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Component Model Use Cases

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This document is obsolete.

For more information, see: http://www.w3.org/2008/webapps/wiki/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.
  • 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.
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.
  • Write application faster by reusing code.
  • Avoid having to exclusively go with one framework.
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.
  • 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.

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.
  • 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.
  • Provide a simple vehicle for Web authors to embed the button.
  • Isolate widget implementation details from the document.
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.

Table-based Charts

Table-based Charts Use Case Parameters
Who Web Framework Engineer
What Provide a way to represent table data markup as charts or diagrams.
Purpose Make it easy for Web authors to create charts and diagrams using table markup.
Desirable Properties
  • Composability -- one should be able to make chart by creating a table, imperatively or declaratively.
  • Performance -- no FOUC or blocking load when charts are loaded.

Timezone selection via Image

Timezone selection via Image Use Case Parameters
Who Web Framework Engineer
What Graphical representation of a timezone selector that shows a world map in addition to/instead of a drop-down list.
Purpose Make it easy for Web authors to spruce up time zone selection (or similar).
Desirable Properties
  • Extensibility -- Basically extending <select>. Should fall back to a simple <select> where components are not supported.
  • Consistency -- Extend the <select> API for item selection.


Entry-helper Use Case Parameters
Who Web Framework Engineer, Web Application Engineer
What Add an entry-helper (drop-down) list to input fields.

Help the user fill in a form field, show suggestions and acceptable values, speed up data entry.

  • Most browser's address bar or web search field
Desirable Properties
  • Extensibility -- Basically extending <input>. Should fall back to a simple <input> where components are not supported.

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
  • 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 of <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.