Update Sliders example

Simplify the "responsive layout" implementation. Just use a QBoxLayout
with changing direction instead of repopulating a QGridLayout, and
change the orientation of one set of sliders instead of creating two
sets in a stacked layout.

Simplify the resizeEvent() implementation accordingly.

Update the documentation snippet text to match the code, and document
the resizeEvent() override.

Pick-to: 6.7 6.6
Fixes: QTBUG-119977
Change-Id: I73a1bb215c956fa283291ebf0ea45ff9a975c727
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

5 files changed, 97 insertions, 136 deletions

diff --git a/examples/widgets/doc/src/sliders.qdoc b/examples/widgets/doc/src/sliders.qdoc
index 871adf0049..9bfb4abdc4 100644
--- a/examples/widgets/doc/src/sliders.qdoc
+++ b/examples/widgets/doc/src/sliders.qdoc
@@ -18,7 +18,8 @@
     manipulated through their properties.
 
     The example also demonstrates how signals and slots can be used to
-    synchronize the behavior of two or more widgets.
+    synchronize the behavior of two or more widgets, and how to override
+    \l{QWidget::}{resizeEvent()} to implement a responsive layout.
 
     \borderedimage sliders-example.png
     \caption Screenshot of the Sliders example
@@ -31,10 +32,8 @@
     QScrollBar and a QDial.
 
     \li \c Window is the main widget combining a QGroupBox and a
-    QStackedWidget. In this example, the QStackedWidget provides a
-    stack of two \c SlidersGroup widgets. The QGroupBox contain
-    several widgets that control the behavior of the slider-like
-    widgets.
+    SlidersGroup. The QGroupBox contains several widgets that control
+    the behavior of the slider-like widgets.
 
     \endlist
 
@@ -56,28 +55,14 @@
 
     \snippet widgets/sliders/window.cpp 0
 
-    In the constructor we first create the two \c SlidersGroup
-    widgets that display the slider widgets horizontally and
-    vertically, and add them to the QStackedWidget. QStackedWidget
-    provides a stack of widgets where only the top widget is visible.
-    With \c createControls() we create a connection from a
-    controlling widget to the QStackedWidget, making the user able to
-    choose between horizontal and vertical orientation of the slider
-    widgets. The rest of the controlling mechanisms is implemented by
-    the same function call.
+    In the constructor we first create the \c SlidersGroup widget
+    that displays the slider widgets. With \c createControls() we
+    create the controlling widgets, and connect those to to the
+    sliders.
 
     \snippet widgets/sliders/window.cpp 1
-    \snippet widgets/sliders/window.cpp 2
-
-    Then we connect the \c horizontalSliders, \c verticalSliders and
-    \c valueSpinBox to each other, so that the slider widgets and the
-    control widget will behave synchronized when the current value of
-    one of them changes. The \c valueChanged() signal is emitted with
-    the new value as argument. The \c setValue() slot sets the
-    current value of the widget to the new value, and emits \c
-    valueChanged() if the new value is different from the old one.
 
-    We put the group of control widgets and the stacked widget in a
+    We put the groups of control widgets and the sliders in a
     horizontal layout before we initialize the minimum, maximum and
     current values. The initialization of the current value will
     propagate to the slider widgets through the connection we made
@@ -85,15 +70,14 @@
     minimum and maximum values propagate through the connections we
     created with \c createControls().
 
+    \snippet widgets/sliders/window.cpp 2
     \snippet widgets/sliders/window.cpp 3
-    \snippet widgets/sliders/window.cpp 4
 
     In the private \c createControls() function, we let a QGroupBox
     (\c controlsGroup) display the control widgets. A group box can
     provide a frame, a title and a keyboard shortcut, and displays
     various other widgets inside itself. The group of control widgets
-    is composed by two checkboxes, three spin boxes (with labels) and
-    one combobox.
+    is composed by two checkboxes, and three spin boxes with labels.
 
     After creating the labels, we create the two checkboxes.
     Checkboxes are typically used to represent features in an
@@ -131,8 +115,8 @@
     bindings are inverted by default: \uicontrol PageDown increases the
     current value, and \uicontrol PageUp decreases it.
 
