UI: Redesign ChoiceParam UI component

[yann-lty]

Description

Re-design the UI control for editing a ChoiceParam.

Exclusive ChoiceParam

The exclusive ChoiceParam component has been resigned to address multiple issues with the current controls.

Before

Behavior

Custom Value indicator

After (this PR)

Behavior

Custom value indicator

Non-exclusive ChoiceParam

This component has been redesigned to display custom values outside the range of possible values.
That may happen when a node description is modified and potentially discard already serialized value in existing scenes.

This can be tried out by pasting this code snippet in Meshroom's script editor:

from meshroom.ui import uiInstance

graph = uiInstance.activeProject
node = graph.addNewNode("FeatureExtraction")
graph.selectedNode = node

graph.setAttribute(node.describerTypes, ["other", "custom"])

Features list

Exclusive ChoiceParam

• Make custom value setting from filter an explicit action.
• Use a less error-looking UI for indicating the use of a custom value.
• Fix value being changed on non explicit actions (eg: when clicking outside the selection popup to discard it).
• Fix incorrect value being displayed in the UI compared to the actual attribute value (eg: after an undo).

Non exclusive ChoiceParam

• Enable support to display/edit value elements outside the list of possible values.

Implementation remarks

FilterComboBox

Rely as much as possible on the behaviors provided by the default ComboBox component to avoid custom logic for e.g keyboard navigation.
Move away from imperative code for handling value binding, simplifying the usage of the FilterComboBox component and making sure that the displayed value is always reflecting the actual attribute's value.
Simplify the filtering logic.

AttributeControls

Introduce a new subfolder (AttributeControls) to host the controls to view and edit attributes, in order to reduce the complexity of AttributeItemDelegate.qml.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.96%. Comparing base (1f42ad3) to head (cb5b0e4).
Report is 21 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2656      +/-   ##
===========================================
+ Coverage    69.93%   69.96%   +0.02%     
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  Files          121      121              
  Lines         7088     7084       -4     
===========================================
- Hits          4957     4956       -1     
+ Misses        2131     2128       -3     

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