Add a custom input test

This shows the minimal work required to hook up an
im context to a custom widget.

tests/input.c

+/* Demonstrates hooking up an input method context to a custom widget.
+ */
+#include <gtk/gtk.h>
+
+G_DECLARE_FINAL_TYPE (DemoWidget, demo_widget, DEMO, WIDGET, GtkWidget)
+
+struct _DemoWidget
+{
+  GtkWidget parent_instance;
+
+  GtkIMContext *im_context;
+  PangoLayout *layout;
+};
+
+struct _DemoWidgetClass
+{
+  GtkWidgetClass parent_class;
+};
+
+G_DEFINE_TYPE (DemoWidget, demo_widget, GTK_TYPE_WIDGET)
+
+static void
+commit_cb (GtkIMContext *context,
+           const char   *str,
+           DemoWidget   *demo)
+{
+  pango_layout_set_text (demo->layout, str, -1);
+  pango_layout_set_attributes (demo->layout, NULL);
+  gtk_widget_queue_draw (GTK_WIDGET (demo));
+}
+
+static void
+preedit_changed_cb (GtkIMContext *context,
+                    DemoWidget   *demo)
+{
+  char *str;
+  PangoAttrList *attrs;
+  int cursor_pos;
+
+  gtk_im_context_get_preedit_string (context, &str, &attrs, &cursor_pos);
+  pango_layout_set_text (demo->layout, str, -1);
+  pango_layout_set_attributes (demo->layout, attrs);
+  g_free (str);
+  pango_attr_list_unref (attrs);
+
+  gtk_widget_queue_draw (GTK_WIDGET (demo));
+}
+
+static gboolean
+key_pressed_cb (GtkEventControllerKey *controller,
+                guint                  keyval,
+                guint                  keycode,
+                GdkModifierType        state,
+                DemoWidget            *demo)
+{
+  if (keyval == GDK_KEY_BackSpace)
+    {
+      pango_layout_set_text (demo->layout, "", -1);
+      pango_layout_set_attributes (demo->layout, NULL);
+      gtk_widget_queue_draw (GTK_WIDGET (demo));
+
+      return TRUE;
+    }
+
+  return FALSE;
+}
+
+static void
+demo_widget_init (DemoWidget *demo)
+{
+  GtkEventController *controller;
+
+  gtk_widget_set_focusable (GTK_WIDGET (demo), TRUE);
+
+  demo->layout = gtk_widget_create_pango_layout (GTK_WIDGET (demo), "");
+
+  demo->im_context = gtk_im_multicontext_new ();
+
+  g_signal_connect (demo->im_context, "commit", G_CALLBACK (commit_cb), demo);
+  g_signal_connect (demo->im_context, "preedit-changed", G_CALLBACK (preedit_changed_cb), demo);
+
+  controller = gtk_event_controller_key_new ();
+  gtk_event_controller_key_set_im_context (GTK_EVENT_CONTROLLER_KEY (controller),
+                                           demo->im_context);
+
+  g_signal_connect (controller, "key-pressed", G_CALLBACK (key_pressed_cb), demo);
+
+  gtk_widget_add_controller (GTK_WIDGET (demo), controller);
+}
+
+static void
+demo_widget_dispose (GObject *object)
+{
+  DemoWidget *demo = DEMO_WIDGET (object);
+
+  g_clear_object (&demo->layout);
+  g_clear_object (&demo->im_context);
+
+  G_OBJECT_CLASS (demo_widget_parent_class)->dispose (object);
+}
+
+static void
+demo_widget_snapshot (GtkWidget   *widget,
+                      GtkSnapshot *snapshot)
+{
+  DemoWidget *demo = DEMO_WIDGET (widget);
+
+  gtk_snapshot_render_layout (snapshot,
+                              gtk_widget_get_style_context (widget),
+                              0, 0,
+                              demo->layout);
+}
+
+static void
+demo_widget_class_init (DemoWidgetClass *class)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (class);
+  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (class);
+
+  object_class->dispose = demo_widget_dispose;
+
+  widget_class->snapshot = demo_widget_snapshot;
+}
+
+static GtkWidget *
+demo_widget_new (void)
+{
+  return g_object_new (demo_widget_get_type (), NULL);
+}
+
+int
+main (int argc, char *argv[])
+{
+  GtkWindow *window;
+  GtkWidget *demo;
+
+  gtk_init ();
+
+  window = GTK_WINDOW (gtk_window_new ());
+
+  demo = demo_widget_new ();
+
+  gtk_window_set_child (window, demo);
+
+  gtk_window_present (window);
+
+  gtk_widget_grab_focus (demo);
+
+  while (g_list_model_get_n_items (gtk_window_get_toplevels ()) > 0)
+    g_main_context_iteration (NULL, TRUE);
+
+  return 0;
+}

tests/meson.build

 gtk_tests = [
   # testname, optional extra sources
+  ['input'],
   ['testpopup'],
   ['testupload'],
   ['testtransform'],