wip: Add a drag surface resize demo

Make the one of the image sources in the clipboard
demo have a throbbing drag icon.

demos/gtk-demo/clipboard.c

@@ -12,6 +12,7 @@
 #include <gtk/gtk.h>
 #include <string.h>
 #include "demoimage.h"
+#include "gtkthrobber.h"
 
 static void
 copy_button_clicked (GtkStack *source_stack,
@@ -364,6 +365,26 @@ drag_prepare (GtkDragSource *drag_source,
   return gdk_content_provider_new_for_value (&value);
 }
 
+static void
+drag_begin (GtkDragSource *drag_source,
+            GdkDrag       *drag,
+            gpointer       user_data)
+{
+  GtkWidget *button;
+  GdkFrameClock *clock;
+  GdkPaintable *paintable;
+
+  button = gtk_event_controller_get_widget (GTK_EVENT_CONTROLLER (drag_source));
+  clock = gtk_widget_get_frame_clock (button);
+  paintable = gtk_throbber_new (clock,
+                                "/transparent/portland-rose.jpg",
+                                0.02, 0.1,
+                                drag);
+
+  gtk_drag_source_set_icon (drag_source, paintable, 10, 10);
+  g_object_unref (paintable);
+}
+
 GtkWidget *
 do_clipboard (GtkWidget *do_widget)
 {
@@ -384,6 +405,7 @@ do_clipboard (GtkWidget *do_widget)
       gtk_builder_cscope_add_callback (scope, open_folder_cb);
       gtk_builder_cscope_add_callback (scope, on_drop);
       gtk_builder_cscope_add_callback (scope, drag_prepare);
+      gtk_builder_cscope_add_callback (scope, drag_begin);
       builder = gtk_builder_new ();
       gtk_builder_set_scope (builder, scope);
       gtk_builder_add_from_resource (builder, "/clipboard/clipboard.ui", NULL);

demos/gtk-demo/clipboard.ui

@@ -91,6 +91,7 @@
                             <child>
                               <object class="GtkDragSource">
                                 <signal name="prepare" handler="drag_prepare"/>
+                                <signal name="drag-begin" handler="drag_begin"/>
                               </object>
                             </child>
                             <child>

