1443944 - Web Replay: Don't use vsync messages to determine when to paint

Status: RESOLVED INVALID

(Core :: General, enhancement)

Description

[Brian Hackett [Laid off!]]

Attachment: patch

Paints in a content process are triggered based on vsync messages sent via IPDL from the UI process.  If a page is updating very rapidly these messages can lag those changes and events that update the DOM might not be painted.  Normally this isn't a problem, but when rewinding a replaying process this can be pretty confusing, as the graphics shown on screen won't reflect what is expected at that point in execution.

The attached patch changes this so that we attempt to paint with each turn of the main thread's event loop.  If nothing has changed, no painting occurs, but while doing this adds a little more overhead to a recording/replaying process it should ensure that paints occur at predictable times and when rewinding the graphics shown will reflect the state of the DOM at the start of the most recent event.

Comment 1

[Brian Hackett [Laid off!]]

https://hg.mozilla.org/projects/ash/rev/c99df075d08ffdfa42d49d92882a338c3434e118

Comment 2

[Brian Hackett [Laid off!]]

Closing this bug, all the changes here will be reviewed in separate bugs dependent on bug 1422587.