W3C

HTML 5.2

Editor’s Draft,

4.11. Interactive elements

4.11.1. The details element

Categories:
Flow content.
Sectioning root.
Interactive content.
Palpable content.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
One summary element followed by flow content.
Tag omission in text/html:
Neither tag is omissible
Content attributes:
Global attributes
open - Whether the details are visible
Allowed ARIA role attribute values:
group role (default - do not set)
Allowed ARIA state and property attributes:
Global aria-* attributes
Any aria-* attributes applicable to the default role.
DOM interface:
interface HTMLDetailsElement : HTMLElement {
  attribute boolean open;
};

The details element represents a disclosure widget from which the user can obtain additional information or controls.

The details element is not appropriate for footnotes. Please see §4.13.5 Footnotes for details on how to mark up footnotes.

If the details element has a summary child element, then the first summary child element represents the summary or legend of the details element. If there is no summary child element, a user agent should provide its own legend (e.g. in English "Details" or Spanish "Detalles").

The legend text should be presented in the language determined from the computed language of the element, if available, rather than from the locale of the browser/system.

The rest of the element’s contents represents the additional information or controls.

The open content attribute is a boolean attribute. If present, it indicates that both the summary and the additional information is to be shown to the user. If the attribute is absent, only the summary is to be shown.

When the element is created, if the attribute is absent, the additional information should be hidden; if the attribute is present, that information should be shown. Subsequently, if the attribute is removed, then the information should be hidden; if the attribute is added, the information should be shown.

The user agent should allow the user to request that the additional information be shown or hidden. To honor a request for the details to be shown, the user agent must set the open attribute on the element to the empty string. To honor a request for the information to be hidden, the user agent must remove the open attribute from the element.

This ability to request that additional information be shown or hidden may simply be the activation behavior of the appropriate summary element, in the case such an element exists. However, if no such element exists, user agents can still provide this ability through some other user interface affordance.

Whenever the open attribute is added to or removed from a details element, the user agent must queue a task that runs the following steps, which are known as the details notification task steps, for this details element:

  1. If another task has been queued to run the details notification task steps for this details element, then abort these steps.

    When the open attribute is toggled several times in succession, these steps essentially get coalesced so that only one event is fired.

  2. Fire a simple event named toggle at the details element.

The task source for this task must be the DOM manipulation task source.

The open IDL attribute must reflect the open content attribute.

The following example shows the details element being used to hide technical details in a progress report.
<section class="progress window">
  <h1>Copying "Really Achieving Your Childhood Dreams"</h1>
  <details>
  <summary>Copying... <progress max="375505392" value="97543282"></progress> 25%</summary>
  <dl>
    <dt>Transfer rate:</dt> <dd>452KB/s</dd>
    <dt>Local filename:</dt> <dd>/home/rpausch/raycd.m4v</dd>
    <dt>Remote filename:</dt> <dd>/var/www/lectures/raycd.m4v</dd>
    <dt>Duration:</dt> <dd>01:16:27</dd>
    <dt>Color profile:</dt> <dd>SD (6-1-6)</dd>
    <dt>Dimensions:</dt> <dd>320×240</dd>
  </dl>
  </details>
</section>
The following shows how a details element can be used to hide some controls by default:
<details>
  <summary><label for=fn>Name & Extension:</label></summary>
  <p><input type=text id=fn name=fn value="Pillar Magazine.pdf">
  <p><label><input type=checkbox name=ext checked> Hide extension</label>
</details>

One could use this in conjunction with other details in a list to allow the user to collapse a set of fields down to a small set of headings, with the ability to open each one.

In these examples, the summary really just summarizes what the controls can change, and not the actual values, which is less than ideal.

