Scripting and Interactivity

SVG content can be interactive (i.e., responsive to user-initiated events) by utilizing the following features in the SVG language:

This chapter describes scripting and DOM event handling in interactive SVG, including under which circumstances events are triggered.

15.2. Supported events

SVG 2 Requirement:	Support anchor change events.
Resolution:	SVG 2 will consider adding HTML document wide events (including hashchange) apply to SVG documents where they make sense.
Purpose:	To allow authors to use the same set of event listener attributes on a root SVG element that they can on an HTML body or root element.
Owner:	Cameron (ACTION-3278)

SVG 2 Requirement:	Have event listener attributes on an appropriate interface.
Resolution:	SVG 2 will move all events listener attributes to Element, in accordance with the similar move in HTML.
Purpose:	To align with HTML.
Owner:	Cameron (ACTION-3283)

SVG 2 Requirement:	Introduce evt as an alias to event in event handlers.
Resolution:	We decide to resolve ISSUE-2176 by introducing evt as an alias to event in event handlers.
Purpose:	To align with HTML.
Owner:	Cameron (ACTION-3093)

SVG 2 Requirement:	Support drag & drop functionality.
Resolution:	SVG 2 may require drag & drop functionality, and we'll investigate HTML5's functionality for that.
Purpose:	To allow easier drag & drop in SVG, and to align with HTML.
Owner:	Erik (ACTION-3328)

A number of events defined in SVG 1.1, SVGLoad, SVGError etc, have been replaced with the equivalent unprefixed events defined in UI EVENTS and HTML.

There should be some more modern examples of using events in svg, e.g touch events (w reference to touch events spec). Device orientation events might also be of interest.

The following table lists the events defined by this specification, or that have further requirements or clarifications compared to the specification(s) where they are defined.

The Event name in the first column is the name to use within SVG's animation elements to define the events which can start or end animations. The UI Event name in the second column is the name to use when defining DOM event listeners ([DOM], section 3.6).

For events not listed in the table, such as events introduced in HTML or UI Events, the respective event type is the name to use within SVG's animation elements.

Requirements in the table on whether an event of a given type bubbles or is cancelable apply only to events that are created and dispatched by the user agent. Events of those types created from script using the createEvent method on the Document interface can be made to bubble or be cancelable with the initEvent method.

Event name and description	UI Event name	Event category	Event attribute name
load The load event is dispatched only to structurally external elements and to the Window, when the corresponding external resources have finished loading. Note that due to it's relationship with Window the load event on ‘svg’ elements is only dispatched when all resources in the document have been completely loaded. The load event and the error event on structurally external elements are mutually exclusive, only one of these events must be dispatched when processing the element in question. load events do not bubble and are not cancelable. In previous SVG specifications the load event was called SVGLoad and could be dispatched immediately after parsing an element but before the related resource(s) were fully loaded.	(same)	none	onload
unload Only applicable to outermost svg elements. The unload event occurs when the DOM implementation removes a document from a window or frame. unload events do not bubble and are not cancelable.	(same)	none	onunload
error The error event occurs when a structurally external element does not load properly or when an error occurs during script execution. error events bubble but are not cancelable.	(same)	none	onerror
beginEvent Occurs when an animation element begins. For details, see the description of Interface TimeEvent in the SMIL Animation specification.	none	none	onbegin
endEvent Occurs when an animation element ends. For details, see the description of Interface TimeEvent in the SMIL Animation specification.	none	none	onend
repeatEvent Occurs when an animation element repeats. It is raised each time the element repeats, after the first iteration. For details, see the description of Interface TimeEvent in the SMIL Animation specification.	none	none	onrepeat

Details on the parameters passed to event listeners for the event types for UI Events can be found in the ([uievents]) and ([DOM]) specifications. For other event types, the parameters passed to event listeners are described elsewhere in this specification.

Likewise, event-value timing specifiers used in animation element ‘begin’ and ‘end’ attributes are resolved to concrete times only in response to "bubbling" and "at target" phase events dispatched to the relevant element.

15.2.1. Relationship with UI Events

As part of SVG DOM support, conforming SVG software must support all (non-deprecated, non-obsolete) event types defined in these specifications, if the relevant events could occur in the software's use. SVG software that does not support user interaction should nonetheless implement support for events that can fire without interaction, such as load and error events.