demos/gtk-demo/gtkthrobber.c

@@ -0,0 +1,174 @@
+/*
+ * Copyright © 2018 Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte@gnome.org>
+ */
+
+#include "gtkthrobber.h"
+
+#include "gtk.h"
+
+struct _GtkThrobber
+{
+  GObject parent_instance;
+
+  GdkFrameClock *clock;
+  GdkTexture *texture;
+  guint clock_tick_id;
+
+  float min, max, scale, delta;
+  float delta2, hot;
+
+  GdkDrag *drag;
+};
+
+struct _GtkThrobberClass
+{
+  GObjectClass parent_class;
+};
+
+static void
+gtk_throbber_paintable_snapshot (GdkPaintable *paintable,
+                               GdkSnapshot  *snapshot,
+                               double        width,
+                               double        height)
+{
+  GtkThrobber *self = GTK_THROBBER (paintable);
+
+  gtk_snapshot_append_texture (snapshot, self->texture, &GRAPHENE_RECT_INIT (0, 0, width, height));
+}
+
+static int
+gtk_throbber_paintable_get_intrinsic_width (GdkPaintable *paintable)
+{
+  GtkThrobber *self = GTK_THROBBER (paintable);
+
+  return gdk_texture_get_width (self->texture) * self->scale;
+}
+
+static int
+gtk_throbber_paintable_get_intrinsic_height (GdkPaintable *paintable)
+{
+  GtkThrobber *self = GTK_THROBBER (paintable);
+
+  return gdk_texture_get_height (self->texture) * self->scale;
+}
+
+static void
+gtk_throbber_paintable_init (GdkPaintableInterface *iface)
+{
+  iface->snapshot = gtk_throbber_paintable_snapshot;
+  iface->get_intrinsic_width = gtk_throbber_paintable_get_intrinsic_width;
+  iface->get_intrinsic_height = gtk_throbber_paintable_get_intrinsic_height;
+}
+
+G_DEFINE_TYPE_EXTENDED (GtkThrobber, gtk_throbber, G_TYPE_OBJECT, 0,
+                        G_IMPLEMENT_INTERFACE (GDK_TYPE_PAINTABLE,
+                                               gtk_throbber_paintable_init))
+
+static void
+gtk_throbber_dispose (GObject *object)
+{
+  GtkThrobber *self = GTK_THROBBER (object);
+
+  gdk_frame_clock_end_updating (self->clock);
+  g_signal_handler_disconnect (self->clock, self->clock_tick_id);
+  self->clock_tick_id = 0;
+
+  g_clear_object (&self->clock);
+  g_clear_object (&self->texture);
+  g_clear_object (&self->drag);
+
+  G_OBJECT_CLASS (gtk_throbber_parent_class)->dispose (object);
+}
+
+static void
+gtk_throbber_class_init (GtkThrobberClass *klass)
+{
+  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
+
+  gobject_class->dispose = gtk_throbber_dispose;
+}
+
+static void
+gtk_throbber_init (GtkThrobber *self)
+{
+}
+
+static void
+on_frame_clock_update (GdkFrameClock *clock,
+                       GtkThrobber   *self)
+{
+  self->scale += self->delta;
+  if (self->scale >= self->max)
+    {
+      self->scale = self->max;
+      self->delta = - self->delta;
+    }
+  else if (self->scale <= self->min)
+    {
+      self->scale = self->min;
+      self->delta = - self->delta;
+    }
+
+  self->hot += self->delta2;
+  if (self->hot >= 1.)
+    {
+      self->hot = 1.;
+      self->delta2 = - self->delta2;
+    }
+  else if (self->hot <= 0.)
+    {
+      self->hot = 0.;
+      self->delta2 = - self->delta2;
+    }
+
+  gdk_paintable_invalidate_size (GDK_PAINTABLE (self));
+
+  gdk_drag_set_hotspot (self->drag,
+                        gdk_texture_get_width (self->texture) * self->scale * self->hot,
+                        gdk_texture_get_height (self->texture) * self->scale * self->hot);
+}
+
+
+GdkPaintable *
+gtk_throbber_new (GdkFrameClock *clock,
+                  const char    *resource_path,
+                  float          min,
+                  float          max,
+                  GdkDrag       *drag)
+{
+  GtkThrobber *self;
+
+  self = g_object_new (GTK_TYPE_THROBBER, NULL);
+
+  self->clock = g_object_ref (clock);
+  self->texture = gdk_texture_new_from_resource (resource_path);
+  self->drag = g_object_ref (drag);
+  self->min = min;
+  self->max = max;
+  self->scale = min;
+  self->delta = (max - min) / (15 * 16);
+  self->delta2 = 1. / (10 * 16);
+  self->hot = 0.;
+
+  self->clock_tick_id = g_signal_connect (self->clock, "update",
+                                          G_CALLBACK (on_frame_clock_update), self);
+
+  gdk_frame_clock_begin_updating (self->clock);
+
+  return GDK_PAINTABLE (self);
+}

demos/gtk-demo/gtkthrobber.h

@@ -0,0 +1,36 @@
+/*
+ * Copyright © 2023 Matthias Clasen
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte@gnome.org>
+ */
+
+#pragma once
+
+#include <gdk/gdk.h>
+
+G_BEGIN_DECLS
+
+#define GTK_TYPE_THROBBER (gtk_throbber_get_type ())
+
+G_DECLARE_FINAL_TYPE (GtkThrobber, gtk_throbber, GTK, THROBBER, GObject)
+
+GdkPaintable *  gtk_throbber_new (GdkFrameClock *clock,
+                                  const char    *resource_path,
+                                  float          min,
+                                  float          max,
+                                  GdkDrag       *drag);
+
+G_END_DECLS

demos/gtk-demo/meson.build

@@ -134,6 +134,7 @@ extra_demo_sources = files([
   'unicode-names.c',
   'suggestionentry.c',
   'language-names.c',
+  'gtkthrobber.c',
 ])
 
 if os_unix