Adding upstream version 43.9.upstream/43.9upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1014 insertions, 0 deletions

diff --git a/src/st/st-scroll-bar.c b/src/st/st-scroll-bar.c
new file mode 100644
index 0000000..72bcd55
--- /dev/null
+++ b/src/st/st-scroll-bar.c
@@ -0,0 +1,1014 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
+/*
+ * st-scroll-bar.c: Scroll bar actor
+ *
+ * Copyright 2008 OpenedHand
+ * Copyright 2008, 2009 Intel Corporation.
+ * Copyright 2009, 2010 Red Hat, Inc.
+ * Copyright 2010 Maxim Ermilov
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU Lesser General Public License,
+ * version 2.1, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope 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 program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/**
+ * SECTION:st-scroll-bar
+ * @short_description: a user interface element to control scrollable areas.
+ *
+ * The #StScrollBar allows users to scroll scrollable actors, either by
+ * the step or page amount, or by manually dragging the handle.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <math.h>
+#include <clutter/clutter.h>
+
+#include "st-scroll-bar.h"
+#include "st-bin.h"
+#include "st-enum-types.h"
+#include "st-private.h"
+#include "st-button.h"
+#include "st-settings.h"
+
+#define PAGING_INITIAL_REPEAT_TIMEOUT 500
+#define PAGING_SUBSEQUENT_REPEAT_TIMEOUT 200
+
+typedef struct _StScrollBarPrivate   StScrollBarPrivate;
+struct _StScrollBarPrivate
+{
+  StAdjustment *adjustment;
+
+  gfloat        x_origin;
+  gfloat        y_origin;
+
+  ClutterInputDevice *grab_device;
+  ClutterGrab *grab;
+
+  ClutterActor *trough;
+  ClutterActor *handle;
+
+  gfloat        move_x;
+  gfloat        move_y;
+
+  /* Trough-click handling. */
+  enum { NONE, UP, DOWN }  paging_direction;
+  guint             paging_source_id;
+  guint             paging_event_no;
+
+  guint             vertical : 1;
+};
+
+G_DEFINE_TYPE_WITH_PRIVATE (StScrollBar, st_scroll_bar, ST_TYPE_WIDGET)
+
+#define ST_SCROLL_BAR_PRIVATE(sb) st_scroll_bar_get_instance_private (ST_SCROLL_BAR (sb))
+
+enum
+{
+  PROP_0,
+
+  PROP_ADJUSTMENT,
+  PROP_VERTICAL,
+
+  N_PROPS
+};
+
+static GParamSpec *props[N_PROPS] = { NULL, };
+
+enum
+{
+  SCROLL_START,
+  SCROLL_STOP,
+
+  LAST_SIGNAL
+};
+
+static guint signals[LAST_SIGNAL] = { 0, };
+
+static gboolean
+handle_button_press_event_cb (ClutterActor       *actor,
+                              ClutterButtonEvent *event,
+                              StScrollBar        *bar);
+
+static void stop_scrolling (StScrollBar *bar);
+
+static void
+st_scroll_bar_set_vertical (StScrollBar *bar,
+                            gboolean     vertical)
+{
+  StScrollBarPrivate *priv = ST_SCROLL_BAR_PRIVATE (bar);
+
+  if (priv->vertical == vertical)
+    return;
+
+  priv->vertical = vertical;
+
+  if (priv->vertical)
+    clutter_actor_set_name (CLUTTER_ACTOR (priv->handle),
+                        "vhandle");
+  else
+    clutter_actor_set_name (CLUTTER_ACTOR (priv->handle),
+                        "hhandle");
+  clutter_actor_queue_relayout (CLUTTER_ACTOR (bar));
+  g_object_notify_by_pspec (G_OBJECT (bar), props[PROP_VERTICAL]);
+}
+
+static void
+st_scroll_bar_get_property (GObject    *gobject,
+                            guint       prop_id,
+                            GValue     *value,
+                            GParamSpec *pspec)
+{
+  StScrollBarPrivate *priv = ST_SCROLL_BAR_PRIVATE (gobject);
+
+  switch (prop_id)
+    {
+    case PROP_ADJUSTMENT:
+      g_value_set_object (value, priv->adjustment);
+      break;
+
+    case PROP_VERTICAL:
+      g_value_set_boolean (value, priv->vertical);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (gobject, prop_id, pspec);
+      break;
+    }
+}
+
+static void
+st_scroll_bar_set_property (GObject      *gobject,
+                            guint         prop_id,
+                            const GValue *value,
+                            GParamSpec   *pspec)
+{
