QgsInterface::adddockwidget slows down when large layers open

[qgib]

Author Name: Johannes Elstner (@fuzzysolutions)
Original Redmine Issue: 20065
Affected QGIS version: 3.2.3
Redmine category:python_plugins

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Having opened a larger vector layer, reloading a plugin using PluginReloader is slower in QGIS 3.2.x than in QGIS 2.18.x (tested with 3.2.3 and 2.18.23, but presumably consistend over other versions).
Using cProfile, if found out its not the plugin itself but its call of QgsInterface::addDockWidget that causes the delay. Closing and re-opening the plugin dockwidget shows the same delay behaviour.

On QGIS 3, addDockWidget takes 5s - 20s, depending on the size of the vector layer and the location of storage (its slower with a layer from a remote network drive). Without any layer opened, its just as fast as normal. My plugin, obviously, contains some QgsMapLayerComboBoxes. Somwhere in the call of addDockWidget there must be a time-expensive call onto the layers that are to be shown in the comboboxes.

[qgib]

Author Name: Johannes Elstner (@fuzzysolutions)

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Not reproducable in QGIS 3.6.1.

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• status_id was changed from Open to Closed