Because the open attribute is added and removed automatically as the user interacts with the control, it can be used in CSS to style the element differently based on its state. Here, a stylesheet is used to animate the color of the summary when the element is opened or closed:
<style>
  details > summary { transition: color 1s; color: black; }
  details[open] > summary { color: red; }
</style>
<details>
  <summary>Automated Status: Operational</summary>
  <p>Velocity: 12m/s</p>
  <p>Direction: North</p>
</details>

4.11.2. The summary element

Categories:
None.
Contexts in which this element can be used:
As the first child of a details element.
Content model:
Either: phrasing content.
Or: one element of heading content.
Tag omission in text/html:
Neither tag is omissible
Content attributes:
Global attributes
Allowed ARIA role attribute values:
button.
Allowed ARIA state and property attributes:
Global aria-* attributes
Any aria-* attributes applicable to the allowed roles.
DOM interface:
Uses HTMLElement.

The first summary child element of a details element represents a summary, caption, or legend for the rest of the contents of the parent details element, if any.

The activation behavior of summary elements is to run the following steps:

  1. If this summary element has no parent node, then abort these steps.
  2. Let parent be this summary element’s parent node.
  3. If parent is not a details element, then abort these steps.
  4. If the open attribute is present on parent, then remove it. Otherwise, set parent’s open attribute to the empty string.

    This will then run the details notification task steps.

4.11.3. The menu element

Categories:
Flow content.
Contexts in which this element can be used:
Where flow content is expected.
As the child of a menu element whose type attribute is in the context menu state.
Content model:
If the element’s type attribute is in the context menu state: in any order, zero or more menuitem elements, zero or more hr elements, zero or more menu elements whose type attributes are in the context menu state, and zero or more script-supporting elements.
Tag omission in text/html:
Neither tag is omissible
Content attributes:
Global attributes
type - Type of menu
Allowed ARIA role attribute values:
menu (default - do not set).
Allowed ARIA state and property attributes:
Global aria-* attributes
Any aria-* attributes applicable to the default role.
DOM interface:
interface HTMLMenuElement : HTMLElement {
  attribute DOMString type;
  attribute DOMString label;
};

The menu element represents a group of commands.

The type attribute is an enumerated attribute indicating the kind of menu being declared. The attribute has one state. The "context" keyword maps to the context menu state, in which the element is declaring a context menu. The missing value default is the null.

If a menu element’s type attribute is in the context menu state, then the element represents commands for a context menu. The user can only examine and interact with the commands if that context menu is activated.

The label attribute gives the label of the menu, to display nested menus in the UI: a context menu containing another menu would use the nested menu’s label attribute for the submenu’s menu label. The label attribute must only be specified on menu elements whose parent element is a menu element.


A menu is a currently relevant menu element if it is the child of a currently relevant menu element, or if it is the designated pop-up menu of a button element that is not inert, does not have a hidden attribute, and is not the descendant of an element with a hidden attribute.


A menu construct consists of an ordered list of zero or more menu item constructs, which can be any of:

To build and show a menu for a particular menu element source and with a particular element subject as a subject, the user agent must run the following steps:

  1. Let pop-up menu be the menu construct created by the build a menu construct algorithm when passed the source element.
  2. Display pop-up menu to the user, and let the algorithm that invoked this one continue.

    If the user selects a menu item construct that corresponds to an element that still represents a command when the user selects it, then the user agent must invoke that command’s Action. If the command’s Action is defined as firing a click event, either directly or via the run synthetic click activation steps algorithm, then the relatedTarget attribute of that click event must be initialized to subject.

    Pop-up menus must not, while being shown, reflect changes in the DOM. The menu is constructed from the DOM before being shown, and is then immutable.

To build a menu construct for an element source, the user agent must run the following steps, which return a menu construct:

  1. Let generated menu be an empty menu construct.
  2. Run the menu item generator steps for the menu element using generated menu as the output.

