Merge branch '4.6' of git@scm.dev.troll.no:qt/qt into 4.6

10 files changed, 300 insertions, 85 deletions

diff --git a/src/corelib/global/qglobal.cpp b/src/corelib/global/qglobal.cpp
index 4974acf..97362af 100644
--- a/src/corelib/global/qglobal.cpp
+++ b/src/corelib/global/qglobal.cpp
@@ -1769,25 +1769,6 @@ static QSysInfo::S60Version cachedS60Version = QSysInfo::S60Version(-1);
 
 QSysInfo::S60Version QSysInfo::s60Version()
 {
-#  ifdef Q_CC_NOKIAX86
-    // For emulator builds. Emulators don't support the trick we use to figure
-    // out which SDK we are running under, so simply hardcode it there.
-#   if defined(__SERIES60_31__)
-    return SV_S60_3_1;
-
-#   elif defined(__S60_32__)
-    return SV_S60_3_2;
-
-#   elif defined(__S60_50__)
-    return SV_S60_5_0;
-
-#   else
-    return SV_S60_Unknown;
-
-#   endif
-
-#  else
-    // For hardware builds.
     if (cachedS60Version != -1)
         return cachedS60Version;
 
@@ -1818,6 +1799,19 @@ QSysInfo::S60Version QSysInfo::s60Version()
         delete contents;
     }
 
+#  ifdef Q_CC_NOKIAX86
+    // Some emulator environments may not contain the version specific .sis files, so
+    // simply hardcode the version on those environments.
+#   if defined(__SERIES60_31__)
+    return cachedS60Version = SV_S60_3_1;
+#   elif defined(__S60_32__)
+    return cachedS60Version = SV_S60_3_2;
+#   elif defined(__S60_50__)
+    return cachedS60Version = SV_S60_5_0;
+#   else
+    return cachedS60Version = SV_S60_Unknown;
+#   endif
+#  else
     return cachedS60Version = SV_S60_Unknown;
 #  endif
 }
@@ -2718,7 +2712,7 @@ int qrand()
     \since 4.6
 
     \brief The QT_TRID_NOOP macro marks an id for dynamic translation.
-    
+
     The only purpose of this macro is to provide an anchor for attaching
     meta data like to qtTrId().
 
diff --git a/src/corelib/kernel/qeventdispatcher_glib.cpp b/src/corelib/kernel/qeventdispatcher_glib.cpp
index 6e457f4..665b73e 100644
--- a/src/corelib/kernel/qeventdispatcher_glib.cpp
+++ b/src/corelib/kernel/qeventdispatcher_glib.cpp
@@ -127,16 +127,11 @@ struct GTimerSource
     GSource source;
     QTimerInfoList timerList;
     QEventLoop::ProcessEventsFlags processEventsFlags;
+    bool runWithIdlePriority;
 };
 
-static gboolean timerSourcePrepare(GSource *source, gint *timeout)
+static gboolean timerSourcePrepareHelper(GTimerSource *src, gint *timeout)
 {
-    gint dummy;
-    if (!timeout)
-        timeout = &dummy;
-
-    GTimerSource *src = reinterpret_cast<GTimerSource *>(source);
-
     timeval tv = { 0l, 0l };
     if (!(src->processEventsFlags & QEventLoop::X11ExcludeTimers) && src->timerList.timerWait(tv))
         *timeout = (tv.tv_sec * 1000) + (tv.tv_usec / 1000);
@@ -146,10 +141,8 @@ static gboolean timerSourcePrepare(GSource *source, gint *timeout)
     return (*timeout == 0);
 }
 
-static gboolean timerSourceCheck(GSource *source)
+static gboolean timerSourceCheckHelper(GTimerSource *src)
 {
-    GTimerSource *src = reinterpret_cast<GTimerSource *>(source);
-
     if (src->timerList.isEmpty()
         || (src->processEventsFlags & QEventLoop::X11ExcludeTimers))
         return false;
@@ -160,9 +153,35 @@ static gboolean timerSourceCheck(GSource *source)
     return true;
 }
 
