Since the node graph can have transform cross nodes, input keyframes may occur
at a different times requiring transforming between sequence time and media
time. This commit implements such a mechanism in all UI classes that need it.
Cuts down on a lot of duplicate code between
TimelineWidget/ViewerWidget/CurveWidget/NodeParamView
and TimelinePanel/ViewerPanel/CurvePanel/ParamPanel since they all use similar
time functions.
When dragging a value in the UI, we use a "single frame update" because we want
to prioritize the currently visible frame to give visual feedback as soon as
possible. Previously, we generated a single frame InvalidateCache() signal
from the widgets themselves, but this had the major downside of not necessarily
emitting the time that the viewer was actually showing (due to either node time
transformations or times differing between the effects panels and the viewer
panels). Now, we send a different signal that viewers can handle themselves to
update the time that they're currently showing. This means the fast updating
will work no matter how many viewers are connected at whatever time each viewer
is set to.
When adjusting a slider, keyframe time, or curve value, it is undesirable to
re-cache the entire affected area while the user is still dragging UI objects.
Since the video is unlikely to be playing, the priority must go to the
currently active frame so the user gets visual feedback on the rendered image
as soon as possible. This was implemented in some areas, but this commit should
have that functionality in all areas.
itsmattkc