pub trait View<T = ()>where
T: ?Sized,{
type State;
// Required methods
fn build(&mut self, cx: &mut BuildCx<'_, '_>, data: &mut T) -> Self::State;
fn rebuild(
&mut self,
state: &mut Self::State,
cx: &mut RebuildCx<'_, '_>,
data: &mut T,
old: &Self,
);
fn event(
&mut self,
state: &mut Self::State,
cx: &mut EventCx<'_, '_>,
data: &mut T,
event: &Event,
) -> bool;
fn layout(
&mut self,
state: &mut Self::State,
cx: &mut LayoutCx<'_, '_>,
data: &mut T,
space: Space,
) -> Size;
fn draw(
&mut self,
state: &mut Self::State,
cx: &mut DrawCx<'_, '_>,
data: &mut T,
);
}Expand description
A single UI component.
This trait is implemented by all UI components. The user interface is built
by composing these components into a view-tree. This operation should be
fast, as it is performed very often.
A view also has an associated state type, that is persistent across view-trees.
When calling View::build, the view will build it’s state. A view containing
another view must also store it’s child’s state. This is usually done by wrapping
it in a tuple (MyState, State).
In case a view contains another view the contents should always be wrapped in
either PodState or SeqState. If this is not done strange issues
are very likely to occur.
For information on styling see style.
View has four primary methods:
View::rebuildis called after a newview-treehas been built, on the new tree. The view can then compare itself to the old tree and update it’s state accordingly. When a view differs from the old tree, it should callRebuildCx::layoutorRebuildCx::drawwhen applicable. This can be quite tedius to write out, so theRebuildderive macro can be used to generate this code.View::eventis called when an event occurs. The should then handle the event and return whether it handled it. Command events can be send usingBaseCx::cmd.View::layoutis called when the view needs to be laid out. A leaf view should compute it’s own size in accordance with the givenSpace, and return it. A container view should pass an appropriateSpaceto it’s contents and the compute it’s own size based on the contents’ size(s).View::drawis called when the view needs to be drawn.
For examples see the implementation of views like Button or Checkbox.
Required Associated Types§
Required Methods§
Sourcefn build(&mut self, cx: &mut BuildCx<'_, '_>, data: &mut T) -> Self::State
fn build(&mut self, cx: &mut BuildCx<'_, '_>, data: &mut T) -> Self::State
Build the view state, see top-level documentation for more information.
Sourcefn rebuild(
&mut self,
state: &mut Self::State,
cx: &mut RebuildCx<'_, '_>,
data: &mut T,
old: &Self,
)
fn rebuild( &mut self, state: &mut Self::State, cx: &mut RebuildCx<'_, '_>, data: &mut T, old: &Self, )
Rebuild the view state, see top-level documentation for more information.
Sourcefn event(
&mut self,
state: &mut Self::State,
cx: &mut EventCx<'_, '_>,
data: &mut T,
event: &Event,
) -> bool
fn event( &mut self, state: &mut Self::State, cx: &mut EventCx<'_, '_>, data: &mut T, event: &Event, ) -> bool
Handle an event, see top-level documentation for more information.
Dyn Compatibility§
This trait is not dyn compatible.
In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.