A better fix for #0004188
Delay calling setPreviewDisplayMode() in ViewProviderPrimitive::setEdit
also fixed issue of not turning off preview mode if the user cancels
editing because there is already a task dialog active.
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fixes#4241
Problem:
PartDesignGui::ViewProvider is responsible for closing the tasks for most of PD features when exiting edit mode
(i.e. unsetEdit()).
For primitives, PartDesignGui::ViewProviderPrimitive is responsible, and neither does it or relies on its parent
VP to do it when calling unsetEdit().
Solution:
Make PartDesignGui::ViewProviderPrimitive::unsetEdit() rely on parent PartDesignGui::ViewProvider to tidy up,
including closing the task dialog.
Reference:
This is the default stack call when closing a document while a PD task using PartDesignGui::Viewprovider is active:
With the recently introduced AttachExtension the PartDesign primitives can be attachable by themself and don't need anymore the helping coordinate system datum. This simplyfies the code and the TreeView largely
