QAbstractScrollArea - add SizeAdjustPolicy and viewportSizeHint

This patch adds SizeAdjustPolicy to QAbstractScrollArea.
If it is set to AdjustToContents it will make use of the new
protected viewportSizeHint() (BC since it was reserved in Qt5).
This function returns a suggested size based on contents.

Change-Id: I5d8aa517e88b8b21c5712e62b4d574c3aad99d3b
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>

5 files changed, 110 insertions, 16 deletions

diff --git a/src/widgets/widgets/qabstractscrollarea.cpp b/src/widgets/widgets/qabstractscrollarea.cpp
index 900e95f4da..e7827055fb 100644
--- a/src/widgets/widgets/qabstractscrollarea.cpp
+++ b/src/widgets/widgets/qabstractscrollarea.cpp
@@ -167,6 +167,7 @@ QT_BEGIN_NAMESPACE
 
 QAbstractScrollAreaPrivate::QAbstractScrollAreaPrivate()
     :hbar(0), vbar(0), vbarpolicy(Qt::ScrollBarAsNeeded), hbarpolicy(Qt::ScrollBarAsNeeded),
+     shownOnce(false), sizeAdjustPolicy(QAbstractScrollArea::AdjustIgnored),
      viewport(0), cornerWidget(0), left(0), top(0), right(0), bottom(0),
      xoffset(0), yoffset(0), viewportFilter(0)
 #ifdef Q_WS_WIN
@@ -527,6 +528,19 @@ void QAbstractScrollAreaPrivate::layoutChildren()
 }
 
 /*!
+    \enum QAbstractScrollArea::SizeAdjustPolicy
+    \since 5.2
+
+    This enum specifies how the size hint of the QAbstractScrollArea should
+    adjust when the size of the viewport changes.
+
+    \value AdjustIgnored                 The scroll area will behave like before - and not do any adjust.
+    \value AdjustToContents              The scroll area will always adjust to the viewport
+    \value AdjustToContentsOnFirstShow   The scroll area will adjust to its viewport the first time it is shown.
+*/
+
+
+/*!
     \internal
 
     Creates a new QAbstractScrollAreaPrivate, \a dd with the given \a parent.
@@ -983,6 +997,13 @@ bool QAbstractScrollArea::event(QEvent *e)
     case QEvent::Resize:
             d->layoutChildren();
             break;
+    case QEvent::Show:
+        if (!d->shownOnce && d->sizeAdjustPolicy == QAbstractScrollArea::AdjustToContentsOnFirstShow) {
+            d->sizeHint = QSize();
+            updateGeometry();
+        }
+        d->shownOnce = true;
+        return QFrame::event(e);
     case QEvent::Paint: {
         QStyleOption option;
         option.initFrom(this);
@@ -1533,17 +1554,70 @@ QSize QAbstractScrollArea::minimumSizeHint() const
 }
 
 /*!
+    Returns the sizeHint property of the scroll area. The size is determined by using
+    viewportSizeHint() plus some extra space for scroll bars, if needed.
     \reimp
 */
 QSize QAbstractScrollArea::sizeHint() const
 {
-    return QSize(256, 192);
-#if 0
     Q_D(const QAbstractScrollArea);
-    int h = qMax(10, fontMetrics().height());
-    int f = 2 * d->frameWidth;
-    return QSize((6 * h) + f, (4 * h) + f);
-#endif
+    if (d->sizeAdjustPolicy == QAbstractScrollArea::AdjustIgnored)
+        return QSize(256, 192);
+
+    if (!d->sizeHint.isValid() || d->sizeAdjustPolicy == QAbstractScrollArea::AdjustToContents) {
+        const int f = 2 * d->frameWidth;
+        const QSize frame( f, f );
+        const QSize scrollbars(d->vbarpolicy == Qt::ScrollBarAlwaysOn ? d->vbar->sizeHint().width() : 0,
+                               d->hbarpolicy == Qt::ScrollBarAlwaysOn ? d->hbar->sizeHint().height() : 0);
+        d->sizeHint = frame + scrollbars + viewportSizeHint();
+    }
+    return d->sizeHint;
+}
+
+/*!
+   \since 5.2
+   Returns the recommended size for the viewport.
+   The default implementation returns viewport()->sizeHint().
+   Note that the size is just the viewport's size, without any scroll bars visible.
+ */
+QSize QAbstractScrollArea::viewportSizeHint() const
+{
+    Q_D(const QAbstractScrollArea);
+    if (d->viewport) {
+        const QSize sh = d->viewport->sizeHint();
+        if (sh.isValid()) {
+            return sh;
+        }
+    }
+    const int h = qMax(10, fontMetrics().height());
+    return QSize(6 * h, 4 * h);
+}
+
+/*!
+    \since 5.2
+    \property QAbstractScrollArea::sizeAdjustPolicy
+    This property holds the policy describing how the size of the scroll area changes when the
+    size of the viewport changes.
+
+    The default policy is QAbstractScrollArea::AdjustIgnored.
+    Changing this property might actually resize the scrollarea.
+*/
+
+QAbstractScrollArea::SizeAdjustPolicy QAbstractScrollArea::sizeAdjustPolicy() const
+{
+    Q_D(const QAbstractScrollArea);
+    return d->sizeAdjustPolicy;
+}
+
+void QAbstractScrollArea::setSizeAdjustPolicy(SizeAdjustPolicy policy)
+{
+    Q_D(QAbstractScrollArea);
+    if (d->sizeAdjustPolicy == policy)
+        return;
+
+    d->sizeAdjustPolicy = policy;
+    d->sizeHint = QSize();
+    updateGeometry();
 }
 
