Code

Connector tool: make connectors avoid the convex hull of shapes.
[inkscape.git] / src / event-context.cpp
index e5f81a2b9d58ce02122f60437523161c6644eea7..9b846f2b7e51a5f54e88c6e15363e33be52dcae8 100644 (file)
 #include "shortcuts.h"
 #include "desktop.h"
 #include "desktop-handles.h"
+#include "sp-namedview.h"
 #include "selection.h"
 #include "file.h"
 #include "interface.h"
 #include "macros.h"
 #include "tools-switch.h"
-#include "prefs-utils.h"
+#include "preferences.h"
 #include "message-context.h"
 #include "gradient-drag.h"
 #include "object-edit.h"
@@ -141,6 +142,8 @@ sp_event_context_init(SPEventContext *event_context)
     event_context->_selcue = NULL;
     event_context->_grdrag = NULL;
     event_context->space_panning = false;
+    event_context->shape_editor = NULL;
+    event_context->_delayed_snap_event = NULL;
 }
 
 /**
@@ -166,10 +169,12 @@ sp_event_context_dispose(GObject *object)
         ec->desktop = NULL;
     }
 
-    if (ec->prefs_repr) {
-        sp_repr_remove_listener_by_data(ec->prefs_repr, ec);
-        Inkscape::GC::release(ec->prefs_repr);
-        ec->prefs_repr = NULL;
+    if (ec->pref_observer) {
+        delete ec->pref_observer;
+    }
+
+    if (ec->_delayed_snap_event) {
+       delete ec->_delayed_snap_event;
     }
 
     G_OBJECT_CLASS(parent_class)->dispose(object);
@@ -229,7 +234,7 @@ gint gobble_key_events(guint keyval, gint mask)
            && event_next->key.keyval == keyval
            && (!mask || (event_next->key.state & mask))) {
         if (event_next->type == GDK_KEY_PRESS)
-            i ++; 
+            i ++;
         // kill it
         gdk_event_free(event_next);
         // get next
@@ -338,17 +343,11 @@ static gint sp_event_context_private_root_handler(SPEventContext *event_context,
     static unsigned int zoom_rb = 0;
 
     SPDesktop *desktop = event_context->desktop;
+    Inkscape::Preferences *prefs = Inkscape::Preferences::get();
 
-    tolerance = prefs_get_int_attribute_limited(
-            "options.dragtolerance","value", 0, 0, 100);
-    double const zoom_inc = prefs_get_double_attribute_limited(
-            "options.zoomincrement", "value", M_SQRT2, 1.01, 10);
-    double const acceleration = prefs_get_double_attribute_limited(
-            "options.scrollingacceleration", "value", 0, 0, 6);
-    int const key_scroll = prefs_get_int_attribute_limited(
-            "options.keyscroll", "value", 10, 0, 1000);
-    int const wheel_scroll = prefs_get_int_attribute_limited(
-            "options.wheelscroll", "value", 40, 0, 1000);
+    /// @todo REmove redundant /value in preference keys
+    tolerance = prefs->getIntLimited(
+            "/options/dragtolerance/value", 0, 0, 100);
 
     gint ret = FALSE;
 
