Neptune 3 UI - Application Architecture
Neptune 3 uses a common architecture for all applications. The architecture approach is called Core UI Architecture.
In general, Neptune 3 differentiates between UI primitives (e.g. rectangles and images) and controls (e.g. buttons) as individual UI types. To combine several UI types, panels or views are being used. These are specific container types to layout other containers as child UI types or controls. UI primitives are only used inside controls, as the controls have supports for styling the UI. The difference between a panel and a view is that the view interfaces with the stores (the business layer of the application).
An application is usually designed around a specific context, hence, it often uses a particular area of the service API and it can also depend on common services to be aware of the overall system state. The aim of the Core UI Architecture is to avoid having such service dependencies end up directly into the UI but they should be wrapped as a Store entity. The Store is the only entity that is allowed to talk to service instances. Besides being the adapter to the service interfaces, it provides the necessary business logic to achieve a clean UI. Finally, the UI should only contain visual logic and be free of any business logic.
However, the UI itself is divided into several UI elements which are allowed to have a reference to the store and those which are not allowed to. The purpose to strictly manage the dependecies is to allow these components to stay testable in a later stage of the project.
apps/music/ stores/ MusicStore.qml views/ TopView.qml BottomView.qml panels/ AlbumArtPanel.qml MusicBrowseList.qml controls/ MusicControls.qml MusicProgressBar.qml Main.qml
- Stores: Encapsulate the access to the service API and contain required business logic
- Views: Have a reference to a store which provides the necessary information
- Panels: Container for other controls and panels. A panel should not have any dependency to a store or a view
- Controls: Re-usable visual element which has no external data dependencies, besides primitives
- Helpers: Collection of operations which can also be scheduled as jobs. In addition, helpers should not import any store as well.
A store encapsulates the business logic inside the application. It is a pure data driven object. A store can have child stores which can be forwarded to sub-trees of the UI. A store is the only portion of the UI layer which uses the service layer.
A view is a container for UI panels which is the only one that depends on a store within the application. Other UI parts need to be clear that they do not have any dependencies to any stores as views do. As mentioned before, in order to allow these components to stay testable.
The above image is an example of a simple widget view in a music application. It is a container of the music control panel and an album art panel. This view takes the information from the music store that is interfaced with the music service which provides a collection of songs to the application.
A panel is a container for other panels and controls. Normally panel is a layout of controls that have a set of functionalities to support the application, such as Music Control Panel as shown below:
A control in this context is an application specific control that is being used only by the application itself. For example the play, previous and next button that are shown in the previous image.
A helper is an object which contains computing functions and not properties. Typical helper is a set of JS functions in which if required, it could be later moved into C++ depending on the needs. A helper is also showing how much complex computing is done in the UI layer and serves as an indicator to optimize the external API. Using helpers requires the developer to carefully think which computing functions are moved out of stores and other places into these helpers. Ideally all for, while loops or longer computing functions shall be moved into the helper functions.
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