[gtk+] Add press and hold support to set zoom scroll mode

[Matthias Clasen <matthiasc src gnome org>]

commit c3e172e5469caf21d12a3f4bb1f8c831e7c42888
Author: William Jon McCann <william jon mccann gmail com>
Date:   Thu Jul 18 17:35:42 2013 -0400

    Add press and hold support to set zoom scroll mode
    
    Triggering zoom scroll mode by Shift click was too much
    of an easter egg. It also requires using keyboard and
    mouse together, which is hard to do for many users.
    
    Instead, we now trigger zoom scroll mode by click-and-hold
    (or touch-and-hold).
    
    https://bugzilla.gnome.org/show_bug.cgi?id=704703

 gtk/gtkrange.c |   86 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 82 insertions(+), 4 deletions(-)
---
diff --git a/gtk/gtkrange.c b/gtk/gtkrange.c
index 64496fe..f99c309 100644
--- a/gtk/gtkrange.c
+++ b/gtk/gtkrange.c
@@ -36,6 +36,7 @@
 #include "gtkmain.h"
 #include "gtkmarshalers.h"
 #include "gtkorientableprivate.h"
+#include "gtkpressandholdprivate.h"
 #include "gtkprivate.h"
 #include "gtkscale.h"
 #include "gtkscrollbar.h"
@@ -62,6 +63,7 @@
 #define UPDATE_DELAY        300  /* Delay for queued update */
 #define TIMEOUT_INITIAL     500
 #define TIMEOUT_REPEAT      50
+#define ZOOM_HOLD_TIME      500
 
 typedef struct _GtkRangeStepTimer GtkRangeStepTimer;
 
@@ -142,6 +144,8 @@ struct _GtkRangePrivate
 
   /* Whether we're doing fine adjustment */
   guint zoom                   : 1;
+  guint zoom_set               : 1;
+  GtkPressAndHold *press_and_hold;
 
   /* Fill level */
   guint show_fill_level        : 1;
@@ -1499,6 +1503,8 @@ gtk_range_destroy (GtkWidget *widget)
 
   gtk_range_remove_step_timer (range);
 
+  g_clear_object (&priv->press_and_hold);
+
   if (priv->adjustment)
     {
       g_signal_handlers_disconnect_by_func (priv->adjustment,
@@ -2347,6 +2353,33 @@ range_grab_add (GtkRange      *range,
 }
 
 static void
+update_zoom_state (GtkRange *range,
+                   gboolean  enabled)
+{
+  GtkStyleContext *context;
+
+  context = gtk_widget_get_style_context (GTK_WIDGET (range));
+
+  if (enabled)
+    gtk_style_context_add_class (context, "fine-tune");
+  else
+    gtk_style_context_remove_class (context, "fine-tune");
+  gtk_widget_queue_draw (GTK_WIDGET (range));
+
+  range->priv->zoom = enabled;
+}
+
+static void
+update_zoom_set (GtkRange *range,
+                 gboolean  zoom_set)
+{
+  if (zoom_set)
+    g_clear_object (&range->priv->press_and_hold);
+
+  range->priv->zoom_set = zoom_set;
+}
+
+static void
 range_grab_remove (GtkRange *range)
 {
   GtkRangePrivate *priv = range->priv;
@@ -2368,7 +2401,8 @@ range_grab_remove (GtkRange *range)
       location != MOUSE_OUTSIDE)
     gtk_widget_queue_draw (GTK_WIDGET (range));
 
-  priv->zoom = FALSE;
+  update_zoom_state (range, FALSE);
+  update_zoom_set (range, FALSE);
 }
 
 static GtkScrollType
@@ -2511,6 +2545,16 @@ gtk_range_key_press (GtkWidget   *widget,
   return GTK_WIDGET_CLASS (gtk_range_parent_class)->key_press_event (widget, event);
 }
 
+static void
+hold_action (GtkPressAndHold *pah,
+             gint             x,
+             gint             y,
+             GtkRange        *range)
+{
+  update_zoom_state (range, TRUE);
+  update_zoom_set (range, TRUE);
+}
+
 static gint
 gtk_range_button_press (GtkWidget      *widget,
                        GdkEventButton *event)
@@ -2657,7 +2701,32 @@ gtk_range_button_press (GtkWidget      *widget,
         {
           /* Shift-click in the slider = fine adjustment */
           if (event->state & GDK_SHIFT_MASK)
-            priv->zoom = TRUE;
+            {
+              update_zoom_state (range, TRUE);
+              update_zoom_set (range, TRUE);
+            }
+          else
+            {
+              if (!priv->press_and_hold)
+                {
+                  gint drag_threshold;
+
+                  g_object_get (gtk_widget_get_settings (widget),
+                                "gtk-dnd-drag-threshold", &drag_threshold,
+                                NULL);
+                  priv->press_and_hold = gtk_press_and_hold_new ();
+
+                  g_object_set (priv->press_and_hold,
+                                "drag-threshold", drag_threshold,
+                                "hold-time", ZOOM_HOLD_TIME,
+                                NULL);
+
+                  g_signal_connect (priv->press_and_hold, "hold",
+                                    G_CALLBACK (hold_action), range);
+                }
+
+              gtk_press_and_hold_process_event (priv->press_and_hold, (GdkEvent *)event);
+            }
         }
 
       if (priv->orientation == GTK_ORIENTATION_VERTICAL)
@@ -2803,7 +2872,11 @@ gtk_range_button_release (GtkWidget      *widget,
       priv->grab_button == event->button)
     {
       if (priv->grab_location == MOUSE_SLIDER)
-        update_slider_position (range, priv->mouse_x, priv->mouse_y);
+        {
+          update_slider_position (range, priv->mouse_x, priv->mouse_y);
+          if (priv->press_and_hold)
+            gtk_press_and_hold_process_event (priv->press_and_hold, (GdkEvent *)event);
+        }
 
       stop_scrolling (range);
       
@@ -2905,7 +2978,12 @@ gtk_range_motion_notify (GtkWidget      *widget,
     gtk_widget_queue_draw (widget);
 
   if (priv->grab_location == MOUSE_SLIDER)
-    update_slider_position (range, event->x, event->y);
+    {
+      if (!priv->zoom_set && priv->press_and_hold != NULL)
+        gtk_press_and_hold_process_event (priv->press_and_hold, (GdkEvent *)event);
+
+      update_slider_position (range, event->x, event->y);
+    }
 
   /* We handled the event if the mouse was in the range_rect */
   return priv->mouse_location != MOUSE_OUTSIDE;