Implement heightForWidth support for QTabWidget and QStackedLayout.

In order to add the support we also had to add hasHeightForWidth to
QWidget that calls the new virtual hasHeightForWidth() in QWidgetPrivate

Task-number: QTBUG-7792
Reviewed-by: Paul

6 files changed, 48 insertions, 3 deletions

diff --git a/src/gui/kernel/qlayoutitem.cpp b/src/gui/kernel/qlayoutitem.cpp
index 6a91d95..e615b2d 100644
--- a/src/gui/kernel/qlayoutitem.cpp
+++ b/src/gui/kernel/qlayoutitem.cpp
@@ -516,9 +516,7 @@ bool QWidgetItem::hasHeightForWidth() const
 {
     if (isEmpty())
         return false;
-    if (wid->layout())
-        return wid->layout()->hasHeightForWidth();
-    return wid->sizePolicy().hasHeightForWidth();
+    return wid->hasHeightForWidth();
 }
 
 /*!
diff --git a/src/gui/kernel/qstackedlayout.cpp b/src/gui/kernel/qstackedlayout.cpp
index 7559066..4b49638 100644
--- a/src/gui/kernel/qstackedlayout.cpp
+++ b/src/gui/kernel/qstackedlayout.cpp
@@ -475,6 +475,32 @@ void QStackedLayout::setGeometry(const QRect &rect)
     }
 }
 
+bool QStackedLayout::hasHeightForWidth() const
+{
+    const int n = count();
+
+    for (int i = 0; i < n; ++i) {
+        if (QLayoutItem *item = itemAt(i)) {
+            if (item->hasHeightForWidth())
+                return true;
+        }
+    }
+    return false;
+}
+
+int QStackedLayout::heightForWidth(int width) const
+{
+    const int n = count();
+
+    int hfw = 0;
+    for (int i = 0; i < n; ++i) {
+        if (QLayoutItem *item = itemAt(i)) {
+            hfw = qMax(hfw, item->heightForWidth(width));
+        }
+    }
+    return hfw;
+}
+
 /*!
     \enum QStackedLayout::StackingMode
     \since 4.4
diff --git a/src/gui/kernel/qstackedlayout.h b/src/gui/kernel/qstackedlayout.h
index c069149..842b62b 100644
--- a/src/gui/kernel/qstackedlayout.h
+++ b/src/gui/kernel/qstackedlayout.h
@@ -95,6 +95,8 @@ public:
     QLayoutItem *itemAt(int) const;
     QLayoutItem *takeAt(int);
     void setGeometry(const QRect &rect);
+    bool hasHeightForWidth() const;
+    int heightForWidth(int width) const;
 
 Q_SIGNALS:
     void widgetRemoved(int index);
diff --git a/src/gui/kernel/qwidget.cpp b/src/gui/kernel/qwidget.cpp
index e88026c..7a8b700 100644
--- a/src/gui/kernel/qwidget.cpp
+++ b/src/gui/kernel/qwidget.cpp
@@ -3816,6 +3816,11 @@ void QWidget::setMaximumSize(int maxw, int maxh)
     d->updateGeometry_helper(d->extra->minw == d->extra->maxw && d->extra->minh == d->extra->maxh);
 }
 
+bool QWidgetPrivate::hasHeightForWidth() const
+{
+    return layout ? layout->hasHeightForWidth() : size_policy.hasHeightForWidth();
+}
+
 /*!
     \overload
 
@@ -7961,6 +7966,18 @@ QSize QWidget::minimumSizeHint() const
     return QSize(-1, -1);
 }
 
+/*!
+    \internal
+    This is a bit hackish, but ideally this would have been a virtual
+    function so that subclasses could reimplement their own function.
+    Instead we add a virtual function to QWidgetPrivate.
+*/
+bool QWidget::hasHeightForWidth() const
+{
+    Q_D(const QWidget);
+    return d->hasHeightForWidth();
+}
+
 
 /*!
     \fn QWidget *QWidget::parentWidget() const
diff --git a/src/gui/kernel/qwidget.h b/src/gui/kernel/qwidget.h
index e12148b..6e5de7d 100644
--- a/src/gui/kernel/qwidget.h
+++ b/src/gui/kernel/qwidget.h
@@ -524,6 +524,7 @@ public:
 
     virtual QSize sizeHint() const;
     virtual QSize minimumSizeHint() const;
+    bool hasHeightForWidth() const;
 
     QSizePolicy sizePolicy() const;
     void setSizePolicy(QSizePolicy);
diff --git a/src/gui/kernel/qwidget_p.h b/src/gui/kernel/qwidget_p.h
index 89ea256..05a859c 100644
--- a/src/gui/kernel/qwidget_p.h
+++ b/src/gui/kernel/qwidget_p.h
@@ -493,6 +493,7 @@ public:
 
     bool setMinimumSize_helper(int &minw, int &minh);
     bool setMaximumSize_helper(int &maxw, int &maxh);
+    virtual bool hasHeightForWidth() const;
     void setConstraints_sys();
     QWidget *childAt_helper(const QPoint &, bool) const;
     void updateGeometry_helper(bool forceUpdate);