    The menu item generator steps for a menu element using a specific menu construct output as output are as follows: For each child node of the menu in tree order, run the appropriate steps from the following list:

    If the child is a menuitem element that defines a command
    Append the command to output, respecting the command’s facets. If the menuitem element has a default attribute, mark the command as being a default command.
    If the child is an hr element
    Append a separator to output.
    If the child is a menu element with no label attribute
    Append a separator to output, then run the menu item generator steps for this child menu element, using output as the output, then append another separator to output.
    If the child is a menu element with a label attribute
    Let submenu be the result of running the build a menu construct steps for the child menu element. Then, append submenu to output, using the value of the child menu element’s label attribute as the submenu label.
    Otherwise
    Ignore the child node.
  3. Remove from output any menu construct whose submenu label is the empty string.
  4. Remove from output any menu item construct representing a command whose Label is the empty string.
  5. Collapse all sequences of two or more adjacent separators in output to a single separator.
  6. If the first menu item construct in output is a separator, then remove it.
  7. If the last menu item construct in output is a separator, then remove it.
  8. Return output.

The type IDL attribute must reflect the content attribute of the same name, limited to only known values.

The label IDL attribute must reflect the content attribute of the same name.

4.11.4. The menuitem element

Categories:
None.
Contexts in which this element can be used:
As a child of a menu element whose type attribute is in the context menu state.
Content model:
Text content.
Tag omission in text/html:
Neither tag is omissible
Content attributes:
Global attributes
type - Type of command
label - User-visible label
icon - Icon for the command
disabled Whether the command or control is disabled
default - Mark the command as being a default command
Also, the title attribute has special semantics on this element.
Allowed ARIA role attribute values:
menuitem (default - do not set).
Allowed ARIA state and property attributes:
Global aria-* attributes
Any aria-* attributes applicable to the default role.
DOM interface:
interface HTMLMenuItemElement : HTMLElement {
  attribute DOMString type;
  attribute DOMString label;
  attribute DOMString icon;
  attribute boolean disabled;
  attribute boolean default;
};

The menuitem element represents a command that the user can invoke from a popup menu (either a context menu or the menu of a menu button).

A menuitem element with a label attribute, or with text content defines a new command.


The type attribute is an enumerated attribute with one keyword and state. The "command" keyword maps to the Command state. The missing value default is the Command state.

The Command state
The element represents a normal command with an associated action.

The label attribute can be used to give the name of the command, as shown to the user. If the attribute is specified, it must have a value that is not the empty string.

If the label attribute is not present, and there is text content in the element, that provides the name of the content as shown to the user.

The icon attribute gives a picture that represents the command. If the attribute is specified, the attribute’s value must contain a valid non-empty URL potentially surrounded by spaces. To obtain the absolute URL of the icon when the attribute’s value is not the empty string, the attribute’s value must be parsed relative to the element’s node document. When the attribute is absent, or its value is the empty string, or parsing its value fails, there is no icon.

The disabled attribute is a boolean attribute that, if present, indicates that the command is not available in the current state.

The distinction between disabled and hidden is subtle. A command would be disabled if, in the same context, it could be enabled if only certain aspects of the situation were changed. A command would be marked as hidden if, in that situation, the command will never be enabled. For example, in the context menu for a water faucet, the command "open" might be disabled if the faucet is already open, but the command "eat" would be marked hidden since the faucet could never be eaten.


The title attribute gives a hint describing the command, which might be shown to the user to help him.

The default attribute indicates, if present, that the command is the one that would have been invoked if the user had directly activated the menu’s subject instead of using the menu. The default attribute is a boolean attribute.


The type IDL attribute must reflect the content attribute of the same name, limited to only known values.

The label, icon, disabled, and default IDL attributes must reflect the respective content attributes of the same name.


If the element’s Disabled State is false (enabled) then the element’s activation behavior is to do nothing.

Firing a synthetic click event at the element does not cause any of the actions described above to happen.

If the element’s Disabled State is true (disabled) then the element has no activation behavior.

The menuitem element is not rendered except as part of a context menu.

