Component Model Use Cases

These use cases represent a set of problems we are trying to solve by implementing a component model for the web.

Custom Controls

Current practice for sizable web applications is to use JavaScript libraries to provide a system to support the construction of custom controls. Implementing these controls can be made simpler and more interoperable with runtime support.

Layout Manager

Layout Manager Use Case Parameters

Who	Web Framework Engineer
What	Build a layout library, consisting of a UI layout primitives, such as panel, resizeable panel, tab group, stack, accordion containers, etc.
Purpose	Allow web application developers to easily build constrained layout and populate it with arbitrary HTML content. Provide a way for developers to build their own layout primitives by extending the provided ones.
Examples	Dijit Layout GWT Panels Sencha Panels SproutCore Views
Desirable Properties	Composability -- a method to compose layouts with both UI primitives and DOM elements. Extensibility -- a way to build on layout primitives to create new ones. Encapsulation -- styles, defined to hold layout in place should not be in danger of being stomped on by the author stylesheets. Performance -- layouts built with layout manager should appear quickly, avoiding re-flows and FOUC-like symptoms.

Widget Mix-and-Match

Mix-and-matching Use Case Parameters

Who	Web Application Engineer
What	Build an application using multiple existing controls from several frameworks.
Purpose	Write application faster by reusing code. Avoid having to exclusively go with one framework.
Examples	How do you access Dijit elements in JQuery Using SproutCore 2.0 with jQuery UI Which JavaScript framework (jQuery vs Dojo vs … )?
Desirable Properties	Consistency -- a compatible way to expose properties and methods across widget frameworks. Composability -- a method to compose with cross-framework widgets.

Rendering Form Controls with SVG

SVG Form Controls Use Case Parameters

Who	Web Application Engineer or Web Framework Engineer
What	Create a set of UI controls that act like standard HTML forms controls, but use SVG for rendering.
Purpose	Provide custom appearance of form controls, consistent with overall the Web application theme. Make the form controls scale beautifully for various resolutions and form factors.
Examples	SproutCore's ImageButtonView, Sencha's Number -- examples of extensive themed form control hierarchy.
Desirable Properties	Consistency -- the controls should act just like any other DOM elements. Encapsulation -- the document shouldn't be able to accidentally mess up the rendering of the controls. Performance -- load quickly, avoid FOUC-like symptoms when using controls.

Contacts Widget

Contacts Widget Use Case Parameters

Who	Web Application Engineer
What	Build a drop-in Contacts widget, which has a pre-defined appearance and shows a list of your contacts, with a way to change the widget to compact or full view and to tell the widget to refresh its state.
Purpose	Use the widget anywhere in the application without having to worry about styles affecting its appearance. Hide details of loading contact data and other plumbing of the widget from the consuming code with a stable API.
Examples	A screenshot of Google+ "in your circles" widget
Desirable Properties	Encapsulation -- means to ensure style of the document does not affect the widget, and widget's logic is kept to the widget. Composability -- easily added anywhere in the DOM tree.

Like/+1 Button

Like/+1 Button Use Case Parameters

Who	Web Application Engineer
What	Build a drop-in widget with a pre-defined appearance of a button, showing a count of likes/+1s for this instance of a button (count is stored at a central location), embeddable on any document on the Web.
Purpose	Provide a simple vehicle for Web authors to embed the button. Isolate widget implementation details from the document.
Examples	Facebook Like button embedding instructions Google +1 button embedding instructions
Desirable Properties	Encapsulation -- means to ensure style of the document does not affect the widget, and widget's logic is kept to the widget. Confinement -- a way to completely isolate the widget implementation from the document in which it is being embedded. Performance -- don't block the page load.

Built-in HTML Elements

Many non-trivial (i.e. with additional behavior and styling beyond the standard box model) elements that exist in HTML today could be implemented using HTML/CSS/JS. It makes sense to provide a standardized way to accomplish this, with the short-term goals of reducing the size of browsers C++ code and making new element implementation easier, and the long-term goal of converging built-in HTML element implementations across browsers.

Built-in HTML Elements Use Case Parameters

Who	Browser Engineer
What	Implement a built-in HTML element by composing or extending existing HTML elements
Purpose	Reduce amount of custom UI code (fewer bugs, less code rot, leading to fewer future bugs). Remove magic: make it easier for authors to grok control behavior in familiar terms, allow authors to style controls using CSS. Stretch: specify built-in element behavior in terms of the component model specification.
Desirable Properties	Encapsulation -- ensure that implementation details are not exposed to the document Desugaring -- explain appearance and behavior of controls in terms of CSS/DOM.

Media Controls For The Video Element

Using DOM elements, build a media controls panel for the video element. The media controls include:

• timeline slider
• stop/start, replay, closed-captioning, forward, rewind and volume buttons, and
• a volume control, which is revealed when hovering over the volume button.

The implementation details of the media controls should not be accessible or perceptible from outside of the video element. Document styles should not interfere with the styles of the media controls panel. However, we must provide a way for an author to explicitly style all parts of the media controls panel.

Details/Summary Elements

Implement details and summary elements. According to the spec, the first summary element found in the flow content is used to represent a summary or legend of details. In case a summary element is not found, the UA is supposed to auto-generate some fallback content. The details element itself needs to have a marker indicating whether details element is open or closed - i.e., whether all contents or <details> are shown, or only the summary.

Just like media controls, the implementation should not be accessible by the consumer of the elements. For example, the reordering of flow content to position summary element as first item in the disclosure widget should be imperceptible to DOM traversal methods.