@@ -375,7 +374,9 @@ static gint sp_event_context_private_root_handler(SPEventContext *event_context,
             switch (event->button.button) {
                 case 1:
                     if (event_context->space_panning) {
-                        panning = 1;
+                       // When starting panning, make sure there are no snap events pending because these might disable the panning again
+                       sp_event_context_discard_delayed_snap_event(event_context);
+                       panning = 1;
                         sp_canvas_item_grab(SP_CANVAS_ITEM(desktop->acetate),
                             GDK_KEY_RELEASE_MASK | GDK_BUTTON_RELEASE_MASK | GDK_POINTER_MOTION_MASK | GDK_POINTER_MOTION_HINT_MASK,
                             NULL, event->button.time-1);
@@ -383,10 +384,12 @@ static gint sp_event_context_private_root_handler(SPEventContext *event_context,
                     }
                     break;
                 case 2:
-                    if (event->button.state == GDK_SHIFT_MASK) {
+                    if (event->button.state & GDK_SHIFT_MASK) {
                         zoom_rb = 2;
                     } else {
-                        panning = 2;
+                       // When starting panning, make sure there are no snap events pending because these might disable the panning again
+                                               sp_event_context_discard_delayed_snap_event(event_context);
+                                               panning = 2;
                         sp_canvas_item_grab(SP_CANVAS_ITEM(desktop->acetate),
                             GDK_BUTTON_RELEASE_MASK | GDK_POINTER_MOTION_MASK | GDK_POINTER_MOTION_HINT_MASK,
                             NULL, event->button.time-1);
@@ -396,7 +399,9 @@ static gint sp_event_context_private_root_handler(SPEventContext *event_context,
                 case 3:
                     if (event->button.state & GDK_SHIFT_MASK
                             || event->button.state & GDK_CONTROL_MASK) {
-                        panning = 3;
+                       // When starting panning, make sure there are no snap events pending because these might disable the panning again
+                                               sp_event_context_discard_delayed_snap_event(event_context);
+                       panning = 3;
                         sp_canvas_item_grab(SP_CANVAS_ITEM(desktop->acetate),
                                 GDK_BUTTON_RELEASE_MASK | GDK_POINTER_MOTION_MASK | GDK_POINTER_MOTION_HINT_MASK,
                                 NULL, event->button.time);
@@ -416,7 +421,7 @@ static gint sp_event_context_private_root_handler(SPEventContext *event_context,
                         || (panning == 3 && !(event->motion.state & GDK_BUTTON3_MASK))
                    ) {
                     /* Gdk seems to lose button release for us sometimes :-( */
-                    panning = 0;
+                       panning = 0;
                     sp_canvas_item_ungrab(SP_CANVAS_ITEM(desktop->acetate),
                             event->button.time);
                     ret = TRUE;
@@ -463,7 +468,7 @@ static gint sp_event_context_private_root_handler(SPEventContext *event_context,
                     Inkscape::Rubberband::get(desktop)->move(motion_dt);
                 } else {
                     Inkscape::Rubberband::get(desktop)->start(desktop, motion_dt);
-                } 
+                }
                 if (zoom_rb == 2)
                     gobble_motion_events(GDK_BUTTON2_MASK);
             }
@@ -479,6 +484,7 @@ static gint sp_event_context_private_root_handler(SPEventContext *event_context,
                 }
                 Geom::Point const event_w(event->button.x, event->button.y);
                 Geom::Point const event_dt(desktop->w2d(event_w));
+                double const zoom_inc = prefs->getDoubleLimited("/options/zoomincrement/value", M_SQRT2, 1.01, 10);
                 desktop->zoom_relative_keep_point(event_dt,
                           (event->button.state & GDK_SHIFT_MASK) ? 1/zoom_inc : zoom_inc);
                 desktop->updateNow();
@@ -490,7 +496,7 @@ static gint sp_event_context_private_root_handler(SPEventContext *event_context,
 
