QGraphicsAnchorLayoutPrivate: Handling floating items as an invalid layout situation

We make use of the anchor visited on findPaths() to keep track of how many items are visited when
walking on the graph. We can use this information of how many items are reachable (non-float) in order to check
if we have floating items (not reachable from any graph vertex). If so, we have a situation not supported by now.

Signed-off-by: Jesus Sanchez-Palencia <jesus.palencia@openbossa.org>
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@openbossa.org>

2 files changed, 53 insertions, 1 deletions

diff --git a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
index 8139b2b..e760642 100644
--- a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
+++ b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
@@ -1841,6 +1841,11 @@ void QGraphicsAnchorLayoutPrivate::findPaths(Orientation orientation)
             queue.enqueue(qMakePair(pair.second, v));
         }
     }
+
+    // We will walk through every reachable items (non-float) and mark them
+    // by keeping their references on m_nonFloatItems. With this we can easily
+    // identify non-float and float items.
+    identifyNonFloatItems(visited, orientation);
 }
 
 /*!
@@ -1999,6 +2004,46 @@ QGraphicsAnchorLayoutPrivate::getGraphParts(Orientation orientation)
 }
 
 /*!
+ \internal
+
+  Use all visited Anchors on findPaths() so we can identify non-float Items.
+*/
+void QGraphicsAnchorLayoutPrivate::identifyNonFloatItems(QSet<AnchorData *> visited, Orientation orientation)
+{
+    m_nonFloatItems[orientation].clear();
+
+    foreach (const AnchorData *ad, visited)
+        identifyNonFloatItems_helper(ad, orientation);
+}
+
+/*!
+ \internal
+
+  Given an anchor, if it is an internal anchor and Normal we must mark it's item as non-float.
+  If the anchor is Sequential or Parallel, we must iterate on its children recursively until we reach
+  internal anchors (items).
+*/
+void QGraphicsAnchorLayoutPrivate::identifyNonFloatItems_helper(const AnchorData *ad, Orientation orientation)
+{
+    Q_Q(QGraphicsAnchorLayout);
+
+    switch(ad->type) {
+    case AnchorData::Normal:
+        if (ad->from->m_item == ad->to->m_item && ad->to->m_item != q)
+            m_nonFloatItems[orientation].insert(ad->to->m_item);
+        break;
+    case AnchorData::Sequential:
+        foreach (const AnchorData *d, static_cast<const SequentialAnchorData *>(ad)->m_edges)
+            identifyNonFloatItems_helper(d, orientation);
+        break;
+    case AnchorData::Parallel:
+        identifyNonFloatItems_helper(static_cast<const ParallelAnchorData *>(ad)->firstEdge, orientation);
+        identifyNonFloatItems_helper(static_cast<const ParallelAnchorData *>(ad)->secondEdge, orientation);
+        break;
+    }
+}
+
+/*!
   \internal
 
   Use the current vertices distance to calculate and set the geometry of
@@ -2491,7 +2536,11 @@ bool QGraphicsAnchorLayoutPrivate::hasConflicts() const
 {
     QGraphicsAnchorLayoutPrivate *that = const_cast<QGraphicsAnchorLayoutPrivate*>(this);
     that->calculateGraphs();
-    return graphHasConflicts[0] || graphHasConflicts[1];
+
+    bool floatConflict = (m_nonFloatItems[0].size() < items.size())
+                         || (m_nonFloatItems[1].size() < items.size());
+
+    return graphHasConflicts[0] || graphHasConflicts[1] || floatConflict;
 }
 
 #ifdef QT_DEBUG
diff --git a/src/gui/graphicsview/qgraphicsanchorlayout_p.h b/src/gui/graphicsview/qgraphicsanchorlayout_p.h
index aac4f96..1a74d85 100644
--- a/src/gui/graphicsview/qgraphicsanchorlayout_p.h
+++ b/src/gui/graphicsview/qgraphicsanchorlayout_p.h
@@ -445,6 +445,8 @@ public:
     void constraintsFromPaths(Orientation orientation);
     QList<QSimplexConstraint *> constraintsFromSizeHints(const QList<AnchorData *> &anchors);
     QList<QList<QSimplexConstraint *> > getGraphParts(Orientation orientation);
+    void identifyNonFloatItems(QSet<AnchorData *> visited, Orientation orientation);
+    void identifyNonFloatItems_helper(const AnchorData *ad, Orientation orientation);
 
     inline AnchorVertex *internalVertex(const QPair<QGraphicsLayoutItem*, Qt::AnchorPoint> &itemEdge) const
     {
@@ -511,6 +513,7 @@ public:
     // ###
     bool graphSimplified[2];
     bool graphHasConflicts[2];
+    QSet<QGraphicsLayoutItem *> m_nonFloatItems[2];
 
     uint calculateGraphCacheDirty : 1;
 };