User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:2.0b7pre) Gecko/20100925 Firefox/4.0b7pre Build Identifier: Built from http://hg.mozilla.org/mozilla-central/rev/71e8b5aee972 If you middle-click at the very left edge of the screen when the window is maximized and then move the mouse up or down (while not moving to the right), auto-scrolling fails. This is probably a regression from 3.6, but I have no idea how recent it is. Reproducible: Sometimes Steps to Reproduce: 1.Middle-click at the left edge of the screen while the window is maximized. 2.Attempt to scroll up or down. Actual Results: Scrolling fails. Expected Results: Scrolling should work. This is actually 100% reproducible, but if you accidentally move the mouse even 1px to the right it will scroll normally.

This caused by checked in 7804b5cf4313 Robert O'Callahan — Bug 130078. Part 2. Remove widgets from all subframes. And If you always display Menu Bar, the problem does not happen. May be dup of Bug 598601

Turns out it's a problem of the custom hit testing. The far left of the screen is being treated as a resizer border (HTLEFT) instead of client area. (Very similar to bug 575493)

I'll take

It was a off-by-one problem making the top and left borders 9-pixels wide instead of 8. On the right and bottom this wasn't visible because the rect returned by GetWindowRect is exclusive at the bottom-right edge.

Comment on attachment 479857 [details] [diff] [review] Patch thanks.