                 // in slow complex drawings, some of the motion events are lost;
                 // to make up for this, we scroll it once again to the button-up event coordinates
-                // (i.e. canvas will always get scrolled all the way to the mouse release point, 
+                // (i.e. canvas will always get scrolled all the way to the mouse release point,
                 // even if few intermediate steps were visible)
                 Geom::Point const motion_w(event->button.x, event->button.y);
                 Geom::Point const moved_w( motion_w - button_w );
@@ -499,7 +505,7 @@ static gint sp_event_context_private_root_handler(SPEventContext *event_context,
                 ret = TRUE;
             } else if (zoom_rb == event->button.button) {
                 zoom_rb = 0;
-                boost::optional<Geom::Rect> const b = Inkscape::Rubberband::get(desktop)->getRectangle();
+                Geom::OptRect const b = Inkscape::Rubberband::get(desktop)->getRectangle();
                 Inkscape::Rubberband::get(desktop)->stop();
                 if (b && !within_tolerance) {
                     desktop->set_display_area(*b, 10);
@@ -508,13 +514,17 @@ static gint sp_event_context_private_root_handler(SPEventContext *event_context,
             }
             break;
         case GDK_KEY_PRESS:
-            switch (get_group0_keyval(&event->key)) {
+               {
+               double const acceleration = prefs->getDoubleLimited("/options/scrollingacceleration/value", 0, 0, 6);
+               int const key_scroll = prefs->getIntLimited("/options/keyscroll/value", 10, 0, 1000);
+
+               switch (get_group0_keyval(&event->key)) {
                 // GDK insists on stealing these keys (F1 for no idea what, tab for cycling widgets
                 // in the editing window). So we resteal them back and run our regular shortcut
                 // invoker on them.
                 unsigned int shortcut;
-                case GDK_Tab: 
-                case GDK_ISO_Left_Tab: 
+                case GDK_Tab:
+                case GDK_ISO_Left_Tab:
                 case GDK_F1:
                     shortcut = get_group0_keyval(&event->key);
                     if (event->key.state & GDK_SHIFT_MASK)
@@ -603,7 +613,7 @@ static gint sp_event_context_private_root_handler(SPEventContext *event_context,
                     }
                     break;
                 case GDK_space:
-                    if (prefs_get_int_attribute("options.spacepans","value", 0) == 1) {
+                    if (prefs->getBool("/options/spacepans/value")) {
                         event_context->space_panning = true;
                         event_context->_message_context->set(Inkscape::INFORMATION_MESSAGE, _("<b>Space+mouse drag</b> to pan canvas"));
                         ret= TRUE;
@@ -622,6 +632,7 @@ static gint sp_event_context_private_root_handler(SPEventContext *event_context,
                 default:
                     break;
             }
+               }
             break;
         case GDK_KEY_RELEASE:
             switch (get_group0_keyval(&event->key)) {
@@ -636,7 +647,7 @@ static gint sp_event_context_private_root_handler(SPEventContext *event_context,
                             desktop->updateNow();
                         }
                         ret= TRUE;
-                    } 
+                    }
                     break;
                 case GDK_Q:
                 case GDK_q:
@@ -652,7 +663,9 @@ static gint sp_event_context_private_root_handler(SPEventContext *event_context,
         case GDK_SCROLL:
         {
             bool ctrl = (event->scroll.state & GDK_CONTROL_MASK);
-            bool wheelzooms = (prefs_get_int_attribute("options.wheelzooms","value", 0) == 1);
+            bool wheelzooms = prefs->getBool("/options/wheelzooms/value");
+            int const wheel_scroll = prefs->getIntLimited("/options/wheelscroll/value", 40, 0, 1000);
+
             /* shift + wheel, pan left--right */
             if (event->scroll.state & GDK_SHIFT_MASK) {
                 switch (event->scroll.direction) {
@@ -669,6 +682,7 @@ static gint sp_event_context_private_root_handler(SPEventContext *event_context,
                 /* ctrl + wheel, zoom in--out */
             } else if ((ctrl && !wheelzooms) || (!ctrl && wheelzooms)) {
                 double rel_zoom;
+                double const zoom_inc = prefs->getDoubleLimited("/options/zoomincrement/value", M_SQRT2, 1.01, 10);
                 switch (event->scroll.direction) {
                     case GDK_SCROLL_UP:
                         rel_zoom = zoom_inc;
@@ -738,34 +752,30 @@ sp_event_context_private_item_handler(SPEventContext *ec, SPItem *item, GdkEvent
 }
 
 /**
- * Gets called when attribute changes value.
+ * @brief An observer that relays pref changes to the derived classes
  */
-static void
-sp_ec_repr_attr_changed(Inkscape::XML::Node */*prefs_repr*/, gchar const *key, gchar const */*oldval*/, gchar const *newval,
-                        bool /*is_interactive*/, gpointer data)
-{
-    SPEventContext *ec;
-
-    ec = SP_EVENT_CONTEXT(data);
-
-    if (((SPEventContextClass *) G_OBJECT_GET_CLASS(ec))->set) {
-        ((SPEventContextClass *) G_OBJECT_GET_CLASS(ec))->set(ec, key, newval);
+class ToolPrefObserver : public Inkscape::Preferences::Observer {
+public:
+    ToolPrefObserver(Glib::ustring const &path, SPEventContext *ec) :
+        Inkscape::Preferences::Observer(path),
+        _ec(ec) {}
+    virtual void notify(Inkscape::Preferences::Entry const &val)
+    {
+        if (((SPEventContextClass *) G_OBJECT_GET_CLASS(_ec))->set) {
+            ((SPEventContextClass *) G_OBJECT_GET_CLASS(_ec))->set(_ec,
+                const_cast<Inkscape::Preferences::Entry*>(&val));
+        }
     }
-}
-
-Inkscape::XML::NodeEventVector sp_ec_event_vector = {
-    NULL, /* Child added */
-    NULL, /* Child removed */
-    sp_ec_repr_attr_changed,
-    NULL, /* Content changed */
-    NULL /* Order changed */
+private:
+    SPEventContext * const _ec;
 };
 
