Ebook view 'sticky' when scrolling up

[truth1ness]

On my mac I've noticed that scrolling up slowing is 'sticky' in the calibre ebook viewer. If you scroll slow enough it stops even though scrolling down at the same speed works fine. I thought it was my imagination at first but it is very consistent and it's the same on my trackpad and magic mouse so this is not a hardware thing. Also no other program exhibits this behavior, including Calibre itself. For some reason it seems like there is a threshold scrolling rate to scroll up but not to scroll down in the ebook reader. I often overshoot when I speed up my scroll to get over the threshold. This is really very frustrating for reference/text books where I'm constantly moving around up and down the material.

[kovidgoyal]

Is this in paged mode or scroll mode?

[truth1ness]

It's on scroll mode.

[kovidgoyal]

I get the same behavior either backwards or forwards on my OS X machine (albeit that is a MAc Mini with an Apple mouse). And looking at the code, I see nothing asymmetrical there:

https://github.com/kovidgoyal/calibr...tview.py#L1284

[truth1ness]

I've tested a second Mac (Mac mini this time) with an apple magic trackpad and an iMac with a clean OSX install with a Magic Mouse and all three computers and 4 input devices show the exact same asymmetrical behavior.

You are not able to reproduce it because the Apple Mouse which you have scrolls in small discrete movements (I have one and tested it and you are right this model does not have the assymetry) each of which overcome the scroll rate threshold. However, "continuous" touch scroll devices like the Apple Magic Mouse, Apple Magic Trackpad, and any Macbook Trackpad all seem to have this problem and scrolling up is very disjointed. I've not seen this happen in any other program with any of these devices.

Here is a recording I made with the live input of my Magic Mouse scroll sensor displayed while I first scroll up then down and you can see the book area barely scrolls up until the third try when I go fast.

Interestingly, in the second half of the recording I then do the same up/down scroll in the Table of Contents area and there is no problem, it scrolls perfectly symmetrically no matter how slow I go. So this is a problem specific to the main text window only. The TOC right next to it scrolls perfectly.

[kovidgoyal]

Well, without the hardware in question there is nothing I can do about it. As I pointed out above, there is no asymmetry in the actual code handling wheel events. Which means the asymmetry, if any, occurs at a lower level than that of calibre code. It might be possible to compensate for it in calibre, but doing so is impossible without being able to reproduce.

[truth1ness]

Arg, I was crossing my fingers that you'd have access to a trackpad somewhere.

It's a long shot but I'm wondering, since all the other scroll windows in Calibre work fine, like the TOC scrollbar, could the book text area scrolling use that same scrolling module/code instead of the custom one it is using now? The main text window seems to be following separate settings/behaviors than all the other scroll windows in Calibre like the TOC which works great.

The scroll rate of the book text area is also like triple the speed of all the other normal scroll windows in Calibre or elsewhere on my mac (you can see how far down just a small movement scrolls in the recording). I wonder if this speed discrepancy might also be related to the issue.

[kovidgoyal]

You cannot not have a custom implementation since scrolling has to load new files when you reach the end of the current html file, or turn pages if you have it setup to turn pages.

[kovidgoyal]

If I were you, I'd just use the arrow keys to scroll.