+    \snippet widgets/sliders/window.cpp 4
     \snippet widgets/sliders/window.cpp 5
-    \snippet widgets/sliders/window.cpp 6
 
     Then we create the spin boxes. QSpinBox allows the user to choose
     a value by clicking the up and down buttons or pressing the \uicontrol
@@ -141,14 +125,15 @@
     manually. The spin boxes control the minimum, maximum and current
     values for the QSlider, QScrollBar, and QDial widgets.
 
-    We create a QComboBox that allows the user to choose the
-    orientation of the slider widgets. The QComboBox widget is a
-    combined button and popup list. It provides a means of presenting
-    a list of options to the user in a way that takes up the minimum
-    amount of screen space.
+    \snippet widgets/sliders/window.cpp 6
 
-    \snippet widgets/sliders/window.cpp 7
-    \snippet widgets/sliders/window.cpp 8
+    Then we connect the \c slidersGroup and the \c valueSpinBox to each
+    other, so that the slider widgets and the control widget will behave
+    synchronized when the current value of one of them changes.
+    The \c valueChanged() signal is emitted with the new value as
+    argument. The \c setValue() slot sets the current value of the
+    widget to the new value, and emits \c valueChanged() if the new
+    value is different from the old one.
 
     We synchronize the behavior of the control widgets and the slider
     widgets through their signals and slots. We connect each control
@@ -158,6 +143,17 @@
     lay out the control widgets in a QGridLayout within the \c
     controlsGroup group box.
 
+    \snippet widgets/sliders/window.cpp 7
+
+    Lastly, we override resizeEvent() from QWidget. We guard against
+    dividing by zero, and otherwise compute the aspect ratio of the
+    widget. If the window has a portrait format, then we set the
+    layout to organize the groups of control widgets and sliders
+    vertically, and we give the sliders a horizontal orientation.
+    If the window has a landscape format, then we change the layout
+    to show the sliders and controlling widgets side by side, and
+    give the sliders a vertical orientation.
+
     \section1 SlidersGroup Class Definition
 
     \snippet widgets/sliders/slidersgroup.h 0
@@ -170,7 +166,8 @@
     slot with equivalent functionality to the ones in QAbstractSlider
     and QSpinBox. In addition, we implement several other public
     slots to set the minimum and maximum value, and invert the slider
-    widgets' appearance as well as key bindings.
+    widgets' appearance as well as key bindings, and set the
+    orientation.
 
     \section1 SlidersGroup Class Implementation
 
@@ -183,24 +180,21 @@
     focus. The Qt::StrongFocus policy means that the widget accepts
     focus by both tabbing and clicking.
 
+    \snippet widgets/sliders/slidersgroup.cpp 1
+
     Then we connect the widgets with each other, so that they will
     stay synchronized when the current value of one of them changes.
 
-    \snippet widgets/sliders/slidersgroup.cpp 1
-    \snippet widgets/sliders/slidersgroup.cpp 2
-
     We connect \c {dial}'s \c valueChanged() signal to the
     \c{SlidersGroup}'s \c valueChanged() signal, to notify the other
     widgets in the application (i.e., the control widgets) of the
     changed value.
 
-    \snippet widgets/sliders/slidersgroup.cpp 3
     \codeline
     \snippet widgets/sliders/slidersgroup.cpp 4
 
-    Finally, depending on the \l {Qt::Orientation}{orientation} given
-    at the time of construction, we choose and create the layout for
-    the slider widgets within the group box.
+    Finally, we create the layout for the slider widgets within the
+    group box. We start with a horizontal arrangement of the sliders.
 
