QGraphicsAnchorLayout: Add support for expanding SizePolicy with simplification

Updating "refreshSizeHints" and "updateChildrenSizes" methods for standard,
parallel and sequential anchors, in order to support the expanding SizePolicy
flag.

This adds the logic required to calculate equivalent expected/nominal expanding
size (AnchorData::expSize) as well as the logic to propagate the effective
size when in the expanding state (AnchorData::sizeAtExpected).

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

2 files changed, 36 insertions, 27 deletions

diff --git a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
index cf1429c..20ff03b 100644
--- a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
+++ b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
@@ -146,15 +146,11 @@ void AnchorData::refreshSizeHints(qreal effectiveSpacing)
             maxSize /= 2;
         }
 
-        // ###
-        expSize = prefSize;
-        // if (policy & QSizePolicy::ExpandFlag) {
-        //     isExpanding = 1;
-        //     expSize = maxSize;
-        // } else {
-        //     isExpanding = 0;
-        //     expSize = prefSize;
-        // }
+        if (policy & QSizePolicy::ExpandFlag) {
+            expSize = maxSize;
+        } else {
+            expSize = prefSize;
+        }
 
         // Set the anchor effective sizes to preferred.
         //
@@ -175,8 +171,6 @@ void AnchorData::refreshSizeHints(qreal effectiveSpacing)
         expSize = effectiveSpacing;
         maxSize = effectiveSpacing;
 
-        isExpanding = 0;
-
         sizeAtMinimum = prefSize;
         sizeAtPreferred = prefSize;
         sizeAtExpanding = prefSize;
@@ -188,8 +182,8 @@ void ParallelAnchorData::updateChildrenSizes()
 {
     firstEdge->sizeAtMinimum = secondEdge->sizeAtMinimum = sizeAtMinimum;
     firstEdge->sizeAtPreferred = secondEdge->sizeAtPreferred = sizeAtPreferred;
+    firstEdge->sizeAtExpanding = secondEdge->sizeAtExpanding = sizeAtExpanding;
     firstEdge->sizeAtMaximum = secondEdge->sizeAtMaximum = sizeAtMaximum;
-    firstEdge->sizeAtExpanding = secondEdge->sizeAtExpanding = sizeAtPreferred;
 
     firstEdge->updateChildrenSizes();
     secondEdge->updateChildrenSizes();
@@ -215,11 +209,11 @@ void ParallelAnchorData::refreshSizeHints_helper(qreal effectiveSpacing,
     minSize = qMax(firstEdge->minSize, secondEdge->minSize);
     maxSize = qMin(firstEdge->maxSize, secondEdge->maxSize);
 
-    prefSize = qMax(firstEdge->prefSize, secondEdge->prefSize);
-    prefSize = qMin(prefSize, maxSize);
+    expSize = qMax(firstEdge->expSize, secondEdge->expSize);
+    expSize = qMin(expSize, maxSize);
 
-    // ###
-    expSize = prefSize;
+    prefSize = qMax(firstEdge->prefSize, secondEdge->prefSize);
+    prefSize = qMin(prefSize, expSize);
 
     // See comment in AnchorData::refreshSizeHints() about sizeAt* values
     sizeAtMinimum = prefSize;
@@ -260,6 +254,21 @@ static qreal getFactor(qreal value, qreal min, qreal pref, qreal max)
     }
 }
 
+static qreal getExpandingFactor(const qreal &expSize, const qreal &sizeAtPreferred,
+                                const qreal &sizeAtExpanding, const qreal &sizeAtMaximum)
+{
+    const qreal lower = qMin(sizeAtPreferred, sizeAtMaximum);
+    const qreal upper = qMax(sizeAtPreferred, sizeAtMaximum);
+    const qreal boundedExpSize = qBound(lower, expSize, upper);
+
+    const qreal bandSize = sizeAtMaximum - boundedExpSize;
+    if (bandSize == 0) {
+        return 0;
+    } else {
+        return (sizeAtExpanding - boundedExpSize) / bandSize;
+    }
+}
+
 void SequentialAnchorData::updateChildrenSizes()
 {
     // ### REMOVE ME
@@ -269,15 +278,18 @@ void SequentialAnchorData::updateChildrenSizes()
     Q_ASSERT(sizeAtMinimum < maxSize || qFuzzyCompare(sizeAtMinimum, maxSize));
     Q_ASSERT(sizeAtPreferred > minSize || qFuzzyCompare(sizeAtPreferred, minSize));
     Q_ASSERT(sizeAtPreferred < maxSize || qFuzzyCompare(sizeAtPreferred, maxSize));
+    Q_ASSERT(sizeAtExpanding > minSize || qFuzzyCompare(sizeAtExpanding, minSize));
+    Q_ASSERT(sizeAtExpanding < maxSize || qFuzzyCompare(sizeAtExpanding, 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).
 
-    qreal minFactor = getFactor(sizeAtMinimum, minSize, prefSize, maxSize);
-    qreal prefFactor = getFactor(sizeAtPreferred, minSize, prefSize, maxSize);
-    qreal maxFactor = getFactor(sizeAtMaximum, minSize, prefSize, maxSize);
+    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);
 
     for (int i = 0; i < m_edges.count(); ++i) {
         AnchorData *e = m_edges.at(i);
@@ -291,8 +303,10 @@ void SequentialAnchorData::updateChildrenSizes()
         bandSize = maxFactor > 0 ? e->maxSize - e->prefSize : e->prefSize - e->minSize;
         e->sizeAtMaximum = e->prefSize + bandSize * maxFactor;
 
-        // ###
-        e->sizeAtExpanding = e->sizeAtPreferred;
+        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->updateChildrenSizes();
     }
@@ -324,9 +338,6 @@ void SequentialAnchorData::refreshSizeHints_helper(qreal effectiveSpacing,
         maxSize += edge->maxSize;
     }
 
-    // ###
-    expSize = prefSize;
-
     // See comment in AnchorData::refreshSizeHints() about sizeAt* values
     sizeAtMinimum = prefSize;
     sizeAtPreferred = prefSize;
diff --git a/src/gui/graphicsview/qgraphicsanchorlayout_p.h b/src/gui/graphicsview/qgraphicsanchorlayout_p.h
index 8f67b2c..aac4f96 100644
--- a/src/gui/graphicsview/qgraphicsanchorlayout_p.h
+++ b/src/gui/graphicsview/qgraphicsanchorlayout_p.h
@@ -156,8 +156,7 @@ struct AnchorData : public QSimplexVariable {
           sizeAtMinimum(0), sizeAtPreferred(0),
           sizeAtExpanding(0), sizeAtMaximum(0),
           graphicsAnchor(0), skipInPreferred(0),
-          type(Normal), hasSize(true), isLayoutAnchor(false),
-          isExpanding(false) {}
+          type(Normal), hasSize(true), isLayoutAnchor(false) {}
 
     virtual void updateChildrenSizes() {}
     virtual void refreshSizeHints(qreal effectiveSpacing);
@@ -214,7 +213,6 @@ struct AnchorData : public QSimplexVariable {
     uint type : 2;            // either Normal, Sequential or Parallel
     uint hasSize : 1;         // if false, get size from style.
     uint isLayoutAnchor : 1;  // if this anchor is connected to a layout 'edge'
-    uint isExpanding : 1;     // if true, expands before other anchors
 };
 
 #ifdef QT_DEBUG