[Rotate and perspective] module rotate main image only once in the process of editing about darktable HOT 4 OPEN

I would have said it's working as designed and showing a preview of the effect while the module is open (similar to how the crop module always shows a cropping frame, whether or not activated), but there is a problem even so - if you collapse the module while it is inactive, reopening it doesn't apply the effect, and re-enabling it shows a crop box (or crops, if still collapsed) without applying rotation/perspective. The cropping appears to match what it would be if the effect were being applied.

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@ralfbrown, BTW, we have some very similiar UI issue, when you left not collapsed [graduated density] module: the line showing gradient direction just disappears and no longer visible, when you return to the module in darkroom mode. Please, look reproduction in screencast. To make this line visible again you need to collapse the module (and maybe even reset it).

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@ralfbrown this might be related to the other "riddle" in this module, calculating borders for keep-ratio while rotating only works safely if the module is active, not via shortcuts and alike.

I have tried to understand this, ATM I guess it's related to preview pipe runs, could you have a deeper look?

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