+static gboolean timerSourcePrepare(GSource *source, gint *timeout)
+{
+    gint dummy;
+    if (!timeout)
+        timeout = &dummy;
+
+    GTimerSource *src = reinterpret_cast<GTimerSource *>(source);
+    if (src->runWithIdlePriority) {
+        if (timeout)
+            *timeout = -1;
+        return false;
+    }
+
+    return timerSourcePrepareHelper(src, timeout);
+}
+
+static gboolean timerSourceCheck(GSource *source)
+{
+    GTimerSource *src = reinterpret_cast<GTimerSource *>(source);
+    if (src->runWithIdlePriority)
+        return false;
+    return timerSourceCheckHelper(src);
+}
+
 static gboolean timerSourceDispatch(GSource *source, GSourceFunc, gpointer)
 {
-    (void) reinterpret_cast<GTimerSource *>(source)->timerList.activateTimers();
+    GTimerSource *timerSource = reinterpret_cast<GTimerSource *>(source);
+    timerSource->runWithIdlePriority = true;
+    (void) timerSource->timerList.activateTimers();
     return true; // ??? don't remove, right again?
 }
 
@@ -175,6 +194,53 @@ static GSourceFuncs timerSourceFuncs = {
     NULL
 };
 
+struct GIdleTimerSource
+{
+    GSource source;
+    GTimerSource *timerSource;
+};
+
+static gboolean idleTimerSourcePrepare(GSource *source, gint *timeout)
+{
+    GIdleTimerSource *idleTimerSource = reinterpret_cast<GIdleTimerSource *>(source);
+    GTimerSource *timerSource = idleTimerSource->timerSource;
+    if (!timerSource->runWithIdlePriority) {
+        // Yield to the normal priority timer source
+        if (timeout)
+            *timeout = -1;
+        return false;
+    }
+
+    return timerSourcePrepareHelper(timerSource, timeout);
+}
+
+static gboolean idleTimerSourceCheck(GSource *source)
+{
+    GIdleTimerSource *idleTimerSource = reinterpret_cast<GIdleTimerSource *>(source);
+    GTimerSource *timerSource = idleTimerSource->timerSource;
+    if (!timerSource->runWithIdlePriority) {
+        // Yield to the normal priority timer source
+        return false;
+    }
+    return timerSourceCheckHelper(timerSource);
+}
+
+static gboolean idleTimerSourceDispatch(GSource *source, GSourceFunc, gpointer)
+{
+    GTimerSource *timerSource = reinterpret_cast<GIdleTimerSource *>(source)->timerSource;
+    (void) timerSourceDispatch(&timerSource->source, 0, 0);
+    return true;
+}
+
+static GSourceFuncs idleTimerSourceFuncs = {
+    idleTimerSourcePrepare,
+    idleTimerSourceCheck,
+    idleTimerSourceDispatch,
+    NULL,
+    NULL,
+    NULL
+};
+
 struct GPostEventSource
 {
     GSource source;
@@ -235,14 +301,15 @@ QEventDispatcherGlibPrivate::QEventDispatcherGlibPrivate(GMainContext *context)
         g_main_context_ref(mainContext);
     } else {
         QCoreApplication *app = QCoreApplication::instance();
-	if (app && QThread::currentThread() == app->thread()) {
-	    mainContext = g_main_context_default();
-	    g_main_context_ref(mainContext);
-	} else {
-	    mainContext = g_main_context_new();
-	}
+        if (app && QThread::currentThread() == app->thread()) {
+            mainContext = g_main_context_default();
+            g_main_context_ref(mainContext);
+        } else {
+            mainContext = g_main_context_new();
+        }
     }
 
+    // setup post event source
     postEventSource = reinterpret_cast<GPostEventSource *>(g_source_new(&postEventSourceFuncs,
                                                                         sizeof(GPostEventSource)));
     postEventSource->serialNumber = 1;
@@ -257,14 +324,21 @@ QEventDispatcherGlibPrivate::QEventDispatcherGlibPrivate(GMainContext *context)
     g_source_set_can_recurse(&socketNotifierSource->source, true);
     g_source_attach(&socketNotifierSource->source, mainContext);
 
