Add an animated text example

tests/meson.build

@@ -1,5 +1,6 @@
 gtk_tests = [
   # testname, optional extra sources
+  ['movingtext'],
   ['bigfont'],
   ['testsections'],
   ['testfilelauncher'],

tests/movingtext.c

@@ -0,0 +1,210 @@
+#include <gtk/gtk.h>
+
+#define DEMO_TYPE_WIDGET (demo_widget_get_type ())
+G_DECLARE_FINAL_TYPE (DemoWidget, demo_widget, DEMO, WIDGET, GtkWidget)
+
+struct _DemoWidget
+{
+  GtkWidget parent_instance;
+
+  guint tick_cb;
+  guint64 start_time;
+  guint64 stop_time;
+
+  char *text;
+
+  float angle;
+  float size;
+};
+
+struct _DemoWidgetClass
+{
+  GtkWidgetClass parent_class;
+};
+
+G_DEFINE_TYPE (DemoWidget, demo_widget, GTK_TYPE_WIDGET)
+
+static gboolean
+tick_cb (GtkWidget     *widget,
+         GdkFrameClock *frame_clock,
+         gpointer       user_data)
+{
+  DemoWidget *self = DEMO_WIDGET (widget);
+  guint64 now;
+
+  now = gdk_frame_clock_get_frame_time (frame_clock);
+
+  if (self->start_time == 0)
+    self->start_time = now;
+
+  self->angle = 360 * (now - self->start_time) / (double)(G_TIME_SPAN_SECOND * 10);
+  self->size = 150 + 130 * sin (2 * G_PI * (now - self->start_time) / (double)(G_TIME_SPAN_SECOND * 5));
+
+  gtk_widget_queue_draw (widget);
+
+  return G_SOURCE_CONTINUE;
+}
+
+static gboolean
+pressed_cb (GtkEventController *controller,
+            guint               keyval,
+            guint               keycode,
+            GdkModifierType     state,
+            gpointer            data)
+{
+  DemoWidget *self = (DemoWidget *)gtk_event_controller_get_widget (controller);
+
+  if (keyval == GDK_KEY_space)
+    {
+      GdkFrameClock *frame_clock;
+      guint64 now;
+
+      frame_clock = gtk_widget_get_frame_clock (GTK_WIDGET (self));
+      now = gdk_frame_clock_get_frame_time (frame_clock);
+
+      if (self->tick_cb)
+        {
+          gtk_widget_remove_tick_callback (GTK_WIDGET (self), self->tick_cb);
+          self->tick_cb = 0;
+          self->stop_time = now;
+        }
+      else
+        {
+          self->start_time += now - self->stop_time;
+          self->tick_cb = gtk_widget_add_tick_callback (GTK_WIDGET (self), tick_cb, NULL, NULL);
+        }
+    }
+
+  return TRUE;
+}
+
+static void
+demo_widget_init (DemoWidget *self)
+{
+  GtkEventController *controller;
+
+  self->start_time = 0;
+  self->tick_cb = gtk_widget_add_tick_callback (GTK_WIDGET (self), tick_cb, NULL, NULL);
+
+  controller = gtk_event_controller_key_new ();
+  g_signal_connect (controller, "key-pressed", G_CALLBACK (pressed_cb), NULL);
+  gtk_widget_add_controller (GTK_WIDGET (self), controller);
+  gtk_widget_set_focusable (GTK_WIDGET (self), TRUE);
+}
+
+static void
+demo_widget_snapshot (GtkWidget   *widget,
+                      GtkSnapshot *snapshot)
+{
+  DemoWidget *self = DEMO_WIDGET (widget);
+  PangoLayout *layout;
+  int width, height;
+  int pwidth, pheight;
+  PangoFontDescription *desc;
+  GdkRGBA color;
+
+  width = gtk_widget_get_width (widget);
+  height = gtk_widget_get_height (widget);
+
+  gtk_widget_get_color (widget, &color);
+
+  layout = gtk_widget_create_pango_layout (GTK_WIDGET (self), self->text);
+  desc = pango_font_description_new ();
+  pango_font_description_set_family (desc, "Cantarell");
+  pango_font_description_set_weight (desc, 520);
+  pango_font_description_set_size (desc, self->size * PANGO_SCALE);
+  pango_layout_set_font_description (layout, desc);
+  pango_font_description_free (desc);
+  pango_layout_get_pixel_size (layout, &pwidth, &pheight);
+
+  gtk_snapshot_save (snapshot);
+
+  gtk_snapshot_translate (snapshot, &GRAPHENE_POINT_INIT (0.5 * width, 0.5 * height));
+  gtk_snapshot_rotate (snapshot, self->angle);
+  gtk_snapshot_translate (snapshot, &GRAPHENE_POINT_INIT (- 0.5 * pwidth, - 0.5 * pheight));
+
+  gtk_snapshot_append_layout (snapshot, layout, &color);
+
+  gtk_snapshot_restore (snapshot);
+
+  g_object_unref (layout);
+}
+
+static void
+demo_widget_dispose (GObject *object)
+{
+  DemoWidget *self = DEMO_WIDGET (object);
+
+  g_free (self->text);
+
+  G_OBJECT_CLASS (demo_widget_parent_class)->dispose (object);
+}
+
+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 (const char *text,
+                 gsize       length)
+{
+  DemoWidget *demo;
+
+  demo = g_object_new (DEMO_TYPE_WIDGET, NULL);
+
+  demo->text = g_strndup (text, length);
+
+  return GTK_WIDGET (demo);
+}
+
+int
+main (int argc, char *argv[])
+{
+  GtkWidget *window;
+  GtkWidget *demo;
+  char *text = NULL;
+  gsize length;
+
+  gtk_init ();
+
+  window = gtk_window_new ();
+
+  if (argc > 1)
+    {
+      GError *error = NULL;
+
+      if (!g_file_get_contents (argv[1], &text, &length, &error))
+        {
+          g_warning ("%s", error->message);
+          g_error_free (error);
+          text = NULL;
+        }
+    }
+
+  if (!text)
+    {
+      text = g_strdup ("Best Aa");
+      length = strlen (text);
+    }
+
+  demo = demo_widget_new (text, length);
+  gtk_window_set_child (GTK_WINDOW (window), demo);
+
+  g_free (text);
+
+  gtk_window_present (GTK_WINDOW (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;
+}