854477 - popup menu display corruption on OS-X HiDPI display when external monitor is present

Status: NEW

(Core :: Widget: Cocoa, defect)

Description

[Brian Warner [:warner :bwarner]]

Attachment: screenshot of menu-display problem

I've been seeing a funny display bug for a couple of months now. When my OS-X laptop (with a retina display) is attached to an external non-retina LCD (a Dell U2410), and the Firefox window is on the laptop's display, then selecting a menu from the bookmark toolbar renders the white background of the menu list a bit weirdly. It seems to be compositing some pixels from the wrong part of the screen (the bottom portion of the window, including the Dock and OS-X wallpaper background from beyond the FF window) into the otherwise-white background.

I've attached a screenshot: look carefully at the dark rectangular background in the top half of the popup, and the yellow bar, and compare them to the yellow NoScript banner and the right edge of the tablet frame shown in the content window.

It seems like the first inch or so of the menu background is a translucent version of the bottom-right corner of the window. The remainder of the menu background is correct: a translucent version of whatever was under that spot on the FF window.

It's easier to see if you have a bookmark folder with lot of entries (so it is tall) and a single very long entry (so the popup is wide, but most of the menu is empty, so you can see the background more easily).

If you move the mouse into the pop-up bookmark window, causing some items to be highlighted, the background is re-rendered correctly, and the problem goes away.

This seems to happen in the same circumstances as bug 853252 (only on the laptop's built-in HiDPI display, and only when an external monitor is attached).

I see the same problem appear in the right-click context menu, sometimes.

Comment 1

[Jonathan Kew [:jfkthame]]

I wondered if the patch in bug 853252 might be relevant here, but I can still reproduce this problem even with that applied.

Note that (AFAICT) this only occurs if the external display is the primary screen (with the system menu bar); if the menu bar is on the internal screen, it doesn't happen.