Here is an example of a pop-up menu button with three options that let the user toggle between left, center, and right alignment. One could imagine such a toolbar as part of a text editor. The menu also has a separator followed by another menu item labeled "Publish", though that menu item is disabled.
<button contextmenu="editmenu">Commands...</button>
<menu type="context" id="editmenu">
  <menuitem label="Left" icon="icons/alL.png" onclick="setAlign('left')">
  </menuitem>
  <menuitem label="Center" icon="icons/alC.png" onclick="setAlign('center')">
  </menuitem>
  <menuitem label="Right" icon="icons/alR.png" onclick="setAlign('right')">
  </menuitem>
  <hr>
  <menuitem disabled label="Publish" icon="icons/pub.png" onclick="publish()">
  </menuitem>
</menu>

4.11.5. Context menus

4.11.5.1. Declaring a context menu

The contextmenu attribute gives the element’s context menu. The value must be the ID of a menu element in the same tree whose type attribute is in the context menu state.

When a user right-clicks on an element with a contextmenu attribute, the user agent will first fire a contextmenu event at the element, and then, if that event is not canceled, a show event at the menu element.

Here is an example of a context menu for an input control:
<form name="npc">
  <label>Character name: <input name=char type=text contextmenu=namemenu required></label>
  <menu type=context id=namemenu>
  <menuitem label="Pick random name" onclick="document.forms.npc.elements.char.value = getRandomName()">
    </menuitem>
  <menuitem label="Prefill other fields based on name" onclick="prefillFields(document.forms.npc.elements.char.value)">
    </menuitem>
  </menu>
</form>

This adds two items to the control’s context menu, one called "Pick random name", and one called "Prefill other fields based on name". They invoke scripts that are not shown in the example above.

4.11.5.2. Processing model

Each element has an assigned context menu, which can be null. If an element A has a contextmenu attribute, and there is an element with the ID given by A’s contextmenu attribute’s value in A’s tree, and the first such element in tree order is a menu element, then A’s assigned context menu is that element. Otherwise, if A has a parent element, then A’s assigned context menu is the assigned context menu of its parent element. Otherwise, A’s assigned context menu is null.

When an element’s context menu is requested (e.g., by the user right-clicking the element, or pressing a context menu key), the user agent must apply the appropriate rules from the following list:

If the user requested a context menu using a pointing device
The user agent must fire a trusted event with the name contextmenu, that bubbles and is cancelable, and that uses the MouseEvent interface, at the element for which the menu was requested. The context information of the event must be initialized to the same values as the last MouseEvent user interaction event that was fired as part of the gesture that was interpreted as a request for the context menu.
Otherwise
The user agent must fire a synthetic mouse event named contextmenu that bubbles and is cancelable at the element for which the menu was requested.

Typically, therefore, the firing of the contextmenu event will be the default action of a mouseup or keyup event. The exact sequence of events is user agent-dependent, as it will vary based on platform conventions.

The default action of the contextmenu event depends on whether or not the element for which the menu was requested has a non-null assigned context menu when the event dispatch has completed, as follows.

If the assigned context menu of the element for which the menu was requested is null, the default action must be for the user agent to show its default context menu, if it has one.

Otherwise, let subject be the element for which the menu was requested, and let menu be the assigned context menu of target immediately after the contextmenu event’s dispatch has completed. The user agent must fire a trusted event with the name show at menu, using the RelatedEvent interface, with the relatedTarget attribute initialized to subject. The event must be cancelable.

If this event (the show event) is not canceled, then the user agent must build and show the menu for menu with subject as the subject.

When it presents a context menu, the user agent should also provide access to its default context menu. For example, it could merge the menu items from the two menus together, provide the page’s context menu as a submenu of the default menu, or handle right-clicks that have the Shift key depressed by showing the default context menu instead of firing the contextmenu event.


In this example, an image of cats is given a context menu with four possible commands:
<img src="cats.jpeg" alt="Cats" contextmenu=catsmenu>
<menu type="context" id="catsmenu">
  <menuitem label="Pet the kittens" onclick="kittens.pet()">
  <menuitem label="Cuddle with the kittens" onclick="kittens.cuddle()">
  <menu label="Feed the kittens">
    <menuitem label="Fish" onclick="kittens.feed(fish)">
    <menuitem label="Chicken" onclick="kittens.feed(chicken)">
  </menu>
</menu>

When a user of a mouse-operated visual Web browser right-clicks on the image, the browser might pop up a context menu like this:

A context menu, shown over a picture of cats, with four lines: the first two offering the menu items described in the markup above ('Pet the kittens' and 'Cuddle with the kittens'), the third giving a submenu labeled 'Feed the kittens', and the fourth, after a horizontal splitter, consisting of only a downwards-pointing disclosure triangle.

