The IDPF announced the Fixed Layout specification on the 15th March 2012. Here it is 17th March 2012 and we are able to have the first IDPF sample fixed layout ePub3 books up for viewing on AZARDI Online.
It was relatively straight-forward to map the IDPF specification to the AZARDI fixed layout method as the match was very close. There are only so many ways fixed layout can be done!
You can view the IDPF samples A Voyage of Life and Page Blanche here on the AZARDI OL demo site.
We have also uploaded the IDPF sample version of Moby Dick with two chapters containing SMIL overlays for those interested in this area of the ePub3 feature list.
The specification doesn't particular address elastic viewports, but does leave the decision up to the reading device.
Reading Systems must clip XHTML content to the ICB dimensions declared in the viewport meta tag, and therefore content positioned outside of the initial containing block is not going to be visible. When the ICB aspect ratio does not match the aspect ratio of the Reading System content display area, Reading Systems may position the ICB inside the area to accommodate the user interface; in other words, added letter-boxing space may appear on either side (or both) of the content.
Obviously this is written for tablets and fixed viewport sizes. Given the flexible viewing available in AZARDI DT and AZARDI OL, we don't really need to crop or use letterboxing, but did have to decide on scaling. So at present we are sticking with a fixed max-width 1024PX, max-height of 700PX at present until we do more work on presentation options.
We have had to define a new concept - "Scalable Fixed Layout". It's on the drawing board! Effectively let the user fill the viewport, or not.
The below quotes for the books are taken from the ePub3 samples project at http://code.google.com/p/epub-samples/wiki/SamplesListing
An extract of a fixed layout document, using XHTML spine items that embed bitmaps. This sample has both the rendition:orientation and the rendition:spread properties set to 'auto'.
The auto options means the orientation and spread can more or less be anything the reading device wants it to be. We decided to process this as a single page book for AZARDI OL as we don't yet have a user spread option. The book contains blank left pages, so it is a little strange in this presentation. At 700PX high the text on page 4 is not really readable. It is fixed size in this version but we will work on making it spread-adaptive and optionally-sizable in a future release of AZARDI. Meanwhile if you have a really big monitor it is going to look a little lonely on the screen. It's a work in progress.
A Voyage of Life
A mixed reflowable and fixed layout document (the first section is reflowable, and the remainder fixed). This sample also contains an experimental "textual overlay"; the paintings in the fixed pages can be tapped or clicked to toggle the display of a commentary box. Note that the primary purpose of this sample is to exhibit mixed reflowable/fixed content; the textual overlay component is experimental and not recommended for replication. This sample has the rendition:orientation property set to 'landscape', and the rendition:spread property set to 'none'.
AZARDI obeys the orientation and spread properties. The page sizes passed the AZARDI display resolution test so they are presented at the ePub size without scaling. Interestingly the pages are all different heights, which AZARDI accomodates quite happily.
AZARDI maps the IDPF specification properties to its own fixed layout engine values because it has to handle a lot more cases than the tablet viewport problem. Since we have had fixed layout capabilities since September 2011, the requirements had been 90% handled in AZARDI. It wasn't hard to map the IDPF values to AZARDI values. AZARDI also inserts/provides its own Initial Containing Blocks (ICB) to get screen presentation control which bypasses any <body> styles.
This was our first shot at implementing the IDPF Fixed Layout Specification. It wasn't a complete failure and defines the journey ahead.
In this version we had to decide what size to make the book, so applied our compromise pseudo-device 700px height for availability in the maximum number of browsers. We will shortly make size and orientation user adjustable with some more tap/click button options when a book calls for fixed layout presentation.
The flexibility of the browser means we can have a spread option if the IDPF properties specify it. AZARDI always obeys the publisher/designer intention with fixed layout. The mobile versions will have to take into account the letterboxing options specified. To crop or box, that is the question?
Now that we have a Fixed Layout specification we will use it to update the AZARDI defaults and maintain backward compatability for those hundreds of books using the AZARDI fixed layout spec.
And finally. Our thanks to the IDPF and members for making these samples available.