[gui] Attributes form designer: show indicators for field constraints and default values (Request in QGIS)

[qgis-bot]

Request for documentation

From pull request qgis/QGIS#62651
Author: @gacarrillor
QGIS version: 4.0

[gui] Attributes form designer: show indicators for field constraints and default values

PR Description:

Follow-up #61544 (more details at QEP).

This PR introduces right-aligned indicator icons (like those that are used in the QGIS layer tree for filters and missing data sources, among others) for field constraints and default values in the attribute form designer.

The indicators will only be shown when field constraints and/or default values are present, and details about specific configurations will be displayed via tool tips. No other interaction with the indicators (e.g., clicking to change some behavior) is implemented.

When in Drag and Drop mode, the indicators are shown in the Form Layout panel. Otherwise, they are always shown in the Available Widgets panel.

Screenshots:

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NOTES ON ICON DESIGN:

• To demonstrate how indicators work, this PR introduces 4 (temporary) icons:
  • Constraints present and all are soft.
  • Constraints present and there's at least one whose strength is hard.
  • Default value present and the Apply default value on update is checked.
  • Default value present and the Apply default value on update is unchecked.
• Those 4 icons will be remade and replaced in a follow-up work package by @nirvn, making sure these are ready prior to QGIS 4.0.0.

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Funded by the QGIS user group Switzerland.

Commits tagged with [need-docs] or [FEATURE]

[gacarrillor]

Note that the PR #62651 brought everything needed but the final icons.

Therefore, documentation for the PR (or at least proper screenshot(s)) needs to wait until new icons are provided. Which should happen before QGIS 4.0.