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>

dist/changes-5.2.0

@@ -0,0 +1,27 @@
+Qt 5.2 introduces many new features and improvements as well as bugfixes
+over the 5.1.x series. For more details, refer to the online documentation
+included in this distribution. The documentation is also available online:
+
+  http://qt-project.org/doc/qt-5.2
+
+The Qt version 5.2 series is binary compatible with the 5.1.x series.
+Applications compiled for 5.1 will continue to run with 5.2.
+
+Some of the changes listed in this file include issue tracking numbers
+corresponding to tasks in the Qt Bug Tracker:
+
+  http://bugreports.qt-project.org/
+
+Each of these identifiers can be entered in the bug tracker to obtain more
+information about a particular change.
+
+****************************************************************************
+*                          Library                                         *
+****************************************************************************
+
+QtWidgets
+---------
+
+- QAbstractScrollArea now has a SizeAdjustPolicy. If it is set to AdjustToContents
+  it will make use of the new protected viewportSizeHint() (binary compatible since it
+  was reserved in Qt5). This function returns a suggested size based on contents.

examples/widgets/itemviews/spreadsheet/main.cpp

@@ -42,14 +42,15 @@
 #include "spreadsheet.h"
 
 #include <QApplication>
+#include <QLayout>
 
 int main(int argc, char** argv) {
     Q_INIT_RESOURCE(spreadsheet);
     QApplication app(argc, argv);
     SpreadSheet sheet(10, 6);
     sheet.setWindowIcon(QPixmap(":/images/interview.png"));
-    sheet.resize(640, 420);
     sheet.show();
+    sheet.layout()->setSizeConstraint(QLayout::SetFixedSize);
     return app.exec();
 }
 

examples/widgets/itemviews/spreadsheet/spreadsheet.cpp

@@ -64,6 +64,7 @@ SpreadSheet::SpreadSheet(int rows, int cols, QWidget *parent)
     toolBar->addWidget(formulaInput);
 
     table = new QTableWidget(rows, cols, this);
+    table->setSizeAdjustPolicy(QTableWidget::AdjustToContents);
     for (int c = 0; c < cols; ++c) {
         QString character(QChar('A' + c));
         table->setHorizontalHeaderItem(c, new QTableWidgetItem(character));

src/widgets/itemviews/qabstractitemview.cpp

@@ -1108,6 +1108,7 @@ void QAbstractItemView::reset()
         QAccessible::updateAccessibility(&accessibleEvent);
     }
 #endif
+    d->updateGeometry();
 }
 
 /*!
@@ -1124,6 +1125,7 @@ void QAbstractItemView::setRootIndex(const QModelIndex &index)
     }
     d->root = index;
     d->doDelayedItemsLayout();
+    d->updateGeometry();
 }
 
 /*!
@@ -2668,8 +2670,10 @@ void QAbstractItemView::updateEditorGeometries()
 */
 void QAbstractItemView::updateGeometries()
 {
+    Q_D(QAbstractItemView);
     updateEditorGeometries();
-    d_func()->fetchMoreTimer.start(0, this); //fetch more later
+    d->fetchMoreTimer.start(0, this); //fetch more later
+    d->updateGeometry();
 }
 
 /*!
@@ -3231,6 +3235,7 @@ void QAbstractItemView::dataChanged(const QModelIndex &topLeft, const QModelInde
         QAccessible::updateAccessibility(&accessibleEvent);
     }
 #endif
+    d->updateGeometry();
 }
 
 /*!
@@ -3332,6 +3337,7 @@ void QAbstractItemViewPrivate::_q_rowsRemoved(const QModelIndex &index, int star
         QAccessible::updateAccessibility(&accessibleEvent);
     }
 #endif
+    updateGeometry();
 }
 
 /*!
@@ -3412,6 +3418,7 @@ void QAbstractItemViewPrivate::_q_columnsRemoved(const QModelIndex &index, int s
         QAccessible::updateAccessibility(&accessibleEvent);
     }
 #endif
+    updateGeometry();
 }
 
