QGraphicsAnchorLayout: fix calculation of sizeAt* values for Sequential

This commit implements what's described in the previous commit

    QGraphicsAnchorLayout: fix expected values for parallel test

When filling the sizeAt* values (the three points used for interpolation
when setting geometry), now sequential anchors distribute the sizes
to the children in a fair way, i.e. proportionally in relation to the
existing min/pref/max hints.

Each value is defined in relation of the pref (either as a shrinkage in
pref or a grow in pref). In both cases the shrinking/growing factor is
the same for all children.

When we implement support for QSizePolicies, this distribution might be
changed by setting size policies for a certain item or anchor.

This makes two tests work -- so no more expected fail. Also fixed a typo
in one test's expected results.

2 files changed, 75 insertions, 11 deletions

diff --git a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
index 9f1878141a..d54ea8d836 100644
--- a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
+++ b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
@@ -127,17 +127,83 @@ void ParallelAnchorData::refreshSizeHints(qreal effectiveSpacing)
     sizeAtMaximum = prefSize;
 }
 
+static qreal getFactor(qreal value, qreal min, qreal pref, qreal max, bool *minToPref)
+{
+    // ### 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)) {
+        *minToPref = true;
+        return 0.0;
+
+    } else if (qFuzzyCompare(value, pref)) {
+        *minToPref = true;
+        return 1.0;
+
+    } else if (qFuzzyCompare(value, max)) {
+        *minToPref = false;
+        return 1.0;
+
+    } else if (value < pref) {
+        *minToPref = true;
+        // Since value < pref and value != pref and min <= value,
+        // we can assert that min < pref.
+        Q_ASSERT(min < pref);
+        return (value - min) / (pref - min);
+
+    } else {
+        *minToPref = false;
+        // Since value > pref and value != pref and max >= value,
+        // we can assert that max > pref.
+        Q_ASSERT(max > pref);
+        return (value - pref) / (max - pref);
+    }
+}
+
 void SequentialAnchorData::updateChildrenSizes()
 {
-    qreal minFactor = sizeAtMinimum / minSize;
-    qreal prefFactor = sizeAtPreferred / prefSize;
-    qreal maxFactor = sizeAtMaximum / maxSize;
+    // ### REMOVE ME
+    // ### check whether we are guarantee to get those or we need to warn stuff at this
+    // point.
+    Q_ASSERT(sizeAtMinimum > minSize || qFuzzyCompare(sizeAtMinimum, minSize));
+    Q_ASSERT(sizeAtMinimum < maxSize || qFuzzyCompare(sizeAtMinimum, maxSize));
+    Q_ASSERT(sizeAtPreferred > minSize || qFuzzyCompare(sizeAtPreferred, minSize));
+    Q_ASSERT(sizeAtPreferred < maxSize || qFuzzyCompare(sizeAtPreferred, maxSize));
+    Q_ASSERT(sizeAtMaximum > minSize || qFuzzyCompare(sizeAtMaximum, minSize));
+    Q_ASSERT(sizeAtMaximum < maxSize || qFuzzyCompare(sizeAtMaximum, maxSize));
+
+    // Band here refers if the value is in the Minimum To Preferred
+    // band (the lower band) or the Preferred To Maximum (the upper band).
+
+    bool minLowerBand;
+    qreal minFactor = getFactor(sizeAtMinimum, minSize, prefSize, maxSize, &minLowerBand);
+
+    bool prefLowerBand;
+    qreal prefFactor = getFactor(sizeAtPreferred, minSize, prefSize, maxSize, &prefLowerBand);
+
+    bool maxLowerBand;
+    qreal maxFactor = getFactor(sizeAtMaximum, minSize, prefSize, maxSize, &maxLowerBand);
 
     for (int i = 0; i < m_edges.count(); ++i) {
-        m_edges[i]->sizeAtMinimum = m_edges[i]->minSize * minFactor;
-        m_edges[i]->sizeAtPreferred = m_edges[i]->prefSize * prefFactor;
-        m_edges[i]->sizeAtMaximum = m_edges[i]->maxSize * maxFactor;
-        m_edges[i]->updateChildrenSizes();
+        AnchorData *e = m_edges.at(i);
+
+        if (minLowerBand)
+            e->sizeAtMinimum = e->minSize + ((e->prefSize - e->minSize) * minFactor);
+        else
+            e->sizeAtMinimum = e->prefSize + ((e->maxSize - e->prefSize) * minFactor);
+
+        if (prefLowerBand)
+            e->sizeAtPreferred = e->minSize + ((e->prefSize - e->minSize) * prefFactor);
+        else
+            e->sizeAtPreferred = e->prefSize + ((e->maxSize - e->prefSize) * prefFactor);
+
+        if (maxLowerBand)
+            e->sizeAtMaximum = e->minSize + ((e->prefSize - e->minSize) * maxFactor);
+        else
+            e->sizeAtMaximum = e->prefSize + ((e->maxSize - e->prefSize) * maxFactor);
+
+        e->updateChildrenSizes();
     }
 }
 
diff --git a/tests/auto/qgraphicsanchorlayout/tst_qgraphicsanchorlayout.cpp b/tests/auto/qgraphicsanchorlayout/tst_qgraphicsanchorlayout.cpp
index 3bab0ce6fc..dcda12dfe0 100644
--- a/tests/auto/qgraphicsanchorlayout/tst_qgraphicsanchorlayout.cpp
+++ b/tests/auto/qgraphicsanchorlayout/tst_qgraphicsanchorlayout.cpp
@@ -234,7 +234,6 @@ void tst_QGraphicsAnchorLayout::parallel()
     // solution found by the solver at runtime.
     p.resize(layoutMaximumSize);
     QCOMPARE(a->geometry(), QRectF(0, 0, 200, 100));
-    QEXPECT_FAIL("", "see commit 23441f49a23cbf936b60140c5c8a6d5cb3ca00a7 for explanation", Abort);
     QCOMPARE(b->geometry(), QRectF(200, 100, 175, 100));
     QCOMPARE(c->geometry(), QRectF(200, 200, 350, 100));
     QCOMPARE(d->geometry(), QRectF(375, 300, 175, 100));
@@ -609,9 +608,8 @@ void tst_QGraphicsAnchorLayout::proportionalPreferred()
     qreal factor = 12.0 / 24.0;
 
     QCOMPARE(c->size().width(), d->size().width());
-    QEXPECT_FAIL("", "see commit 23441f49a23cbf936b60140c5c8a6d5cb3ca00a7 for explanation", Abort);
-    QCOMPARE(a->size().width() * factor, 10 * factor);
-    QCOMPARE(c->size().width() * factor, 14 * factor);
+    QCOMPARE(a->size().width(), 10 * factor);
+    QCOMPARE(c->size().width(), 14 * factor);
     QCOMPARE(p.size(), QSizeF(12, 400));
 }