QGAL: remove the caching of simplified graph

After discussion with Jan-Arve, we decided to remove for good the
caching of simplified graph. This avoided recalculating the
simplification (but not the simplex) in some situations. Since vertex
simplification, this was temporarily disabled already.

To know whether if we could the cached version or not, we needed to
track individual anchors to see whether they reached size 0 or they
were 0 and changed the size. This is because the vertex simplification
depend on that fact.

Now the simplified version of the graph exists only during the
execution of calculateGraphs() function. This and next commits clear up
the code to take advantage of that fact.

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

3 files changed, 22 insertions, 72 deletions

diff --git a/src/gui/graphicsview/qgraphicsanchorlayout.cpp b/src/gui/graphicsview/qgraphicsanchorlayout.cpp
index 872ec3c..7e5929e 100644
--- a/src/gui/graphicsview/qgraphicsanchorlayout.cpp
+++ b/src/gui/graphicsview/qgraphicsanchorlayout.cpp
@@ -477,9 +477,6 @@ void QGraphicsAnchorLayout::removeAt(int index)
         return;
 
     // Removing an item affects both horizontal and vertical graphs
-    d->restoreSimplifiedGraph(QGraphicsAnchorLayoutPrivate::Horizontal);
-    d->restoreSimplifiedGraph(QGraphicsAnchorLayoutPrivate::Vertical);
-
     d->removeCenterConstraints(item, QGraphicsAnchorLayoutPrivate::Horizontal);
     d->removeCenterConstraints(item, QGraphicsAnchorLayoutPrivate::Vertical);
     d->removeAnchors(item);
diff --git a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
index 8520ebd..5b1e36c 100644
--- a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
+++ b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
@@ -62,8 +62,6 @@ QGraphicsAnchorPrivate::QGraphicsAnchorPrivate(int version)
 
 QGraphicsAnchorPrivate::~QGraphicsAnchorPrivate()
 {
-    // ###
-    layoutPrivate->restoreSimplifiedGraph(QGraphicsAnchorLayoutPrivate::Orientation(data->orientation));
     layoutPrivate->removeAnchor(data->from, data->to);
 }
 
@@ -529,7 +527,6 @@ QGraphicsAnchorLayoutPrivate::QGraphicsAnchorLayoutPrivate()
         interpolationProgress[i] = -1;
 
         spacings[i] = -1;
-        graphSimplified[i] = false;
         graphHasConflicts[i] = false;
 
         layoutFirstVertex[i] = 0;
@@ -735,16 +732,18 @@ static AnchorData *createSequence(Graph<AnchorVertex, AnchorData> *graph,
 */
 bool QGraphicsAnchorLayoutPrivate::simplifyGraph(Orientation orientation)
 {
-    static bool noSimplification = !qgetenv("QT_ANCHORLAYOUT_NO_SIMPLIFICATION").isEmpty();
-    if (noSimplification || items.isEmpty())
+    if (items.isEmpty())
         return true;
 
-    if (graphSimplified[orientation])
-        return true;
-
-#if 0
+#if defined(QT_DEBUG) && 0
     qDebug("Simplifying Graph for %s",
            orientation == Horizontal ? "Horizontal" : "Vertical");
+
+    static int count = 0;
+    if (orientation == Horizontal) {
+        count++;
+        dumpGraph(QString::fromAscii("%1-full").arg(count));
+    }
 #endif
 
     // Vertex simplification
@@ -762,13 +761,16 @@ bool QGraphicsAnchorLayoutPrivate::simplifyGraph(Orientation orientation)
 
     // Note that if we are not feasible, we fallback and make sure that the graph is fully restored
     if (!feasible) {
-        graphSimplified[orientation] = true;
         restoreSimplifiedGraph(orientation);
         restoreVertices(orientation);
         return false;
     }
 
-    graphSimplified[orientation] = true;
+#if defined(QT_DEBUG) && 0
+    dumpGraph(QString::fromAscii("%1-simplified-%2").arg(count).arg(
+                  QString::fromAscii(orientation == Horizontal ? "Horizontal" : "Vertical")));
+#endif
+
     return true;
 }
 
@@ -1173,10 +1175,6 @@ void QGraphicsAnchorLayoutPrivate::restoreSimplifiedConstraints(ParallelAnchorDa
 
 void QGraphicsAnchorLayoutPrivate::restoreSimplifiedGraph(Orientation orientation)
 {
-    if (!graphSimplified[orientation])
-        return;
-    graphSimplified[orientation] = false;
-
 #if 0
     qDebug("Restoring Simplified Graph for %s",
            orientation == Horizontal ? "Horizontal" : "Vertical");
@@ -1331,8 +1329,6 @@ void QGraphicsAnchorLayoutPrivate::deleteLayoutEdges()
 
 void QGraphicsAnchorLayoutPrivate::createItemEdges(QGraphicsLayoutItem *item)
 {
-    Q_ASSERT(!graphSimplified[Horizontal] && !graphSimplified[Vertical]);
-
     items.append(item);
 
