[Bugs] #3413 UNSP: Read: number of pages in epub books can change

[Sugar Labs Bugs]

#3413: Read: number of pages in epub books can change
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    Reporter:  godiard                    |          Owner:  godiard    
        Type:  defect                     |         Status:  new        
    Priority:  Unspecified by Maintainer  |      Milestone:  0.96       
   Component:  Read                       |        Version:  Unspecified
    Severity:  Unspecified                |       Keywords:             
Distribution:  Unspecified                |   Status_field:  Unconfirmed
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 The epub files do not have information aboout pages, because the
 information is stored in files by chapters, and as a continuum html text.

 The epub backend in the Read activity use a webkit widget to load the html
 file, and execute a javascript to calulate the document height, and based
 on this value, calculate the number of pages. The problem we have is,
 running this javascript code return different values at times. We use this
 value to calculate the position needed to scroll to position the document
 when the activity start at the same position the reader left the last
 session. Also based inthe scroll position, we update the toolbar widget
 with the page number, and show the bookmarks related to the page.

 I researched how other book readers calculate the pages, and there are not
 a uniform solution.

 * readers using the Adobe code to display calculate the number of pages
 based in the size of the chapter file. [1] and [2]

 * fbreader use the library ZLibrary to calculate the number of pages [3]
 but this number are not related with the size in the webview, then are not
 useful for us without change a lot our code.

 * Other epub readers use css and javascript to paginate the text,
 but this does not resolve for us how to update the information in our
 toolbar. [4] [5]

 I have tried modifying the javascript code, but the returned values
 continue being different


 [1] http://bookclubs.barnesandnoble.com/t5/NOOK-Book-Discussion/EPUBs-and-
 page-numbering/td-p/691602

 [2] http://www.mobileread.com/forums/archive/index.php/t-166173.html

 [3] http://stackoverflow.com/questions/6027477/how-the-fbreader-do-the-
 pagination-of-html-files-in-epub

 [4] http://stackoverflow.com/questions/2808652/how-to-implement-page-
 break-in-epub-reader

 [5] http://stackoverflow.com/questions/3636052/html-book-like-
 pagination?tab=active#tab-top

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Ticket URL: <http://bugs.sugarlabs.org/ticket/3413>
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