When the user clicks the disclosure triangle, such a user agent would expand the context menu in place, to show the browser’s own commands:

This would result in the same basic interface, but with a longer menu; the disclosure triangle having been replaced by items such as 'View Image', 'Copy Image', 'Copy Image Location', and so forth.

4.11.5.3. The RelatedEvent interfaces
[Constructor(DOMString type, optional RelatedEventInit eventInitDict)]
interface RelatedEvent : Event {
  readonly attribute EventTarget? relatedTarget;
};

dictionary RelatedEventInit : EventInit {
  EventTarget? relatedTarget = null;
};
event . relatedTarget
Returns the other event target involved in this event. For example, when a show event fires on a menu element, the other event target involved in the event would be the element for which the menu is being shown.

The relatedTarget attribute must return the value it was initialized to. It represents the other event target that is related to the event.

4.11.6. Commands

4.11.6.1. Facets

A command is the abstraction behind menu items, buttons, and links. Once a command is defined, other parts of the interface can refer to the same command, allowing many access points to a single feature to share facets such as the Disabled State.

Commands are defined to have the following facets:

Label

The name of the command as seen by the user.

Access Key

A key combination selected by the user agent that triggers the command. A command might not have an Access Key.

Hidden State

Whether the command is hidden or not (basically, whether it should be shown in menus).

Disabled State

Whether the command is relevant and can be triggered or not.

Action

The actual effect that triggering the command will have. This could be a scripted event handler, a URL to which to navigate, or a form submission.

User agents may expose the commands that match the following criteria:

User agents are encouraged to do this especially for commands that have Access Keys, as a way to advertise those keys to the user.

For example, such commands could be listed in the user agent’s menu bar.

4.11.6.2. Using the a element to define a command

An a element with an href attribute defines a command.

The Label of the command is the string given by the element’s textContent IDL attribute.

The Access Key of the command is the element’s assigned access key, if any.

The Hidden State of the command is true (hidden) if the element has a hidden attribute, and false otherwise.

The Disabled State facet of the command is true if the element or one of its ancestors is inert, and false otherwise.

The Action of the command, if the element has a defined activation behavior, is to run synthetic click activation steps on the element. Otherwise, it is just to fire a click event at the element.

4.11.6.3. Using the button element to define a command

A button element always defines a command.

The Label, Access Key, Hidden State, and Action facets of the command are determined as for a elements (see the previous section).

The Disabled State of the command is true if the element or one of its ancestors is inert, or if the element’s disabled state is set, and false otherwise.

4.11.6.4. Using the input element to define a command

An input element whose type attribute is in one of the Submit Button, Reset Button, Image Button, Button, Radio Button, or Checkbox states defines a command.

The Label of the command is determined as follows:

The Access Key of the command is the element’s assigned access key, if any.

The Hidden State of the command is true (hidden) if the element has a hidden attribute, and false otherwise.

The Disabled State of the command is true if the element or one of its ancestors is inert, or if the element’s disabled state is set, and false otherwise.

The Action of the command, if the element has a defined activation behavior, is to run synthetic click activation steps on the element. Otherwise, it is just to fire a click event at the element.

4.11.6.5. Using the option element to define a command

An option element with an ancestor select element and either no value attribute or a value attribute that is not the empty string defines a command.

The Label of the command is the value of the option element’s label attribute, if there is one, or else the value of option element’s textContent IDL attribute, with leading and trailing white space stripped, and with any sequences of two or more space characters replaced by a single U+0020 SPACE character.

The Access Key of the command is the element’s assigned access key, if any.

The Hidden State of the command is true (hidden) if the element has a hidden attribute, and false otherwise.

The Disabled State of the command is true if the element is disabled, or if its nearest ancestor select element is disabled, or if it or one of its ancestors is inert, and false otherwise.