+  StScrollBar *bar = ST_SCROLL_BAR (gobject);
+
+  switch (prop_id)
+    {
+    case PROP_ADJUSTMENT:
+      st_scroll_bar_set_adjustment (bar, g_value_get_object (value));
+      break;
+
+    case PROP_VERTICAL:
+      st_scroll_bar_set_vertical (bar, g_value_get_boolean (value));
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (gobject, prop_id, pspec);
+      break;
+    }
+}
+
+static void
+st_scroll_bar_dispose (GObject *gobject)
+{
+  StScrollBar *bar = ST_SCROLL_BAR (gobject);
+  StScrollBarPrivate *priv = st_scroll_bar_get_instance_private (bar);
+
+  if (priv->adjustment)
+    st_scroll_bar_set_adjustment (bar, NULL);
+
+  if (priv->handle)
+    {
+      clutter_actor_destroy (priv->handle);
+      priv->handle = NULL;
+    }
+
+  if (priv->trough)
+    {
+      clutter_actor_destroy (priv->trough);
+      priv->trough = NULL;
+    }
+
+  G_OBJECT_CLASS (st_scroll_bar_parent_class)->dispose (gobject);
+}
+
+static void
+st_scroll_bar_unmap (ClutterActor *actor)
+{
+  CLUTTER_ACTOR_CLASS (st_scroll_bar_parent_class)->unmap (actor);
+
+  stop_scrolling (ST_SCROLL_BAR (actor));
+}
+
+static void
+scroll_bar_allocate_children (StScrollBar           *bar,
+                              const ClutterActorBox *box)
+{
+  StScrollBarPrivate *priv = st_scroll_bar_get_instance_private (bar);
+  StThemeNode *theme_node = st_widget_get_theme_node (ST_WIDGET (bar));
+  ClutterActorBox content_box, trough_box;
+
+  st_theme_node_get_content_box (theme_node, box, &content_box);
+
+  trough_box.x1 = content_box.x1;
+  trough_box.y1 = content_box.y1;
+  trough_box.x2 = content_box.x2;
+  trough_box.y2 = content_box.y2;
+  clutter_actor_allocate (priv->trough, &trough_box);
+
+  if (priv->adjustment)
+    {
+      float handle_size, position, avail_size;
+      gdouble value, lower, upper, page_size, increment, min_size, max_size;
+      ClutterActorBox handle_box = { 0, };
+
+      st_adjustment_get_values (priv->adjustment,
+                                &value,
+                                &lower,
+                                &upper,
+                                NULL,
+                                NULL,
+                                &page_size);
+
+      if ((upper == lower)
+          || (page_size >= (upper - lower)))
+        increment = 1.0;
+      else
+        increment = page_size / (upper - lower);
+
+      min_size = 32.;
+      st_theme_node_lookup_length (theme_node, "min-size", FALSE, &min_size);
+      max_size = G_MAXINT16;
+      st_theme_node_lookup_length (theme_node, "max-size", FALSE, &max_size);
+
+      if (upper - lower - page_size <= 0)
+        position = 0;
+      else
+        position = (value - lower) / (upper - lower - page_size);
+
+      if (priv->vertical)
+        {
+          avail_size = content_box.y2 - content_box.y1;
+          handle_size = increment * avail_size;
+          handle_size = CLAMP (handle_size, min_size, max_size);
+
+          handle_box.x1 = content_box.x1;
+          handle_box.y1 = content_box.y1 + position * (avail_size - handle_size);
+
+          handle_box.x2 = content_box.x2;
+          handle_box.y2 = handle_box.y1 + handle_size;
+        }
+      else
+        {
+          ClutterTextDirection direction;
+
+          avail_size = content_box.x2 - content_box.x1;
+          handle_size = increment * avail_size;
+          handle_size = CLAMP (handle_size, min_size, max_size);
+
+          direction = clutter_actor_get_text_direction (CLUTTER_ACTOR (bar));
+          if (direction == CLUTTER_TEXT_DIRECTION_RTL)
+            {
+              handle_box.x2 = content_box.x2 - position * (avail_size - handle_size);
+              handle_box.x1 = handle_box.x2 - handle_size;
+            }
+          else
+            {
+              handle_box.x1 = content_box.x1 + position * (avail_size - handle_size);
+              handle_box.x2 = handle_box.x1 + handle_size;
+            }
+
+          handle_box.y1 = content_box.y1;
+          handle_box.y2 = content_box.y2;
+        }
+