SVG animation elements (defined in the SVG Animations Level 2 specification) support additional events and event attributes. The following event types are triggered due to state changes in animations.

The event attributes for these animation events have no effect on other elements.

15.3. User interface events

On user agents which support interactivity, it is common for authors to define SVG documents such that they are responsive to user interface events. Among the set of possible user events are pointer events, keyboard events, and document events.

In response to user interface (UI) events, the author might start an animation, perform a hyperlink to another Web page, highlight part of the document (e.g., change the color of the graphics elements which are under the pointer), initiate a "roll-over" (e.g., cause some previously hidden graphics elements to appear near the pointer) or launch a script which communicates with a remote database.

15.4. Pointer events

User interface events that occur because of user actions performed on a pointer device are called pointer events.

Many systems support pointer devices such as a mouse or trackball. On systems which use a mouse, pointer events consist of actions such as mouse movements and mouse clicks. On systems with a different pointer device, the pointing device often emulates the behavior of the mouse by providing a mechanism for equivalent user actions, such as a button to press which is equivalent to a mouse click.

For each pointer event, the SVG user agent determines the target element of a given pointer event. The target element is the topmost graphics element whose relevant graphical content is under the pointer at the time of the event. (See property pointer-events for a description of how to determine whether an element's relevant graphical content is under the pointer, and thus in which circumstances that graphic element can be the target element for a pointer event.) When an element is not displayed (i.e., when the display property on that element or one of its ancestors has a value of none), that element cannot be the target of pointer events.

If a target element for the pointer event exists, then the event is dispatched to that element according to the normal event flow ([uievents], section 3.1). For shadow trees created by the ‘use’ element or via script, the event must follow Dispatching Events [dom]

If a target element for the pointer event does not exist, then the event is ignored.

15.5. Hit-testing and processing order for user interface events

There are two distinct aspects of pointer-device interaction with an element or area:

15.5.1. Hit-testing

Determining whether a pointer event results in a positive hit-test depends upon the position of the pointer, the size and shape of the graphics element, and the computed value of the pointer-events property on the element. The definition of the pointer-events property below describes the exact region that is sensitive to pointer events for a given type of graphics element.

Note that the ‘svg’ element is not a graphics element, and in a Conforming SVG Stand-Alone File a outermost svg element will never be the target of pointer events, though events can bubble to this element. If a pointer event does not result in a positive hit-test on a graphics element, then it should evoke any user-agent-specific window behavior, such as a presenting a context menu.

This specification does not define the behavior of pointer events on the outermost svg element for SVG images which are embedded by reference or inclusion within another document, e.g., whether the outermost svg element embedded in an HTML document intercepts mouse click events; future specifications may define this behavior, but for the purpose of this specification, the behavior is implementation-specific.

15.5.2. Event processing

An element which is the target of a user interface event may have particular interaction behaviors, depending upon the type of element and whether it has explicit associated interactions, such as scripted event listeners, CSS pseudo-classes matches, or declarative animations with event-based timing. The algorithm and order for processing user interface events for a given target element, after dispatching the DOM event, is as follows:

15.6. The ‘pointer-events’ property

In different circumstances, authors may want to control under what conditions particular graphic elements can become the target of pointer events. For example, the author might want a given element to receive pointer events only when the pointer is over the stroked perimeter of a given shape. In other cases, the author might want a given element to ignore pointer events under all circumstances so that graphical elements underneath the given element will become the target of pointer events.

The effects of masking and clipping differ with respect to pointer events. A clip path is a geometric boundary, and a given point is clearly either inside or outside that boundary; thus, pointer events must be captured normally over the rendered areas of a clipped element, but must not be captured over the clipped areas, as described in the definition of clipping paths. By contrast, a mask is not a binary transition, but a pixel operation, and different behavior for fully transparent and almost-but-not-fully-transparent may be confusingly arbitrary; as a consequence, for elements with a mask applied, pointer events must still be captured even in areas where the mask goes to zero opacity. If an author wishes to achieve an effect where the transparent parts of a mask allow pointer events to pass to an element below, a combination of masking and clipping may be used.

The filter property has no effect on pointer events processing, and must in this context be treated as if the filter wasn't specified.

For example, suppose a circle with a stroke of red (i.e., the outline is solid red) and a fill of none (i.e., the interior is not painted) is rendered directly on top of a rectangle with a fill of blue. The author might want the circle to be the target of pointer events only when the pointer is over the perimeter of the circle. When the pointer is over the interior of the circle, the author might want the underlying rectangle to be the target element of pointer events.

