Good point. I believe that the answer is no in general, but there are special cases in which the flow tree must be rebuilt at least in part. Normally the flow tree can be reused on window resize/device rotation/CSS animation, but there are special cases in which it can't (e.g. media queries). But we can test for that up front.
Patrick On August 28, 2014 7:14:02 PM PDT, Cameron Zwarich <zwar...@mozilla.com> wrote: >Do such events always cause the layout task to require DOM access to >create the flow tree? If so, the layout task would still have to wait >for the script task to finish, meaning that layout still can’t occur >unless forced by script. > >Cameron > >On Aug 28, 2014, at 7:10 PM, Patrick Walton <pwal...@mozilla.com> >wrote: > >> It might happen if layout is flushed from outside the script task; >window resizing/device rotation being what immediately comes to mind, >as today in Servo those events go straight from compositor to layout >without hitting the script task at all. (As an alternative design, we >could route such events through the script task; this would remove the >necessity of the mutex but would block layout for such events if script >is running, even if the script hasn't touched the DOM.) >> >> Patrick >> >> On August 28, 2014 7:05:09 PM PDT, Robert O'Callahan ><rob...@ocallahan.org> wrote: >> On Fri, Aug 29, 2014 at 12:56 PM, Cameron Zwarich ><zwar...@mozilla.com> >> wrote: >> >> Is it strictly enforced that the script task never sees inconsistent >views >> of layout? This came up in the other thread about threading, but >what >> prevents this incorrect scenario? >> >> 1) The script task takes the mutex to access one property of layout. >> 2) The script task releases the mutex. >> 3) Layout changes the property that was accessed. >> 4) The script task takes the mutex again to access the same >property, in >> the same turn of the event loop without modifying layout in any >intervening >> work since the last attempt. >> 5) The script task reads a different value from before. >> >> >> I'm confused. Before or during step 1, the layout must be brought up >to >> date (flushed, in Gecko >> parlance). So step 3 shouldn't happen since layout >> would already be fully up to date. >> >> Rob >> >> -- >> Sent from my Android phone with K-9 Mail. Please excuse my brevity. -- Sent from my Android phone with K-9 Mail. Please excuse my brevity. _______________________________________________ dev-servo mailing list dev-servo@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-servo