 /*!
@@ -1559,16 +1633,6 @@ void QAbstractScrollArea::setupViewport(QWidget *viewport)
     Q_UNUSED(viewport);
 }
 
-/*!
-    \internal
-
-    This method is reserved for future use.
-*/
-QSize QAbstractScrollArea::viewportSizeHint() const
-{
-    return QSize();
-}
-
 QT_END_NAMESPACE
 
 #include "moc_qabstractscrollarea.cpp"
diff --git a/src/widgets/widgets/qabstractscrollarea.h b/src/widgets/widgets/qabstractscrollarea.h
index ccf16b5e5c..fb9562db1b 100644
--- a/src/widgets/widgets/qabstractscrollarea.h
+++ b/src/widgets/widgets/qabstractscrollarea.h
@@ -56,13 +56,22 @@ class QAbstractScrollAreaPrivate;
 class Q_WIDGETS_EXPORT QAbstractScrollArea : public QFrame
 {
     Q_OBJECT
+
+    Q_ENUMS(SizeAdjustPolicy)
     Q_PROPERTY(Qt::ScrollBarPolicy verticalScrollBarPolicy READ verticalScrollBarPolicy WRITE setVerticalScrollBarPolicy)
     Q_PROPERTY(Qt::ScrollBarPolicy horizontalScrollBarPolicy READ horizontalScrollBarPolicy WRITE setHorizontalScrollBarPolicy)
+    Q_PROPERTY(SizeAdjustPolicy sizeAdjustPolicy READ sizeAdjustPolicy WRITE setSizeAdjustPolicy)
 
 public:
     explicit QAbstractScrollArea(QWidget* parent=0);
     ~QAbstractScrollArea();
 
+    enum SizeAdjustPolicy {
+        AdjustIgnored,
+        AdjustToContentsOnFirstShow,
+        AdjustToContents
+    };
+
     Qt::ScrollBarPolicy verticalScrollBarPolicy() const;
     void setVerticalScrollBarPolicy(Qt::ScrollBarPolicy);
     QScrollBar *verticalScrollBar() const;
@@ -89,6 +98,9 @@ public:
 
     virtual void setupViewport(QWidget *viewport);
 
+    SizeAdjustPolicy sizeAdjustPolicy() const;
+    void setSizeAdjustPolicy(SizeAdjustPolicy policy);
+
 protected:
     QAbstractScrollArea(QAbstractScrollAreaPrivate &dd, QWidget *parent = 0);
     void setViewportMargins(int left, int top, int right, int bottom);
diff --git a/src/widgets/widgets/qabstractscrollarea_p.h b/src/widgets/widgets/qabstractscrollarea_p.h
index 34d767fe29..3093c2f812 100644
--- a/src/widgets/widgets/qabstractscrollarea_p.h
+++ b/src/widgets/widgets/qabstractscrollarea_p.h
@@ -75,6 +75,10 @@ public:
     QScrollBar *hbar, *vbar;
     Qt::ScrollBarPolicy vbarpolicy, hbarpolicy;
 
+    bool shownOnce;
+    mutable QSize sizeHint;
+    QAbstractScrollArea::SizeAdjustPolicy sizeAdjustPolicy;
+
     QWidget *viewport;
     QWidget *cornerWidget;
     QRect cornerPaintingRect;
diff --git a/src/widgets/widgets/qscrollarea.cpp b/src/widgets/widgets/qscrollarea.cpp
index 93c335c56b..2a6d4620d7 100644
--- a/src/widgets/widgets/qscrollarea.cpp
+++ b/src/widgets/widgets/qscrollarea.cpp
@@ -407,6 +407,18 @@ QSize QScrollArea::sizeHint() const
     return sz.boundedTo(QSize(36 * h, 24 * h));
 }
 
+/*!
+    \reimp
+ */
+QSize QScrollArea::viewportSizeHint() const
+{
+    Q_D(const QScrollArea);
+    if (d->widget) {
+        return d->resizable ? d->widget->sizeHint() : d->widget->size();
+    }
+    const int h = fontMetrics().height();
+    return QSize(6 * h, 4 * h);
+}
 
 
 /*!
diff --git a/src/widgets/widgets/qscrollarea.h b/src/widgets/widgets/qscrollarea.h
index 576c9bc9e0..70af5fbbd7 100644
--- a/src/widgets/widgets/qscrollarea.h
+++ b/src/widgets/widgets/qscrollarea.h
@@ -69,6 +69,8 @@ public:
     void setWidgetResizable(bool resizable);
 
     QSize sizeHint() const;
+    QSize viewportSizeHint() const;
+
     bool focusNextPrevChild(bool next);
 
     Qt::Alignment alignment() const;