+      clutter_actor_allocate (priv->handle, &handle_box);
+    }
+}
+
+static void
+st_scroll_bar_get_preferred_width (ClutterActor *self,
+                                   gfloat        for_height,
+                                   gfloat       *min_width_p,
+                                   gfloat       *natural_width_p)
+{
+  StScrollBar *bar = ST_SCROLL_BAR (self);
+  StScrollBarPrivate *priv = st_scroll_bar_get_instance_private (bar);
+  StThemeNode *theme_node = st_widget_get_theme_node (ST_WIDGET (self));
+  gfloat trough_min_width, trough_natural_width;
+  gfloat handle_min_width, handle_natural_width;
+
+  st_theme_node_adjust_for_height (theme_node, &for_height);
+
+  _st_actor_get_preferred_width (priv->trough, for_height, TRUE,
+                                 &trough_min_width, &trough_natural_width);
+
+  _st_actor_get_preferred_width (priv->handle, for_height, TRUE,
+                                 &handle_min_width, &handle_natural_width);
+
+  if (priv->vertical)
+    {
+      if (min_width_p)
+        *min_width_p = MAX (trough_min_width, handle_min_width);
+
+      if (natural_width_p)
+        *natural_width_p = MAX (trough_natural_width, handle_natural_width);
+    }
+  else
+    {
+      if (min_width_p)
+        *min_width_p = trough_min_width + handle_min_width;
+
+      if (natural_width_p)
+        *natural_width_p = trough_natural_width + handle_natural_width;
+    }
+
+  st_theme_node_adjust_preferred_width (theme_node, min_width_p, natural_width_p);
+}
+
+static void
+st_scroll_bar_get_preferred_height (ClutterActor *self,
+                                    gfloat        for_width,
+                                    gfloat       *min_height_p,
+                                    gfloat       *natural_height_p)
+{
+  StScrollBar *bar = ST_SCROLL_BAR (self);
+  StScrollBarPrivate *priv = st_scroll_bar_get_instance_private (bar);
+  StThemeNode *theme_node = st_widget_get_theme_node (ST_WIDGET (self));
+  gfloat trough_min_height, trough_natural_height;
+  gfloat handle_min_height, handle_natural_height;
+
+  st_theme_node_adjust_for_width (theme_node, &for_width);
+
+  _st_actor_get_preferred_height (priv->trough, for_width, TRUE,
+                                  &trough_min_height, &trough_natural_height);
+
+  _st_actor_get_preferred_height (priv->handle, for_width, TRUE,
+                                  &handle_min_height, &handle_natural_height);
+
+  if (priv->vertical)
+    {
+      if (min_height_p)
+        *min_height_p = trough_min_height + handle_min_height;
+
+      if (natural_height_p)
+        *natural_height_p = trough_natural_height + handle_natural_height;
+    }
+  else
+    {
+      if (min_height_p)
+        *min_height_p = MAX (trough_min_height, handle_min_height);
+
+      if (natural_height_p)
+        *natural_height_p = MAX (trough_natural_height, handle_natural_height);
+    }
+
+  st_theme_node_adjust_preferred_height (theme_node, min_height_p, natural_height_p);
+}
+
+static void
+st_scroll_bar_allocate (ClutterActor          *actor,
+                        const ClutterActorBox *box)
+{
+  StScrollBar *bar = ST_SCROLL_BAR (actor);
+
+  clutter_actor_set_allocation (actor, box);
+
+  scroll_bar_allocate_children (bar, box);
+}
+
+static void
+scroll_bar_update_positions (StScrollBar *bar)
+{
+  ClutterActorBox box;
+
+  /* Due to a change in the adjustments, we need to reposition our
+   * children; since adjustments changes can come from allocation
+   * changes in the scrolled area, we can't just queue a new relayout -
+   * we may already be in a relayout cycle. On the other hand, if
+   * a relayout is already queued, we can't just go ahead and allocate
+   * our children, since we don't have a valid allocation, and calling
+   * clutter_actor_get_allocation_box() will trigger an immediate
+   * stage relayout. So what we do is go ahead and immediately
+   * allocate our children if we already have a valid allocation, and
+   * otherwise just wait for the queued relayout.
