Overview

Terminal.Gui is a library intended to create console-based applications using C#. The framework has been designed to make it easy to write applications that will work on monochrome terminals, as well as modern color terminals with mouse support.

This library works across Windows, Linux and MacOS.

This library provides a text-based toolkit as works in a way similar to graphic toolkits. There are many controls that can be used to create your applications and it is event based, meaning that you create the user interface, hook up various events and then let the a processing loop run your application, and your code is invoked via one or more callbacks.

The simplest application looks like this:

using Terminal.Gui;

class Demo {
    static int Main ()
    {
        Application.Init ();

	var n = MessageBox.Query (50, 7, "Question", "Do you like console apps?", "Yes", "No");

	return n;
    }
}

This example shows a prompt and returns an integer value depending on which value was selected by the user (Yes, No, or if they use chose not to make a decision and instead pressed the ESC key).

More interesting user interfaces can be created by composing some of the various views that are included. In the following sections, you will see how applications are put together.

In the example above, you can see that we have initialized the runtime by calling the Init method in the Application class - this sets up the environment, initializes the color schemes available for your application and clears the screen to start your application.

The Application class, additionally creates an instance of the [Toplevel]((../api/Terminal.Gui/Terminal.Gui.Toplevel.html) class that is ready to be consumed, this instance is available in the Application.Top property, and can be used like this:

using Terminal.Gui;

class Demo {
    static int Main ()
    {
        Application.Init ();

        var label = new Label ("Hello World") {
            X = Pos.Center (),
            Y = Pos.Center (),
            Height = 1,
        };
        Application.Top.Add (label);
        Application.Run ();
    }
}

Typically, you will want your application to have more than a label, you might want a menu, and a region for your application to live in, the following code does this:

using Terminal.Gui;

class Demo {
    static int Main ()
    {
        Application.Init ();
        var menu = new MenuBar (new MenuBarItem [] {
			new MenuBarItem ("_File", new MenuItem [] {
				new MenuItem ("_Quit", "", () => { Application.Top.Running = false; })
			}),
		});
        
        var win = new Window ("Hello") {
			X = 0,
			Y = 1,
			Width = Dim.Fill (),
			Height = Dim.Fill () - 1
		};

        // Add both menu and win in a single call
        Application.Top.Add (menu, win);
        Application.Run ();
    }
}

Views

All visible elements on a Terminal.Gui application are implemented as Views. Views are self-contained objects that take care of displaying themselves, can receive keyboard and mouse input and participate in the focus mechanism.

Every view can contain an arbitrary number of children views. These are called the Subviews. You can add a view to an existing view, by calling the Add method, for example, to add a couple of buttons to a UI, you can do this:

void SetupMyView (View myView)
{
    var label = new Label ("Username: ") {
        X = 1,
        Y = 1,
        Width = 20,
        Height = 1
    };
    myView.Add (label);

    var username = new TextField ("") {
        X = 1,
        Y = 2,
        Width = 30,
        Height = 1
    }
    myView.Add (username);
}

The container of a given view is called the SuperView and it is a property of every View.

Among the many kinds of views, you typically will create a Toplevel view or a [Window] (../api/Terminal.Gui/Terminal.Gui.Window.html) which are special kinds of views that can be executed modally - that is, the view can take over all input and returns only when the user chooses to complete their work there.

Modal views take over all the event processing, and do not let other views receive any events while they are running.

There are many views that you can use to spice up your application:

Dialogs

Dialogs are instances of a Window that are centered in the screen, and are intended to be used modally - that is, they run, and they are expected to return a result before resuming execution of your application.

Dialogs are a subclass of Window and additionally expose the AddButton API which manages the layout of any button passed to it, ensuring that the buttons are at the bottom of the dialog.

Input Handling

Every view has a focused view, and if that view has nested views, one of those is the focused view. This is called the focus chain, and at any given time, only one View has the focus.

The library binds the key Tab to focus the next logical view, and the Shift-Tab combination to focus the previous logical view.

Keyboard processing is divided in three stages: HotKey processing, regular processing and cold key processing.

Hot key processing happens first, and it gives all the views in the current toplevel a chance to monitor whether the key needs to be treated specially. This for example handles the scenarios where the user pressed Alt-o, and a view with a highlighted "o" is being displayed.
If no view processed the hotkey, then the key is sent to the currently focused view.
If the key was not processed by the normal processing, all views are given a chance to process the keystroke in their cold processing stage. Examples include the processing of the "return" key in a dialog when a button in the dialog has been flagged as the "default" action.

The most common case is the normal processing, which sends the keystrokes to the currently focused view.

Mouse events are processed in visual order, and the event will be sent to the view on the screen. The only exception is that no mouse events are delivered to background views when a modal view is running.

Color Schemes

All views have been configured with a color scheme that will work both in color terminals as well as the more limited black and white terminals.

The various styles are captured in the Colors class which defined color schemes for the normal views, the menu bar, popup dialog boxes and error dialog boxes.

The ColorScheme represents four values, the color used for Normal text, the color used for normal text when a view is focused an the colors for the hot-keys both in focused and unfocused modes.

By using ColorSchemes you ensure that your application will work correctbly both in color and black and white terminals.

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Overview

Views

Dialogs

Input Handling

Color Schemes

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