-    // setup timerSource
+    // setup normal and idle timer sources
     timerSource = reinterpret_cast<GTimerSource *>(g_source_new(&timerSourceFuncs,
                                                                 sizeof(GTimerSource)));
     (void) new (&timerSource->timerList) QTimerInfoList();
     timerSource->processEventsFlags = QEventLoop::AllEvents;
+    timerSource->runWithIdlePriority = false;
     g_source_set_can_recurse(&timerSource->source, true);
-    g_source_set_priority(&timerSource->source, G_PRIORITY_DEFAULT_IDLE);
     g_source_attach(&timerSource->source, mainContext);
+
+    idleTimerSource = reinterpret_cast<GIdleTimerSource *>(g_source_new(&idleTimerSourceFuncs,
+                                                                        sizeof(GIdleTimerSource)));
+    idleTimerSource->timerSource = timerSource;
+    g_source_set_can_recurse(&idleTimerSource->source, true);
+    g_source_set_priority(&idleTimerSource->source, G_PRIORITY_DEFAULT_IDLE);
+    g_source_attach(&idleTimerSource->source, mainContext);
 }
 
 QEventDispatcherGlib::QEventDispatcherGlib(QObject *parent)
@@ -272,12 +346,9 @@ QEventDispatcherGlib::QEventDispatcherGlib(QObject *parent)
 {
 }
 
-QEventDispatcherGlib::QEventDispatcherGlib(GMainContext *mainContext,
-					   QObject *parent)
-    : QAbstractEventDispatcher(*(new QEventDispatcherGlibPrivate(mainContext)),
-			       parent)
-{
-}
+QEventDispatcherGlib::QEventDispatcherGlib(GMainContext *mainContext, QObject *parent)
+    : QAbstractEventDispatcher(*(new QEventDispatcherGlibPrivate(mainContext)), parent)
+{ }
 
 QEventDispatcherGlib::~QEventDispatcherGlib()
 {
@@ -289,6 +360,9 @@ QEventDispatcherGlib::~QEventDispatcherGlib()
     g_source_destroy(&d->timerSource->source);
     g_source_unref(&d->timerSource->source);
     d->timerSource = 0;
+    g_source_destroy(&d->idleTimerSource->source);
+    g_source_unref(&d->idleTimerSource->source);
+    d->idleTimerSource = 0;
 
     // destroy socket notifier source
     for (int i = 0; i < d->socketNotifierSource->pollfds.count(); ++i) {
@@ -324,11 +398,16 @@ bool QEventDispatcherGlib::processEvents(QEventLoop::ProcessEventsFlags flags)
     // tell postEventSourcePrepare() and timerSource about any new flags
     QEventLoop::ProcessEventsFlags savedFlags = d->timerSource->processEventsFlags;
     d->timerSource->processEventsFlags = flags;
-    
+
+    if (!(flags & QEventLoop::EventLoopExec)) {
+        // force timers to be sent at normal priority
+        d->timerSource->runWithIdlePriority = false;
+    }
+
     bool result = g_main_context_iteration(d->mainContext, canWait);
     while (!result && canWait)
         result = g_main_context_iteration(d->mainContext, canWait);
-    
+
     d->timerSource->processEventsFlags = savedFlags;
 
     if (canWait)
diff --git a/src/corelib/kernel/qeventdispatcher_glib_p.h b/src/corelib/kernel/qeventdispatcher_glib_p.h
index 8dbc44d..6a4e726 100644
--- a/src/corelib/kernel/qeventdispatcher_glib_p.h
+++ b/src/corelib/kernel/qeventdispatcher_glib_p.h
@@ -98,6 +98,7 @@ protected:
 struct GPostEventSource;
 struct GSocketNotifierSource;
 struct GTimerSource;
+struct GIdleTimerSource;
 
 class Q_CORE_EXPORT QEventDispatcherGlibPrivate : public QAbstractEventDispatcherPrivate
 {
@@ -108,6 +109,7 @@ public:
     GPostEventSource *postEventSource;
     GSocketNotifierSource *socketNotifierSource;
     GTimerSource *timerSource;
+    GIdleTimerSource *idleTimerSource;
 };
 
