The preview draws two background images — BackgroundImage and, above it, ActiveBackgroundImage
(the static art) — while the mini-pane reads the scene snapshot. The default-restore path only
called UpdateBackgroundImage, so the thumbnails updated and the preview did not.
It now calls UpdateActiveBackground as well.
Also adds the generic cure behind the Background bug: OnSelectedElementPropertyChanged invalidates
the scene bake for ANY property change. A static layer's pixels are cached by element identity, so
a property edit without invalidation repaints nothing and the control looks dead — the failure was
never specific to UseDefaultBackground, only first noticed there.
Background + thumbnail tests pass (21); Release 0 warnings.
gramps
41b3933b08