QGAL: allow parallel anchors simplify center anchors

This commit make possible to parallelize anchors that are center
anchors, i.e. that have extra constraints (stored in
itemCenterConstraints).

This is trivial to support since the parallel anchor will have the same
size as its children, so it can just "take the place" of its children in
the constraints. Restore function was added as well.

To manipulate internal structures, relevant static functions were
promoted to methods.

Signed-off-by: Caio Marcelo de Oliveira Filho <caio.oliveira@openbossa.org>
Reviewed-by: Eduardo M. Fleury <eduardo.fleury@openbossa.org>

2 files changed, 82 insertions, 16 deletions

diff --git a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
index ff3fe69..ef89612 100644
--- a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
+++ b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
@@ -536,34 +536,67 @@ inline static qreal checkAdd(qreal a, qreal b)
 /*!
     \internal
 
-    Adds \a newAnchor to the graph \a g.
+    Adds \a newAnchor to the graph.
 
     Returns the newAnchor itself if it could be added without further changes to the graph. If a
     new parallel anchor had to be created, then returns the new parallel anchor. If a parallel anchor
     had to be created and it results in an unfeasible setup, \a feasible is set to false, otherwise
     true.
+
+    Note that in the case a new parallel anchor is created, it might also take over some constraints
+    from its children anchors.
 */
-static AnchorData *addAnchorMaybeParallel(Graph<AnchorVertex, AnchorData> *g,
-                                          AnchorData *newAnchor, bool *feasible)
+AnchorData *QGraphicsAnchorLayoutPrivate::addAnchorMaybeParallel(AnchorData *newAnchor, bool *feasible)
 {
+    Orientation orientation = Orientation(newAnchor->orientation);
+    Graph<AnchorVertex, AnchorData> &g = graph[orientation];
     *feasible = true;
 
     // If already exists one anchor where newAnchor is supposed to be, we create a parallel
     // anchor.
-    if (AnchorData *oldAnchor = g->takeEdge(newAnchor->from, newAnchor->to)) {
+    if (AnchorData *oldAnchor = g.takeEdge(newAnchor->from, newAnchor->to)) {
         ParallelAnchorData *parallel = new ParallelAnchorData(oldAnchor, newAnchor);
 
+        // The parallel anchor will "replace" its children anchors in
+        // every center constraint that they appear.
+
+        // ### If the dependent (center) anchors had reference(s) to their constraints, we
+        // could avoid traversing all the itemCenterConstraints.
+        QList<QSimplexConstraint *> &constraints = itemCenterConstraints[orientation];
+
+        AnchorData *children[2] = { oldAnchor, newAnchor };
+        QList<QSimplexConstraint *> *childrenConstraints[2] = { &parallel->m_firstConstraints,
+                                                                &parallel->m_secondConstraints };
+
+        for (int i = 0; i < 2; ++i) {
+            AnchorData *child = children[i];
+            QList<QSimplexConstraint *> *childConstraints = childrenConstraints[i];
+
+            if (!child->isCenterAnchor)
+                continue;
+
+            parallel->isCenterAnchor = true;
+
+            for (int i = 0; i < constraints.count(); ++i) {
+                QSimplexConstraint *c = constraints[i];
+                if (c->variables.contains(child)) {
+                    childConstraints->append(c);
+                    qreal v = c->variables.take(child);
+                    c->variables.insert(parallel, v);
+                }
+            }
+        }
+
         // At this point we can identify that the parallel anchor is not feasible, e.g. one
         // anchor minimum size is bigger than the other anchor maximum size.
         *feasible = parallel->refreshSizeHints_helper(0, false);
         newAnchor = parallel;
     }
 
-    g->createEdge(newAnchor->from, newAnchor->to, newAnchor);
+    g.createEdge(newAnchor->from, newAnchor->to, newAnchor);
     return newAnchor;
 }
 
-
 /*!
     \internal
 
@@ -858,7 +891,7 @@ bool QGraphicsAnchorLayoutPrivate::simplifyGraphIteration(QGraphicsAnchorLayoutP
         // If 'beforeSequence' and 'afterSequence' already had an anchor between them, we'll
         // create a parallel anchor between the new sequence and the old anchor.
         bool newFeasible;
-        AnchorData *newAnchor = addAnchorMaybeParallel(&g, sequence, &newFeasible);
+        AnchorData *newAnchor = addAnchorMaybeParallel(sequence, &newFeasible);
 
         if (!newFeasible) {
             *feasible = false;
@@ -880,7 +913,7 @@ bool QGraphicsAnchorLayoutPrivate::simplifyGraphIteration(QGraphicsAnchorLayoutP
     return false;
 }
 
-static void restoreSimplifiedAnchor(Graph<AnchorVertex, AnchorData> &g, AnchorData *edge)
+void QGraphicsAnchorLayoutPrivate::restoreSimplifiedAnchor(AnchorData *edge)
 {
 #if 0
     static const char *anchortypes[] = {"Normal",
@@ -889,6 +922,8 @@ static void restoreSimplifiedAnchor(Graph<AnchorVertex, AnchorData> &g, AnchorDa
     qDebug("Restoring %s edge.", anchortypes[int(edge->type)]);
 #endif
 
