[Data-defined Assistant] Symbols preview doesn't update if "Apply transform curve" checkbox is unchecked

[qgib]

Author Name: Harrissou Santanna (@DelazJ)
Original Redmine Issue: 17062
Affected QGIS version: master
Redmine category:symbology

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Point Layer Symbology Properties > select Assistant from the Data Defined button near the Size property
In the new dialog, set the input options
Expand the Apply transform curve: there is straight line
Enable the checkbox and play with it --> The symbol representation will change accordingly in the right panel
Uncheck the "Apply transform curve" option: instead of having the symbols restored at the initial representation in the right panel, you still get the transformed one.

I can't tell whether this has an effect on the canvas given that no symbol is rendered (see #24960). But reopening the assistant dialog show the initial good preview with an unchecked "apply transform curve"

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• InactiveTransformCurve.PNG (Harrissou Santanna)

[qgib]

Author Name: Giovanni Manghi (@gioman)

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Please check if this issue is still valid on QGIS 3.4.5 or 3.6.

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• status_id was changed from Open to Feedback

[Pedro-Murteira]

This is still an issue on QGIS 3.22.3.