 QT_END_NAMESPACE
diff --git a/src/corelib/kernel/qeventdispatcher_unix.cpp b/src/corelib/kernel/qeventdispatcher_unix.cpp
index a912971..5a0afb8 100644
--- a/src/corelib/kernel/qeventdispatcher_unix.cpp
+++ b/src/corelib/kernel/qeventdispatcher_unix.cpp
@@ -446,10 +446,10 @@ bool QTimerInfoList::timerWait(timeval &tm)
     // Find first waiting timer not already active
     QTimerInfo *t = 0;
     for (QTimerInfoList::const_iterator it = constBegin(); it != constEnd(); ++it) {
-	if (!(*it)->inTimerEvent) {
-	    t = *it;
-	    break;
-	}
+        if (!(*it)->inTimerEvent) {
+            t = *it;
+            break;
+        }
     }
 
     if (!t)
diff --git a/src/corelib/statemachine/qabstracttransition.cpp b/src/corelib/statemachine/qabstracttransition.cpp
index a81fe0f..8b858c7 100644
--- a/src/corelib/statemachine/qabstracttransition.cpp
+++ b/src/corelib/statemachine/qabstracttransition.cpp
@@ -187,7 +187,7 @@ QAbstractState *QAbstractTransition::targetState() const
     Q_D(const QAbstractTransition);
     if (d->targetStates.isEmpty())
         return 0;
-    return d->targetStates.first();
+    return d->targetStates.first().data();
 }
 
 /*!
@@ -211,7 +211,7 @@ QList<QAbstractState*> QAbstractTransition::targetStates() const
     Q_D(const QAbstractTransition);
     QList<QAbstractState*> result;
     for (int i = 0; i < d->targetStates.size(); ++i) {
-        QAbstractState *target = d->targetStates.at(i);
+        QAbstractState *target = d->targetStates.at(i).data();
         if (target)
             result.append(target);
     }
@@ -225,7 +225,7 @@ void QAbstractTransition::setTargetStates(const QList<QAbstractState*> &targets)
 {
     Q_D(QAbstractTransition);
 
-    for (int i=0; i<targets.size(); ++i) {
+    for (int i = 0; i < targets.size(); ++i) {
         QAbstractState *target = targets.at(i);
         if (!target) {
             qWarning("QAbstractTransition::setTargetStates: target state(s) cannot be null");
diff --git a/src/corelib/statemachine/qabstracttransition_p.h b/src/corelib/statemachine/qabstracttransition_p.h
index 7465243..5b4df1b 100644
--- a/src/corelib/statemachine/qabstracttransition_p.h
+++ b/src/corelib/statemachine/qabstracttransition_p.h
@@ -56,7 +56,7 @@
 #include <private/qobject_p.h>
 
 #include <QtCore/qlist.h>
-#include <QtCore/qpointer.h>
+#include <QtCore/qsharedpointer.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -80,7 +80,7 @@ public:
     QStateMachine *machine() const;
     void emitTriggered();
 
-    QList<QPointer<QAbstractState> > targetStates;
+    QList<QWeakPointer<QAbstractState> > targetStates;
 
 #ifndef QT_NO_ANIMATION
     QList<QAbstractAnimation*> animations;
diff --git a/src/corelib/statemachine/qstate.cpp b/src/corelib/statemachine/qstate.cpp
index 70026b8..a6e4a57 100644
--- a/src/corelib/statemachine/qstate.cpp
+++ b/src/corelib/statemachine/qstate.cpp
@@ -291,9 +291,9 @@ QAbstractTransition *QState::addTransition(QAbstractTransition *transition)
     }
 
