Struct druid::UpdateCtx

pub struct UpdateCtx<'a, 'b> { /* fields omitted */ }

A mutable context provided to data update methods of widgets.

Widgets should call request_paint whenever a data change causes a change in the widget's appearance, to schedule a repaint.

Implementations

impl UpdateCtx<'_, '_>

pub fn widget_id(&self) -> WidgetId

get the WidgetId of the current widget.

pub fn window(&self) -> &WindowHandle

Returns a reference to the current WindowHandle.

pub fn window_id(&self) -> WindowId

Get the WindowId of the current window.

pub fn text(&mut self) -> &mut PietText

Get an object which can create text layouts.

impl UpdateCtx<'_, '_>

pub fn size(&self) -> Size

The layout size.

This is the layout size as ultimately determined by the parent container, on the previous layout pass.

Generally it will be the same as the size returned by the child widget's layout method.

pub fn is_hot(&self) -> bool

The "hot" (aka hover) status of a widget.

A widget is "hot" when the mouse is hovered over it. Widgets will often change their appearance as a visual indication that they will respond to mouse interaction.

The hot status is computed from the widget's layout rect. In a container hierarchy, all widgets with layout rects containing the mouse position have hot status.

Discussion: there is currently some confusion about whether a widget can be considered hot when some other widget is active (for example, when clicking to one widget and dragging to the next). The documentation should clearly state the resolution.

pub fn is_active(&self) -> bool

The active status of a widget.

Active status generally corresponds to a mouse button down. Widgets with behavior similar to a button will call set_active on mouse down and then up.

When a widget is active, it gets mouse events even when the mouse is dragged away.

pub fn is_focused(&self) -> bool

The focus status of a widget.

Returns true if this specific widget is focused. To check if any descendants are focused use has_focus.

Focus means that the widget receives keyboard events.

A widget can request focus using the request_focus method. It's also possible to register for automatic focus via register_for_focus.

If a widget gains or loses focus it will get a LifeCycle::FocusChanged event.

Only one widget at a time is focused. However due to the way events are routed, all ancestors of that widget will also receive keyboard events.

pub fn has_focus(&self) -> bool

The (tree) focus status of a widget.

Returns true if either this specific widget or any one of its descendants is focused. To check if only this specific widget is focused use is_focused,

impl UpdateCtx<'_, '_>

pub fn set_cursor(&mut self, cursor: &Cursor)

Set the cursor icon.

This setting will be retained until clear_cursor is called, but it will only take effect when this widget is either hot or active. If a child widget also sets a cursor, the child widget's cursor will take precedence. (If that isn't what you want, use override_cursor instead.)

pub fn override_cursor(&mut self, cursor: &Cursor)

Override the cursor icon.

This setting will be retained until clear_cursor is called, but it will only take effect when this widget is either hot or active. This will override the cursor preferences of a child widget. (If that isn't what you want, use set_cursor instead.)

pub fn clear_cursor(&mut self)

Clear the cursor icon.

This undoes the effect of set_cursor and override_cursor.

impl UpdateCtx<'_, '_>

pub fn request_paint(&mut self)

Request a paint pass. This is equivalent to calling request_paint_rect for the widget's paint_rect.

pub fn request_paint_rect(&mut self, rect: Rect)

Request a paint pass for redrawing a rectangle, which is given relative to our layout rectangle.

pub fn request_layout(&mut self)

Request a layout pass.

A Widget's layout method is always called when the widget tree changes, or the window is resized.

If your widget would like to have layout called at any other time, (such as if it would like to change the layout of children in response to some event) it must call this method.

pub fn request_anim_frame(&mut self)

Request an animation frame.

pub fn children_changed(&mut self)

Indicate that your children have changed.

Widgets must call this method after adding a new child.

pub fn set_menu<T: Any>(&mut self, menu: MenuDesc<T>)

Set the menu of the window containing the current widget. T must be the application's root Data type (the type provided to AppLauncher::launch).

impl UpdateCtx<'_, '_>

pub fn submit_command(&mut self, cmd: impl Into<Command>)

Submit a Command to be run after this event is handled.

Commands are run in the order they are submitted; all commands submitted during the handling of an event are executed before the update method is called; events submitted during update are handled after painting.

Target::Auto commands will be sent to the window containing the widget.

pub fn get_external_handle(&self) -> ExtEventSink

Returns an ExtEventSink that can be moved between threads, and can be used to submit commands back to the application.

pub fn request_timer(&mut self, deadline: Duration) -> TimerToken

Request a timer event.

The return value is a token, which can be used to associate the request with the event.

impl UpdateCtx<'_, '_>

pub fn has_requested_update(&mut self) -> bool

Returns true if this widget or a descendent as explicitly requested an update call.

This should only be needed in advanced cases; see EventCtx::request_update for more information.

pub fn env_changed(&self) -> bool

Returns true if the current Env has changed since the previous update call.

pub fn env_key_changed<T>(&self, key: &impl KeyLike<T>) -> bool

Returns true if the given key has changed since the last update call.

The argument can be anything that is resolveable from the Env, such as a Key or a KeyOrValue.