+   */
+  if (!clutter_actor_has_allocation (CLUTTER_ACTOR (bar)))
+    return;
+
+  clutter_actor_get_allocation_box (CLUTTER_ACTOR (bar), &box);
+  scroll_bar_allocate_children (bar, &box);
+}
+
+static void
+bar_reactive_notify_cb (GObject    *gobject,
+                        GParamSpec *arg1,
+                        gpointer    user_data)
+{
+  StScrollBar *bar = ST_SCROLL_BAR (gobject);
+  StScrollBarPrivate *priv = st_scroll_bar_get_instance_private (bar);
+
+  clutter_actor_set_reactive (priv->handle,
+                              clutter_actor_get_reactive (CLUTTER_ACTOR (bar)));
+}
+
+static GObject*
+st_scroll_bar_constructor (GType                  type,
+                           guint                  n_properties,
+                           GObjectConstructParam *properties)
+{
+  GObjectClass *gobject_class;
+  GObject *obj;
+  StScrollBar *bar;
+
+  gobject_class = G_OBJECT_CLASS (st_scroll_bar_parent_class);
+  obj = gobject_class->constructor (type, n_properties, properties);
+
+  bar  = ST_SCROLL_BAR (obj);
+
+  g_signal_connect (bar, "notify::reactive",
+                    G_CALLBACK (bar_reactive_notify_cb), NULL);
+
+  return obj;
+}
+
+static void
+adjust_with_direction (StAdjustment           *adj,
+                       ClutterScrollDirection  direction)
+{
+  gdouble delta;
+
+  switch (direction)
+    {
+    case CLUTTER_SCROLL_UP:
+    case CLUTTER_SCROLL_LEFT:
+      delta = -1.0;
+      break;
+    case CLUTTER_SCROLL_RIGHT:
+    case CLUTTER_SCROLL_DOWN:
+      delta = 1.0;
+      break;
+    case CLUTTER_SCROLL_SMOOTH:
+    default:
+      g_assert_not_reached ();
+      break;
+    }
+
+  st_adjustment_adjust_for_scroll_event (adj, delta);
+}
+
+static gboolean
+st_scroll_bar_scroll_event (ClutterActor       *actor,
+                            ClutterScrollEvent *event)
+{
+  StScrollBarPrivate *priv = ST_SCROLL_BAR_PRIVATE (actor);
+  ClutterTextDirection direction;
+  ClutterScrollDirection scroll_dir;
+
+  if (clutter_event_is_pointer_emulated ((ClutterEvent *) event))
+    return TRUE;
+
+  direction = clutter_actor_get_text_direction (actor);
+  scroll_dir = event->direction;
+
+  switch (scroll_dir)
+    {
+    case CLUTTER_SCROLL_SMOOTH:
+      {
+        gdouble delta_x, delta_y;
+        clutter_event_get_scroll_delta ((ClutterEvent *)event, &delta_x, &delta_y);
+
+        if (direction == CLUTTER_TEXT_DIRECTION_RTL)
+          delta_x *= -1;
+
+        if (priv->vertical)
+          st_adjustment_adjust_for_scroll_event (priv->adjustment, delta_y);
+        else
+          st_adjustment_adjust_for_scroll_event (priv->adjustment, delta_x);
+      }
+      break;
+    case CLUTTER_SCROLL_LEFT:
+    case CLUTTER_SCROLL_RIGHT:
+      if (direction == CLUTTER_TEXT_DIRECTION_RTL)
+          scroll_dir = scroll_dir == CLUTTER_SCROLL_LEFT ? CLUTTER_SCROLL_RIGHT
+                                                         : CLUTTER_SCROLL_LEFT;
+    /* Fall through */
+    case CLUTTER_SCROLL_UP:
+    case CLUTTER_SCROLL_DOWN:
+      adjust_with_direction (priv->adjustment, scroll_dir);
+      break;
+    default:
+      g_return_val_if_reached (FALSE);
+      break;
+    }
+
+  return TRUE;
+}
+
+static void
+st_scroll_bar_class_init (StScrollBarClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+  ClutterActorClass *actor_class = CLUTTER_ACTOR_CLASS (klass);
+
+  object_class->get_property = st_scroll_bar_get_property;
+  object_class->set_property = st_scroll_bar_set_property;
+  object_class->dispose      = st_scroll_bar_dispose;
+  object_class->constructor  = st_scroll_bar_constructor;
+
+  actor_class->get_preferred_width  = st_scroll_bar_get_preferred_width;
+  actor_class->get_preferred_height = st_scroll_bar_get_preferred_height;
+  actor_class->allocate       = st_scroll_bar_allocate;
+  actor_class->scroll_event   = st_scroll_bar_scroll_event;
+  actor_class->unmap          = st_scroll_bar_unmap;
+
+  /**
+   * StScrollBar:adjustment:
+   *
+   * The #StAdjustment controlling the #StScrollBar.
