QGraphicsAnchorLayout: Fix sequential anchor distribution w/ expanding sizes

After the addition of expanding SizePolicy, the distribution of sequential
anchors became wrong.

We must now account for three intervals of distribution instead of only two.
This commit also unifies the logic used by the sequential group anchor and
the edge interpolator.

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

1 files changed, 76 insertions, 86 deletions

diff --git a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
index 1cbea8e..ff42cb5 100644
--- a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
+++ b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
@@ -250,44 +250,61 @@ void ParallelAnchorData::refreshSizeHints_helper(qreal effectiveSpacing,
      0 is at Preferred
      1 is at Maximum
 */
-static qreal getFactor(qreal value, qreal min, qreal pref, qreal max)
-{
-    // ### Maybe remove some of the assertions? (since outside is asserting us)
-    Q_ASSERT(value > min || qFuzzyCompare(value, min));
-    Q_ASSERT(value < max || qFuzzyCompare(value, max));
-
-    if (qFuzzyCompare(value, min)) {
-        return -1.0;
-    } else if (qFuzzyCompare(value, pref)) {
-        return 0.0;
-    } else if (qFuzzyCompare(value, max)) {
-        return 1.0;
-    } else if (value < pref) {
-        // Since value < pref and value != pref and min <= value,
-        // we can assert that min < pref.
-        Q_ASSERT(min < pref);
-        return (value - min) / (pref - min) - 1;
+static QPair<QGraphicsAnchorLayoutPrivate::Interval, qreal> getFactor(qreal value, qreal min,
+                                                                      qreal pref, qreal exp,
+                                                                      qreal max)
+{
+    QGraphicsAnchorLayoutPrivate::Interval interval;
+    qreal lower;
+    qreal upper;
+
+    if (value < pref) {
+        interval = QGraphicsAnchorLayoutPrivate::MinToPreferred;
+        lower = min;
+        upper = pref;
+    } else if (value < exp) {
+        interval = QGraphicsAnchorLayoutPrivate::PreferredToExpanding;
+        lower = pref;
+        upper = exp;
     } else {
-        // Since value > pref and value != pref and max >= value,
-        // we can assert that max > pref.
-        Q_ASSERT(max > pref);
-        return (value - pref) / (max - pref);
+        interval = QGraphicsAnchorLayoutPrivate::ExpandingToMax;
+        lower = exp;
+        upper = max;
     }
+
+    qreal progress;
+    if (upper == lower) {
+        progress = 0;
+    } else {
+        progress = (value - lower) / (upper - lower);
+    }
+
+    return qMakePair(interval, progress);
 }
 
-static qreal getExpandingFactor(const qreal &expSize, const qreal &sizeAtPreferred,
-                                const qreal &sizeAtExpanding, const qreal &sizeAtMaximum)
+static qreal interpolate(const QPair<QGraphicsAnchorLayoutPrivate::Interval, qreal> &factor,
+                         qreal min, qreal pref,
+                         qreal exp, qreal max)
 {
-    const qreal lower = qMin(sizeAtPreferred, sizeAtMaximum);
-    const qreal upper = qMax(sizeAtPreferred, sizeAtMaximum);
-    const qreal boundedExpSize = qBound(lower, expSize, upper);
+    qreal lower;
+    qreal upper;
 
-    const qreal bandSize = sizeAtMaximum - boundedExpSize;
-    if (bandSize == 0) {
-        return 0;
-    } else {
-        return (sizeAtExpanding - boundedExpSize) / bandSize;
+    switch (factor.first) {
+    case QGraphicsAnchorLayoutPrivate::MinToPreferred:
+        lower = min;
+        upper = pref;
+        break;
+    case QGraphicsAnchorLayoutPrivate::PreferredToExpanding:
+        lower = pref;
+        upper = exp;
+        break;
+    case QGraphicsAnchorLayoutPrivate::ExpandingToMax:
+        lower = exp;
+        upper = max;
+        break;
     }
+
+    return lower + factor.second * (upper - lower);
 }
 
 void SequentialAnchorData::updateChildrenSizes()
@@ -307,27 +324,22 @@ void SequentialAnchorData::updateChildrenSizes()
     // Band here refers if the value is in the Minimum To Preferred
     // band (the lower band) or the Preferred To Maximum (the upper band).
 
-    const qreal minFactor = getFactor(sizeAtMinimum, minSize, prefSize, maxSize);
-    const qreal prefFactor = getFactor(sizeAtPreferred, minSize, prefSize, maxSize);
-    const qreal maxFactor = getFactor(sizeAtMaximum, minSize, prefSize, maxSize);
-    const qreal expFactor = getExpandingFactor(expSize, sizeAtPreferred, sizeAtExpanding, sizeAtMaximum);
+    const QPair<QGraphicsAnchorLayoutPrivate::Interval, qreal> minFactor =
+        getFactor(sizeAtMinimum, minSize, prefSize, expSize, maxSize);
+    const QPair<QGraphicsAnchorLayoutPrivate::Interval, qreal> prefFactor =
+        getFactor(sizeAtPreferred, minSize, prefSize, expSize, maxSize);
+    const QPair<QGraphicsAnchorLayoutPrivate::Interval, qreal> expFactor =
+        getFactor(sizeAtExpanding, minSize, prefSize, expSize, maxSize);
+    const QPair<QGraphicsAnchorLayoutPrivate::Interval, qreal> maxFactor =
+        getFactor(sizeAtMaximum, minSize, prefSize, expSize, maxSize);
 
     for (int i = 0; i < m_edges.count(); ++i) {
         AnchorData *e = m_edges.at(i);
 