 /**
  * Creates new SPEventContext object and calls its virtual setup() function.
+ * @todo This is bogus. pref_path should be a private property of the inheriting objects.
  */
 SPEventContext *
-sp_event_context_new(GType type, SPDesktop *desktop, Inkscape::XML::Node *prefs_repr, unsigned int key)
+sp_event_context_new(GType type, SPDesktop *desktop, gchar const *pref_path, unsigned int key)
 {
     g_return_val_if_fail(g_type_is_a(type, SP_TYPE_EVENT_CONTEXT), NULL);
     g_return_val_if_fail(desktop != NULL, NULL);
@@ -775,10 +785,13 @@ sp_event_context_new(GType type, SPDesktop *desktop, Inkscape::XML::Node *prefs_
     ec->desktop = desktop;
     ec->_message_context = new Inkscape::MessageContext(desktop->messageStack());
     ec->key = key;
-    ec->prefs_repr = prefs_repr;
-    if (ec->prefs_repr) {
-        Inkscape::GC::anchor(ec->prefs_repr);
-        sp_repr_add_listener(ec->prefs_repr, &sp_ec_event_vector, ec);
+    ec->pref_observer = NULL;
+
+    if (pref_path) {
+        ec->pref_observer = new ToolPrefObserver(pref_path, ec);
+
+        Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+        prefs->addObserver(*(ec->pref_observer));
     }
 
     if (((SPEventContextClass *) G_OBJECT_GET_CLASS(ec))->setup)
@@ -848,10 +861,11 @@ sp_event_context_read(SPEventContext *ec, gchar const *key)
     g_return_if_fail(SP_IS_EVENT_CONTEXT(ec));
     g_return_if_fail(key != NULL);
 
-    if (ec->prefs_repr) {
-        gchar const *val = ec->prefs_repr->attribute(key);
-        if (((SPEventContextClass *) G_OBJECT_GET_CLASS(ec))->set)
-            ((SPEventContextClass *) G_OBJECT_GET_CLASS(ec))->set(ec, key, val);
+    if (((SPEventContextClass *) G_OBJECT_GET_CLASS(ec))->set) {
+        Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+        Inkscape::Preferences::Entry val = prefs->getEntry(
+            ec->pref_observer->observed_path + '/' + key );
+        ((SPEventContextClass *) G_OBJECT_GET_CLASS(ec))->set(ec, &val);
     }
 }
 
@@ -864,6 +878,11 @@ sp_event_context_activate(SPEventContext *ec)
     g_return_if_fail(ec != NULL);
     g_return_if_fail(SP_IS_EVENT_CONTEXT(ec));
 
