this can be achieved by calling Plasma::ToolTipManager::self()->setState(Plasma::ToolTipManager::Inhibited) somewhere in the shell (e.g. during app setup in main())

it could also be set to ToolTipManager::Deactivated, but then even calls to show(), used by plasmoids to show informational tips on demand, would not work and that may not be desired. 

if there are zero use cases for tooltips, the Deactivated is the better choice for performance and resource usage. from a quick grepping of the sources, this seems to be the case.

I sense this is not purely about Plasma::Tooltip.

Robby, with which apps / tooltips did you see this behaviour specifically?

I see tooltips regularly after I started KDE's systemsettings from Search and Launch Containments Quicklaunch panel. I remember some other points, but not sure where exactly.

Ok, so Plasma::Tooltip doesn't have to do anything with it, as system settings is a QWidget-based UI. Also, systemsetting's tooltips are XXL, making it even more annoying.

I've disabled the extended tooltip in system settings. I'm afraid we can't do much more, other than structurally moving to touch-friendly (non-tooltip) apps...

Ow, probably makes sense to be a bit more specific here:

A new version of the plasma-tablet-config package is uploaded, which does the above.

Robby: can you try if that helps in your case (you can also change it manually in systemsetting's configuration dialog, uncheck "Show detailed tooltips").

for plasma ones i do agree they should be disabled shell level

I'll give it a try this evening after my regular work day :-)

I upgraded active packages and at least for systemsettings the tooltips seem to be gone.
Newertheless, if it is generally desired that tooltips are deactivated, I think this bug is not finally fixed?

we could build Qt with QT_NO_TOOLTIP and thereby kill all Qt tooltips. it looks like the easiest way to achieve this is to patch src/corelib/global/qfeatures.h to uncomment the #define QT_NO_TOOLTIP line.

alternatively, qconfig could be used to generate a custom features file to pass to configure ala:

http://doc.qt.nokia.com/main-snapshot/fine-tuning-features.html

Ah, interesting link. Let's reopen to remind us of this...

Just a note - System Settings and other similar applications (such as Dolphin, KInfoCenter - who all use the same tooltip classes) don't use the QTooltip classes, but their own implementation based on tracking the mouse on a QAbstractItemView.

Needs a fix in the oxygen style, as tooltips are controlled there.

Plasma Active is no longer under development.