If the option’s nearest ancestor select element has a multiple attribute, the Action of the command is to pick the option element. Otherwise, the Action is to toggle the option element.

4.11.6.6. Using the menuitem element to define a command

A menuitem element always defines a command.

The Label of the command is the value of the element’s label attribute, if there is one, or the empty string if it doesn’t.

The Access Key of the command is the element’s assigned access key, if any.

The Hidden State of the command is true (hidden) if the element has a hidden attribute, and false otherwise.

The Disabled State of the command is true if the element or one of its ancestors is inert, or if the element has a disabled attribute, and false otherwise.

The Action of the command, if the element has a defined activation behavior, is to run synthetic click activation steps on the element. Otherwise, it is just to fire a click event at the element.

4.11.6.7. Using the accesskey attribute on a label element to define a command

A label element that has an assigned access key and a labeled control and whose labeled control defines a command, itself defines a command.

The Label of the command is the string given by the element’s textContent IDL attribute.

The Access Key of the command is the element’s assigned access key.

The Hidden State, Disabled State, and Action facets of the command are the same as the respective facets of the element’s labeled control.

4.11.6.8. Using the accesskey attribute on a legend element to define a command

A legend element that has an assigned access key and is a child of a fieldset element that has a descendant that is not a descendant of the legend element and is neither a label element nor a legend element but that defines a command, itself defines a command.

The Label of the command is the string given by the element’s textContent IDL attribute.

The Access Key of the command is the element’s assigned access key.

The Hidden State, Disabled State, and Action facets of the command are the same as the respective facets of the first element in tree order that is a descendant of the parent of the legend element that defines a command but is not a descendant of the legend element and is neither a label nor a legend element.

4.11.6.9. Using the accesskey attribute to define a command on other elements

An element that has an assigned access key defines a command.

If one of the earlier sections that define elements that define commands define that this element defines a command, then that section applies to this element, and this section does not. Otherwise, this section applies to that element.

The Label of the command depends on the element. If the element is a labeled control, the textContent of the first label element in tree order whose labeled control is the element in question is the Label (in DOM terms, this is the string given by element.labels[0].textContent). Otherwise, the Label is the textContent of the element itself.

The Access Key of the command is the element’s assigned access key.

The Hidden State of the command is true (hidden) if the element has a hidden attribute, and false otherwise.

The Disabled State of the command is true if the element or one of its ancestors is inert, and false otherwise.

The Action of the command is to run the following steps:

  1. Run the focusing steps for the element.
  2. If the element has a defined activation behavior, run synthetic click activation steps on the element.
  3. Otherwise, if the element does not have a defined activation behavior, fire a click event at the element.

4.11.7. The dialog element

Categories:
Flow content.
Sectioning root.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Flow content.
Tag omission in text/html:
Neither tag is omissible
Content attributes:
Global attributes
open - Whether the dialog box is showing
Allowed ARIA role attribute values:
dialog (default - do not set) or alertdialog.
Allowed ARIA state and property attributes:
Global aria-* attributes
Any aria-* attributes applicable to the default or allowed roles.
DOM interface:
interface HTMLDialogElement : HTMLElement {
  attribute boolean open;
  attribute DOMString returnValue;
  void show(optional (MouseEvent or Element) anchor);
  void showModal(optional (MouseEvent or Element) anchor);
  void close(optional DOMString returnValue);
};

The dialog element represents a part of an application that a user interacts with to perform a task, for example a dialog box, inspector, or window.

The open attribute is a boolean attribute. When specified, it indicates that the dialog element is active and that the user can interact with it.

The following is an example of a modal dialog which provides a form for a user to add coins to their wallet, as part of an online game.

...
<body>
<div> <!-- body content --> </div>
<dialog>
  <h1>Add to Wallet</h1>
  <label for="num">How many gold coins do you want to add to your wallet?</label>
  <div><input name=amt id="num" type=number min=0 step=0.01 value=100></div>
  <p><strong>You add coins at your own risk.</strong></p>
  <div><label><input name=round type=checkbox> Only add perfectly round coins </label>
  <div><input type=button onclick="submit()" value="Add Coins"></div>
</dialog>
</body>
...

