Any symbols (including class properties) that should be visible
outside the module it's defined in need to be defined as global.
For now gjs still allows the access for 'const', but get rid of
the warnings spill now by changing it.
https://bugzilla.gnome.org/show_bug.cgi?id=785084
The actor allocation will be invalid on CLUTTER_TOUCH_BEGIN, because
it comes together with a CLUTTER_ENTER event that will recalculate
styles, and queue a relayout in result.
The net result is that on CLUTTER_TOUCH_BEGIN, the relayout has been
already queued, so the slider width comes up as 0, and the value ends
up as 1. Later touch events already happen on a validated actor, so
it is corrected. Still, not fun when modifying the volume slider on a
touchscreen.
We are already emitting a 'drag-end' signal when no more dragging
is happening, so it makes sense to emit a 'drag-begin' too when
starting, so that apps interested in implementing different logic
between those two events can easily do it without needing to deal
with the underlying 'button-press-event' signal for the actor.
https://bugzilla.gnome.org/show_bug.cgi?id=761208
This is a regression from splitting the slider out that never got fixed.
Restore the previous (useful) behavior by adding a public API to the
slider that lets us pass an event through.
https://bugzilla.gnome.org/show_bug.cgi?id=704368
