History Inconsistencies in E-Book Viewer

[Emily Palmieri]

Calibre version: 2.14
Operating System: Windows 7 x64

In the e-book viewer, the history (navigated with the Back and Forward buttons) behaves slightly differently depending on the order of operations used to view a given set of pages. These pages are viewed in the same order, but the way they are recorded in the history depends on the user turning the page at a certain time and their use of the Back or Forward buttons. It's easier to explain with some examples...

Suppose I'm viewing Chapter 1 and perform the following operations:
Operations 1
#. Action (Place in the book resulting from the action)
1. Click Chapter 2 in the Table of Contents. (Page 1 Chapter 2)
2. Turn the page. (Page 2 Chapter 2)
3. Click the Back button. (Page 1 Chapter 1)
4. Click the Forward button. (Page 2 Chapter 2)

With this order of operations, I end up on page 2 of Chapter 2, the last page that I happened to view before clicking the Back button. Now suppose I start at Chapter 1 again but perform the following operations:
Operations 2
#. Action (Place in the book resulting from the action)
1. Click Chapter 2 in the Table of Contents. (Page 1 Chapter 2)
2. Click the Back button. (Page 1 Chapter 1)
3. Click the Foward button. (Page 1 Chapter 2)
4. Turn the page. (Page 2 Chapter 2)
5. Click the Back button. (Page 1 Chapter 1)
6. Click the Forward button. (Page 1 Chapter 2)

With this order of operations, I end up on page 1 of Chapter 2 even though steps 4-6 of Operations 2 is identical to steps 2-4 in Operations 1. It appears that under some conditions the page number recorded in the history when the Back button is pressed is the user's current position while in other conditions the page number of the most recent anchor point is recorded in the history. I would expect it to be one or the other all the time. Personally, I think recording the user's current position (i.e. Page 2 Chapter 2) at all times would be more useful, but that's a request more than a bug.

I've also noticed the following, similar problem. Suppose I perform the following actions starting from Chapter 1.
Operations 3
#. Action (Place in the book resulting from the action)
1. Click Chapter 3 in the Table of Contents. (Page 1 Chapter 3)
2. Click the Back button. (Page 1 Chapter 1)
3. Turn the page. (Page 2 Chapter 1)
4. Click Chapter 3 in the Table of Contents. (Page 1 Chapter 3)

If I use the Back button to review my history, I'll find that it contains the following entries in order from least to most recent:
History 1
1. Page 1 Chapter 1
2. Page 2 Chapter 1
3. Page 1 Chapter 3

I could continue adding to the history in this way with the following steps:
Operations 3 (Continued)
5. Click Chapter 5 in the Table of Contents. (Page 1 Chapter 5)
6. Click the Back button. (Page 1 Chapter 3)
7. Turn the page. (Page 2 Chapter 3)
8. Click Chapter 5 in the Table of Contents. (Page 1 Chapter 5)

Now my history looks like this:
History 1
1. Page 1 Chapter 1
2. Page 2 Chapter 1
3. Page 1 Chapter 3
4. Page 2 Chapter 3
5. Page 1 Chapter 5

I can start from Chapter 1 and view the same pages but produce a different history with the following steps:
Oberations 4
#. Action (Place in the book resulting from the action)
1. Click Chapter 3 in the Table of Contents. (Page 1 Chapter 3)
2. Click the Back button. (Page 1 Chapter 1)
3. Turn the page. (Page 2 Chapter 1)
4. Click the Forward button. (Page 1 Chapter 3)
5. Click Chapter 5. (Page 1 Chapter 5)
6. Click the Back button. (Page 1 Chapter 3)
7. Turn the page. (Page 2 Chapter 3)
8. Click the Forward button. (Page 1 Chapter 5)

History 2
1. Page 1 Chapter 1
2. Page 1 Chapter 3
3. Page 1 Chapter 5

Another set of operations starting from Chapter 1 and viewing these same pages produces yet another history:
Operations 5
1. Turn the page. (Page 2 Chapter 1)
2. Click Chapter 3 in the Table of Contents. (Page 1 Chapter 3)
3. Turn the page. (Page 2 Chapter 3)
4. Click Chapter 5 in the Table of Contents. (Page 1 Chapter 5)

History 3
1. Page 2 Chapter 1
2. Page 2 Chapter 3
3. Page 1 Chapter 5

Either History 2 or History 3 seems more reasonable to me than History 1 or some combination of the three.

[Kovid Goyal (kovid)]

Closing since the viewr has been completely re-written for calibre 4.