Add to Wallet Dialog

A dialog element without an open attribute specified should not be shown to the user. This requirement may be implemented indirectly through the style layer. For example, user agents that support the suggested default rendering implement this requirement using the CSS rules described in §10 Rendering.

The tabindex attribute must not be specified on dialog elements.

dialog . show( [ anchor ] )

Displays the dialog element.

The argument, if provided, provides an anchor point to which the element will be fixed.

dialog . showModal( [ anchor ] )

Displays the dialog element and makes it the top-most modal dialog.

The argument, if provided, provides an anchor point to which the element will be fixed.

This method honors the autofocus attribute.

dialog . close( [ result ] )

Closes the dialog element.

The argument, if provided, provides a return value.

dialog . returnValue [ = result ]

Returns the dialog’s return value.

Can be set, to update the return value.

When the show() method is invoked, the user agent must run the following steps:

  1. If the element already has an open attribute, then abort these steps.
  2. Add an open attribute to the dialog element, whose value is the empty string.
  3. If the show() method was invoked with an argument, set up the position of the dialog element, using that argument as the anchor. Otherwise, set the dialog to the normal alignment mode.
  4. Run the dialog focusing steps for the dialog element.

Each Document has a stack of dialog elements known as the pending dialog stack. When a Document is created, this stack must be initialized to be empty.

When an element is added to the pending dialog stack, it must also be added to the top layer. When an element is removed from the pending dialog stack, it must be removed from the top layer. [FULLSCREEN]

When the showModal() method is invoked, the user agent must run the following steps:

  1. Let subject be the dialog element on which the method was invoked.
  2. If subject already has an open attribute, then throw an InvalidStateError exception and abort these steps.
  3. If subject is not in a Document, then throw an InvalidStateError exception and abort these steps.
  4. Add an open attribute to subject, whose value is the empty string.
  5. If the showModal() method was invoked with an argument, set up the position of subject, using that argument as the anchor. Otherwise, set the dialog to the centered alignment mode.
  6. Let subject’s node document be blocked by the modal dialog subject.
  7. Push subject onto subject’s node document’s pending dialog stack.
  8. Run the dialog focusing steps for subject.

The dialog focusing steps for a dialog element subject are as follows:

  1. If for some reason subject is not a control group owner at this point, or if it is inert, abort these steps.
  2. Let control be the first non-inert focusable area in subject’s control group whose DOM anchor has an autofocus attribute specified.

    If there isn’t one, then let control be the first non-inert focusable area in subject’s control group.

    If there isn’t one of those either, then let control be subject.

  3. Run the focusing steps for control.

If at any time a dialog element is removed from a Document, then if that dialog is in that Document’s pending dialog stack, the following steps must be run:

  1. Let subject be that dialog element and document be the Document from which it is being removed.
  2. Remove subject from document’s pending dialog stack.
  3. If document’s pending dialog stack is not empty, then let document be blocked by the modal dialog that is at the top of document’s pending dialog stack. Otherwise, let document be no longer blocked by a modal dialog at all.

When the close() method is invoked, the user agent must close the dialog that the method was invoked on. If the method was invoked with an argument, that argument must be used as the return value; otherwise, there is no return value.

When a dialog element subject is to be closed, optionally with a return value result, the user agent must run the following steps:

  1. If subject does not have an open attribute, then abort these steps.
  2. Remove subject’s open attribute.
  3. If the argument result was provided, then set the returnValue attribute to the value of result.
  4. If subject is in its Document’s pending dialog stack, then run these substeps:

    1. Remove subject from that pending dialog stack.
    2. If that pending dialog stack is not empty, then let subject’s node document be blocked by the modal dialog that is at the top of the pending dialog stack. Otherwise, let document be no longer blocked by a modal dialog at all.
  5. Queue a task to fire a simple event named close at subject.