 
@@ -3435,6 +3442,7 @@ void QAbstractItemViewPrivate::_q_rowsInserted(const QModelIndex &index, int sta
         QAccessible::updateAccessibility(&accessibleEvent);
     }
 #endif
+    updateGeometry();
 }
 
 /*!
@@ -3459,6 +3467,7 @@ void QAbstractItemViewPrivate::_q_columnsInserted(const QModelIndex &index, int
         QAccessible::updateAccessibility(&accessibleEvent);
     }
 #endif
+    updateGeometry();
 }
 
 /*!
@@ -4084,7 +4093,14 @@ void QAbstractItemViewPrivate::interruptDelayedItemsLayout() const
     delayedPendingLayout = false;
 }
 
-
+void QAbstractItemViewPrivate::updateGeometry()
+{
+    Q_Q(QAbstractItemView);
+    if (sizeAdjustPolicy == QAbstractScrollArea::AdjustIgnored)
+        return;
+    if (sizeAdjustPolicy == QAbstractScrollArea::AdjustToContents || !shownOnce)
+        q->updateGeometry();
+}
 
 QWidget *QAbstractItemViewPrivate::editor(const QModelIndex &index,
                                           const QStyleOptionViewItem &options)

src/widgets/itemviews/qabstractitemview_p.h

@@ -127,6 +127,8 @@ public:
     void doDelayedItemsLayout(int delay = 0);
     void interruptDelayedItemsLayout() const;
 
+    void updateGeometry();
+
     void startAutoScroll()
     {   // ### it would be nice to make this into a style hint one day
         int scrollInterval = (verticalScrollMode == QAbstractItemView::ScrollPerItem) ? 150 : 50;

src/widgets/itemviews/qheaderview.cpp

@@ -549,6 +549,22 @@ QSize QHeaderView::sizeHint() const
     return d->cachedSizeHint;
 }
 
+/*!
+    \reimp
+*/
+
+void QHeaderView::setVisible(bool v)
+{
+    bool actualChange = (v != isVisible());
+    QAbstractItemView::setVisible(v);
+    if (actualChange) {
+        QAbstractScrollArea *parent = qobject_cast<QAbstractScrollArea*>(parentWidget());
+        if (parent)
+            parent->updateGeometry();
+    }
+}
+
+
 /*!
     Returns a suitable size hint for the section specified by \a logicalIndex.
 
@@ -918,6 +934,18 @@ void QHeaderView::resizeSection(int logical, int size)
         d->doDelayedResizeSections();
         r = d->viewport->rect();
     }
+
+    // If the parent is a QAbstractScrollArea with QAbstractScrollArea::AdjustToContents
+    // then we want to change the geometry on that widget. Not doing it at once can/will
+    // cause scrollbars flicker as they would be shown at first but then removed.
+    // In the same situation it will also allow shrinking the whole view when stretchLastSection is set
+    // (It is default on QTreeViews - and it wouldn't shrink since the last stretch was made before the
+    // viewport was resized)
+
+    QAbstractScrollArea *parent = qobject_cast<QAbstractScrollArea *>(parentWidget());
+    if (parent && parent->sizeAdjustPolicy() == QAbstractScrollArea::AdjustToContents)
+        parent->updateGeometry();
+
     d->viewport->update(r.normalized());
     emit sectionResized(logical, oldSize, size);
 }

src/widgets/itemviews/qheaderview.h

@@ -84,6 +84,7 @@ public:
     int offset() const;
     int length() const;
     QSize sizeHint() const;
+    void setVisible(bool v);
     int sectionSizeHint(int logicalIndex) const;
 
     int visualIndexAt(int position) const;

src/widgets/itemviews/qtableview.cpp

@@ -1053,6 +1053,19 @@ QTableView::~QTableView()
 {
 }
 
+/*!
+  \reimp
+*/
+QSize QTableView::viewportSizeHint() const
+{
+    Q_D(const QTableView);
+    QSize result( (d->verticalHeader->isHidden() ? 0 : d->verticalHeader->width()) + d->horizontalHeader->length(),
+                  (d->horizontalHeader->isHidden() ? 0 : d->horizontalHeader->height()) + d->verticalHeader->length());
+    result += QSize(verticalScrollBar()->isVisible() ? verticalScrollBar()->width() : 0,
+                    horizontalScrollBar()->isVisible() ? horizontalScrollBar()->height() : 0);
+    return result;
+}
+
 /*!
   \reimp
 */

src/widgets/itemviews/qtableview.h

@@ -118,6 +118,8 @@ public:
 
     void sortByColumn(int column, Qt::SortOrder order);
 