+    // Make sure no delayed snapping events are carried over after switching contexts
+    // (this is only an additional safety measure against sloppy coding, because each
+    // context should take care of this by itself.
+    sp_event_context_discard_delayed_snap_event(ec);
+
     if (((SPEventContextClass *) G_OBJECT_GET_CLASS(ec))->activate)
         ((SPEventContextClass *) G_OBJECT_GET_CLASS(ec))->activate(ec);
 }
@@ -887,13 +906,36 @@ sp_event_context_deactivate(SPEventContext *ec)
 gint
 sp_event_context_root_handler(SPEventContext * event_context, GdkEvent * event)
 {
-    gint ret;
-
-    ret = ((SPEventContextClass *) G_OBJECT_GET_CLASS(event_context))->root_handler(event_context, event);
+    switch (event->type) {
+               case GDK_MOTION_NOTIFY:
+                       sp_event_context_snap_delay_handler(event_context, NULL, NULL, (GdkEventMotion *)event, DelayedSnapEvent::EVENTCONTEXT_ROOT_HANDLER);
+                       break;
+               case GDK_BUTTON_RELEASE:
+                       if (event_context->_delayed_snap_event) {
+                               // If we have any pending snapping action, then invoke it now
+                               sp_event_context_snap_watchdog_callback(event_context->_delayed_snap_event);
+                       }
+                       break;
+               case GDK_BUTTON_PRESS:
+        case GDK_2BUTTON_PRESS:
+        case GDK_3BUTTON_PRESS:
+                       // Snapping will be on hold if we're moving the mouse at high speeds. When starting
+                       // drawing a new shape we really should snap though.
+                       event_context->desktop->namedview->snap_manager.snapprefs.setSnapPostponedGlobally(false);
+                       break;
+        default:
+               break;
+    }
 
-    set_event_location(event_context->desktop, event);
+    return sp_event_context_virtual_root_handler(event_context, event);
+}
 
-    return ret;
+gint
+sp_event_context_virtual_root_handler(SPEventContext * event_context, GdkEvent * event)
+{
+       gint ret = ((SPEventContextClass *) G_OBJECT_GET_CLASS(event_context))->root_handler(event_context, event);
+       set_event_location(event_context->desktop, event);
+       return ret;
 }
 
 /**
@@ -902,17 +944,43 @@ sp_event_context_root_handler(SPEventContext * event_context, GdkEvent * event)
 gint
 sp_event_context_item_handler(SPEventContext * event_context, SPItem * item, GdkEvent * event)
 {
-    gint ret;
+       switch (event->type) {
+               case GDK_MOTION_NOTIFY:
+                       sp_event_context_snap_delay_handler(event_context, item, NULL, (GdkEventMotion *)event, DelayedSnapEvent::EVENTCONTEXT_ITEM_HANDLER);
+                       break;
+               case GDK_BUTTON_RELEASE:
+                       if (event_context->_delayed_snap_event) {
+                               // If we have any pending snapping action, then invoke it now
+                               sp_event_context_snap_watchdog_callback(event_context->_delayed_snap_event);
+                       }
+                       break;
+               /*case GDK_BUTTON_PRESS:
+               case GDK_2BUTTON_PRESS:
+               case GDK_3BUTTON_PRESS:
+                       // Snapping will be on hold if we're moving the mouse at high speeds. When starting
+                       // drawing a new shape we really should snap though.
+                       event_context->desktop->namedview->snap_manager.snapprefs.setSnapPostponedGlobally(false);
+                       break;
+               */
+               default:
+                       break;
+       }
+
+    return sp_event_context_virtual_item_handler(event_context, item, event);
+}
 
-    ret = ((SPEventContextClass *) G_OBJECT_GET_CLASS(event_context))->item_handler(event_context, item, event);
+gint
+sp_event_context_virtual_item_handler(SPEventContext * event_context, SPItem * item, GdkEvent * event)
+{
+       gint ret = ((SPEventContextClass *) G_OBJECT_GET_CLASS(event_context))->item_handler(event_context, item, event);
 
-    if (! ret) {
-        ret = sp_event_context_root_handler(event_context, event);
-    } else {
-        set_event_location(event_context->desktop, event);
-    }
+       if (! ret) {
+               ret = sp_event_context_virtual_root_handler(event_context, event);
+       } else {
+               set_event_location(event_context->desktop, event);
+       }
 
-    return ret;
+       return ret;
 }
 
 /**
@@ -926,7 +994,7 @@ static void set_event_location(SPDesktop *desktop, GdkEvent *event)
 
     Geom::Point const button_w(event->button.x, event->button.y);
     Geom::Point const button_dt(desktop->w2d(button_w));
-    desktop-> setPosition (button_dt);
+    desktop->setPosition(button_dt);
     desktop->set_coordinate_status(button_dt);
 }
 
