html.spec.whatwg.orgHTML Standard

HTML Living Standard — Last Updated 10 May 2024 One-Page Version html.spec.whatwg.org Multipage Version /multipage Version for . This specification does not have any user agent requirements for the color attribute. The mask-icon keyword is a registered extension to the predefined set of link types , but user agents are not required to support it in any way. link elements have an associated explicitly enabled boolean. It is initially false. The disabled attribute is a boolean attribute that is used with the stylesheet link type. The attribute must only be specified on link elements that have a rel attribute that contains the stylesheet keyword. Whenever the disabled attribute is removed, set the link element’s explicitly enabled attribute to true. Removing the disabled attribute dynamically, e.g., using document.querySelector("link").removeAttribute("disabled") , will fetch and apply the style sheet:link disabled rel = "alternate stylesheet" href = "css/pooh"MDN HTMLLinkElement/fetchPriority Firefox No Safari ? preview+ Chrome 102+ Opera ? Edge 102+ Edge (Legacy) ? Internet Explorer No Firefox Android ? Safari iOS ? Chrome Android ? lication had a page with some text controls and links, and was currently showing a modal dialog, which itself had a text control and a button. The hierarchy of focusable widgets, in this scenario, would include the browser window, which would have, amongst its children, the browser tab containing the HTML application. The tab itself would have as its children the various links and text controls, as well as the dialog. The dialog itself would have as its children the text control and the button. If the widget with focus in this example was the text control in the dialog box, then key input would be channeled from the graphical system to ① the web browser, then to ② the tab, then to ③ the dialog, and finally to ④ the text control. Keyboard events are always targeted at this focused element. 6.6.2 Data model A top-level traversable has system focus when it can receive keyboard input channeled from the operating system, possibly targeted at one of its active document ’s descendant navigables . A top-level traversable has user attention when its system visibility state is " visible ", and it either has system focus or user agent widgets directly related to it can receive keyboard input channeled from the operating system. User attention is lost when a browser window loses focus, whereas system focus might also be lost to other system widgets in the browser window such as a location bar. A Document d is a fully active descendant of a top-level traversable with user attention when d is fully active and d ’s node navigable ’s top-level traversable has user attention . The term focusable area is used to refer to regions of the interface that can further become the target of such keyboard input. Focusable areas can be elements, parts of elements, or other regions managed by the user agent. Each focusable area has a DOM anchor , which is a Node object that represents the position of the focusable area in the DOM. (When the focusable area is itself a Node , it is its own DOM anchor .) The DOM anchor is used in some APIs as a substitute for the focusable area when there is no other DOM object to represent the focusable area . The following table describes what objects can be focusable areas . The cells in the left column describe objects that can be focusable areas ; the cells in the right column describe the DOM anchors for those elements. (The cells that span both columns are non-normative examples.) Focusable area DOM anchor Examples Elements that meet all the following criteria: the element’s tabindex value is non-null, or the element is determined by the user agent to be focusable; the element is either not a shadow host , or has a shadow root whose delegates focus is false; the element is not actually disabled ; the element is not inert ; the element is either being rendered , delegating its rendering to its children , or being used as relevant canvas fallback content . The element itself. iframe , dialog , input type=text , sometimes a href="" (depending on platform conventions). The shapes of area elements in an image map associated with an img element that is being rendered and is not inert . The img element. In the following example, the area element creates two shapes, one on each image. The DOM anchor of the first shape is the first img element, and the DOM anchor of the second shape is the second img element.map id = wallmaparea alt = "Enter Door" coords = "10,10,100,200" href = "door.html" / map...img src = "images/innerwall.jpeg" alt = "There is a white wall here, with a door." usemap = "#wallmap"...img src = "images/outerwall.jpeg" alt = "There is a red wall here, with a door." usemap = "#wallmap"The user-agent provided subwidgets of elements that are being rendered and are not actually disabled or inert . The element for which the focusable area is a subwidget. The controls in the user interface for a video element, the up and down buttons in a spin-control version of input type=number , the part of a details element’s rendering that enables the element to be opened or closed using keyboard input. The scrollable regions of elements that are being rendered and are not inert . The element for which the box that the scrollable region scrolls was created. The CSS ’overflow’ property’s ’scroll’ value typically creates a scrollable region. The viewport of a Document that has a non-null browsing context and is not inert . The Document for which the viewport was created. The contents of an iframe . Any other element or part of an element determined by the user agent to be a focusable area, especially to aid with accessibility or to better match platform conventions. The element. A user agent could make all list item bullets sequentially focusable , so that a user can more easily navigate lists. Similarly, a user agent could make all elements with title attributes sequentially focusable , so that their advisory information can be accessed. A navigable container (e.g. an iframe ) is a focusable area , but key events routed to a navigable container get immediately routed to its content navigable ’s active document . Similarly, in sequential focus navigation a navigable container essentially acts merely as a placeholder for its content navigable ’s active document . One focusable area in each Document is designated the focused area of the document . Which control is so designated changes over time, based on algorithms in this specification. Even if a document is not fully active and not shown to the user, it can still have a focused area of the document . If a document’s fully active state changes, its focused area of the document will stay the same. The currently focused area of a top-level traversable traversable is the focusable area -or-null returned by this algorithm: If traversable does not have system focus , then return null. Let candidate be traversable ’s active document . While candidate ’s focused area is a navigable container with a non-null content navigable : set candidate to the active document of that navigable container ’s content navigable . If candidate ’s focused area is non-null, set candidate to candidate ’s focused area . Return candidate . The current focus chain of a top-level traversable traversable is the focus chain of the currently focused area of traversable , if traversable is non-null, or an empty list otherwise. An element that is the DOM anchor of a focusable area is said to gain focus when that focusable area becomes the currently focused area of a top-level traversable . When an element is the DOM anchor of a focusable area of the currently focused area of a top-level traversable , it is focused . The focus chain of a focusable area subject is the ordered list constructed as follows: Let output be an empty list . Let currentObject be subject . While true: Append currentObject to output . If...