I'm reluctant to submit this bug, since I haven't been able to reduce it, and cannot reproduce it on other machines. It appeared a number of months ago. I'm going to describe the symptoms as accurately as I can, in the hope that they'll ring a bell with someone before it makes it into the wild and affects more users. So far, the issue only appears to affect Gmail. 1. When anything changes on the page (a menu is opened, an email is opened or closed), I can see the change "paint" in strips from the bottom and right edges over the course of a fraction of a second. 2. The insertion point does not blink in plain text fields, and when I move it, it appears to stay in its old location until I start typing. The insertion point *does* blink in rich text fields (contenteditable). 3. When I switch from the tab containing Gmail to another tab and back, the page is blank. I can still move my mouse and see the cursor change, and I can interact with the page (e.g. move messages around with keyboard commands), though nothing I do is visible. This part of the issue comes and goes. It's a problem for a few days, then it isn't. When it is not a problem, the page can be seen to be "painted", like in issue 1, over white, when its tab is selected. Any ideas?
Other than the blanking (which I don't see since upgrading to r63031, though maybe I'm just lucky), I see all three of the issues.
This is largely fixed in recent builds via bug 34009. Gmail becoming blank was bug 40421. There's still some flashing when composing a new mail.
I agree that most issues seem to be fixed, but I still sometimes see #2 (insertion point doesn't blink/isn't always visible).
Simon, your fix for https://bugs.webkit.org/show_bug.cgi?id=49079 seems to have finally fixed the remaining cursor issues! :D