     transition->setParent(this);
-    const QList<QPointer<QAbstractState> > &targets = QAbstractTransitionPrivate::get(transition)->targetStates;
+    const QList<QWeakPointer<QAbstractState> > &targets = QAbstractTransitionPrivate::get(transition)->targetStates;
     for (int i = 0; i < targets.size(); ++i) {
-        QAbstractState *t = targets.at(i);
+        QAbstractState *t = targets.at(i).data();
         if (!t) {
             qWarning("QState::addTransition: cannot add transition to null state");
             return 0;
diff --git a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
index 7041d58..49aabf5 100644
--- a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
+++ b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
@@ -542,7 +542,7 @@ static bool simplifySequentialChunk(Graph<AnchorVertex, AnchorData> *graph,
 void QGraphicsAnchorLayoutPrivate::simplifyGraph(Orientation orientation)
 {
     static bool noSimplification = !qgetenv("QT_ANCHORLAYOUT_NO_SIMPLIFICATION").isEmpty();
-    if (noSimplification)
+    if (noSimplification || items.isEmpty())
         return;
 
     if (graphSimplified[orientation])
diff --git a/src/gui/graphicsview/qsimplex_p.cpp b/src/gui/graphicsview/qsimplex_p.cpp
index e3a991e..1ba24a3 100644
--- a/src/gui/graphicsview/qsimplex_p.cpp
+++ b/src/gui/graphicsview/qsimplex_p.cpp
@@ -48,6 +48,32 @@
 
 QT_BEGIN_NAMESPACE
 
+/*!
+  \class QSimplex
+
+  The QSimplex class is a Linear Programming problem solver based on the two-phase
+  simplex method.
+
+  It takes a set of QSimplexConstraints as its restrictive constraints and an
+  additional QSimplexConstraint as its objective function. Then methods to maximize
+  and minimize the problem solution are provided.
+
+  The two-phase simplex method is based on the following steps:
+  First phase:
+  1.a) Modify the original, complex, and possibly not feasible problem, into a new,
+       easy to solve problem.
+  1.b) Set as the objective of the new problem, a feasible solution for the original
+       complex problem.
+  1.c) Run simplex to optimize the modified problem and check whether a solution for
+       the original problem exists.
+
+  Second phase:
+  2.a) Go back to the original problem with the feasibl (but not optimal) solution
+       found in the first phase.
+  2.b) Set the original objective.
+  3.c) Run simplex to optimize the original problem towards its optimal solution.
+*/
+
 QSimplex::QSimplex() : objective(0), rows(0), columns(0), firstArtificial(0), matrix(0)
 {
 }
@@ -84,15 +110,31 @@ void QSimplex::clearDataStructures()
     objective = 0;
 }
 
+/*!
+  Sets the new constraints in the simplex solver and returns whether the problem
+  is feasible.
+
+  This method sets the new constraints, normalizes them, creates the simplex matrix
+  and runs the first simplex phase.
+*/
 bool QSimplex::setConstraints(const QList<QSimplexConstraint *> newConstraints)
 {
+    ////////////////////////////
+    // Reset to initial state //
+    ////////////////////////////
     clearDataStructures();
 
     if (newConstraints.isEmpty())
         return true;    // we are ok with no constraints
     constraints = newConstraints;
 
-    // Set Variables direct mapping
+    ///////////////////////////////////////
+    // Prepare variables and constraints //
+    ///////////////////////////////////////
+
+    // Set Variables direct mapping.
+    // "variables" is a list that provides a stable, indexed list of all variables
+    // used in this problem.
     QSet<QSimplexVariable *> variablesSet;
     for (int i = 0; i < constraints.size(); ++i)
         variablesSet += \
@@ -100,12 +142,25 @@ bool QSimplex::setConstraints(const QList<QSimplexConstraint *> newConstraints)
     variables = variablesSet.toList();
 
     // Set Variables reverse mapping
+    // We also need to be able to find the index for a given variable, to do that
+    // we store in each variable its index.
     for (int i = 0; i < variables.size(); ++i) {
         // The variable "0" goes at the column "1", etc...
         variables[i]->index = i + 1;
     }
 