+    QSize viewportSizeHint() const;
+
 public Q_SLOTS:
     void selectRow(int row);
     void selectColumn(int column);

src/widgets/itemviews/qtreeview.cpp

@@ -335,6 +335,7 @@ void QTreeView::setHeader(QHeaderView *header)
             this, SLOT(updateGeometries()));
 
     setSortingEnabled(d->sortingEnabled);
+    d->updateGeometry();
 }
 
 /*!
@@ -2618,6 +2619,35 @@ void QTreeView::selectAll()
     }
 }
 
+/*!
+  \reimp
+*/
+QSize QTreeView::viewportSizeHint() const
+{
+    Q_D(const QTreeView);
+    d->executePostedLayout(); // Make sure that viewItems are up to date.
+
+    if (d->viewItems.size() == 0)
+        return QAbstractItemView::viewportSizeHint();
+
+    // Get rect for last item
+    const QRect deepestRect = visualRect(d->viewItems.last().index);
+
+    if (!deepestRect.isValid())
+        return QAbstractItemView::viewportSizeHint();
+
+    QSize result = QSize(d->header->length(), deepestRect.bottom() + 1);
+
+    // add size for header
+    result += QSize(0, d->header->isVisible() ? d->header->height() : 0);
+
+    // add size for scrollbars
+    result += QSize(verticalScrollBar()->isVisible() ? verticalScrollBar()->width() : 0,
+                    horizontalScrollBar()->isVisible() ? horizontalScrollBar()->height() : 0);
+
+    return result;
+}
+
 /*!
   \since 4.2
   Expands all expandable items.

src/widgets/itemviews/qtreeview.h

@@ -144,6 +144,8 @@ public:
     void dataChanged(const QModelIndex &topLeft, const QModelIndex &bottomRight, const QVector<int> &roles = QVector<int>());
     void selectAll();
 
+    QSize viewportSizeHint() const;
+
 Q_SIGNALS:
     void expanded(const QModelIndex &index);
     void collapsed(const QModelIndex &index);

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
@@ -526,6 +527,19 @@ void QAbstractScrollAreaPrivate::layoutChildren()
     viewport->setGeometry(QStyle::visualRect(opt.direction, opt.rect, viewportRect)); // resize the viewport last
 }
 
+/*!
+    \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
 
@@ -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"

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);

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;

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);
+}
 
 
 /*!

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;

tests/manual/widgets/itemviews/qtreeview/main.cpp

@@ -39,17 +39,34 @@
 **
 ****************************************************************************/
 
-
-#include <QtWidgets/QFileSystemModel>
-#include <QtWidgets/QtWidgets>
+#include <QtWidgets>
 
 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
-    QFileSystemModel *model = new QFileSystemModel;
-    model->setRootPath(QDir::currentPath());
-    QTreeView *tree = new QTreeView();
-    tree->setModel(model);
-    tree->show();
-    app.exec();
+    QFileSystemModel model;
+    QWidget window;
+    QTreeView *tree = new QTreeView(&window);
+    tree->setMaximumSize(1000, 600);
+
+    QHBoxLayout *layout = new QHBoxLayout;
+    layout->setSizeConstraint(QLayout::SetFixedSize);
+    layout->addWidget(tree);
+
+    window.setLayout(layout);
+    model.setRootPath("");
+    tree->setSizeAdjustPolicy(QAbstractScrollArea::AdjustToContents);
+    tree->setModel(&model);
+
+    tree->setAnimated(false);
+    tree->setIndentation(20);
+    tree->setSortingEnabled(true);
+    tree->header()->setStretchLastSection(false);
+
+    window.setWindowTitle(QObject::tr("Dir View"));
+    tree->header()->setSectionResizeMode(QHeaderView::ResizeToContents);
+
+    window.show();
+
+    return app.exec();
 }