Files
Terminal.Gui/Examples/UICatalog
Copilot f4b10511c0 Fixes #4495 - Adds SuperViewChanging event to View following Cancellable Work Pattern (#4503)
* Initial plan

* Add SuperViewChanging event infrastructure and tests

Co-authored-by: tig <585482+tig@users.noreply.github.com>

* Refactor SuperViewChanging to follow Cancellable Work Pattern with cancellation support

Co-authored-by: tig <585482+tig@users.noreply.github.com>

* Remove SuperViewChangingEventArgs class and use CancelEventArgs<View?> directly

Co-authored-by: tig <585482+tig@users.noreply.github.com>

* Simplified SuperViewChanged

* Refactor SuperView change to use CWP and event args

Refactored the handling of SuperView changes in the View hierarchy to use the Cancellable Work Pattern (CWP) and standardized event argument types. The SuperView property is now settable only via an internal SetSuperView method, which leverages CWP for property changes and cancellation.

- Updated OnSuperViewChanging to accept ValueChangingEventArgs<View?>.
- SuperViewChanging event now uses EventHandler<ValueChangingEventArgs<View?>>; cancellation is via e.Handled = true.
- OnSuperViewChanged and SuperViewChanged now use ValueChangedEventArgs<View?>.
- All SuperView assignments in Add, Remove, and RemoveAll now use SetSuperView, which returns a bool for cancellation.
- CWPPropertyHelper.ChangeProperty now accepts a sender parameter, passed to event handlers.
- All property changes in View now pass this as sender to ChangeProperty.
- Updated event handler signatures and overrides in MenuBar, StatusBar, TextField, and TextView.
- Updated unit tests to use new event args and cancellation pattern.
- Minor code cleanups and improved comments.

These changes modernize and standardize property change handling, improving API consistency, extensibility, and testability.

* Refactor subview removal and event arg types

Removed redundant index check when removing subviews in View.cs, simplifying the cleanup loop. Updated TextField.OnSuperViewChanged to use a non-nullable ValueChangedEventArgs<View> parameter, enforcing stricter type safety.

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: tig <585482+tig@users.noreply.github.com>
Co-authored-by: Tig <tig@users.noreply.github.com>
2025-12-18 06:32:01 -07:00
..

Terminal.Gui UI Catalog

UI Catalog is a comprehensive sample library for Terminal.Gui. It attempts to satisfy the following goals:

  1. Be an easy-to-use showcase for Terminal.Gui concepts and features.
  2. Provide sample code that illustrates how to properly implement said concepts & features.
  3. Make it easy for contributors to add additional samples in a structured way.

screenshot

Motivation

The original demo.cs sample app for Terminal.Gui is neither good to showcase, nor does it explain different concepts. In addition, because it is built on a single source file, it has proven to cause friction when multiple contributors are simultaneously working on different aspects of Terminal.Gui. See Issue #368 for more background.

API Reference

How To Use

Build and run UI Catalog by typing dotnet run from the UI Catalog folder or by using the Terminal.Gui Visual Studio solution.

Program.cs is the main UI Catalog app and provides a UI for selecting and running Scenarios. Each *Scenario is implemented as a class derived from Scenario and Program.cs uses reflection to dynamically build the UI.

Scenarios are tagged with categories using the [ScenarioCategory] attribute. The left pane of the main screen lists the categories. Clicking on a category shows all the scenarios in that category.

Scenarios can be run either from the UICatalog.exe app UI or by being specified on the command line:

UICatalog.exe <Scenario Name>

e.g.

UICatalog.exe Buttons

Hitting ENTER on a selected Scenario or double-clicking on a Scenario runs that scenario as though it were a stand-alone Terminal.Gui app.

When a Scenario is run, it runs as though it were a standalone Terminal.Gui app. However, scaffolding is provided (in the Scenario base class) that (optionally) takes care of Terminal.Gui initialization.

Contributing by Adding Scenarios

To add a new Scenario simply:

  1. Create a new .cs file in the Scenarios directory that derives from Scenario.
  2. Add a [ScenarioMetaData] attribute to the class specifying the scenario's name and description.
  3. Add one or more [ScenarioCategory] attributes to the class specifying which categories the sceanrio belongs to. If you don't specify a category the sceanrio will show up in "All".
  4. Implement the Setup override which will be called when a user selects the scenario to run.
  5. Optionally, implement the Init and/or Run overrides to provide a custom implementation.

The sample below is provided in the .\UICatalog\Scenarios directory as a generic sample that can be copied and re-named:


namespace UICatalog {
	[ScenarioMetadata (Name: "Generic", Description: "Generic sample - A template for creating new Scenarios")]
	[ScenarioCategory ("Controls")]
	class MyScenario : Scenario {
		public override void Setup ()
		{
			// Put your scenario code here, e.g.
			Win.Add (new Button () { 
Text = "Press me!", 
				X = Pos.Center (),
				Y = Pos.Center (),
				Clicked = () => MessageBox.Query (20, 7, "Hi", "Neat?", "Yes", "No")
			});
		}
	}
}

Scenario provides Win, a Window object that provides a canvas for the Scenario to operate.

The default Window shows the Scenario name and supports exiting the Scenario through the Esc key.

screenshot

To build a more advanced scenario, where control of the Runnable and Window is needed (e.g. for scenarios using MenuBar or StatusBar), simply use Application.Top per normal Terminal.Gui programming, as seen in the Notepad scenario.

For complete control, the Init and Run overrides can be implemented. The base.Init creates Win. The base.Run simply calls Application.Run(Application.Top).

Contribution Guidelines

  • Provide a terse, descriptive Name for Scenarios. Keep them short.
  • Provide a clear Description.
  • Comment Scenario code to describe to others why it's a useful Scenario.
  • Annotate Scenarios with [ScenarioCategory] attributes. Minimize the number of new categories created.
  • Use the Bug Repo Category for Scenarios that reproduce bugs.
    • Include the Github Issue # in the Description.
    • Once the bug has been fixed in develop submit another PR to remove the Scenario (or modify it to provide a good regression test/sample).
  • Tag bugs or suggestions for UI Catalog as Terminal.Gui Github Issues with "UICatalog: ".