Default for Reflowable Content is Spreads; should be Singles

[Kathybluefire]

After talking with Ric, we agree, that the default for reflowable content should be single pages, not spreads. Especially considering mobile devices, spreads are award when text is large. Authors can specify spreads when appropriate, but for the typical ebook, single pages should be the default.

[danielweck]

Taken from #96

"This is also a case for Single pages being the default. This file does not behave in the way people read: both columns move down the page concurrently, and we read the first column, then the second. It's very awkward to get the reader to perform that way. You need to read the first column to the bottom, go to the next file, then back to the previous and read the second column. Not so much."

Book to use to test: https://bluefireproductions.box.com/s/kvy491e757ydkob2vqh5
File Name: O_01_Paginated

[danielweck]

The current behaviour is to view the document using a two-page synthetic spread when the width is greater than the height (landscape aspect ratio), and to switch to single-page view when in portrait mode (which is useful when rotating the display of a mobile phone or tablet device).

On that basis, I disagree with "the default for reflowable content should be single pages, not spreads", because on a typical laptop or tablet landscape display this would result in long horizontal lines of text, which is very difficult to read / scan (this is why "columns" are used in most printed formats to break up the eye scanning distance). Should a user want/need to switch to a wide single page view, they can always do so by setting their user preference via the options dialog. However, I do not think this is an acceptable default.
@rkwright do you agree?

[danielweck]

@KathyAlley @rkwright
Related issue:
#101

As mentioned here and at the issue above, there are font-size implications in addition to viewport width (because the text line eye-scanning distance is a function of both)

[danielweck]

Oh, and here is the decision grid for synthetic spread setting:
https://docs.google.com/spreadsheet/ccc?key=0AoPMUkQhc4wcdDI0anFvWm96N0xRT184ZE96MXFRdFE&usp=drive_web#gid=0

Implemented here:
https://github.com/readium/readium-shared-js/blob/develop/js/helpers.js#L207

[danielweck]

Note that this issue is addressed in the "textWidthMargins" feature branch, which contains single/double spread switch logic based on "column" width (text line length) rather than just orientation aspect ratio (screen rotation):
https://github.com/readium/readium-js-viewer/tree/feature/textWidthMargins
https://github.com/readium/readium-shared-js/tree/feature/textWidthMargins

[danielweck]

Kathy, Ric and I had discussions about this, all is right. Closing issue.
(irrespective of new logic in "textWidthMargins" feature branch)