     // Create horizontal and vertical internal anchors for the item and
@@ -1375,8 +1371,6 @@ void QGraphicsAnchorLayoutPrivate::createCenterAnchors(
         return;
     }
 
-    Q_ASSERT(!graphSimplified[orientation]);
-
     // Check if vertex already exists
     if (internalVertex(item, centerEdge))
         return;
@@ -1443,8 +1437,6 @@ void QGraphicsAnchorLayoutPrivate::removeCenterAnchors(
         return;
     }
 
-    Q_ASSERT(!graphSimplified[orientation]);
-
     // Orientation code
     Qt::AnchorPoint firstEdge;
     Qt::AnchorPoint lastEdge;
@@ -1512,8 +1504,6 @@ void QGraphicsAnchorLayoutPrivate::removeCenterAnchors(
 void QGraphicsAnchorLayoutPrivate::removeCenterConstraints(QGraphicsLayoutItem *item,
                                                            Orientation orientation)
 {
-    Q_ASSERT(!graphSimplified[orientation]);
-
     // Remove the item center constraints associated to this item
     // ### This is a temporary solution. We should probably use a better
     // data structure to hold items and/or their associated constraints
@@ -1579,10 +1569,6 @@ QGraphicsAnchor *QGraphicsAnchorLayoutPrivate::addAnchor(QGraphicsLayoutItem *fi
         return 0;
     }
 
-    // Guarantee that the graph is no simplified when adding this anchor,
-    // anchor manipulation always happen in the full graph
-    restoreSimplifiedGraph(edgeOrientation(firstEdge));
-
     // In QGraphicsAnchorLayout, items are represented in its internal
     // graph as four anchors that connect:
     //  - Left -> HCenter
@@ -1592,12 +1578,10 @@ QGraphicsAnchor *QGraphicsAnchorLayoutPrivate::addAnchor(QGraphicsLayoutItem *fi
 
     // Ensure that the internal anchors have been created for both items.
     if (firstItem != q && !items.contains(firstItem)) {
-        restoreSimplifiedGraph(edgeOrientation(firstEdge) == Horizontal ? Vertical : Horizontal);
         createItemEdges(firstItem);
         addChildLayoutItem(firstItem);
     }
     if (secondItem != q && !items.contains(secondItem)) {
-        restoreSimplifiedGraph(edgeOrientation(firstEdge) == Horizontal ? Vertical : Horizontal);
         createItemEdges(secondItem);
         addChildLayoutItem(secondItem);
     }
@@ -1657,10 +1641,6 @@ void QGraphicsAnchorLayoutPrivate::addAnchor_helper(QGraphicsLayoutItem *firstIt
 
     const Orientation orientation = edgeOrientation(firstEdge);
 
-    // Guarantee that the graph is no simplified when adding this anchor,
-    // anchor manipulation always happen in the full graph
-    restoreSimplifiedGraph(orientation);
-
     // Create or increase the reference count for the related vertices.
     AnchorVertex *v1 = addInternalVertex(firstItem, firstEdge);
     AnchorVertex *v2 = addInternalVertex(secondItem, secondEdge);
@@ -1696,15 +1676,13 @@ QGraphicsAnchor *QGraphicsAnchorLayoutPrivate::getAnchor(QGraphicsLayoutItem *fi
                                                          QGraphicsLayoutItem *secondItem,
                                                          Qt::AnchorPoint secondEdge)
 {
-    Orientation orient = edgeOrientation(firstEdge);
-    restoreSimplifiedGraph(orient);
-
+    const Orientation orientation = edgeOrientation(firstEdge);
     AnchorVertex *v1 = internalVertex(firstItem, firstEdge);
     AnchorVertex *v2 = internalVertex(secondItem, secondEdge);
 
     QGraphicsAnchor *graphicsAnchor = 0;
 
