QGAL: Use constraints of type "equal" for fixed items

We usually create two restrictions for each item, one to tell its
size should be more than its minimum size and other enforcing it to
be at most its maximum size.

Now, for items that have fixed size, ie. minSize == maxSize, we create
a single constraint telling its size should be equal its min/maxSize.

The immediate advantage is to have one less constraint for each of
these items. The indirect advantage is that the simplex solver can
take advantage of such information.

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

1 files changed, 22 insertions, 12 deletions

diff --git a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
index 7dbfba9..a83e619 100644
--- a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
+++ b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
@@ -2032,17 +2032,27 @@ QList<QSimplexConstraint *> QGraphicsAnchorLayoutPrivate::constraintsFromSizeHin
 {
     QList<QSimplexConstraint *> anchorConstraints;
     for (int i = 0; i < anchors.size(); ++i) {
-        QSimplexConstraint *c = new QSimplexConstraint;
-        c->variables.insert(anchors[i], 1.0);
-        c->constant = anchors[i]->minSize;
-        c->ratio = QSimplexConstraint::MoreOrEqual;
-        anchorConstraints += c;
-
-        c = new QSimplexConstraint;
-        c->variables.insert(anchors[i], 1.0);
-        c->constant = anchors[i]->maxSize;
-        c->ratio = QSimplexConstraint::LessOrEqual;
-        anchorConstraints += c;
+        AnchorData *ad = anchors[i];
+
+        if ((ad->minSize == ad->maxSize) || qFuzzyCompare(ad->minSize, ad->maxSize)) {
+            QSimplexConstraint *c = new QSimplexConstraint;
+            c->variables.insert(ad, 1.0);
+            c->constant = ad->minSize;
+            c->ratio = QSimplexConstraint::Equal;
+            anchorConstraints += c;
+        } else {
+            QSimplexConstraint *c = new QSimplexConstraint;
+            c->variables.insert(ad, 1.0);
+            c->constant = ad->minSize;
+            c->ratio = QSimplexConstraint::MoreOrEqual;
+            anchorConstraints += c;
+
+            c = new QSimplexConstraint;
+            c->variables.insert(ad, 1.0);
+            c->constant = ad->maxSize;
+            c->ratio = QSimplexConstraint::LessOrEqual;
+            anchorConstraints += c;
+        }
     }
 
     return anchorConstraints;
@@ -2608,7 +2618,7 @@ void QGraphicsAnchorLayoutPrivate::solveExpanding(const QList<QSimplexConstraint
             hasExpanding = true;
 
         // Lock anchor between boundedExpSize and sizeAtMaximum (ensure 3.a)
-        if (boundedExpSize == ad->sizeAtMaximum) {
+        if (boundedExpSize == ad->sizeAtMaximum || qFuzzyCompare(boundedExpSize, ad->sizeAtMaximum)) {
             // The interval has only one possible value, we can use an "Equal"
             // constraint and don't need to add this variable to the objective.
             QSimplexConstraint *itemC = new QSimplexConstraint;