Net4x.Xamarin.Forms.Platform.GTK 5.0.777

Net4x.Xamarin.Forms.Platform.GTK

The GTK3 backend for Xamarin.Forms — renderers that map the Forms visual tree onto native GTK widgets, built on GtkSharp 3.

dotnet add package Net4x.Xamarin.Forms.Platform.GTK

This is the package a GTK desktop app references; it pulls in Net4x.Xamarin.Forms.Core.

Getting started

using Gtk;
using Xamarin.Forms;
using Xamarin.Forms.Platform.GTK;

[STAThread]
static void Main(string[] args)
{
    GtkThemes.Init();
    Application.Init();
    Forms.Init();

    var window = new FormsWindow();
    window.LoadApplication(new App());
    window.SetApplicationTitle("My App");
    window.SetApplicationIcon("icon.png");
    window.Show();

    Application.Run();
}

Forms.Init() populates the renderer registry by scanning for [assembly: ExportRenderer], ExportCell, ExportImageSourceHandler, ExportFont and ExportEffect attributes; pass extra assemblies to Forms.Init(IEnumerable<Assembly>) when your renderers live outside the app assembly.

Native prerequisites

GTK 3 must be installed on the machine running the app — libgtk-3-0 on Linux, the GTK3 runtime on Windows, gtk+3 via Homebrew on macOS. GtkSharp binds these libraries at runtime; a missing GTK3 shows up as a DllNotFoundException on the first widget touch.

WebView additionally needs WebKit2GTK 4.1 — libwebkit2gtk-4.1-0 on Debian/Ubuntu, webkit2gtk4.1 on Fedora. This one is optional: the backend loads it lazily and, when it is absent, a WebView renders a "WebView unavailable" placeholder instead of throwing, so the rest of the application is unaffected.

Threading

GTK is not thread-safe. Everything that touches a widget must run on the thread that called Forms.Init() — the thread running the GTK main loop. Use Device.BeginInvokeOnMainThread from anywhere else.

Optional features

Nothing is behind an MSBuild switch any more. Every renderer is always compiled in; the two that depend on something outside a base GTK3 install degrade at runtime instead of at build time, so there is no property to set and no need to rebuild this backend from source:

The former EnableGtkOpenGL / EnableGtkWebView properties are gone, along with the OpenTK dependency OpenGLView used to carry: it now runs on Gtk.GLArea, which is part of GTK itself.

Maps

Xamarin.Forms.Maps is supported on GTK, in a separate package:

dotnet add package Net4x.Xamarin.Forms.Maps.GTK

It draws its own Web-Mercator slippy map with Cairo over OpenStreetMap-compatible raster tiles, so it needs no API key and no native dependency beyond GTK 3 itself. MapType, MoveToRegion, VisibleRegion, pan/zoom, Pins and MapElements (Polyline/Polygon/Circle) are implemented, and Geocoder is backed by Nominatim. Call Xamarin.Forms.Maps.GTK.FormsMaps.Init() after Forms.Init(). See that package's README for its known limitations (notably IsShowingUser, which needs an application-supplied position provider because GTK has no location service) and for how to point it at your own tile server before shipping.

Dependencies

Net4x.Xamarin.Forms.Core and GtkSharp 3.24.24.95.

About this fork

Maintenance fork of the 5.0.0 branch of xamarin/Xamarin.Forms, published under the Net4x. package prefix. Upstream Xamarin.Forms reached end of support on May 1, 2024 and was succeeded by .NET MAUI; note that .NET MAUI has no GTK backend, which is why this one is still maintained here.