Section 4.43 Slides

A <slideshow> is a document type of its own: the element replaces <article> or <book> at the top of your source, as a child of <pretext>. A <docinfo> works exactly as for any other document type, and so does the bibliographic information: the show opens with a <title>, an optional <subtitle>, and an optional <frontmatter> whose <bibinfo> (authors, an <event> naming the conference or seminar, a date) feeds a title slide, with an optional <abstract> following.

The body of the show is a sequence of <section>, or, for a short talk, simply a sequence of <slide>. A section here is lighter than its namesake in an article: a <title> and then its slides, nothing else. Each conversion renders a section title as an interstitial title slide, so sections give a long talk its signposts.

A <slide> has a <title> and then holds content much as a division does: paragraphs, displayed mathematics, figures, images, theorems and their kin, programs and consoles, side-by-side layouts. One convenience is particular to the genre: a list (<ol>, <ul>, or <dl>) may sit directly on a slide, bare, without the customary wrapping <p>. This applies only at the top level of a slide (or subslide); a list nested within a list item still requires its paragraph, just as anywhere else.

Presentation is incremental, and two devices control it, identically in every conversion. First, the @pause attribute, with value yes, may be placed on a paragraph, a list, an image, or a side-by-side: that material is held back until the next advance of the show, and a paused list reveals its items one at a time. Second, a <subslide> gathers several blocks that then appear together, all at once, after an advance—while material following the subslide is visible from the outset. The @pause attribute means nothing outside a slideshow, and validation will tell you so.

Content is placed vertically at the top of each slide, by default. The @valign attribute, with value top, middle, or bottom, changes that: on a single <slide>, it places that slide’s content; on a <slides> element within the <defaults> element of <docinfo>, it sets a document-wide default, which a slide’s own @valign still overrides. The title slide, and the interstitial slides announcing each section, follow the document-wide setting.