spline-widget: simplify/fix drawing logic

The linear things should be drawn in drawFunction() since they
change only when some control point is moved and the spline is
recalculated anyway.

Introduce spline::get_value_no_save to avoid clobbering the
tracked value.

Draw linear helper before the spline to avoid occluding it.

Remove some redundant checks for whether _config exists when all
calling sites ensure it already.

I still need to de-camel-case these two classes.

0 files changed, 0 insertions, 0 deletions