The pointer-events property specifies under what circumstances a given element can be the target element for a pointer event. It affects the circumstances under which the following are processed:

For raster images, hit-testing is performed on a whole-image basis (i.e., the rectangular area for the image is the determinant for whether the image receives the event):

Name:	pointer-events
Value:	auto \| bounding-box \| visiblePainted \| visibleFill \| visibleStroke \| visible \| painted \| fill \| stroke \| all \| none
Initial:	auto
Applies to:	container elements, graphics elements and ‘use’
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animation type:	discrete

For ‘foreignObject’ elements, hit-testing is performed on the rectangular area, the object bounding box, of the element. See processing for raster images above. Useragents may allow the foreign content of a ‘foreignObject’ element to be target of hit-testing as well.

15.7. Focus

SVG uses the same focus model as HTML, modified for SVG as described in this section. At most one element in each document is focused at a time; if the document as a whole has system focus, this element becomes the target of all keyboard events.

When an element is focused, the element matches the CSS :focus pseudo-class. Interactive user agents must visually indicate focus (usually with an outline) when the focus changes because of a user input event from the keyboard or other non-pointing device and may indicate focus at all times. Authors may use the :focus pseudo-class to replace the visual indication with one more suitable to the graphic, (such as a stroke on a shape) but should not use it to remove visual indications of focus completely.

The following SVG elements are focusable in an interactive document. Any instance of such an element in a use-element shadow tree is also focusable. For the purpose of the HTML focus model, interactive user agents must treat them as focusable areas whose tabindex focus flag should be set:

the document root element
any element (such as within a ‘foreignObject’) that generates a scrollable region
any directly rendered element with a valid integer ‘tabindex’ attribute

In the case of user-agent supplied controls, the element may have more than one focusable area, for each sub-control.

In addition, all ‘a’ elements that are valid links are focusable, and their tabindex focus flag must be set unless the user agent normally provides an alternative method of keyboard traversal of links.

For compatibility with content that used the SVG Tiny 1.2 focusable attribute, user agents should treat an element with a value of true for that attribute as focusable. In new content, authors should either omit the focusable attribute or use it only in combination with a corresponding tabindex value of 0.

User agents may treat other elements as focusable, particularly if keyboard interaction is the only or primary means of user input. In particular, user agents may support using keyboard focus to reveal ‘title’ element text as tooltips, and may allow focus to reach elements which have been assigned listeners for mouse, pointer, or focus events. Authors should not rely on this behavior; all interactive elements should directly support keyboard interaction.

The sequential focus order is generated from the set of all focusable elements, processing ‘tabindex’ attributes on SVG elements in the same way as tabindex attributes on HTML elements. Content within a use-element shadow tree is inserted in the focus order as if it was child content of the ‘use’ element.

A non-rendered element can never receive focus, regardless of the value of the ‘tabindex’ attribute, If a script programmatically assigns focus to a non-rendered or otherwise un-focusable element, the focusing call is aborted. Note, however, that an element that is not visible or onscreen may still be rendered.

When the user agent supports scrolling or panning of the SVG document, and focus moves to an element that is currently outside the SVG viewport, the user agent should scroll or pan the document until the focused element is within the SVG viewport.

As in HTML, an SVG element that is focusable but does not have a defined activation behavior has an activation behaviour that does nothing (unless a script specifically responds to it).

This means that an element that is only focusable because of its ‘tabindex’ attribute will fire a click event in response to a non-mouse activation (e.g. hitting the "enter" key while the element has focus).

For documents that contain a mix of inline HTML and SVG, focus is handled for the document as a whole (with a combined sequential focus order), not with each inline SVG or HTML fragment as an isolated subdocument.

For example, in the following document, pressing Tab would cycle the focus between elements A, B and C, in that order.

<!DOCTYPE html>
<button id="A" tabindex="1">First thing</button>
<button id="C" tabindex="2">Third thing</button>
<svg width="200" height="200">
  <text id="B" tabindex="1" x="100" y="100">Second thing</text>
</svg>

Note that SVG elements do not have an equivalent of HTML's accesskey attribute.

