Dear Ulrich, yes, with your original code I do see the cell bracket flickering. If I only include the compound expression of Manipulate
in a Dynamic[]
like so
Manipulate[
Dynamic[If[run, \[Phi] += d\[Phi]]; x = Cos[\[Phi]]; y = Sin[\[Phi]];
Graphics[{Red, Point[{x, y}], Blue, Point[{0., 0.}],
Opacity[0.25, Gray],
Rectangle[{-1.1, -1.1}, {1.1, 1.1}]}]], {run, {False, True}},
{{d\[Phi], 0.1}, 0., 0.2},
{x, ControlType -> None},
{y, ControlType -> None},
{{\[Phi], 0.}, ControlType -> None}
]
as already suggested by @David G - the flickering disappears and everything runs smoothly.
Beste Gruesse -- Henrik