@@ -1058,48 +1126,9 @@ sp_event_context_over_item (SPDesktop *desktop, SPItem *item, Geom::Point const
 ShapeEditor *
 sp_event_context_get_shape_editor (SPEventContext *ec)
 {
-    if (SP_IS_NODE_CONTEXT(ec)) {
-        return SP_NODE_CONTEXT(ec)->shape_editor;
-    } else if (SP_IS_LPETOOL_CONTEXT(ec)) {
-        return SP_LPETOOL_CONTEXT(ec)->shape_editor;
-    } else {
-        g_warning("ShapeEditor only exists in Node and Geometric Tool.");
-        return NULL;
-    }
+    return ec->shape_editor;
 }
 
-/**
- * Called when SPEventContext subclass node attribute changed.
- */
-void
-ec_shape_event_attr_changed(Inkscape::XML::Node */*shape_repr*/, gchar const *name,
-                            gchar const */*old_value*/, gchar const */*new_value*/,
-                            bool const /*is_interactive*/, gpointer const data)
-{
-    if (!name
-            || !strcmp(name, "style")
-            || SP_ATTRIBUTE_IS_CSS(sp_attribute_lookup(name))) {
-        // no need to regenrate knotholder if only style changed
-        return;
-    }
-
-    SPEventContext *ec = SP_EVENT_CONTEXT(data);
-
-    if (ec->shape_knot_holder) {
-        delete ec->shape_knot_holder;
-    }
-    ec->shape_knot_holder = NULL;
-
-    SPDesktop *desktop = ec->desktop;
-
-    SPItem *item = sp_desktop_selection(desktop)->singleItem();
-
-    if (item) {
-        ec->shape_knot_holder = sp_item_knot_holder(item, desktop);
-    }
-}
-
-
 void
 event_context_print_event_info(GdkEvent *event, bool print_return) {
     switch (event->type) {
@@ -1143,6 +1172,130 @@ event_context_print_event_info(GdkEvent *event, bool print_return) {
     }
 }
 