+   */
+  props[PROP_ADJUSTMENT] =
+    g_param_spec_object ("adjustment", "Adjustment", "The adjustment",
+                         ST_TYPE_ADJUSTMENT,
+                         ST_PARAM_READWRITE | G_PARAM_EXPLICIT_NOTIFY);
+
+  /**
+   * StScrollBar:vertical:
+   *
+   * Whether the #StScrollBar is vertical. If %FALSE it is horizontal.
+   */
+  props[PROP_VERTICAL] =
+    g_param_spec_boolean ("vertical",
+                          "Vertical Orientation",
+                          "Vertical Orientation",
+                          FALSE,
+                          ST_PARAM_READWRITE | G_PARAM_EXPLICIT_NOTIFY);
+
+  g_object_class_install_properties (object_class, N_PROPS, props);
+
+
+  /**
+   * StScrollBar::scroll-start:
+   * @bar: a #StScrollBar
+   *
+   * Emitted when the #StScrollBar begins scrolling.
+   */
+  signals[SCROLL_START] =
+    g_signal_new ("scroll-start",
+                  G_TYPE_FROM_CLASS (klass),
+                  G_SIGNAL_RUN_LAST,
+                  G_STRUCT_OFFSET (StScrollBarClass, scroll_start),
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 0);
+
+  /**
+   * StScrollBar::scroll-stop:
+   * @bar: a #StScrollBar
+   *
+   * Emitted when the #StScrollBar finishes scrolling.
+   */
+  signals[SCROLL_STOP] =
+    g_signal_new ("scroll-stop",
+                  G_TYPE_FROM_CLASS (klass),
+                  G_SIGNAL_RUN_LAST,
+                  G_STRUCT_OFFSET (StScrollBarClass, scroll_stop),
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 0);
+}
+
+static void
+move_slider (StScrollBar *bar,
+             gfloat       x,
+             gfloat       y)
+{
+  StScrollBarPrivate *priv = st_scroll_bar_get_instance_private (bar);
+  ClutterTextDirection direction;
+  gdouble position, lower, upper, page_size;
+  gfloat ux, uy, pos, size;
+
+  if (!priv->adjustment)
+    return;
+
+  if (!clutter_actor_transform_stage_point (priv->trough, x, y, &ux, &uy))
+    return;
+
+  if (priv->vertical)
+    size = clutter_actor_get_height (priv->trough)
+           - clutter_actor_get_height (priv->handle);
+  else
+    size = clutter_actor_get_width (priv->trough)
+           - clutter_actor_get_width (priv->handle);
+
+  if (size == 0)
+    return;
+
+  if (priv->vertical)
+    pos = uy - priv->y_origin;
+  else
+    pos = ux - priv->x_origin;
+  pos = CLAMP (pos, 0, size);
+
+  st_adjustment_get_values (priv->adjustment,
+                            NULL,
+                            &lower,
+                            &upper,
+                            NULL,
+                            NULL,
+                            &page_size);
+
+  direction = clutter_actor_get_text_direction (CLUTTER_ACTOR (bar));
+  if (!priv->vertical && direction == CLUTTER_TEXT_DIRECTION_RTL)
+    pos = size - pos;
+
+  position = ((pos / size)
+              * (upper - lower - page_size))
+             + lower;
+
+  st_adjustment_set_value (priv->adjustment, position);
+}
+
+static void
+stop_scrolling (StScrollBar *bar)
+{
+  StScrollBarPrivate *priv = st_scroll_bar_get_instance_private (bar);
+  if (!priv->grab_device)
+    return;
+
+  st_widget_remove_style_pseudo_class (ST_WIDGET (priv->handle), "active");
+
+  if (priv->grab)
+    {
+      clutter_grab_dismiss (priv->grab);
+      g_clear_pointer (&priv->grab, clutter_grab_unref);
+    }
+
+  priv->grab_device = NULL;
+  g_signal_emit (bar, signals[SCROLL_STOP], 0);
+}
+
+static gboolean
+handle_motion_event_cb (ClutterActor       *trough,
+                        ClutterMotionEvent *event,
+                        StScrollBar        *bar)
+{
+  StScrollBarPrivate *priv = st_scroll_bar_get_instance_private (bar);