-        qreal bandSize = minFactor > 0 ? e->maxSize - e->prefSize : e->prefSize - e->minSize;
-        e->sizeAtMinimum = e->prefSize + bandSize * minFactor;
-
-        bandSize = prefFactor > 0 ? e->maxSize - e->prefSize : e->prefSize - e->minSize;
-        e->sizeAtPreferred = e->prefSize + bandSize * prefFactor;
-
-        bandSize = maxFactor > 0 ? e->maxSize - e->prefSize : e->prefSize - e->minSize;
-        e->sizeAtMaximum = e->prefSize + bandSize * maxFactor;
-
-        const qreal lower = qMin(e->sizeAtPreferred, e->sizeAtMaximum);
-        const qreal upper = qMax(e->sizeAtPreferred, e->sizeAtMaximum);
-        const qreal edgeBoundedExpSize = qBound(lower, e->expSize, upper);
-        e->sizeAtExpanding = edgeBoundedExpSize + expFactor * (e->sizeAtMaximum - edgeBoundedExpSize);
+        e->sizeAtMinimum = interpolate(minFactor, e->minSize, e->prefSize, e->expSize, e->maxSize);
+        e->sizeAtPreferred = interpolate(prefFactor, e->minSize, e->prefSize, e->expSize, e->maxSize);
+        e->sizeAtExpanding = interpolate(expFactor, e->minSize, e->prefSize, e->expSize, e->maxSize);
+        e->sizeAtMaximum = interpolate(maxFactor, e->minSize, e->prefSize, e->expSize, e->maxSize);
 
         e->updateChildrenSizes();
     }
@@ -2167,39 +2179,26 @@ void QGraphicsAnchorLayoutPrivate::calculateVertexPositions(
   \internal
 
   Calculate interpolation parameters based on current Layout Size.
-  Must once before calling "interpolateEdgeSize()" for each edge.
+  Must be called once before calling "interpolateEdgeSize()" for
+  the edges.
 */
 void QGraphicsAnchorLayoutPrivate::setupEdgesInterpolation(
     Orientation orientation)
 {
     Q_Q(QGraphicsAnchorLayout);
-    qreal lower, upper, current;
 
-    if (orientation == Horizontal) {
-        current = q->contentsRect().width();
-    } else {
-        current = q->contentsRect().height();
-    }
+    qreal current;
+    current = (orientation == Horizontal) ? q->contentsRect().width() : q->contentsRect().height();
 
-    if (current < sizeHints[orientation][Qt::PreferredSize]) {
-        interpolationInterval[orientation] = MinToPreferred;
-        lower = sizeHints[orientation][Qt::MinimumSize];
-        upper = sizeHints[orientation][Qt::PreferredSize];
-    } else if (current < sizeAtExpanding[orientation]) {
-        interpolationInterval[orientation] = PreferredToExpanding;
-        lower = sizeHints[orientation][Qt::PreferredSize];
-        upper = sizeAtExpanding[orientation];
-    } else {
-        interpolationInterval[orientation] = ExpandingToMax;
-        lower = sizeAtExpanding[orientation];
-        upper = sizeHints[orientation][Qt::MaximumSize];
-    }
+    QPair<Interval, qreal> result;
+    result = getFactor(current,
+                       sizeHints[orientation][Qt::MinimumSize],
+                       sizeHints[orientation][Qt::PreferredSize],
+                       sizeAtExpanding[orientation],
+                       sizeHints[orientation][Qt::MaximumSize]);
 
-    if (upper == lower) {
-        interpolationProgress[orientation] = 0;
-    } else {
-        interpolationProgress[orientation] = (current - lower) / (upper - lower);
-    }
+    interpolationInterval[orientation] = result.first;
+    interpolationProgress[orientation] = result.second;
 }
 
 /*!
@@ -2226,20 +2225,11 @@ void QGraphicsAnchorLayoutPrivate::interpolateEdge(AnchorVertex *base,
                                                    AnchorData *edge,
                                                    Orientation orientation)
 {
-    qreal lower, upper;
-
-    if (interpolationInterval[orientation] == MinToPreferred) {
-        lower = edge->sizeAtMinimum;
-        upper = edge->sizeAtPreferred;
-    } else if (interpolationInterval[orientation] == PreferredToExpanding) {
-        lower = edge->sizeAtPreferred;
-        upper = edge->sizeAtExpanding;
-    } else {
-        lower = edge->sizeAtExpanding;
-        upper = edge->sizeAtMaximum;
-    }
+    const QPair<Interval, qreal> factor(interpolationInterval[orientation],
+                                        interpolationProgress[orientation]);
 
-    qreal edgeDistance = (interpolationProgress[orientation] * (upper - lower)) + lower;
+    qreal edgeDistance = interpolate(factor, edge->sizeAtMinimum, edge->sizeAtPreferred,
+                                     edge->sizeAtExpanding, edge->sizeAtMaximum);
 
     Q_ASSERT(edge->from == base || edge->to == base);