+void sp_event_context_snap_delay_handler(SPEventContext *ec, SPItem* const item, SPKnot* const knot, GdkEventMotion *event, DelayedSnapEvent::DelayedSnapEventOrigin origin)
+{
+       static guint32 prev_time;
+       static boost::optional<Geom::Point> prev_pos;
+
+       // Snapping occurs when dragging with the left mouse button down, or when hovering e.g. in the pen tool with left mouse button up
+    bool const c1 = event->state & GDK_BUTTON2_MASK; // We shouldn't hold back any events when other mouse buttons have been
+    bool const c2 = event->state & GDK_BUTTON3_MASK; // pressed, e.g. when scrolling with the middle mouse button; if we do then
+                                                                                                    // Inkscape will get stuck in an unresponsive state
+    bool const c3 = tools_isactive(ec->desktop, TOOLS_CALLIGRAPHIC);
+                                                     // The snap delay will repeat the last motion event, which will lead to
+                                                     // erroneous points in the calligraphy context. And because we don't snap
+                                                     // in this context, we might just as well disable the snap delay all together
+    if (c1 || c2 || c3) {
+       // Make sure that we don't send any pending snap events to a context if we know in advance
+       // that we're not going to snap any way (e.g. while scrolling with middle mouse button)
+       // Any motion event might affect the state of the context, leading to unexpected behavior
+       sp_event_context_discard_delayed_snap_event(ec);
+    } else if (ec->desktop && ec->desktop->namedview->snap_manager.snapprefs.getSnapEnabledGlobally()) {
+               // Snap when speed drops below e.g. 0.02 px/msec, or when no motion events have occurred for some period.
+               // i.e. snap when we're at stand still. A speed threshold enforces snapping for tablets, which might never
+               // be fully at stand still and might keep spitting out motion events.
+               ec->desktop->namedview->snap_manager.snapprefs.setSnapPostponedGlobally(true); // put snapping on hold
+
+               Geom::Point event_pos(event->x, event->y);
+               guint32 event_t = gdk_event_get_time ( (GdkEvent *) event );
+
+               if (prev_pos) {
+                       Geom::Coord dist = Geom::L2(event_pos - *prev_pos);
+                       guint32 delta_t = event_t - prev_time;
+                       gdouble speed = delta_t > 0 ? dist/delta_t : 1000;
+                       //std::cout << "Mouse speed = " << speed << " px/msec " << std::endl;
+                       if (speed > 0.02) { // Jitter threshold, might be needed for tablets
+                               // We're moving fast, so postpone any snapping until the next GDK_MOTION_NOTIFY event. We
+                               // will keep on postponing the snapping as long as the speed is high.
+                               // We must snap at some point in time though, so set a watchdog timer at some time from
+                               // now, just in case there's no future motion event that drops under the speed limit (when
+                               // stopping abruptly)
+                               delete ec->_delayed_snap_event;
+                               ec->_delayed_snap_event = new DelayedSnapEvent(ec, item, knot, event, origin); // watchdog is reset, i.e. pushed forward in time
+                               // If the watchdog expires before a new motion event is received, we will snap (as explained
+                               // above). This means however that when the timer is too short, we will always snap and that the
+                               // speed threshold is ineffective. In the extreme case the delay is set to zero, and snapping will
+                               // be immediate, as it used to be in the old days ;-).
+                       } else { // Speed is very low, so we're virtually at stand still
+                               // But if we're really standing still, then we should snap now. We could use some low-pass filtering,
+                               // otherwise snapping occurs for each jitter movement. For this filtering we'll leave the watchdog to expire,
+                               // snap, and set a new watchdog again.
+                               if (ec->_delayed_snap_event == NULL) { // no watchdog has been set
+                                       // it might have already expired, so we'll set a new one; the snapping frequency will be limited by this
+                                       ec->_delayed_snap_event = new DelayedSnapEvent(ec, item, knot, event, origin);
+                               } // else: watchdog has been set before and we'll wait for it to expire
+                       }
+               } else {
+                       // This is the first GDK_MOTION_NOTIFY event, so postpone snapping and set the watchdog
+                       g_assert(ec->_delayed_snap_event == NULL);
+                       ec->_delayed_snap_event = new DelayedSnapEvent(ec, item, knot, event, origin);
+               }
+
+               prev_pos = event_pos;
+               prev_time = event_t;
+    }
+}
+
+gboolean sp_event_context_snap_watchdog_callback(gpointer data)
+{
+       // Snap NOW! For this the "postponed" flag will be reset and the last motion event will be repeated
+       DelayedSnapEvent *dse = reinterpret_cast<DelayedSnapEvent*>(data);
+
+       if (dse == NULL) {
+               // This might occur when this method is called directly, i.e. not through the timer
+               // E.g. on GDK_BUTTON_RELEASE in sp_event_context_root_handler()
+               return FALSE;
+       }
+
+       SPEventContext *ec = dse->getEventContext();
+       if (ec == NULL || ec->desktop == NULL) {
+               return false;
+       }
+
+       SPDesktop *dt = ec->desktop;
+       dt->namedview->snap_manager.snapprefs.setSnapPostponedGlobally(false);
+
+       switch (dse->getOrigin()) {
+               case DelayedSnapEvent::EVENTCONTEXT_ROOT_HANDLER:
+                       sp_event_context_virtual_root_handler(ec, dse->getEvent());
+                       break;
+               case DelayedSnapEvent::EVENTCONTEXT_ITEM_HANDLER:
+                       {
+                               SPItem* item = NULL;
+                               item = dse->getItem();
+                               if (item && SP_IS_ITEM(item)) {
+                                       sp_event_context_virtual_item_handler(ec, item, dse->getEvent());
+                               }
+                       }
+                       break;
+               case DelayedSnapEvent::KNOT_HANDLER:
+                       {
+                               SPKnot* knot = dse->getKnot();
+                               if (knot && SP_IS_KNOT(knot)) {
+                                       sp_knot_handler_request_position(dse->getEvent(), knot);
+                               }
+                       }
+                       break;
+               default:
+                       g_warning("Origin of snap-delay event has not been defined!;");
+                       break;
+       }
+
+       ec->_delayed_snap_event = NULL;
+       delete dse;
+
+       return FALSE; //Kills the timer and stops it from executing this callback over and over again.
+}
+
+void sp_event_context_discard_delayed_snap_event(SPEventContext *ec)
+{
+       delete ec->_delayed_snap_event;
+       ec->_delayed_snap_event = NULL;
+}
+
+
+
 /*
   Local Variables:
   mode:c++