1185525 - web page read position changes when screen orientation changes

Status: NEW

(Core :: Layout, defect)

Description

[Mathieu Agopian [:magopian]]

This started as an email thread: https://groups.google.com/a/mozilla.com/forum/#!msg/foxfood-feedback/_EOVjp7-5Pk/D3DebXzXixwJ

And this is the answer I got from Kartikaya Gupta:

> The reason this happens is usually because the CSS viewport (the width at
> which the page is laid out to) changes,  so the page reflows and you end up
> with different content at that scroll position. In other words, it's not so
> much that the scroll position changes (i.e. window.scrollY should be the same)
> but that the content moves to a different scroll position and we don't account
> for it.
> 
> This is something we should actually fix and with some recent changes it
> should be easier to do so;

Comment 1

[Kartikaya Gupta (email:[e-mail])]

To fix this in a world post-bug 1178847, the MobileViewportManager code will need to be updated so that the scroll offset is also changed. We'll probably need some heuristics to find what content is currently visible to the user and then figure out the corresponding scroll offset after the reflow. There might already be something like that in the code somewhere.