QGAL: Revamp the edge interpolation code

Simplify the code of interpolateSequentialAnchor to use the distance
values of the sequential anchor itself as base for the children
distances. So the 'base' parameter was removed.

This also allowed out-of-order parallel anchors to be interpolated, and
the 'base' parameter also to be removed from interpolateParallelAnchor.

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

2 files changed, 26 insertions, 29 deletions

diff --git a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
index 95922ca..318ce20 100644
--- a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
+++ b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
@@ -2443,17 +2443,13 @@ void QGraphicsAnchorLayoutPrivate::interpolateEdge(AnchorVertex *base,
 
     // Process child anchors
     if (edge->type == AnchorData::Sequential)
-        interpolateSequentialEdges(edge->from,
-                                   static_cast<SequentialAnchorData *>(edge),
-                                   orientation);
+        interpolateSequentialEdges(static_cast<SequentialAnchorData *>(edge), orientation);
     else if (edge->type == AnchorData::Parallel)
-        interpolateParallelEdges(edge->from,
-                                 static_cast<ParallelAnchorData *>(edge),
-                                 orientation);
+        interpolateParallelEdges(static_cast<ParallelAnchorData *>(edge), orientation);
 }
 
 void QGraphicsAnchorLayoutPrivate::interpolateParallelEdges(
-    AnchorVertex *base, ParallelAnchorData *data, Orientation orientation)
+    ParallelAnchorData *data, Orientation orientation)
 {
     // In parallels the boundary vertices are already calculate, we
     // just need to look for sequential groups inside, because only
@@ -2461,40 +2457,43 @@ void QGraphicsAnchorLayoutPrivate::interpolateParallelEdges(
 
     // First edge
     if (data->firstEdge->type == AnchorData::Sequential)
-        interpolateSequentialEdges(base,
-                                   static_cast<SequentialAnchorData *>(data->firstEdge),
+        interpolateSequentialEdges(static_cast<SequentialAnchorData *>(data->firstEdge),
                                    orientation);
     else if (data->firstEdge->type == AnchorData::Parallel)
-        interpolateParallelEdges(base,
-                                 static_cast<ParallelAnchorData *>(data->firstEdge),
+        interpolateParallelEdges(static_cast<ParallelAnchorData *>(data->firstEdge),
                                  orientation);
 
     // Second edge
     if (data->secondEdge->type == AnchorData::Sequential)
-        interpolateSequentialEdges(base,
-                                   static_cast<SequentialAnchorData *>(data->secondEdge),
+        interpolateSequentialEdges(static_cast<SequentialAnchorData *>(data->secondEdge),
                                    orientation);
     else if (data->secondEdge->type == AnchorData::Parallel)
-        interpolateParallelEdges(base,
-                                 static_cast<ParallelAnchorData *>(data->secondEdge),
+        interpolateParallelEdges(static_cast<ParallelAnchorData *>(data->secondEdge),
                                  orientation);
 }
 
 void QGraphicsAnchorLayoutPrivate::interpolateSequentialEdges(
-    AnchorVertex *base, SequentialAnchorData *data, Orientation orientation)
+    SequentialAnchorData *data, Orientation orientation)
 {
-    AnchorVertex *prev = base;
+    // This method is supposed to handle any sequential anchor, even out-of-order
+    // ones. However, in the current QGAL implementation we should get only the
+    // well behaved ones.
+    Q_ASSERT(data->m_edges.first()->from == data->from);
+    Q_ASSERT(data->m_edges.last()->to == data->to);
 
-    // ### I'm not sure whether this assumption is safe. If not,
-    // consider that m_edges.last() could be used instead (so
-    // at(0) would be the one to be treated specially).
-    Q_ASSERT(base == data->m_edges.at(0)->to || base == data->m_edges.at(0)->from);
+    // At this point, the two outter vertices already have their distance
+    // calculated.
+    // We use the first as the base to calculate the internal ones
+
+    AnchorVertex *prev = data->from;
 
-    // Skip the last
     for (int i = 0; i < data->m_edges.count() - 1; ++i) {
-        AnchorData *child = data->m_edges.at(i);
-        interpolateEdge(prev, child, orientation);
-        prev = child->to;
+        AnchorData *edge = data->m_edges.at(i);
+        interpolateEdge(prev, edge, orientation);
+
+        // Use the recently calculated vertex as the base for the next one
+        const bool edgeIsForward = (edge->from == prev);
+        prev = edgeIsForward ? edge->to : edge->from;
     }
 
     // Treat the last specially, since we already calculated it's end
diff --git a/src/gui/graphicsview/qgraphicsanchorlayout_p.h b/src/gui/graphicsview/qgraphicsanchorlayout_p.h
index 8d77b1a..d8e62b4 100644
--- a/src/gui/graphicsview/qgraphicsanchorlayout_p.h
+++ b/src/gui/graphicsview/qgraphicsanchorlayout_p.h
@@ -475,10 +475,8 @@ public:
     void calculateVertexPositions(Orientation orientation);
     void setupEdgesInterpolation(Orientation orientation);
     void interpolateEdge(AnchorVertex *base, AnchorData *edge, Orientation orientation);
-    void interpolateSequentialEdges(AnchorVertex *base, SequentialAnchorData *edge,
-                                    Orientation orientation);
-    void interpolateParallelEdges(AnchorVertex *base, ParallelAnchorData *edge,
-                                  Orientation orientation);
+    void interpolateSequentialEdges(SequentialAnchorData *edge, Orientation orientation);
+    void interpolateParallelEdges(ParallelAnchorData *edge, Orientation orientation);
 
     // Linear Programming solver methods
     bool solveMinMax(const QList<QSimplexConstraint *> &constraints,