     // Normalize Constraints
+    // In this step, we prepare the constraints in two ways:
+    // Firstly, we modify all constraints of type "LessOrEqual" or "MoreOrEqual"
+    // by the adding slack or surplus variables and making them "Equal" constraints.
+    // Secondly, we need every single constraint to have a direct, easy feasible
+    // solution. Constraints that have slack variables are already easy to solve,
+    // to all the others we add artificial variables.
+    //
+    // At the end we modify the constraints as follows:
+    //  - LessOrEqual: SLACK variable is added.
+    //  - Equal: ARTIFICIAL variable is added.
+    //  - More or Equal: ARTIFICIAL and SURPLUS variables are added.
     int variableIndex = variables.size();
     QList <QSimplexVariable *> artificialList;
 
@@ -138,12 +193,18 @@ bool QSimplex::setConstraints(const QList<QSimplexConstraint *> newConstraints)
         }
     }
 
+    // All original, slack and surplus have already had its index set
+    // at this point. We now set the index of the artificial variables
+    // as to ensure they are at the end of the variable list and therefore
+    // can be easily removed at the end of this method.
     firstArtificial = variableIndex + 1;
     for (int i = 0; i < artificialList.size(); ++i)
         artificialList[i]->index = ++variableIndex;
     artificialList.clear();
 
-    // Matrix
+    /////////////////////////////
+    // Fill the Simplex matrix //
+    /////////////////////////////
 
     // One for each variable plus the Basic and BFS columns (first and last)
     columns = variableIndex + 2;
@@ -188,24 +249,61 @@ bool QSimplex::setConstraints(const QList<QSimplexConstraint *> newConstraints)
         setValueAt(i, columns - 1, c->constant);
     }
 
-    // Set temporary objective: -1 * sum_of_artificial_vars
+    // Set objective for the first-phase Simplex.
+    // Z = -1 * sum_of_artificial_vars
     for (int j = firstArtificial; j < columns - 1; ++j)
         setValueAt(0, j, 1.0);
 
     // Maximize our objective (artificial vars go to zero)
     solveMaxHelper();
 
+    // If there is a solution where the sum of all artificial
+    // variables is zero, then all of them can be removed and yet
+    // we will have a feasible (but not optimal) solution for the
+    // original problem.
+    // Otherwise, we clean up our structures and report there is
+    // no feasible solution.
     if (valueAt(0, columns - 1) != 0.0) {
         qWarning() << "QSimplex: No feasible solution!";
         clearDataStructures();
         return false;
     }
 
-    // Remove artificial variables
+    // Remove artificial variables. We already have a feasible
+    // solution for the first problem, thus we don't need them
+    // anymore.
     clearColumns(firstArtificial, columns - 2);
+
+    #ifdef QT_DEBUG
+    // Ensure that at the end of the simplex each row should either:
+    //  - Have a positive value on the column associated to its variable, or
+    //  - Have zero values in all columns.
+    //
+    // This avoids a regression where restrictions would be lost
+    // due to randomness in the pivotRowForColumn method.
+    for (int i = 1; i < rows; ++i) {
+        int variableIndex = valueAt(i, 0);
+        if (valueAt(i, variableIndex) > 0)
+            continue;
+
+        for (int j = 1; j < columns; ++j) {
+            Q_ASSERT(valueAt(i, j) == 0);
+        }
+    }
+    #endif
+
     return true;
 }
 
+/*!
+  \internal
+
+  Run simplex on the current matrix with the current objective.
+
+  This is the iterative method. The matrix lines are combined
+  as to modify the variable values towards the best solution possible.
+  The method returns when the matrix is in the optimal state.
+*/
 void QSimplex::solveMaxHelper()
 {
     reducedRowEchelon();
@@ -235,23 +333,21 @@ void QSimplex::clearColumns(int first, int last)
 
 void QSimplex::dumpMatrix()
 {
-    printf("---- Simplex Matrix ----\n");
+    qDebug("---- Simplex Matrix ----\n");
 
