[gtk+] range: Add a stepper alternative

[Matthias Clasen <matthiasc src gnome org>]

commit 1c780beb8b194d18ff86ca53f30b0c6c522bfc0d
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Jul 12 01:36:17 2015 -0400

    range: Add a stepper alternative
    
    Make shift right-click on the trough start autoscrolling. The
    autoscrolling is similar to the way steppers operate now, with
    the difference that we vary the scrolling speed based on the
    distance of the pointer from the widget.

 gtk/gtkrange.c |   60 ++++++++++++++++++++++++++++++++++++++++++++++---------
 1 files changed, 50 insertions(+), 10 deletions(-)
---
diff --git a/gtk/gtkrange.c b/gtk/gtkrange.c
index d65364a..9a41f20 100644
--- a/gtk/gtkrange.c
+++ b/gtk/gtkrange.c
@@ -752,6 +752,7 @@ gtk_range_init (GtkRange *range)
    * widget.
    */
   priv->drag_gesture = gtk_gesture_drag_new (GTK_WIDGET (range));
+  gtk_gesture_single_set_button (GTK_GESTURE_SINGLE (priv->drag_gesture), 0);
   g_signal_connect (priv->drag_gesture, "drag-begin",
                     G_CALLBACK (gtk_range_drag_gesture_begin), range);
   g_signal_connect (priv->drag_gesture, "drag-update",
@@ -2479,6 +2480,7 @@ gtk_range_multipress_gesture_pressed (GtkGestureMultiPress *gesture,
   gboolean primary_warps;
   gint page_increment_button, warp_button;
   guint button;
+  GdkModifierType state_mask;
 
   if (!gtk_widget_has_focus (widget))
     gtk_widget_grab_focus (widget);
@@ -2486,6 +2488,7 @@ gtk_range_multipress_gesture_pressed (GtkGestureMultiPress *gesture,
   sequence = gtk_gesture_single_get_current_sequence (GTK_GESTURE_SINGLE (gesture));
   button = gtk_gesture_single_get_current_button (GTK_GESTURE_SINGLE (gesture));
   event = gtk_gesture_get_last_event (GTK_GESTURE (gesture), sequence);
+  gdk_event_get_state (event, &state_mask);
 
   source_device = gdk_event_get_source_device ((GdkEvent *) event);
   source = gdk_device_get_source (source_device);
@@ -2537,7 +2540,16 @@ gtk_range_multipress_gesture_pressed (GtkGestureMultiPress *gesture,
 
       scroll = range_get_scroll_for_grab (range);
 
-      gtk_range_add_step_timer (range, scroll);
+      if (state_mask & GDK_SHIFT_MASK)
+        {
+          remove_autoscroll (range);
+          range->priv->autoscroll_mode = priv->trough_click_forward ? GTK_SCROLL_END : GTK_SCROLL_START;
+          add_autoscroll (range);
+        }
+      else
+        {
+          gtk_range_add_step_timer (range, scroll);
+        }
     }
   else if ((priv->mouse_location == MOUSE_STEPPER_A ||
             priv->mouse_location == MOUSE_STEPPER_B ||
@@ -2601,10 +2613,6 @@ gtk_range_multipress_gesture_pressed (GtkGestureMultiPress *gesture,
         }
       else
         {
-          GdkModifierType state_mask;
-
-          gdk_event_get_state (event, &state_mask);
-
           /* Shift-click in the slider = fine adjustment */
           if (state_mask & GDK_SHIFT_MASK)
             update_zoom_state (range, TRUE);
@@ -2748,20 +2756,53 @@ autoscroll_cb (GtkWidget     *widget,
   gdouble increment;
   gdouble value;
   gboolean handled;
+  gdouble step, page;
+
+  step = gtk_adjustment_get_step_increment (adj);
+  page = gtk_adjustment_get_page_increment (adj);
 
   switch (priv->autoscroll_mode)
     {
     case GTK_SCROLL_STEP_FORWARD:
-      increment = gtk_adjustment_get_step_increment (adj) / AUTOSCROLL_FACTOR;
+      increment = step / AUTOSCROLL_FACTOR;
       break;
     case GTK_SCROLL_PAGE_FORWARD:
-      increment = gtk_adjustment_get_page_increment (adj) / AUTOSCROLL_FACTOR;
+      increment = page / AUTOSCROLL_FACTOR;
       break;
     case GTK_SCROLL_STEP_BACKWARD:
-      increment = - gtk_adjustment_get_step_increment (adj) / AUTOSCROLL_FACTOR;
+      increment = - step / AUTOSCROLL_FACTOR;
       break;
     case GTK_SCROLL_PAGE_BACKWARD:
-      increment = - gtk_adjustment_get_page_increment (adj) / AUTOSCROLL_FACTOR;
+      increment = - page / AUTOSCROLL_FACTOR;
+      break;
+    case GTK_SCROLL_START:
+    case GTK_SCROLL_END:
+      {
+        gdouble x, y;
+        gdouble distance, t;
+
+        /* Vary scrolling speed from slow (ie step) to fast (2 * page),
+         * based on the distance of the pointer from the widget. We start
+         * speeding up if the pointer moves at least 20 pixels away, and
+         * we reach maximum speed when it is 220 pixels away.
+         */
+        if (!gtk_gesture_drag_get_offset (GTK_GESTURE_DRAG (priv->drag_gesture), &x, &y))
+          {
+            x = 0.0;
+            y = 0.0;
+          }
+        if (gtk_orientable_get_orientation (GTK_ORIENTABLE (range)) == GTK_ORIENTATION_HORIZONTAL)
+          distance = fabs (y);
+        else
+          distance = fabs (x);
+        distance = CLAMP (distance - 20, 0.0, 200);
+        t = distance / 100.0;
+        step = (1 - t) * step + t * page;
+        if (priv->autoscroll_mode == GTK_SCROLL_END)
+          increment = step / AUTOSCROLL_FACTOR;
+        else
+          increment = - step / AUTOSCROLL_FACTOR;
+      }
       break;
     default:
       g_assert_not_reached ();
@@ -2944,7 +2985,6 @@ gtk_range_drag_gesture_begin (GtkGestureDrag *gesture,
 {
   if (range->priv->grab_location == MOUSE_SLIDER)
     gtk_gesture_set_state (range->priv->drag_gesture, GTK_EVENT_SEQUENCE_CLAIMED);
-
 }
 
 static void