1391838 - Handle scrolling large blob images

Status: RESOLVED DUPLICATE of bug 1429930

(Core :: Graphics: WebRender, enhancement, P2)

Description

[Jeff Muizelaar [:jrmuizel]]

If we use naive blob image invalidation we'll have to redraw the entire visible area because we have only a single dirty rect. If we split the update into two pieces we can remove the out of view items in one update and then add the new ones in a second piece.

E.g. imagine a very large svg. The current plan is to create a blob image that contains the entire svg. We'll only fill in the top portion with subitems. As we scroll we'll want to remove the old items and add the new ones.

Note to self: there'll be a clip on the blob image to prevent us from display partial items.

Comment 1

[Jeff Muizelaar [:jrmuizel]]

Attachment: Do fallback display item clipping with webrender. r=ethlin

This gives a huge performance improvement when scrolling mozilla.org
However, it can cause us to make very big display items. This should
be resolved with the tiling support from bug 1387550.