-    printf("       ");
+    QString str(QLatin1String("       "));
     for (int j = 0; j < columns; ++j)
-        printf("  <% 2d >", j);
-    printf("\n");
-
+        str += QString::fromAscii("  <%1 >").arg(j, 2);
+    qDebug("%s", qPrintable(str));
     for (int i = 0; i < rows; ++i) {
-        printf("Row %2d:", i);
+        str = QString::fromAscii("Row %1:").arg(i, 2);
 
         qreal *row = matrix + i * columns;
-        for (int j = 0; j < columns; ++j) {
-            printf("  % 2.2f", row[j]);
-        }
-        printf("\n");
+        for (int j = 0; j < columns; ++j)
+            str += QString::fromAscii("%1").arg(row[j], 7, 'f', 2);
+        qDebug("%s", qPrintable(str));
     }
-    printf("------------------------\n\n");
+    qDebug("------------------------\n");
 }
 
 void QSimplex::combineRows(int toIndex, int fromIndex, qreal factor)
@@ -292,6 +388,23 @@ int QSimplex::findPivotColumn()
     return minIndex;
 }
 
+/*!
+  \internal
+
+  For a given pivot column, find the pivot row. That is, the row with the
+  minimum associated "quotient" where:
+
+  - quotient is the division of the value in the last column by the value
+    in the pivot column.
+  - rows with value less or equal to zero are ignored
+  - if two rows have the same quotient, lines are chosen based on the
+    highest variable index (value in the first column)
+
+  The last condition avoids a bug where artificial variables would be
+  left behind for the second-phase simplex, and with 'good'
+  constraints would be removed before it, what would lead to incorrect
+  results.
+*/
 int QSimplex::pivotRowForColumn(int column)
 {
     qreal min = qreal(999999999999.0); // ###
@@ -306,6 +419,8 @@ int QSimplex::pivotRowForColumn(int column)
         if (quotient < min) {
             min = quotient;
             minIndex = i;
+        } else if ((quotient == min) && (valueAt(i, 0) > valueAt(minIndex, 0))) {
+            minIndex = i;
         }
     }
 
@@ -320,6 +435,12 @@ void QSimplex::reducedRowEchelon()
     }
 }
 
+/*!
+  \internal
+
+  Does one iteration towards a better solution for the problem.
+  See 'solveMaxHelper'.
+*/
 bool QSimplex::iterate()
 {
     // Find Pivot column
@@ -351,7 +472,7 @@ bool QSimplex::iterate()
     setValueAt(pivotRow, 0, pivotColumn);
 
     //    dumpMatrix();
-    //    printf("------------ end of iteration --------------\n");
+    //    qDebug("------------ end of iteration --------------\n");
     return true;
 }
 
@@ -361,7 +482,13 @@ bool QSimplex::iterate()
   Both solveMin and solveMax are interfaces to this method.
 
   The enum solverFactor admits 2 values: Minimum (-1) and Maximum (+1).
- */
+
+  This method sets the original objective and runs the second phase
+  Simplex to obtain the optimal solution for the problem. As the internal
+  simplex solver is only able to _maximize_ objectives, we handle the
+  minimization case by inverting the original objective and then
+  maximizing it.
+*/
 qreal QSimplex::solver(solverFactor factor)
 {
     // Remove old objective
@@ -381,16 +508,28 @@ qreal QSimplex::solver(solverFactor factor)
     return factor * valueAt(0, columns - 1);
 }
 
+/*!
+  Minimize the original objective.
+*/
 qreal QSimplex::solveMin()
 {
     return solver(Minimum);
 }
 
+/*!
+  Maximize the original objective.
+*/
 qreal QSimplex::solveMax()
 {
     return solver(Maximum);
 }
 