-    AnchorData *data = graph[orient].edgeData(v1, v2);
+    AnchorData *data = graph[orientation].edgeData(v1, v2);
     if (data)
         graphicsAnchor = acquireGraphicsAnchor(data);
     return graphicsAnchor;
@@ -1789,12 +1767,9 @@ void QGraphicsAnchorLayoutPrivate::removeAnchor(AnchorVertex *firstVertex,
 void QGraphicsAnchorLayoutPrivate::removeAnchor_helper(AnchorVertex *v1, AnchorVertex *v2)
 {
     Q_ASSERT(v1 && v2);
-    // Guarantee that the graph is no simplified when removing this anchor,
-    // anchor manipulation always happen in the full graph
-    Orientation o = edgeOrientation(v1->m_edge);
-    restoreSimplifiedGraph(o);
 
     // Remove edge from graph
+    const Orientation o = edgeOrientation(v1->m_edge);
     graph[o].removeEdge(v1, v2);
 
     // Decrease vertices reference count (may trigger a deletion)
@@ -1867,8 +1842,6 @@ void QGraphicsAnchorLayoutPrivate::removeVertex(QGraphicsLayoutItem *item, Qt::A
 
 void QGraphicsAnchorLayoutPrivate::removeAnchors(QGraphicsLayoutItem *item)
 {
-    Q_ASSERT(!graphSimplified[Horizontal] && !graphSimplified[Vertical]);
-
     // remove the center anchor first!!
     removeCenterAnchors(item, Qt::AnchorHorizontalCenter, false);
     removeVertex(item, Qt::AnchorLeft);
@@ -1971,20 +1944,8 @@ void QGraphicsAnchorLayoutPrivate::calculateGraphs()
 {
     if (!calculateGraphCacheDirty)
         return;
-
-#if defined(QT_DEBUG) && 0
-    static int count = 0;
-    count++;
-    dumpGraph(QString::fromAscii("%1-before").arg(count));
-#endif
-
     calculateGraphs(Horizontal);
     calculateGraphs(Vertical);
-
-#if defined(QT_DEBUG) && 0
-    dumpGraph(QString::fromAscii("%1-after").arg(count));
-#endif
-
     calculateGraphCacheDirty = false;
 }
 
@@ -2032,18 +1993,9 @@ void QGraphicsAnchorLayoutPrivate::calculateGraphs(
     lastCalculationUsedSimplex[orientation] = false;
 #endif
 
-    // ### This is necessary because now we do vertex simplification, we still don't know
-    // differentiate between invalidate()s that doesn't need resimplification and those which
-    // need. For example, when size hint of an item changes, this may cause an anchor to reach 0 or to
-    // leave 0 and get a size. In both cases we need resimplify.
-    //
-    // ### one possible solution would be tracking all the 0-sized anchors, if this set change, we need
-    // resimplify.
-    restoreSimplifiedGraph(orientation);
+    static bool simplificationEnabled = qgetenv("QT_ANCHORLAYOUT_NO_SIMPLIFICATION").isEmpty();
 
-    // Reset the nominal sizes of each anchor based on the current item sizes.  This function
-    // works with both simplified and non-simplified graphs, so it'll work when the
-    // simplification is going to be reused.
+    // Reset the nominal sizes of each anchor based on the current item sizes.
     if (!refreshAllSizeHints(orientation)) {
         qWarning("QGraphicsAnchorLayout: anchor setup is not feasible.");
         graphHasConflicts[orientation] = true;
@@ -2051,7 +2003,7 @@ void QGraphicsAnchorLayoutPrivate::calculateGraphs(
     }
 
     // Simplify the graph
-    if (!simplifyGraph(orientation)) {
+    if (simplificationEnabled && !simplifyGraph(orientation)) {
         qWarning("QGraphicsAnchorLayout: anchor setup is not feasible.");
         graphHasConflicts[orientation] = true;
         return;
@@ -2115,6 +2067,9 @@ void QGraphicsAnchorLayoutPrivate::calculateGraphs(
     qDeleteAll(constraints[orientation]);
     constraints[orientation].clear();
     graphPaths[orientation].clear(); // ###
+
+    if (simplificationEnabled)
+        restoreSimplifiedGraph(orientation);
 }
 
 /*!
diff --git a/src/gui/graphicsview/qgraphicsanchorlayout_p.h b/src/gui/graphicsview/qgraphicsanchorlayout_p.h
index cb8c4dd..7e2e00e 100644
--- a/src/gui/graphicsview/qgraphicsanchorlayout_p.h
+++ b/src/gui/graphicsview/qgraphicsanchorlayout_p.h
@@ -570,8 +570,6 @@ public:
     Interval interpolationInterval[2];
     qreal interpolationProgress[2];
 
-    // ###
-    bool graphSimplified[2];
     bool graphHasConflicts[2];
     QSet<QGraphicsLayoutItem *> m_floatItems[2];