15.8. Event attributes

The contents of event attributes are always interpreted as ECMAScript, as if processed with the media type 'application/ecmascript'. [rfc2046][rfc4329]

Implementors may view the setting of event attributes as the creation and registration of an EventListener on the EventTarget. Such event listeners are invoked only for the "bubbling" and "at target" phases, as if false were specified for the useCapture argument to addEventListener. This EventListener behaves in the same manner as any other which may be registered on the EventTarget.

If the attribute representing the event listener is changed, this may be viewed as the removal of the previously registered EventListener and the registration of a new one. Futhermore, no specification is made as to the order in which event attributes will receive the event with regards to the other EventListeners on the EventTarget.

In ECMAScript, one way to establish an event listener is to define a function and pass that function to the addEventListener method:

function myAction1(evt) {
  // process the event
}
// ... later ...
myElement.addEventListener("click", myAction1, false)

In ECMAScript, the character data content of an event attribute becomes the definition of the ECMAScript function which gets invoked in response to the event. As with all registered ECMAScript event listener functions, this function receives an Event object as a parameter, and the name of the Event object is evt. For example, it is possible to write:

<rect onclick="MyClickHandler(evt)" .../>

which will pass the Event object evt into function MyClickHandler.

15.8.1. Animation event attributes

Name	Value	Initial value	Animatable
onbegin, onend, onrepeat	(see below)	(none)	no

15.9. The ‘script’ element

SVG 2 Requirement:	Consider allowing async/defer on ‘script’.
Resolution:	SVG 2 will allow async/defer on ‘script’.
Purpose:	To align with HTML.
Owner:	Cameron (ACTION-3280)

SVG 2 Requirement:	Incorporate SVG Tiny 1.2 script processing model.
Resolution:	SVG 2 will define how inline scriptable content will be processed, in a compatible way to HTML5
Purpose:	To have consistent script running behavior across HTML and SVG.
Owner:	Cameron (ACTION-3282)

A ‘script’ element is equivalent to the ‘script’ element in HTML and thus is the place for scripts (e.g., ECMAScript). Any functions defined within any ‘script’ element have a "global" scope across the entire current document.

The script's text content is never directly rendered; the display value for the ‘script’ element must always be set to none by the user agent style sheet, and this declaration must have importance over any other CSS rule or presentation attribute.

Before attempting to execute the ‘script’ element the resolved media type value for ‘type’ must be inspected. If the SVG user agent does not support the scripting language then the ‘script’ element must not be executed.

This example defines a function circle_click which is called by the ‘onclick’ event attribute on the ‘circle’ element. The drawing below on the left is the initial image. The drawing below on the right shows the result after clicking on the circle.

  <?xml version="1.0" standalone="no"?>
  <svg width="6cm" height="5cm" viewBox="0 0 600 500"
       xmlns="http://www.w3.org/2000/svg">
    <desc>Example script01 - invoke an ECMAScript function from an onclick event
    </desc>
    <!-- ECMAScript to change the radius with each click -->
    <script type="application/ecmascript"> <![CDATA[
      function circle_click(evt) {
        var circle = evt.target;
        var currentRadius = circle.getAttribute("r");
        if (currentRadius == 100)
          circle.setAttribute("r", currentRadius*2);
        else
          circle.setAttribute("r", currentRadius*0.5);
      }
    ]]> </script>

    <!-- Outline the drawing area with a blue line -->
    <rect x="1" y="1" width="598" height="498" fill="none" stroke="blue"/>

    <!-- Act on each click event -->
    <circle onclick="circle_click(evt)" cx="300" cy="225" r="100"
            fill="red"/>

    <text x="300" y="480"
          font-family="Verdana" font-size="35" text-anchor="middle">

      Click on circle to change its size
    </text>
  </svg>

An example demonstrating the effect of the ‘onclick’ event handler on an SVG shape.

View this example as SVG (SVG-enabled browsers only)

Name	Value	Initial value	Animatable
crossorigin	[ anonymous \| use-credentials ]?	(see HTML definition of attribute)	yes

Name	Value	Initial value	Animatable
type	(see below)	application/ecmascript	no

Name	Value	Initial value	Animatable
href	URL [URL]	(none)	no

15.10. DOM interfaces

15.10.1. Interface SVGScriptElement

The crossOrigin IDL attribute reflects the ‘crossorigin’ content attribute.

Chapter 15: Scripting and Interactivity

15.1. Introduction