added GTK4 support

examples/gtk3/connect_args.nim

@@ -0,0 +1,53 @@
+# nim c connect_args.nim
+import gintro/[gtk, glib, gobject, gio]
+
+type
+  O = object
+    i: int
+
+proc b1Callback(button: Button; str: string) =
+  echo str
+
+proc b2Callback(button: Button; o: O) =
+  echo "Value of field i in object o = ", o.i
+
+proc b3Callback(button: Button; r: ref O) =
+  echo "Value of field i in ref to object O = ", r.i
+
+proc b4Callback(button: Button; w: ApplicationWindow) =
+  if w.title == "Nim with GTK3":
+    w.title = "GTK3 with Nim"
+  else:
+    w.title = "Nim with GTK3"
+
+proc appActivate (app: Application) =
+  var o: O
+  var r: ref O
+  new r
+  o.i = 1234567
+  r.i = 7654321
+  let window = newApplicationWindow(app)
+  let box = newBox(Orientation.vertical, 0)
+  window.title = "Parameters for callbacks"
+  let b1 = newButton("Nim with GTK3")
+  let b2 = newButton("Passing an object from stack")
+  let b3 = newButton("Passing an object from heap")
+  let b4 = newButton("Passing a Widget")
+  b1.connect("clicked",  b1Callback, "is much fun.")
+  b2.connect("clicked",  b2Callback, o)
+  b3.connect("clicked",  b3Callback, r)
+  b4.connect("clicked",  b4Callback, window)
+  box.add(b1)
+  box.add(b2)
+  box.add(b3)
+  box.add(b4)
+  window.add(box)
+  window.showAll
+
+proc main =
+  let app = newApplication("org.gtk.example")
+  connect(app, "activate", appActivate)
+  discard app.run
+
+main()
+