Fix a crash and add more safety checks to catch NULL pointers

(bzr r9713)

3 files changed, 31 insertions, 5 deletions

diff --git a/src/object-snapper.cpp b/src/object-snapper.cpp
index 23af26d47..1540fbabc 100644
--- a/src/object-snapper.cpp
+++ b/src/object-snapper.cpp
@@ -264,7 +264,8 @@ void Inkscape::ObjectSnapper::_snapNodes(SnappedConstraints &sc,
 
     _collectNodes(p.getSourceType(), p.getSourceNum() == 0);
 
-    if (unselected_nodes != NULL) {
+    if (unselected_nodes != NULL && unselected_nodes->size() > 0) {
+        g_assert(_points_to_snap_to != NULL);
         _points_to_snap_to->insert(_points_to_snap_to->end(), unselected_nodes->begin(), unselected_nodes->end());
     }
 
diff --git a/src/snap.cpp b/src/snap.cpp
index f17ae1e14..bcdf6c94f 100644
--- a/src/snap.cpp
+++ b/src/snap.cpp
@@ -46,7 +46,11 @@ SnapManager::SnapManager(SPNamedView const *v) :
     guide(this, 0),
     object(this, 0),
     snapprefs(),
-    _named_view(v)
+    _named_view(v),
+    _rotation_center_source_item(NULL),
+    _guide_to_ignore(NULL),
+    _desktop(NULL),
+    _unselected_nodes(NULL)
 {
 }
 
@@ -89,6 +93,7 @@ SnapManager::SnapperList
 SnapManager::getGridSnappers() const
 {
     SnapperList s;
+
     if (_desktop && _desktop->gridsEnabled() && snapprefs.getSnapToGrids()) {
         for ( GSList const *l = _named_view->grids; l != NULL; l = l->next) {
             Inkscape::CanvasGrid *grid = (Inkscape::CanvasGrid*) l->data;
@@ -219,6 +224,7 @@ void SnapManager::preSnap(Inkscape::SnapCandidatePoint const &p)
     if (_snapindicator) {
         _snapindicator = false; // prevent other methods from drawing a snap indicator; we want to control this here
         Inkscape::SnappedPoint s = freeSnap(p);
+        g_assert(_desktop != NULL);
         if (s.getSnapped()) {
             _desktop->snapindicator->set_new_snaptarget(s, true);
         } else {
@@ -380,7 +386,7 @@ Inkscape::SnappedPoint SnapManager::constrainedSnap(Inkscape::SnapCandidatePoint
 
     if (result.getSnapped()) {
         // only change the snap indicator if we really snapped to something
-        if (_snapindicator) {
+        if (_snapindicator && _desktop) {
             _desktop->snapindicator->set_new_snaptarget(result);
         }
         return result;
@@ -430,7 +436,7 @@ Inkscape::SnappedPoint SnapManager::multipleConstrainedSnaps(Inkscape::SnapCandi
 
     if (result.getSnapped()) {
         // only change the snap indicator if we really snapped to something
-        if (_snapindicator) {
+        if (_snapindicator && _desktop) {
             _desktop->snapindicator->set_new_snaptarget(result);
         }
         return result;
@@ -1024,7 +1030,7 @@ Inkscape::SnappedPoint SnapManager::findBestSnap(Inkscape::SnapCandidatePoint co
                                                  bool noCurves,
                                                  bool allowOffScreen) const
 {
-
+    g_assert(_desktop != NULL);
 
     /*
     std::cout << "Type and number of snapped constraints: " << std::endl;
@@ -1146,6 +1152,9 @@ void SnapManager::setup(SPDesktop const *desktop,
                         SPGuide *guide_to_ignore)
 {
     g_assert(desktop != NULL);
+    if (_desktop != NULL) {
+        g_warning("The snapmanager has been set up before, but unSetup() hasn't been called afterwards. It possibly held invalid pointers");
+    }
     _items_to_ignore.clear();
     _items_to_ignore.push_back(item_to_ignore);
     _desktop = desktop;
@@ -1178,6 +1187,9 @@ void SnapManager::setup(SPDesktop const *desktop,
                         SPGuide *guide_to_ignore)
 {
     g_assert(desktop != NULL);
+    if (_desktop != NULL) {
+        g_warning("The snapmanager has been set up before, but unSetup() hasn't been called afterwards. It possibly held invalid pointers");
+    }
     _items_to_ignore = items_to_ignore;
     _desktop = desktop;
     _snapindicator = snapindicator;
@@ -1192,6 +1204,11 @@ void SnapManager::setupIgnoreSelection(SPDesktop const *desktop,
                                       std::vector<Inkscape::SnapCandidatePoint> *unselected_nodes,
                                       SPGuide *guide_to_ignore)
 {
+    g_assert(desktop != NULL);
+    if (_desktop != NULL) {
+        // Someone has been naughty here! This is dangerous
+        g_warning("The snapmanager has been set up before, but unSetup() hasn't been called afterwards. It possibly held invalid pointers");
+    }
     _desktop = desktop;
     _snapindicator = snapindicator;
     _unselected_nodes = unselected_nodes;
@@ -1284,6 +1301,7 @@ void SnapManager::_displaySnapsource(Inkscape::SnapCandidatePoint const &p) cons
         bool p_is_a_bbox = p.getSourceType() & Inkscape::SNAPSOURCE_BBOX_CATEGORY;
         bool p_is_other = p.getSourceType() & Inkscape::SNAPSOURCE_OTHER_CATEGORY;
 
+        g_assert(_desktop != NULL);
         if (snapprefs.getSnapEnabledGlobally() && (p_is_other || (p_is_a_node && snapprefs.getSnapModeNode()) || (p_is_a_bbox && snapprefs.getSnapModeBBox()))) {
             _desktop->snapindicator->set_new_snapsource(p);
         } else {
diff --git a/src/ui/tool/node.cpp b/src/ui/tool/node.cpp
index 4c8cc74d8..f6fb6cc54 100644
--- a/src/ui/tool/node.cpp
+++ b/src/ui/tool/node.cpp
@@ -966,6 +966,11 @@ void Node::dragged(Geom::Point &new_pos, GdkEventMotion *event)
             }
         }
         sm.setupIgnoreSelection(_desktop, true, &unselected);
+    } else {
+        // even if we won't really snap, we might still call the one of the
+        // constrainedSnap() methods to enforce the constraints, so we need
+        // to setup the snapmanager anyway
+        sm.setup(_desktop);
     }
 
     if (held_control(*event)) {
@@ -1029,6 +1034,8 @@ void Node::dragged(Geom::Point &new_pos, GdkEventMotion *event)
         new_pos = sp.getPoint();
     }
 
+    sm.unSetup();
+
     SelectableControlPoint::dragged(new_pos, event);
 }