Feature Request: Support Drop-down List for Integer Parameters with Additional Constraints

[himaj47]

Description:
We would like to request a new feature in rqt_reconfigure to support integer parameters that have additional constraints defined in their parameter descriptor. Specifically, we propose adding support for defining constraints as a CSV-formatted string containing key-value pairs, where:

• Values (strings) are user-friendly labels displayed in the drop-down list.
• Keys (integers) are the actual values passed in parameter update calls.

Proposed Format in Parameter Descriptor:

The additional constraints can be provided as a CSV-formatted string:

0,value0
1,value1
2,value2

For example, a parameter could have constraints like:

"additional_constraints": "\n0,Low\n1,Medium\n2,High"

Expected Behavior in rqt_reconfigure:

1. When an integer parameter has an additional_constraints field formatted as a CSV string, rqt_reconfigure should render it as a drop-down list instead of a numeric input field.
2. The drop-down list should display the Values (e.g., "Low", "Medium", "High").
3. When the user selects an option, rqt_reconfigure should send the corresponding integer value (e.g., 1, 2, or 3) in the parameter update request.

Use Case:

This feature would be particularly useful for defining categorical integer parameters, making them more user-friendly in rqt_reconfigure. Currently, users need to manually enter integer values without seeing their corresponding labels.

[himaj47]

Issue #150 is resolved. I've created a new branch feat/drop_down_list to introduce changes listed below:

Changes Made

• Added DropDownListEditor class in params_editor script which parses the additional_constraints as key-value pairs in CSV format and fills the drop-down list, while passing the corresponding integer value (keys) in parameter updates.

• Introduced key-value pair {"DROP_DOWN_LIST": DropDownListEditor} in EDITOR_TYPES

• Updated add_editor_widgets function to check if an integer parameter's descriptor has an additional_constraints and assign DropDownListEditor instead of the default integer editor if it does.

This is How it looks