+  if (!priv->grab_device)
+    return FALSE;
+
+  move_slider (bar, event->x, event->y);
+  return TRUE;
+}
+
+static gboolean
+handle_button_release_event_cb (ClutterActor       *trough,
+                                ClutterButtonEvent *event,
+                                StScrollBar        *bar)
+{
+  if (event->button != 1)
+    return FALSE;
+
+  stop_scrolling (bar);
+  return TRUE;
+}
+
+static gboolean
+handle_button_press_event_cb (ClutterActor       *actor,
+                              ClutterButtonEvent *event,
+                              StScrollBar        *bar)
+{
+  StScrollBarPrivate *priv = st_scroll_bar_get_instance_private (bar);
+  ClutterInputDevice *device = clutter_event_get_device ((ClutterEvent*) event);
+  ClutterActor *stage;
+
+  if (event->button != 1)
+    return FALSE;
+
+  if (!clutter_actor_transform_stage_point (priv->handle,
+                                            event->x,
+                                            event->y,
+                                            &priv->x_origin,
+                                            &priv->y_origin))
+    return FALSE;
+
+  st_widget_add_style_pseudo_class (ST_WIDGET (priv->handle), "active");
+
+  /* Account for the scrollbar-trough-handle nesting. */
+  priv->x_origin += clutter_actor_get_x (priv->trough);
+  priv->y_origin += clutter_actor_get_y (priv->trough);
+
+  g_assert (!priv->grab_device);
+
+  stage = clutter_actor_get_stage (actor);
+  priv->grab = clutter_stage_grab (CLUTTER_STAGE (stage), priv->handle);
+  priv->grab_device = device;
+  g_signal_emit (bar, signals[SCROLL_START], 0);
+
+  return TRUE;
+}
+
+static gboolean
+trough_paging_cb (StScrollBar *self)
+{
+  StScrollBarPrivate *priv = st_scroll_bar_get_instance_private (self);
+  ClutterTextDirection direction;
+  g_autoptr (ClutterTransition) transition = NULL;
+  StSettings *settings;
+  gfloat handle_pos, event_pos, tx, ty;
+  gdouble value, new_value;
+  gdouble page_increment;
+  gdouble slow_down_factor;
+  gboolean ret;
+
+  gulong mode;
+
+  if (priv->paging_event_no == 0)
+    {
+      /* Scroll on after initial timeout. */
+      mode = CLUTTER_EASE_OUT_CUBIC;
+      ret = FALSE;
+      priv->paging_event_no = 1;
+      priv->paging_source_id = g_timeout_add (
+        PAGING_INITIAL_REPEAT_TIMEOUT,
+        (GSourceFunc) trough_paging_cb,
+        self);
+      g_source_set_name_by_id (priv->paging_source_id, "[gnome-shell] trough_paging_cb");
+    }
+  else if (priv->paging_event_no == 1)
+    {
+      /* Scroll on after subsequent timeout. */
+      ret = FALSE;
+      mode = CLUTTER_EASE_IN_CUBIC;
+      priv->paging_event_no = 2;
+      priv->paging_source_id = g_timeout_add (
+        PAGING_SUBSEQUENT_REPEAT_TIMEOUT,
+        (GSourceFunc) trough_paging_cb,
+        self);
+      g_source_set_name_by_id (priv->paging_source_id, "[gnome-shell] trough_paging_cb");
+    }
+  else
+    {
+      /* Keep scrolling. */
+      ret = TRUE;
+      mode = CLUTTER_LINEAR;
+      priv->paging_event_no++;
+    }
+
+  /* Do the scrolling */
+  st_adjustment_get_values (priv->adjustment,
+                            &value, NULL, NULL,
+                            NULL, &page_increment, NULL);
+
+  if (priv->vertical)
+    handle_pos = clutter_actor_get_y (priv->handle);
+  else
+    handle_pos = clutter_actor_get_x (priv->handle);
+
+  clutter_actor_transform_stage_point (CLUTTER_ACTOR (priv->trough),
+                                       priv->move_x,
+                                       priv->move_y,
+                                       &tx, &ty);
+
+  direction = clutter_actor_get_text_direction (CLUTTER_ACTOR (self));