+    Graph<AnchorVertex, AnchorData> &g = graph[edge->orientation];
+
     if (edge->type == AnchorData::Normal) {
         g.createEdge(edge->from, edge->to, edge);
 
@@ -897,26 +932,47 @@ static void restoreSimplifiedAnchor(Graph<AnchorVertex, AnchorData> &g, AnchorDa
 
         for (int i = 0; i < sequence->m_edges.count(); ++i) {
             AnchorData *data = sequence->m_edges.at(i);
-            restoreSimplifiedAnchor(g, data);
+            restoreSimplifiedAnchor(data);
         }
 
         delete sequence;
 
     } else if (edge->type == AnchorData::Parallel) {
         ParallelAnchorData* parallel = static_cast<ParallelAnchorData*>(edge);
+        restoreSimplifiedConstraints(parallel);
 
         // ### Because of the way parallel anchors are created in the anchor simplification
         // algorithm, we know that one of these will be a sequence, so it'll be safe if the other
         // anchor create an edge between the same vertices as the parallel.
         Q_ASSERT(parallel->firstEdge->type == AnchorData::Sequential
                  || parallel->secondEdge->type == AnchorData::Sequential);
-        restoreSimplifiedAnchor(g, parallel->firstEdge);
-        restoreSimplifiedAnchor(g, parallel->secondEdge);
+        restoreSimplifiedAnchor(parallel->firstEdge);
+        restoreSimplifiedAnchor(parallel->secondEdge);
 
         delete parallel;
     }
 }
 
+void QGraphicsAnchorLayoutPrivate::restoreSimplifiedConstraints(ParallelAnchorData *parallel)
+{
+    if (!parallel->isCenterAnchor)
+        return;
+
+    for (int i = 0; i < parallel->m_firstConstraints.count(); ++i) {
+        QSimplexConstraint *c = parallel->m_firstConstraints[i];
+        qreal v = c->variables[parallel];
+        c->variables.remove(parallel);
+        c->variables.insert(parallel->firstEdge, v);
+    }
+
+    for (int i = 0; i < parallel->m_secondConstraints.count(); ++i) {
+        QSimplexConstraint *c = parallel->m_secondConstraints[i];
+        qreal v = c->variables[parallel];
+        c->variables.remove(parallel);
+        c->variables.insert(parallel->secondEdge, v);
+    }
+}
+
 void QGraphicsAnchorLayoutPrivate::restoreSimplifiedGraph(Orientation orientation)
 {
     if (!graphSimplified[orientation])
@@ -937,7 +993,7 @@ void QGraphicsAnchorLayoutPrivate::restoreSimplifiedGraph(Orientation orientatio
         AnchorData *edge = g.edgeData(v1, v2);
         if (edge->type != AnchorData::Normal) {
             g.takeEdge(v1, v2);
-            restoreSimplifiedAnchor(g, edge);
+            restoreSimplifiedAnchor(edge);
         }
     }
 }
diff --git a/src/gui/graphicsview/qgraphicsanchorlayout_p.h b/src/gui/graphicsview/qgraphicsanchorlayout_p.h
index d8e62b4..d7b3cfd 100644
--- a/src/gui/graphicsview/qgraphicsanchorlayout_p.h
+++ b/src/gui/graphicsview/qgraphicsanchorlayout_p.h
@@ -275,6 +275,9 @@ struct ParallelAnchorData : public AnchorData
 
     AnchorData* firstEdge;
     AnchorData* secondEdge;
+
+    QList<QSimplexConstraint *> m_firstConstraints;
+    QList<QSimplexConstraint *> m_secondConstraints;
 };
 
 /*!
@@ -433,20 +436,27 @@ public:
 
     QLayoutStyleInfo &styleInfo() const;
 
-    // Activation methods
-    bool simplifyGraph(Orientation orientation);
-    bool simplifyGraphIteration(Orientation orientation, bool *feasible);
-    void restoreSimplifiedGraph(Orientation orientation);
+    AnchorData *addAnchorMaybeParallel(AnchorData *newAnchor, bool *feasible);
 
+    // Activation
     void calculateGraphs();
     void calculateGraphs(Orientation orientation);
 
+    // Simplification
+    bool simplifyGraph(Orientation orientation);
+    bool simplifyGraphIteration(Orientation orientation, bool *feasible);
+
+    void restoreSimplifiedGraph(Orientation orientation);
+    void restoreSimplifiedAnchor(AnchorData *edge);
+    void restoreSimplifiedConstraints(ParallelAnchorData *parallel);
+
     bool calculateTrunk(Orientation orientation, const GraphPath &trunkPath,
                         const QList<QSimplexConstraint *> &constraints,
                         const QList<AnchorData *> &variables);
     bool calculateNonTrunk(const QList<QSimplexConstraint *> &constraints,
                            const QList<AnchorData *> &variables);
 
+    // Support functions for calculateGraph()
     bool refreshAllSizeHints(Orientation orientation);
     void findPaths(Orientation orientation);
     void constraintsFromPaths(Orientation orientation);