+/*!
+  \internal
+
+  Reads results from the simplified matrix and saves them in the
+  "result" member of each QSimplexVariable.
+*/
 void QSimplex::collectResults()
 {
     // All variables are zero unless overridden below.
diff --git a/src/gui/kernel/qapplication_s60.cpp b/src/gui/kernel/qapplication_s60.cpp
index 27e8602..8daac42 100644
--- a/src/gui/kernel/qapplication_s60.cpp
+++ b/src/gui/kernel/qapplication_s60.cpp
@@ -480,7 +480,7 @@ void QSymbianControl::HandlePointerEvent(const TPointerEvent& pEvent)
             alienWidget = qwidget;
         S60->mousePressTarget = alienWidget;
     }
-    
+
     alienWidget = S60->mousePressTarget;
 
     if (alienWidget != S60->lastPointerEventTarget)
@@ -600,7 +600,7 @@ TKeyResponse QSymbianControl::OfferKeyEvent(const TKeyEvent& keyEvent, TEventCod
             if (keyCode >= Qt::Key_Left && keyCode <= Qt::Key_Down || keyCode == Qt::Key_Select) {
                 /*Explanation about virtualMouseAccel:
                  Tapping an arrow key allows precise pixel positioning
-                 Holding an arrow key down, acceleration is applied to allow cursor 
+                 Holding an arrow key down, acceleration is applied to allow cursor
                  to be quickly moved to another part of the screen by key repeats.
                  */
                 if (S60->virtualMouseLastKey == keyCode) {
@@ -668,7 +668,7 @@ TKeyResponse QSymbianControl::OfferKeyEvent(const TKeyEvent& keyEvent, TEventCod
             }
         }
 #endif
-        
+
         Qt::KeyboardModifiers mods = mapToQtModifiers(keyEvent.iModifiers);
         QKeyEventEx qKeyEvent(type == EEventKeyUp ? QEvent::KeyRelease : QEvent::KeyPress, keyCode,
                 mods, qt_keymapper_private()->translateKeyEvent(keyCode, mods),
@@ -993,13 +993,13 @@ void qt_init(QApplicationPrivate * /* priv */, int)
         S60->hasTouchscreen = true;
         S60->virtualMouseRequired = false;
     }
-    
+
     if (touch) {
         QApplicationPrivate::navigationMode = Qt::NavigationModeNone;
     } else {
         QApplicationPrivate::navigationMode = Qt::NavigationModeKeypadDirectional;
     }
-    
+
 #ifndef QT_NO_CURSOR
     //Check if window server pointer cursors are supported or not
 #ifndef Q_SYMBIAN_FIXED_POINTER_CURSORS
@@ -1063,7 +1063,7 @@ void qt_cleanup()
     // it dies.
     delete QApplicationPrivate::inputContext;
     QApplicationPrivate::inputContext = 0;
-    
+
     //Change mouse pointer back
     S60->wsSession().SetPointerCursorMode(EPointerCursorNone);
 
@@ -1383,7 +1383,8 @@ int QApplication::s60ProcessEvent(TWsEvent *event)
             } else if ((visChangedEvent->iFlags & TWsVisibilityChangedEvent::EPartiallyVisible)
                        && !w->d_func()->maybeBackingStore()) {
                 w->d_func()->topData()->backingStore = new QWidgetBackingStore(w);
-                w->update();
+                w->d_func()->invalidateBuffer(w->rect());
+                w->repaint();
             }
             return 1;
         }
@@ -1599,7 +1600,7 @@ void QApplicationPrivate::setNavigationMode(Qt::NavigationMode mode)
     const bool isCursorOn = (mode == Qt::NavigationModeCursorAuto
         && !S60->hasTouchscreen)
         || mode == Qt::NavigationModeCursorForceVisible;
-    
+
     if (!wasCursorOn && isCursorOn) {
         //Show the cursor, when changing from another mode to cursor mode
         qt_symbian_set_cursor_visible(true);
@@ -1629,7 +1630,7 @@ void QApplication::restoreOverrideCursor()
     if (qApp->d_func()->cursor_list.isEmpty())
         return;
     qApp->d_func()->cursor_list.removeFirst();
-    
+
     if (!qApp->d_func()->cursor_list.isEmpty()) {
         qt_symbian_setGlobalCursor(qApp->d_func()->cursor_list.first());
     }