Project: moodle
Issue MDL-42928: Reimplement scroll locking for full-screen dialogues
IMO, this is a serious usability issue as many of our dialogues contain scrollable content. When these are open and you attempt to scroll, you'll find that the page scrolls too. Whilst this isn't a major issue for desktop computers, those using trackpads (predominantly laptops), and those with touch screens (predominantly tablets) who swipe to get down the list will find that the whole page starts to move once the bottom (or top) of the list is reached. In the case of the Activity Chooser, this is a serious regression. This patch re-introduces scroll locking but using a different method. Rather than removing the scrollbars, we instead set the scrollTop and scrollLeft to the positions they were in when the dialogue was opened. We do this on every scroll event. When the dialogue is closed, we stop forcing the scroll and release control back to the user.
Story points: 100