Webtoon Reader

[majora2007]

Implement a webtoon reader which scrolls vertically and keeps track of the current page in view. Ensure that:

• It accurately tracks the page number while users are scrolling quick or slow,
• Allows jumping to pages and correctly prefetches around current page
• User does not see the loading animation 95% of the time
• Supports LARGE image panels (ie, 10 MB each)
• Supports multiple sized (height) image stitching
• Run smoothly and lag free on low end devices
• DOM Pruning that is performant without lag spikes

Current Bugs

• When on 2nd to last page, sometimes the trigger for the last page doesn't hit
• Scrolling Backwards, sometimes a page will be skipped, despite how slow/fast you go
• Jumping to a page (forward) doesn't scroll to the actual page (sits on the first page of prefetch range)
• Switching reading modes to webtoon reader doesn't scroll to the correct page
• On First load, if you load to page 3, pages 1 & 2 aren't prefetched, so you can never read them
• When performing a GoToPage, if you jump outside of the orginal prefetch range, the prefetch code might build a range that does not include the newly set page number. (ie page 4 -> 20, generates prefetch of 13-19)
• Go To Page doesn't ALWAYS trigger a scroll event (this fails if we jump backwards after first load, the prev scroll bug triggers and so the scroll doesn't work)
• On Mobile, pages get duplicated
• If you go to last pages and scroll up and down really quick, blank images will appear at the end
• Jump to page 1/last page doesn't trigger the webtoon reader to scroll

Other Issues

• There is noticeable page jank when scrolling (and a prefetch occurs) on lower end mobile devices
• Reading direction button should be disabled when in webtoon reader mode