QGraphicsAnchorLayout: Fix memory management issue in QSimplex solver

Both QGraphicsAnchorLayoutPrivate::solveMinMax() and solvePreferred()
were deleting the linear programming contraints while QSimplex still
had them.

For solveMinMax(), move the creation of constraints out of that
method.

For solvePreferred(), create the simplex solver in the heap so it can
be deleted before the constraints are.

Signed-off-by: Eduardo M. Fleury <eduardo.fleury@openbossa.org>
Reviewed-by: Anselmo Lacerda S. de Melo <anselmo.melo@openbossa.org>

1 files changed, 52 insertions, 49 deletions

diff --git a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
index 8158f48..644ed6b 100644
--- a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
+++ b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
@@ -506,6 +506,9 @@ void QGraphicsAnchorLayoutPrivate::calculateGraphs(
     // of the "trunk" set of constraints and variables.
     // ### does trunk always exist? empty = trunk is the layout left->center->right
     QList<QSimplexConstraint *> trunkConstraints = parts[0];
+    QList<QSimplexConstraint *> sizeHintConstraints;
+    sizeHintConstraints = constraintsFromSizeHints(getVariables(trunkConstraints));
+    trunkConstraints += sizeHintConstraints;
 
     // For minimum and maximum, use the path between the two layout sides as the
     // objective function.
@@ -540,6 +543,10 @@ void QGraphicsAnchorLayoutPrivate::calculateGraphs(
     }
     sizeHints[orientation][Qt::PreferredSize] = pref;
 
+    // Delete the constraints, we won't use them anymore.
+    qDeleteAll(sizeHintConstraints);
+    sizeHintConstraints.clear();
+
     // For the other parts that not the trunk, solve only for the preferred size
     // that is the size they will remain at, since they are not stretched by the
     // layout.
@@ -548,11 +555,10 @@ void QGraphicsAnchorLayoutPrivate::calculateGraphs(
     for (int i = 1; i < parts.count(); ++i) {
         QList<QSimplexConstraint *> partConstraints = parts[i];
         QList<AnchorData *> partVariables = getVariables(partConstraints);
+        Q_ASSERT(!partVariables.isEmpty());
 
-        // ###
-        if (partVariables.isEmpty())
-            continue;
-
+        sizeHintConstraints = constraintsFromSizeHints(partVariables);
+        partConstraints += sizeHintConstraints;
         solvePreferred(partConstraints);
 
         // Propagate size at preferred to other sizes. Semi-floats
@@ -563,6 +569,10 @@ void QGraphicsAnchorLayoutPrivate::calculateGraphs(
             ad->sizeAtMinimum = ad->sizeAtPreferred;
             ad->sizeAtMaximum = ad->sizeAtPreferred;
         }
+
+        // Delete the constraints, we won't use them anymore.
+        qDeleteAll(sizeHintConstraints);
+        sizeHintConstraints.clear();
     }
 
     // Clean up our data structures. They are not needed anymore since
@@ -731,6 +741,33 @@ void QGraphicsAnchorLayoutPrivate::constraintsFromPaths(Orientation orientation)
 }
 
 /*!
+  \internal
+
+  Create LP constraints for each anchor based on its minimum and maximum
+  sizes, as specified in its size hints
+*/
+QList<QSimplexConstraint *> QGraphicsAnchorLayoutPrivate::constraintsFromSizeHints(
+    const QList<AnchorData *> &anchors)
+{
+    QList<QSimplexConstraint *> anchorConstraints;
+    for (int i = 0; i < anchors.size(); ++i) {
+        QSimplexConstraint *c = new QSimplexConstraint;
+        c->variables.insert(anchors[i], 1.0);
+        c->constant = anchors[i]->minSize;
+        c->ratio = QSimplexConstraint::MoreOrEqual;
+        anchorConstraints += c;
+
+        c = new QSimplexConstraint;
+        c->variables.insert(anchors[i], 1.0);
+        c->constant = anchors[i]->maxSize;
+        c->ratio = QSimplexConstraint::LessOrEqual;
+        anchorConstraints += c;
+    }
+
+    return anchorConstraints;
+}
+
+/*!
   \Internal
 */
 QList< QList<QSimplexConstraint *> >
@@ -976,25 +1013,8 @@ QPair<qreal, qreal>
 QGraphicsAnchorLayoutPrivate::solveMinMax(QList<QSimplexConstraint *> constraints,
                                           GraphPath path)
 {
-    QList<AnchorData *> variables = getVariables(constraints);
-    QList<QSimplexConstraint *> itemConstraints;
-
-    for (int i = 0; i < variables.size(); ++i) {
-        QSimplexConstraint *c = new QSimplexConstraint;
-        c->variables.insert(variables[i], 1.0);
-        c->constant = variables[i]->minSize;
-        c->ratio = QSimplexConstraint::MoreOrEqual;
-        itemConstraints += c;
-
-        c = new QSimplexConstraint;
-        c->variables.insert(variables[i], 1.0);
-        c->constant = variables[i]->maxSize;
-        c->ratio = QSimplexConstraint::LessOrEqual;
-        itemConstraints += c;
-    }
-
     QSimplex simplex;
-    simplex.setConstraints(constraints + itemConstraints);
+    simplex.setConstraints(constraints);
 
