TapAction is a GestureAction-subclass that handles clicks and
tap gestures. It is meant to provide a replacement for ClickAction
using GestureAction:
• it handles events trasparently without capturing them, so that it
can coexists with other GestureActions;
• the ::tap signal is not emitted if the drag threshold is exceeded;
• building upon GestureAction the amount of code is greatly reduced.
TapAction provides:
• tap signal, notifying users when a tap has been performed.
The image-content example program has been updated replacing its
ClickAction usage with TapAction.
https://bugzilla.gnome.org/show_bug.cgi?id=683948
