Module kas_widgets::view

View widgets and shared data

So called “view widgets” allow separation of data and view. The system has some similarities with the Model-View-Controller (MVC) pattern, but with different separations of responsibility. Perhaps we should instead call the pattern Model-View-Driver?

Shared data and model

Shared data must implement several traits, namely those in kas::updatable and one of the “view” traits: SingleData, ListData or MatrixData. These traits together form the “model”.

For simpler cases it is not always necessary to implement your own shared data type, for example SharedRc<i32> implements SingleData and &'static [&'static str] implements ListData. The SharedRc type provides the UpdateHandle required to synchronise views.

Adapters

• FilteredList presents a filtered list over a ListData

View widgets and drivers

Standard widgets may be used to view data items, but to construct these a driver is required. These implement the Driver trait which constructs widgets from data items and optionally also the reverse binding.

The user may implement a Driver or may use a standard one:

• driver::Default constructs a default view widget over various data types
• driver::DefaultNav is a variant of the above, ensuring items support keyboard navigation (e.g. useful to allow selection of static items)
• driver::CheckBox and driver::RadioBox support the bool type
• driver::Slider constructs a slider with a fixed range

In MVC terminology, the driver is perhaps most similar to the controller, while the widgets constructed by the driver are the view, but this analogy is not quite accurate.

Views

Something else is required to construct one or more view widgets over the data model as well as to perform event handling (at a minimum, forwarding events to the appropriate view widgets), and that thing is here referred to as the view (MVC terminology, it is part view and part controller, while not being the whole of either).

These views are widgets and provide additional services:

• updating view widgets when the model is changed
• notifying other users of the data when view widgets update the data
• ideally allowing O(v) performance where v is the number of visible data items, thus allowing good scaling to large data sets (this depends on the performance of the model)
• supporting scrolling (see super::Scrollable)
• supporting item selection
• controlling scrolling and selection via otherwise unhandled events

The following views are provided:

• SingleView creates a view over a SingleData object (no scrolling or selection support)
• ListView creates a scrollable list view over a ListData object

Re-exports

pub use driver::Driver;

Modules

driver

View drivers

Structs

ListView

List view widget

MatrixView

Matrix view widget

SingleView

Single view widget

Enums

SelectionError

Selection errors

SelectionMode

Selection mode used by ListView