+  if (!priv->vertical && direction == CLUTTER_TEXT_DIRECTION_RTL)
+    page_increment *= -1;
+
+  if (priv->vertical)
+    event_pos = ty;
+  else
+    event_pos = tx;
+
+  if (event_pos > handle_pos)
+    {
+      if (priv->paging_direction == NONE)
+        {
+          /* Remember direction. */
+          priv->paging_direction = DOWN;
+        }
+      if (priv->paging_direction == UP)
+        {
+          /* Scrolled far enough. */
+          return FALSE;
+        }
+      new_value = value + page_increment;
+    }
+  else
+    {
+      if (priv->paging_direction == NONE)
+        {
+          /* Remember direction. */
+          priv->paging_direction = UP;
+        }
+      if (priv->paging_direction == DOWN)
+        {
+          /* Scrolled far enough. */
+          return FALSE;
+        }
+      new_value = value - page_increment;
+    }
+
+  /* Stop existing transition, if one exists */
+  st_adjustment_remove_transition (priv->adjustment, "value");
+
+  settings = st_settings_get ();
+  g_object_get (settings, "slow-down-factor", &slow_down_factor, NULL);
+
+  /* FIXME: Creating a new transition for each scroll is probably not the best
+  * idea, but it's a lot less involved than extending the current animation */
+  transition = g_object_new (CLUTTER_TYPE_PROPERTY_TRANSITION,
+                             "property-name", "value",
+                             "interval", clutter_interval_new (G_TYPE_DOUBLE, value, new_value),
+                             "duration", (guint)(PAGING_SUBSEQUENT_REPEAT_TIMEOUT * slow_down_factor),
+                             "progress-mode", mode,
+                             "remove-on-complete", TRUE,
+                             NULL);
+  st_adjustment_add_transition (priv->adjustment, "value", transition);
+
+  return ret;
+}
+
+static gboolean
+trough_button_press_event_cb (ClutterActor       *actor,
+                              ClutterButtonEvent *event,
+                              StScrollBar        *self)
+{
+  StScrollBarPrivate *priv;
+
+  g_return_val_if_fail (self, FALSE);
+
+  if (event->button != 1)
+    return FALSE;
+
+  priv = st_scroll_bar_get_instance_private (self);
+  if (priv->adjustment == NULL)
+    return FALSE;
+
+  priv->move_x = event->x;
+  priv->move_y = event->y;
+  priv->paging_direction = NONE;
+  priv->paging_event_no = 0;
+  trough_paging_cb (self);
+
+  return TRUE;
+}
+
+static gboolean
+trough_button_release_event_cb (ClutterActor       *actor,
+                                ClutterButtonEvent *event,
+                                StScrollBar        *self)
+{
+  StScrollBarPrivate *priv = st_scroll_bar_get_instance_private (self);
+
+  if (event->button != 1)
+    return FALSE;
+
+  g_clear_handle_id (&priv->paging_source_id, g_source_remove);
+
+  return TRUE;
+}
+
+static gboolean
+trough_leave_event_cb (ClutterActor *actor,
+                       ClutterEvent *event,
+                       StScrollBar  *self)
+{
+  StScrollBarPrivate *priv = st_scroll_bar_get_instance_private (self);
+
+  if (priv->paging_source_id)
+    {
+      g_clear_handle_id (&priv->paging_source_id, g_source_remove);
+      return TRUE;
+    }
+
+  return FALSE;
+}
+
+static void
+st_scroll_bar_notify_reactive (StScrollBar *self)
+{
+  StScrollBarPrivate *priv = st_scroll_bar_get_instance_private (self);
+
+  gboolean reactive = clutter_actor_get_reactive (CLUTTER_ACTOR (self));
+
+  clutter_actor_set_reactive (CLUTTER_ACTOR (priv->trough), reactive);
+  clutter_actor_set_reactive (CLUTTER_ACTOR (priv->handle), reactive);
+}
+
+static void
+st_scroll_bar_init (StScrollBar *self)
+{
+  StScrollBarPrivate *priv = st_scroll_bar_get_instance_private (self);