     \snippet widgets/sliders/slidersgroup.cpp 5
     \snippet widgets/sliders/slidersgroup.cpp 6
@@ -233,4 +227,12 @@
     \l{QAbstractSlider::invertedAppearance}{invertedAppearance} and
     \l{QAbstractSlider::invertedControls}{invertedControls}
     properties.
+
+    \snippet widgets/sliders/slidersgroup.cpp 15
+
+    The setOrientation() slot controls the direction of the layout
+    and the orientation of the sliders. In a horizontal group, the
+    sliders have a horizontal orientation, and are laid out on top
+    of each other. In a vertical group, the sliders have a vertical
+    orientation, and are laid out next to each other.
 */
diff --git a/examples/widgets/widgets/sliders/slidersgroup.cpp b/examples/widgets/widgets/sliders/slidersgroup.cpp
index c5d01cdb37..87841c43f9 100644
--- a/examples/widgets/widgets/sliders/slidersgroup.cpp
+++ b/examples/widgets/widgets/sliders/slidersgroup.cpp
@@ -9,39 +9,28 @@
 #include <QSlider>
 
 //! [0]
-SlidersGroup::SlidersGroup(Qt::Orientation orientation, const QString &title,
-                           QWidget *parent)
+SlidersGroup::SlidersGroup(const QString &title, QWidget *parent)
     : QGroupBox(title, parent)
 {
-    slider = new QSlider(orientation);
+    slider = new QSlider;
     slider->setFocusPolicy(Qt::StrongFocus);
     slider->setTickPosition(QSlider::TicksBothSides);
     slider->setTickInterval(10);
     slider->setSingleStep(1);
 
-    scrollBar = new QScrollBar(orientation);
+    scrollBar = new QScrollBar;
     scrollBar->setFocusPolicy(Qt::StrongFocus);
 
     dial = new QDial;
     dial->setFocusPolicy(Qt::StrongFocus);
 
+//! [0] //! [1]
     connect(slider, &QSlider::valueChanged, scrollBar, &QScrollBar::setValue);
     connect(scrollBar, &QScrollBar::valueChanged, dial, &QDial::setValue);
     connect(dial, &QDial::valueChanged, slider, &QSlider::setValue);
-//! [0] //! [1]
     connect(dial, &QDial::valueChanged, this, &SlidersGroup::valueChanged);
-//! [1] //! [2]
-
-//! [2] //! [3]
-    QBoxLayout::Direction direction;
-//! [3] //! [4]
-
-    if (orientation == Qt::Horizontal)
-        direction = QBoxLayout::TopToBottom;
-    else
-        direction = QBoxLayout::LeftToRight;
-
-    QBoxLayout *slidersLayout = new QBoxLayout(direction);
+//! [1] //! [4]
+    slidersLayout = new QBoxLayout(QBoxLayout::LeftToRight);
     slidersLayout->addWidget(slider);
     slidersLayout->addWidget(scrollBar);
     slidersLayout->addWidget(dial);
@@ -96,3 +85,14 @@ void SlidersGroup::invertKeyBindings(bool invert)
     dial->setInvertedControls(invert);
 }
 //! [14]
+
+//! [15]
+void SlidersGroup::setOrientation(Qt::Orientation orientation)
+{
+    slidersLayout->setDirection(orientation == Qt::Horizontal
+                                ? QBoxLayout::TopToBottom
+                                : QBoxLayout::LeftToRight);
+    scrollBar->setOrientation(orientation);
+    slider->setOrientation(orientation);
+}
+//! [15]
diff --git a/examples/widgets/widgets/sliders/slidersgroup.h b/examples/widgets/widgets/sliders/slidersgroup.h
index 66821ca558..7e7d887018 100644
--- a/examples/widgets/widgets/sliders/slidersgroup.h
+++ b/examples/widgets/widgets/sliders/slidersgroup.h
@@ -10,6 +10,7 @@ QT_BEGIN_NAMESPACE
 class QDial;
 class QScrollBar;
 class QSlider;
+class QBoxLayout;
 QT_END_NAMESPACE
 