The returnValue IDL attribute, on getting, must return the last value to which it was set. On setting, it must be set to the new value. When the element is created, it must be set to the empty string.


Canceling dialogs: When a Document’s pending dialog stack is not empty, user agents may provide a user interface that, upon activation, queues a task to fire a simple event named cancel that is cancelable at the top dialog element on the Document’s pending dialog stack. The default action of this event must be to check if that element has an open attribute, and if it does, close the dialog with no return value.

An example of such a UI mechanism would be the user pressing the "Escape" key.


All dialog elements are always in one of three modes: normal alignment, centered alignment, and magic alignment. When a dialog element is created, it must be placed in the normal alignment mode. In this mode, normal CSS requirements apply to the element. The centered alignment mode is only used for dialog elements that are in the top layer. [FULLSCREEN] [CSS-2015]

When an element subject is placed in centered alignment mode, and when it is in that mode and has new rendering boxes created, the user agent must set up the element such that its top static position, for the purposes of calculating the used value of the top property, is the value that would place the element’s top margin edge as far from the top of the viewport as the element’s bottom margin edge from the bottom of the viewport, if the element’s height is less than the height of the viewport, and otherwise is the value that would place the element’s top margin edge at the top of the viewport.

If there is a dialog element with centered alignment and that is being rendered when its browsing context changes viewport width (as measured in CSS pixels), then the user agent must recreate the element’s boxes, recalculating its top static position as in the previous paragraph.

This top static position of a dialog element with centered alignment must remain the element’s top static position until its boxes are recreated. (The element’s static position is only used in calculating the used value of the top property in certain situations; it’s not used, for instance, to position the element if its position property is set to static.)

When a user agent is to set up the position of an element subject using an anchor anchor, it must run the following steps:

  1. If anchor is a MouseEvent object, then run these substeps:

    1. If anchor’s target element does not have a rendered box, or is in a different document than subject, then let subject be in the centered alignment mode, and abort the set up the position steps.
    2. Let anchor element be an anonymous element rendered as a box with zero height and width (so its margin and border boxes both just form a point), positioned so that its top and left are at the coordinate identified by the event, and whose properties all compute to their initial values.

    Otherwise, let anchor element be anchor.

  2. Put subject in the magic alignment mode, aligned to anchor element.

While an element A has magic alignment, aligned to an element B, the following requirements apply:

The trivial example of an element that does not have a rendered box is one whose display property computes to none. However, there are many other cases; e.g., table columns do not have boxes (their properties merely affect other boxes).

If an element to which another element is anchored changes rendering, the anchored element will be repositioned accordingly. (In other words, the requirements above are live, they are not just calculated once per anchored element.)

The 'absolute-anchored' keyword is not a keyword that can be specified in CSS; the position property can only compute to this value if the dialog element is positioned via the APIs described above.

User agents in visual interactive media should allow the user to pan the viewport to access all parts of a dialog element’s border box, even if the element is larger than the viewport and the viewport would otherwise not have a scroll mechanism (e.g., because the viewport’s overflow property is set to hidden).


The open IDL attribute must reflect the open content attribute.

4.11.7.1. Anchor points

This section will eventually be moved to a CSS specification; it is specified here only on an interim basis until an editor can be found to own this.

Name: anchor-point
Value: [ none | <position> ]
Initial: none
Applies to: all elements
Inherited: no
Percentages: refer to width or height of box; see prose
Media: visual
Computed value: The specified value, but with any lengths replaced by their corresponding absolute length
Canonical order: per grammar
Animatable: no

The anchor-point property specifies a point to which dialog boxes are to be aligned.

If the value is a <position>, the anchor point is the point given by the value, which must be interpreted relative to the element’s first rendered box’s margin box. Percentages must be calculated relative to the element’s first rendered box’s margin box (specifically, its width for the horizontal position and its height for the vertical position). [CSS-VALUES] [CSS-2015]

If the value is the keyword none, then no explicit anchor point is defined. The user agent will pick an anchor point automatically if necessary (as described in the definition of the open() method above).