     // Obtain the objective constraint
     QSimplexConstraint objective;
@@ -1011,6 +1031,7 @@ QGraphicsAnchorLayoutPrivate::solveMinMax(QList<QSimplexConstraint *> constraint
     qreal min = simplex.solveMin();
 
     // Save sizeAtMinimum results
+    QList<QSimplexVariable *> variables = simplex.constraintsVariables();
     for (int i = 0; i < variables.size(); ++i) {
         AnchorData *ad = static_cast<AnchorData *>(variables[i]);
         ad->sizeAtMinimum = ad->result;
@@ -1025,32 +1046,12 @@ QGraphicsAnchorLayoutPrivate::solveMinMax(QList<QSimplexConstraint *> constraint
         ad->sizeAtMaximum = ad->result;
     }
 
-    qDeleteAll(itemConstraints);
-
     return qMakePair<qreal, qreal>(min, max);
 }
 
 void QGraphicsAnchorLayoutPrivate::solvePreferred(QList<QSimplexConstraint *> constraints)
 {
     QList<AnchorData *> variables = getVariables(constraints);
-
-    // ###
-    QList<QSimplexConstraint *> itemConstraints;
-
-    for (int i = 0; i < variables.size(); ++i) {
-        QSimplexConstraint *c = new QSimplexConstraint;
-        c->variables.insert(variables[i], 1.0);
-        c->constant = variables[i]->minSize;
-        c->ratio = QSimplexConstraint::MoreOrEqual;
-        itemConstraints += c;
-
-        c = new QSimplexConstraint;
-        c->variables.insert(variables[i], 1.0);
-        c->constant = variables[i]->maxSize;
-        c->ratio = QSimplexConstraint::LessOrEqual;
-        itemConstraints += c;
-    }
-
     QList<QSimplexConstraint *> preferredConstraints;
     QList<QSimplexVariable *> preferredVariables;
     QSimplexConstraint objective;
@@ -1094,13 +1095,12 @@ void QGraphicsAnchorLayoutPrivate::solvePreferred(QList<QSimplexConstraint *> co
     }
 
 
-    QSimplex simplex;
-    simplex.setConstraints(constraints + itemConstraints + preferredConstraints);
-
-    simplex.setObjective(&objective);
+    QSimplex *simplex = new QSimplex;
+    simplex->setConstraints(constraints + preferredConstraints);
+    simplex->setObjective(&objective);
 
     // Calculate minimum values
-    simplex.solveMin();
+    simplex->solveMin();
 
     // Save sizeAtPreferred results
     for (int i = 0; i < variables.size(); ++i) {
@@ -1108,8 +1108,11 @@ void QGraphicsAnchorLayoutPrivate::solvePreferred(QList<QSimplexConstraint *> co
         ad->sizeAtPreferred = ad->result;
     }
 
-    qDeleteAll(itemConstraints);
+    // Make sure we delete the simplex solver -before- we delete the
+    // constraints used by it.
+    delete simplex;
+
+    // Delete constraints and variables we created.
     qDeleteAll(preferredConstraints);
     qDeleteAll(preferredVariables);
-
 }