Add manual bindings for async functions

[fsobolev]

• I agree that my contribution may be licensed either under MIT or any version of LGPL license.

Added:

• Gtk.FileDialog.OpenAsync
• Gtk.FileDialog.SaveAsync
• Gtk.FileDialog.SelectFolderAsync
• Gtk.FileLauncher.LaunchAsync
• Gtk.FileLauncher.OpenContainingFolderAsync
• Gtk.UriLauncher.LaunchAsync

I don't think that throwing an exception on error like it's done in WebView is desired behavior, error is set even if a dialog was simply cancelled by the user, which is definitely not a critical error and I think just checking for null/false makes more sense:

Related: #900

[fsobolev]

/home/runner/work/gir.core/gir.core/src/Libs/Gtk-4.0/Public/FileDialog.cs(1,1): error CHARSET: Fix file encoding. [/home/runner/work/gir.core/gir.core/src/Libs/Gtk-4.0/Gtk-4.0.csproj]
/home/runner/work/gir.core/gir.core/src/Libs/Gtk-4.0/Public/FileLauncher.cs(1,1): error CHARSET: Fix file encoding. [/home/runner/work/gir.core/gir.core/src/Libs/Gtk-4.0/Gtk-4.0.csproj]
/home/runner/work/gir.core/gir.core/src/Libs/Gtk-4.0/Public/UriLauncher.cs(1,1): error CHARSET: Fix file encoding. [/home/runner/work/gir.core/gir.core/src/Libs/Gtk-4.0/Gtk-4.0.csproj]

Ugh... What does that mean? 😓 Files are just ASCII text.

[badcel]

You should be able to run dotnet format GirCore.Libs.slnf in folder src which should fix those things. If it does not work you can try to specify the csproj from GTK directly to only Format the GTK project.

[badcel]

One more thing is necessary. If the ...Finish method can return null (see documentation) then it is necessary to check the return value for IntPtr.Zero after the GLib.Error.ThrowOnError:

Rough sample:

if(result == IntPtr.Zero)
{
tcs.SetResult(null);
}
else
{
//here original code to get and set the result in the task completion source.
}

[fsobolev]

Added Gtk.FileLauncher.OpenContainingFolderAsync

[badcel]

Looks good to me. Thanks for your contribution 🚀