v2.25 BUG FIX: E-book viewer

[ribik]

BUG FIX: E-book viewer: When displaying multiple pages per screen fix whole screen scrolling so that it works as expected even at the end of the file, when their might be fewer pages left than would fill the screen.

It works perfectly if you are scrolling forward.
But - if you are scrolling backward: for the sections (parts, chapters, *.xhtml's) where it was not needed to add dummy div ('page') coffee script adds empty page, so the behaviour is essentialy the same as it was - only in reverse direction.
Can someone, please, check and confirm this?
Best regards

[kovidgoyal]

No, the behavior is not exactly the same. Previously when scrolling backwards to a new html file you would get all columns filled with text, now you get only one column filled with text.

If you mean that when scrolling backwards towards the start of the file, the behavior is the same as it was when scrolling forwards to the end of the file, that is true. I prefer that inserting blank pages before the start of the text, which just looks weird.

[ribik]

Thank you, Kovid for prompt answer.

What I was trying to say is following:

you scroll through chapter#1 (separate xhtml) and at the end of it there was no need for coffee to add blank page - there were two 'pages' of text displayed.

next scroll reads in chapter#2 (another xhtml) and everything is ok.

and then, if you scroll back to chapter#1, you expect to see the very same two pages of text you've seen before the forward scroll.

but there is 'right page' shown on the left and right page is blank (added by coffee, I guess)

I hope this is somewhat clearer now. Does it suppose to behave like that?

P.S. and consequently when you keep scrolling toward the start of the chapter#1 you will get 'pages 2 & 3' displayed and after that 'pages 1 & 2'.

[kovidgoyal]

Scrolling back to a previous file will not show you the same pages you saw before. You will see one page of text and n - 1 (where n is the number of pages on screen) empty pages always. I could conceivably have the viewer hide the empty pages and instead show you the last n pages of text, when scrolling backwards instead, but it will still not necessarily be what you saw when scrolling forward.

And as for seeing pages 2 & 3 and then 2 & 1 that is the same as it was before. You wills ee the exact same behavior in previous versions when scrolling backwards through a chapter with an odd number of pages.

[ribik]

it will still not necessarily be what you saw when scrolling forward

I got it now. I took a more detailed look into the coffee script.
Being selfish , for me it's all about getting the on screen reading as close as possible to the real book reading. I really understand that Calibre is not primarily e-book reader and yet - it does a lot better job at it than so many other exclusive readers. I greatly appreciate the tremendous work you have put into it, nicely done.
I can really get quite good along with the viewer (finally, who reads books backwards ).
Thank you again, and have a nice time.

[ribik]

File: ebooks.oeb.display.paged.js

PagedDisplay.prototype.column_at = function(xpos) {

var section_page, new_xpos;

section_page = Math.floor(xpos / this.page_width);

if (section_page % 2 === 1) {

section_page -=1;

new_xpos = section_page * this.page_width;

section_page = this.scroll_to_xpos(new_xpos);

}

return Math.floor(xpos / this.page_width);

};

This is how I wanted it to work. I know it is a "dirty hack", but it works perfectly for my needs, because I have two pages per screen. Backward scroll now works as it should. I'm sure it can be done better, to work with multi-columns (section_page % this.cols_per_screen), but for my reading it's ok.