tonecurve: fix serious logical flaw. This should fix #9855
(cherry picked from commit dd3fd4d93c1b01a1ef7ebcc0411f1e936a67d4cc)
Set lt position when changing image in dr with keys
(cherry picked from commit 10bcb0df6e6e816dfa1391029900b4d95ca4005c)
masks: avoid graphical glitches at maximum zoom level. fixes #9867
(cherry picked from commit b3012d8f008301ba8436c9142b2336adf70eabd8)