winit.

Implementations

impl EventState

pub fn has_input_focus(&self, w_id: &Id) -> Option<bool>

Get whether this widget has input focus

Return values:

• None if the widget does not have selection focus
• Some(false) if the widget has selection focus but not keyboard or IME focus
• Some(true) if the widget has keyboard and/or IME focus

pub fn modifiers(&self) -> ModifiersState

Get the current modifier state

pub fn set_ime_cursor_area(&mut self, target: &Id, rect: Rect)

Set IME cursor area

This should be called after receiving Event::Ime(Ime::Enabled), and any time that the rect parameter changes, until Event::Ime(Ime::Disabled) is received.

This sets the text cursor’s area, rect, relative to the widget’s own coordinate space. If never called, then the widget’s whole rect is used.

This does nothing if target does not have IME-enabled input focus.

pub fn cancel_ime_focus(&mut self, target: &Id)

Explicitly clear Input Method Editor focus on target

This method may be used to disable IME focus while retaining selection focus. IME focus is lost automatically when selection focus is lost.

impl EventState

pub fn has_nav_focus(&self, w_id: &Id) -> bool

Get whether this widget has navigation focus

pub fn nav_focus(&self) -> Option<&Id>

Get the current navigation focus, if any

This is the widget selected by navigating the UI with the Tab key.

Note: changing navigation focus (e.g. via EventCx::clear_nav_focus, EventCx::request_nav_focus or EventCx::next_nav_focus) does not immediately affect the result of this method.

impl EventState

Mouse and touch methods

pub fn is_depressed(&self, w_id: &Id) -> bool

Check whether the given widget is visually depressed

pub fn is_under_mouse(&self, w_id: &Id) -> bool

Get whether the widget is under the mouse pointer

pub fn any_grab_on(&self, id: &Id) -> bool

Returns true if there is a mouse or touch grab on id or any descendant of id

pub fn press_velocity(&self, source: PressSource) -> Option<Vec2>

Get velocity of the mouse pointer or a touch

The velocity is calculated at the time this method is called using existing samples of motion.

Where the source is a mouse this always succeeds. For touch events this requires an active grab and is not guaranteed to succeed; currently only a limited number of presses with mode GrabMode::Grab are tracked for velocity.

impl EventState

pub fn send<M: Debug + 'static>(&mut self, id: Id, msg: M)

Send a message to id

When calling this method, be aware that some widgets use an inner component to handle events, thus calling with the outer widget’s id may not have the desired effect. Tile::try_probe and EventCx::next_nav_focus are usually able to find the appropriate event-handling target.

This uses a tree traversal as with event handling, thus ancestors will have a chance to handle an unhandled event and any messages on the stack after their child.

Special cases sent as an Event

When M is Command, this will send Event::Command to the widget.

When M is ScrollDelta, this will send Event::Scroll to the widget.

Other messages

The message is pushed to the message stack. The target widget may pop or peek the message from Events::handle_messages.

Send target

The target id may be under another window. In this case, sending may be delayed slightly.

If id = Id::default() and a send target has been assigned for M, then msg will be sent to that target.

If id identifies a widget, that widget must be configured but does not need to be sized.

If id does not resolve a widget, the message is dropped with only a DEBUG log message of the form _replay: $WIDGET cannot find path to $ID. This is not considered an error since it happens frequently (e.g. any widget using asynchronous loading sends itself a message; if the view changes before loading completes then that widget may no longer be accessible or no longer exist).

Ordering and failure

Messages sent via send and send_erased should be received in the same order sent relative to other messages sent from the same window via these methods.

Message delivery may fail for widgets not currently visible. This is dependent on widgets implementation of Widget::child_node (e.g. in the case of virtual scrolling, the target may have scrolled out of range).

pub fn send_erased(&mut self, id: Id, msg: Erased)

Push a type-erased message to the stack

This is a lower-level variant of Self::send.

pub fn send_async<Fut, M>(&mut self, id: Id, fut: Fut)

where Fut: IntoFuture<Output = M> + 'static, M: Debug + 'static,

Send a message to id via a Future

The future is polled after event handling and after drawing and is able to wake the event loop. This future is executed on the main thread; for high-CPU tasks use Self::send_spawn instead.

