[72 hours] Issue 140: media-overlay-active

[Markus Gylling]

This is the proposed solution to issue 140 [1]. Deadline for objections: 23:59 UTC Wednesday 22 June.

Instead of defining a pseudo-class or a reserved CSS class name for styling the active text element during Media Overlay playback, it is proposed to allow content producers to use any CSS class name, and to make this class name discoverable by Reading Systems by declaring it in the package file metadata. For example:

<meta property="media:active-class">-epub-media-overlay-active</meta>

Any valid CSS class name is legal; for example:

<meta property="media:active-class">text-highlight</meta>

The metadata property "media:active-class" is part of the metadata vocabulary defined for Media Overlays by the EPUB3 specification. The provided value for the "media:active-class" metadata property must conform to the CSS syntax for class names. There must be at most one such metadata entry per publication.

The "media:active-class" metadata entry is optional, and if omitted, Reading Systems can apply any arbitrary style to the active Media Overlay element (the behavior is implementation-specific).

The email thread leading to this proposal is available at [2].

[1] http://code.google.com/p/epub-revision/issues/detail?id=140
[2] http://groups.google.com/group/epub-working-group/browse_thread/thread/1eba33a3b544b6e2

[Kevin Ballard]

Isn't the <meta> tag defined with the attributes name/content, not the attribute property? Here's the relevant bit of the OPF schema:

<define name="OPF20.meta-element">
  <element name="meta">
    <ref name="OPF20.optional-id-attribute"/>
    <ref name="OPF20.optional-xml-lang-attribute"/>
    <attribute name="name">
      <text/>
    </attribute>
    <attribute name="content">
      <text/>
    </attribute>
    <optional>
      <attribute name="scheme">
        <text/>
      </attribute>
    </optional>
    <ref name="OPF20.meta-content"/>
  </element>
</define>

<define name="OPF20.meta-content">
  <empty/>
</define>

This leads me to believe that the tag <meta property="media:active-class">text-highlight</meta> isn't valid, and that we should be using <meta name="media:active-class" content="text-highlight"/> instead.

-Kevin Ballard

[matt.g...@bell.net]

Hi Kevin,
 
That's the definition from OPF 2.0. The 3.0 schema changed the definition of the meta element -- and does not define @content -- so the example is correct as:

 
<meta property="media:active-class">text-highlight</meta>
 

Matt
 

---

From: kbal...@apple.com
Subject: Re: [72 hours] Issue 140: media-overlay-active
Date: Tue, 21 Jun 2011 17:52:06 -0700
To: epub-work...@googlegroups.com; markus....@gmail.com