Does anyone know how to turn off transparency for the Juk popup announcements? On a dark background the popups become unreadable due to the transparency.

Are you referring to the tooltip that appears when you hover over the icon in the system tray? If so, you may wish to investigate the Blur compositing effect ( it should only be transparent if Compositing is enabled if it is the tooltip )

No. If you right-click on the juk icon in the System Tray, there is an option for Popup Track Announcement. It creates a small window above the System Tray when a new track starts playing, listing track info (title, artist, album) and two buttons (next & prev track.)

In 4.5.1 the announcement window is now transparent. On a dark background the text of the window (which is black) virtually disappears. The buttons, however, are still non-transparent.

I much preferred the 4.4.5 behaviour, as it was readable.

On KDE Trunk, the text has a glow behind it, which when combined with the Blur effect on the tooltip background, makes it perfectly readable. Do you have the Blur desktop effect enabled?

Blur is apparently enabled by default. (I certainly don't remember turning the effect on, but on it is.)

I believe that we're having a bit of miscommunication. The tooltip (created when I hover the mouse over Juk's system tray icon) is perfectly readable. The text in the tooltip has the "glow" you describe, and the Blur effect is obvious.

The pop-up track announcement (auto-generated when a new track starts playing, no hover necessary) has no "glow" and the Blur effect does not appear to be working.

If the pop-up track announcement looked more like the tooltip, that would be ideal.

Are you referring to this? http://imagebin.ca/view/U4qxJQlO.html'

If so, what colour theme do you use? Oxygen seems to work fine, but it may be due to scheme misuse by Juk if it doesn't work in other schemes.

Yes, that's exactly what I'm referring to. That was how the track popup looked in 4.4.5: Solid background with black text.

Here's how the announcement looks like for me now, in 4.5.1:
http://imagebin.ca/view/SsuXUm.html

Note that the box, (with the exception of the "Next" and "Previous" buttons is completely transparent. This first shot is against the Winter Track wallpaper. You can clearly see the snow through the transparency effect.

This next image:
http://imagebin.ca/view/m3fTC-i.html

Is the track announcement over the JK Bridge at Night wallpaper. (Another favourite.) Once again, you can clearly see the dark vegetation through the transparency effect. However, since the vegetation is black, you can't read the track info. The buttons, which are solid, are easily readable.

This is with largely default settings. The only things I tend to change on my KDE setup are Launch Feedback, Mouse Focus, and the addition of a convenient shortcut to walk through the desktop list.

I see it fade out after about 2-3 seconds, but it doesn't cause an effect like that ( as the border fades too )

Can you reproduce under a new user?

I have a "guest" account on my box. I deleted the .kde4 directory and started from scratch. Same effect.

Ok, you will likely need to wait until KDE 4.6 is released to get it fixed.
Your distribution may have unstable packages available which will allow you to test Trunk if you wish. I would recommend waiting however.

Edited to remove stupidity.

Never mind.

I didn't realize I had compositing turned off. Which, of course, changed everything.