The future must resolve to a message on completion. Its message is then sent to id via stack traversal identically to Self::send.

Cancellation, ordering and failure

Futures passed to these methods should only be cancelled if they fail to complete before the window is closed, and even in this case will be polled at least once.

Messages sent via send_async, send_async_erased and send_spawn may be received in any order.

Message delivery may fail for widgets not currently visible. This is dependent on widgets implementation of Widget::child_node (e.g. in the case of virtual scrolling, the target may have scrolled out of range).

pub fn send_async_erased<Fut>(&mut self, id: Id, fut: Fut)

where Fut: IntoFuture<Output = Erased> + 'static,

Send a type-erased message to id via a Future

This is a low-level variant of Self::send_async.

pub fn send_spawn<Fut, M>(&mut self, id: Id, fut: Fut)

where Fut: IntoFuture<Output = M> + 'static, Fut::IntoFuture: Send, M: Debug + Send + 'static,

Available on crate feature spawn only.

Spawn a task, run on a thread pool

The future is spawned to a thread-pool before the event-handling loop sleeps, and is able to wake the loop on completion. Tasks involving significant CPU work should use this method over Self::send_async.

This method is simply a wrapper around async_global_executor::spawn and Self::send_async; if a different multi-threaded executor is available, that may be used instead. See also async_global_executor documentation of configuration.

impl EventState

pub fn request_timer(&mut self, id: Id, handle: TimerHandle, delay: Duration)

Schedule a timed update

Widget updates may be used for delayed action. For animation, prefer to use Draw::animate or Self::request_frame_timer.

Widget id will receive Event::Timer with this handle at approximately time = now + delay (or possibly a little later due to frame-rate limiters and processing time).

Requesting an update with delay == 0 is valid, except from an Event::Timer handler (where it may cause an infinite loop).

Multiple timer requests with the same id and handle are merged (see TimerHandle documentation).

pub fn request_frame_timer(&mut self, id: Id, handle: TimerHandle)

Schedule a frame timer update

Widget id will receive Event::Timer with this handle either before or soon after the next frame is drawn.

This may be useful for animations which mutate widget state. Animations which don’t mutate widget state may use Draw::animate instead.

It is expected that handle.earliest() == true (style guide).

impl EventState

pub fn platform(&self) -> Platform

Get the platform

pub fn window_has_focus(&self) -> bool

True when the window has focus

impl EventState

pub fn is_disabled(&self, w_id: &Id) -> bool

Check whether a widget is disabled

A widget is disabled if any ancestor is.

pub fn config(&self) -> &WindowConfig

Access configuration data

All widgets will be reconfigured if configuration data changes.

pub fn config_enable_pan(&self, source: PressSource) -> bool

Is mouse panning enabled?

pub fn config_enable_mouse_text_pan(&self) -> bool

Is mouse text panning enabled?

pub fn config_test_pan_thresh(&self, dist: Offset) -> bool

Test pan threshold against config, adjusted for scale factor

Returns true when dist is large enough to switch to pan mode.

pub fn redraw(&mut self, id: impl HasId)

Notify that a widget must be redrawn

This method is designed to support partial redraws though these are not currently implemented. See also Self::action_redraw.

pub fn region_moved(&mut self)

Notify that widgets under self may have moved

This updates the widget(s) under mouse and touch events.

pub fn close_own_window(&mut self)

Request that the window be closed

pub fn action_moved(&mut self, action: impl Into<Option<ActionMoved>>)

Notify of an ActionMoved or Option<ActionMoved>

pub fn action_redraw(&mut self, action: impl Into<Option<ActionRedraw>>)

Notify of an ActionRedraw or Option<ActionRedraw>

This will force a redraw of the whole window. See also Self::redraw.