 //! [0]
@@ -18,8 +19,7 @@ class SlidersGroup : public QGroupBox
     Q_OBJECT
 
 public:
-    SlidersGroup(Qt::Orientation orientation, const QString &title,
-                 QWidget *parent = nullptr);
+    SlidersGroup(const QString &title, QWidget *parent = nullptr);
 
 signals:
     void valueChanged(int value);
@@ -30,11 +30,13 @@ public slots:
     void setMaximum(int value);
     void invertAppearance(bool invert);
     void invertKeyBindings(bool invert);
+    void setOrientation(Qt::Orientation orientation);
 
 private:
     QSlider *slider;
     QScrollBar *scrollBar;
     QDial *dial;
+    QBoxLayout *slidersLayout;
 };
 //! [0]
 
diff --git a/examples/widgets/widgets/sliders/window.cpp b/examples/widgets/widgets/sliders/window.cpp
index a2c2fe89eb..c62c3b83f5 100644
--- a/examples/widgets/widgets/sliders/window.cpp
+++ b/examples/widgets/widgets/sliders/window.cpp
@@ -13,29 +13,15 @@
 Window::Window(QWidget *parent)
     : QWidget(parent)
 {
-    horizontalSliders = new SlidersGroup(Qt::Horizontal, tr("Horizontal"));
-    verticalSliders = new SlidersGroup(Qt::Vertical, tr("Vertical"));
-
-    stackedWidget = new QStackedWidget;
-    stackedWidget->addWidget(horizontalSliders);
-    stackedWidget->addWidget(verticalSliders);
+    slidersGroup = new SlidersGroup(tr("Sliders"));
 
     createControls(tr("Controls"));
 //! [0]
 
 //! [1]
-    connect(horizontalSliders, &SlidersGroup::valueChanged,
-//! [1] //! [2]
-            verticalSliders, &SlidersGroup::setValue);
-    connect(verticalSliders, &SlidersGroup::valueChanged,
-            valueSpinBox, &QSpinBox::setValue);
-    connect(valueSpinBox, &QSpinBox::valueChanged,
-            horizontalSliders, &SlidersGroup::setValue);
-
-    layout = new QGridLayout;
-    layout->addWidget(stackedWidget, 0, 1);
-    layout->addWidget(controlsGroup, 0, 0);
-
+    layout = new QBoxLayout(QBoxLayout::LeftToRight);
+    layout->addWidget(controlsGroup);
+    layout->addWidget(slidersGroup);
     setLayout(layout);
 
     minimumSpinBox->setValue(0);
@@ -44,11 +30,11 @@ Window::Window(QWidget *parent)
 
     setWindowTitle(tr("Sliders"));
 }
-//! [2]
+//! [1]
 
-//! [3]
+//! [2]
 void Window::createControls(const QString &title)
-//! [3] //! [4]
+//! [2] //! [3]
 {
     controlsGroup = new QGroupBox(title);
 
@@ -59,9 +45,9 @@ void Window::createControls(const QString &title)
     invertedAppearance = new QCheckBox(tr("Inverted appearance"));
     invertedKeyBindings = new QCheckBox(tr("Inverted key bindings"));
 
-//! [4] //! [5]
+//! [3] //! [4]
     minimumSpinBox = new QSpinBox;
-//! [5] //! [6]
+//! [4] //! [5]
     minimumSpinBox->setRange(-100, 100);
     minimumSpinBox->setSingleStep(1);
 
@@ -73,30 +59,19 @@ void Window::createControls(const QString &title)
     valueSpinBox->setRange(-100, 100);
     valueSpinBox->setSingleStep(1);
 
-    orientationCombo = new QComboBox;
-    orientationCombo->addItem(tr("Horizontal slider-like widgets"));
-    orientationCombo->addItem(tr("Vertical slider-like widgets"));
-
-//! [6] //! [7]
-    connect(orientationCombo, &QComboBox::activated,
-//! [7] //! [8]
-            stackedWidget, &QStackedWidget::setCurrentIndex);
-    connect(minimumSpinBox, &QSpinBox::valueChanged,
-            horizontalSliders, &SlidersGroup::setMinimum);
+//! [5] //! [6]
+    connect(slidersGroup, &SlidersGroup::valueChanged,
+            valueSpinBox, &QSpinBox::setValue);
+    connect(valueSpinBox, &QSpinBox::valueChanged,
+            slidersGroup, &SlidersGroup::setValue);
     connect(minimumSpinBox, &QSpinBox::valueChanged,
-            verticalSliders, &SlidersGroup::setMinimum);
-    connect(maximumSpinBox, &QSpinBox::valueChanged,
-            horizontalSliders, &SlidersGroup::setMaximum);
+            slidersGroup, &SlidersGroup::setMinimum);
     connect(maximumSpinBox, &QSpinBox::valueChanged,
-            verticalSliders, &SlidersGroup::setMaximum);
+            slidersGroup, &SlidersGroup::setMaximum);
     connect(invertedAppearance, &QCheckBox::toggled,
-            horizontalSliders, &SlidersGroup::invertAppearance);
-    connect(invertedAppearance, &QCheckBox::toggled,
-            verticalSliders, &SlidersGroup::invertAppearance);
-    connect(invertedKeyBindings, &QCheckBox::toggled,
-            horizontalSliders, &SlidersGroup::invertKeyBindings);
+            slidersGroup, &SlidersGroup::invertAppearance);
     connect(invertedKeyBindings, &QCheckBox::toggled,
-            verticalSliders, &SlidersGroup::invertKeyBindings);
+            slidersGroup, &SlidersGroup::invertKeyBindings);
 