+
+  priv->trough = (ClutterActor *) st_bin_new ();
+  clutter_actor_set_reactive ((ClutterActor *) priv->trough, TRUE);
+  clutter_actor_set_name (CLUTTER_ACTOR (priv->trough), "trough");
+  clutter_actor_add_child (CLUTTER_ACTOR (self),
+                           CLUTTER_ACTOR (priv->trough));
+  g_signal_connect (priv->trough, "button-press-event",
+                    G_CALLBACK (trough_button_press_event_cb), self);
+  g_signal_connect (priv->trough, "button-release-event",
+                    G_CALLBACK (trough_button_release_event_cb), self);
+  g_signal_connect (priv->trough, "leave-event",
+                    G_CALLBACK (trough_leave_event_cb), self);
+
+  priv->handle = (ClutterActor *) st_button_new ();
+  clutter_actor_set_name (CLUTTER_ACTOR (priv->handle), "hhandle");
+  clutter_actor_add_child (CLUTTER_ACTOR (self),
+                           CLUTTER_ACTOR (priv->handle));
+  g_signal_connect (priv->handle, "button-press-event",
+                    G_CALLBACK (handle_button_press_event_cb), self);
+  g_signal_connect (priv->handle, "button-release-event",
+                    G_CALLBACK (handle_button_release_event_cb), self);
+  g_signal_connect (priv->handle, "motion-event",
+                    G_CALLBACK (handle_motion_event_cb), self);
+
+  clutter_actor_set_reactive (CLUTTER_ACTOR (self), TRUE);
+
+  g_signal_connect (self, "notify::reactive",
+                    G_CALLBACK (st_scroll_bar_notify_reactive), NULL);
+}
+
+StWidget *
+st_scroll_bar_new (StAdjustment *adjustment)
+{
+  return g_object_new (ST_TYPE_SCROLL_BAR,
+                       "adjustment", adjustment,
+                       NULL);
+}
+
+static void
+on_notify_value (GObject     *object,
+                 GParamSpec  *pspec,
+                 StScrollBar *bar)
+{
+  scroll_bar_update_positions (bar);
+}
+
+static void
+on_changed (StAdjustment *adjustment,
+            StScrollBar  *bar)
+{
+  scroll_bar_update_positions (bar);
+}
+
+void
+st_scroll_bar_set_adjustment (StScrollBar  *bar,
+                              StAdjustment *adjustment)
+{
+  StScrollBarPrivate *priv;
+
+  g_return_if_fail (ST_IS_SCROLL_BAR (bar));
+
+  priv = st_scroll_bar_get_instance_private (bar);
+
+  if (adjustment == priv->adjustment)
+    return;
+
+  if (priv->adjustment)
+    {
+      g_signal_handlers_disconnect_by_func (priv->adjustment,
+                                            on_notify_value,
+                                            bar);
+      g_signal_handlers_disconnect_by_func (priv->adjustment,
+                                            on_changed,
+                                            bar);
+      g_object_unref (priv->adjustment);
+      priv->adjustment = NULL;
+    }
+
+  if (adjustment)
+    {
+      priv->adjustment = g_object_ref (adjustment);
+
+      g_signal_connect (priv->adjustment, "notify::value",
+                        G_CALLBACK (on_notify_value),
+                        bar);
+      g_signal_connect (priv->adjustment, "changed",
+                        G_CALLBACK (on_changed),
+                        bar);
+
+      clutter_actor_queue_relayout (CLUTTER_ACTOR (bar));
+    }
+
+  g_object_notify_by_pspec (G_OBJECT (bar), props[PROP_ADJUSTMENT]);
+}
+
+/**
+ * st_scroll_bar_get_adjustment:
+ * @bar: a #StScrollbar
+ *
+ * Gets the #StAdjustment that controls the current position of @bar.
+ *
+ * Returns: (transfer none): an #StAdjustment
+ */
+StAdjustment *
+st_scroll_bar_get_adjustment (StScrollBar *bar)
+{
+  g_return_val_if_fail (ST_IS_SCROLL_BAR (bar), NULL);
+
+  return ((StScrollBarPrivate *)ST_SCROLL_BAR_PRIVATE (bar))->adjustment;
+}
+