Using Gtk4 With C# and Gir.Core Hello World Tutorial

mkdir GtkTutorials
cd GtkTutorials
dotnet new console -f net8.0 -o HelloWorld
dotnet new gitignore
dotnet new sln
dotnet sln add HelloWorld/

cd HelloWorld
dotnet add package GirCore.Gtk-4.0 --version 0.5.0

dotnet new class -n HelloWorld

 1namespace HelloWorld
 2{
 3    // Define a class named HelloWorld that extends Gtk.Window.
 4    // Gtk.Window represents a top-level window in a GTK application.
 5    public class HelloWorld : Gtk.Window
 6    {
 7        // Constructor for the HelloWorld class.
 8        // This method sets up the window and its contents.
 9        public HelloWorld()
10        {
11            // Set the title of the window.
12            Title = "Hello World App";
13
14            // Set the default size of the window to 300 pixels wide and 30 pixels tall.
15            // This is the initial size when the window is first displayed.
16            SetDefaultSize(300, 30);
17
18            // Create a new button widget.
19            // Gtk.Button is a clickable UI element.
20            var helloButton = Gtk.Button.New();
21
22            // Set the text label displayed on the button.
23            helloButton.Label = "Say Hello";
24
25            // Add margins around the button to create spacing from the edges of the window.
26            // Margins are specified in pixels.
27            helloButton.SetMarginStart(10);  // Left margin
28            helloButton.SetMarginEnd(10);    // Right margin
29            helloButton.SetMarginTop(10);    // Top margin
30            helloButton.SetMarginBottom(10); // Bottom margin
31
32            // Add the button to the window.
33            // The `Child` property represents the main widget contained in the window.
34            // Here, we set the button as the only child of the window.
35            // In a real application you would set the child to be one of the Gtk Layout widgets 
36            // so you can have multiple widgets in the window.
37            Child = helloButton;
38
39            // Attach an event handler to the button's "OnClicked" event.
40            // This event is triggered when the user clicks the button.
41            helloButton.OnClicked += (_, _) =>
42            {
43                // Print "Hello World!" to the console when the button is clicked.
44                Console.WriteLine("Hello World!\n");
45            };
46        }
47    }
48}

 1// Create a new GTK application instance.
 2// "com.example.helloworld" is the unique application ID used to identify the app.
 3// The application ID should be a domain name you control. 
 4// If you don't own a domain name you can use a project specific domain such as github pages. 
 5// e.g. io.github.projectname
 6// Gio.ApplicationFlags.FlagsNone indicates no special flags are being used.
 7var application = Gtk.Application.New("com.example.helloworld", Gio.ApplicationFlags.FlagsNone);
 8
 9// Attach an event handler to the application's "OnActivate" event.
10// This event is triggered when the application is started or activated.
11application.OnActivate += (sender, args) =>
12{
13    // Create a new instance of the main application window.
14    var window = new HelloWorld.HelloWorld();
15
16    // Set the "Application" property of the window to the current application instance.
17    // This links the window to the application, allowing them to work together.
18    window.Application = (Gtk.Application) sender;
19
20    // Show the window on the screen.
21    // This makes the window visible to the user.
22    window.Show();
23};
24
25// Start the application's event loop and process user interactions.
26// RunWithSynchronizationContext ensures proper thread synchronization for GTK.
27// The "null" parameter takes the arguments from the commandline. As there are no arguments
28// supported in this tutorial the parameter is not filled and thus null.
29return application.RunWithSynchronizationContext(null);

dotnet run