Check knot's pattern still exists before update

Stop crash when pattern changed via swatch palette,
and knot is still present.

https://gitlab.com/inkscape/inkscape/issues/70

3 files changed, 34 insertions, 3 deletions

diff --git a/src/knot-holder-entity.cpp b/src/knot-holder-entity.cpp
index 7abd16cba..e8f97e453 100644
--- a/src/knot-holder-entity.cpp
+++ b/src/knot-holder-entity.cpp
@@ -172,6 +172,27 @@ static Geom::Point sp_pattern_knot_get(SPPattern const *pat, gdouble x, gdouble
     return Geom::Point(x, y) * pat->getTransform();
 }
 
+bool
+PatternKnotHolderEntityXY::knot_missing() const
+{
+    SPPattern *pat = _fill ? SP_PATTERN(item->style->getFillPaintServer()) : SP_PATTERN(item->style->getStrokePaintServer());
+    return (pat == nullptr);
+}
+
+bool
+PatternKnotHolderEntityAngle::knot_missing() const
+{
+    SPPattern *pat = _fill ? SP_PATTERN(item->style->getFillPaintServer()) : SP_PATTERN(item->style->getStrokePaintServer());
+    return (pat == nullptr);
+}
+
+bool
+PatternKnotHolderEntityScale::knot_missing() const
+{
+    SPPattern *pat = _fill ? SP_PATTERN(item->style->getFillPaintServer()) : SP_PATTERN(item->style->getStrokePaintServer());
+    return (pat == nullptr);
+}
+
 Geom::Point
 PatternKnotHolderEntityXY::knot_get() const
 {
@@ -183,7 +204,6 @@ Geom::Point
 PatternKnotHolderEntityAngle::knot_get() const
 {
     SPPattern *pat = _fill ? SP_PATTERN(item->style->getFillPaintServer()) : SP_PATTERN(item->style->getStrokePaintServer());
-
     return sp_pattern_knot_get(pat, pat->width(), 0);
 }
 
diff --git a/src/knot-holder-entity.h b/src/knot-holder-entity.h
index e6d2ba231..1aa686f65 100644
--- a/src/knot-holder-entity.h
+++ b/src/knot-holder-entity.h
@@ -63,6 +63,7 @@ public:
        should be derived from KnotHolderEntity and override these functions */
     virtual void knot_set(Geom::Point const &p, Geom::Point const &origin, unsigned int state) = 0;
     virtual void knot_ungrabbed(Geom::Point const &p, Geom::Point const &origin, unsigned int state) = 0;
+    virtual bool knot_missing() const { return false; }
     virtual Geom::Point knot_get() const = 0;
     virtual void knot_click(unsigned int /*state*/) {}
 
@@ -108,6 +109,7 @@ protected:
 class PatternKnotHolderEntityXY : public KnotHolderEntity {
 public:
     PatternKnotHolderEntityXY(bool fill) : KnotHolderEntity(), _fill(fill) {}
+    bool knot_missing() const override;
     Geom::Point knot_get() const override;
     void knot_ungrabbed(Geom::Point const &p, Geom::Point const &origin, guint state) override {};
     void knot_set(Geom::Point const &p, Geom::Point const &origin, unsigned int state) override;
@@ -119,6 +121,7 @@ private:
 class PatternKnotHolderEntityAngle : public KnotHolderEntity {
 public:
     PatternKnotHolderEntityAngle(bool fill) : KnotHolderEntity(), _fill(fill) {}
+    bool knot_missing() const override;
     Geom::Point knot_get() const override;
     void knot_ungrabbed(Geom::Point const &p, Geom::Point const &origin, guint state) override {};
     void knot_set(Geom::Point const &p, Geom::Point const &origin, unsigned int state) override;
@@ -129,6 +132,7 @@ private:
 class PatternKnotHolderEntityScale : public KnotHolderEntity {
 public:
     PatternKnotHolderEntityScale(bool fill) : KnotHolderEntity(), _fill(fill) {}
+    bool knot_missing() const override;
     Geom::Point knot_get() const override;
     void knot_ungrabbed(Geom::Point const &p, Geom::Point const &origin, guint state) override {};
     void knot_set(Geom::Point const &p, Geom::Point const &origin, unsigned int state) override;
diff --git a/src/knotholder.cpp b/src/knotholder.cpp
index 9594a233f..d12f61a98 100644
--- a/src/knotholder.cpp
+++ b/src/knotholder.cpp
@@ -105,8 +105,15 @@ void KnotHolder::updateControlSizes()
 
 void KnotHolder::update_knots()
 {
-    for (auto e : entity) {
-        e->update_knot();
+    for (auto e = entity.begin(); e != entity.end(); ) {
+        // check if pattern was removed without deleting the knot
+        if ((*e)->knot_missing()) {
+            delete (*e);
+            e = entity.erase(e);
+        } else {
+            (*e)->update_knot();
+            ++e;
+        }
     }
 }