     QGridLayout *controlsLayout = new QGridLayout;
     controlsLayout->addWidget(minimumLabel, 0, 0);
@@ -107,40 +82,26 @@ void Window::createControls(const QString &title)
     controlsLayout->addWidget(valueSpinBox, 2, 1);
     controlsLayout->addWidget(invertedAppearance, 0, 2);
     controlsLayout->addWidget(invertedKeyBindings, 1, 2);
-    controlsLayout->addWidget(orientationCombo, 3, 0, 1, 3);
     controlsGroup->setLayout(controlsLayout);
 
 }
-//! [8]
+//! [6]
 
 
-void Window::resizeEvent(QResizeEvent *e)
+//! [7]
+void Window::resizeEvent(QResizeEvent *)
 {
-    Q_UNUSED(e);
     if (width() == 0 || height() == 0)
         return;
 
-     const double aspectRatio = double(width()) / double(height());
-
-    if ((aspectRatio < 1.0) && (oldAspectRatio > 1.0)) {
-        layout->removeWidget(controlsGroup);
-        layout->removeWidget(stackedWidget);
+    const double aspectRatio = double(width()) / double(height());
 
-        layout->addWidget(stackedWidget, 1, 0);
-        layout->addWidget(controlsGroup, 0, 0);
-
-        oldAspectRatio = aspectRatio;
-    }
-    else if ((aspectRatio > 1.0) && (oldAspectRatio < 1.0)) {
-        layout->removeWidget(controlsGroup);
-        layout->removeWidget(stackedWidget);
-
-        layout->addWidget(stackedWidget, 0, 1);
-        layout->addWidget(controlsGroup, 0, 0);
-
-        oldAspectRatio = aspectRatio;
+    if (aspectRatio < 1.0) {
+        layout->setDirection(QBoxLayout::TopToBottom);
+        slidersGroup->setOrientation(Qt::Horizontal);
+    } else if (aspectRatio > 1.0) {
+        layout->setDirection(QBoxLayout::LeftToRight);
+        slidersGroup->setOrientation(Qt::Vertical);
     }
 }
-
-
-
+//! [7]
diff --git a/examples/widgets/widgets/sliders/window.h b/examples/widgets/widgets/sliders/window.h
index fa627eabd3..8d7338f27c 100644
--- a/examples/widgets/widgets/sliders/window.h
+++ b/examples/widgets/widgets/sliders/window.h
@@ -29,9 +29,7 @@ private:
     void createControls(const QString &title);
     void resizeEvent(QResizeEvent *e);
 
-    SlidersGroup *horizontalSliders;
-    SlidersGroup *verticalSliders;
-    QStackedWidget *stackedWidget;
+    SlidersGroup *slidersGroup;
 
     QGroupBox *controlsGroup;
     QLabel *minimumLabel;
@@ -42,9 +40,7 @@ private:
     QSpinBox *minimumSpinBox;
     QSpinBox *maximumSpinBox;
     QSpinBox *valueSpinBox;
-    QComboBox *orientationCombo;
-    QGridLayout *layout;
-    double oldAspectRatio;
+    QBoxLayout *layout;
 };
 //! [0]