Layouts docs: pass parent widget in the ctor

This is a follow up from commit 1e904ab342c1aaa; changing more
documentation to pass a widget * in the ctor of a layout, rather
than creating a parent-less layout then calling setLayout().

Change-Id: I4fc59c6cfa46ccd279a153acd67335a6daf22ff9
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

src/corelib/doc/snippets/fileinfo/main.cpp

@@ -31,14 +31,16 @@ int main(int argc, char *argv[])
     qDebug() << fileInfo5.fileName();
     qDebug() << fileInfo6.fileName();
 
+    QGroupBox *groupBox = new QGroupBox(QStringLiteral("QFileInfo::dir() test"));
+
+    QVBoxLayout *vbox = new QVBoxLayout(groupBox);
+
     QPushButton* button1 = new QPushButton(fileInfo1.dir().path());
     QPushButton* button2 = new QPushButton(fileInfo2.dir().path());
     QPushButton* button3 = new QPushButton(fileInfo3.dir().path());
     QPushButton* button4 = new QPushButton(fileInfo4.dir().path());
     QPushButton* button5 = new QPushButton(fileInfo5.dir().path());
     QPushButton* button6 = new QPushButton(fileInfo6.dir().path());
-
-    QVBoxLayout* vbox = new QVBoxLayout;
     vbox->addWidget(button1);
     vbox->addWidget(button2);
     vbox->addWidget(button3);
@@ -47,8 +49,6 @@ int main(int argc, char *argv[])
     vbox->addWidget(button6);
     vbox->addStretch(1);
 
-    QGroupBox *groupBox = new QGroupBox("QFileInfo::dir() test");
-    groupBox->setLayout(vbox);
     groupBox->show();
 
     return app.exec();

src/corelib/doc/snippets/qsignalmapper/buttonwidget.cpp

@@ -11,7 +11,7 @@ ButtonWidget::ButtonWidget(const QStringList &texts, QWidget *parent)
 {
     signalMapper = new QSignalMapper(this);
 
-    QGridLayout *gridLayout = new QGridLayout;
+    QGridLayout *gridLayout = new QGridLayout(this);
     for (int i = 0; i < texts.size(); ++i) {
         QPushButton *button = new QPushButton(texts[i]);
         connect(button, &QPushButton::clicked, signalMapper, &QSignalMapper::map);
@@ -23,8 +23,6 @@ ButtonWidget::ButtonWidget(const QStringList &texts, QWidget *parent)
     connect(signalMapper, &QSignalMapper::mappedString,
 //! [1] //! [2]
             this, &ButtonWidget::clicked);
-
-    setLayout(gridLayout);
 }
 //! [2]
 
@@ -32,13 +30,12 @@ ButtonWidget::ButtonWidget(const QStringList &texts, QWidget *parent)
 ButtonWidget::ButtonWidget(const QStringList &texts, QWidget *parent)
     : QWidget(parent)
 {
-    QGridLayout *gridLayout = new QGridLayout;
+    QGridLayout *gridLayout = new QGridLayout(this);
     for (int i = 0; i < texts.size(); ++i) {
         QString text = texts[i];
         QPushButton *button = new QPushButton(text);
         connect(button, &QPushButton::clicked, [this, text] { clicked(text); });
         gridLayout->addWidget(button, i / 3, i % 3);
     }
-    setLayout(gridLayout);
 }
 //! [3]

src/gui/doc/snippets/separations/finalwidget.cpp

@@ -28,10 +28,9 @@ FinalWidget::FinalWidget(QWidget *parent, const QString &name,
     imageLabel->setMinimumSize(labelSize);
     nameLabel = new QLabel(name);
 
-    QVBoxLayout *layout = new QVBoxLayout;
+    QVBoxLayout *layout = new QVBoxLayout(this);
     layout->addWidget(imageLabel, 1);
     layout->addWidget(nameLabel, 0);
-    setLayout(layout);
 }
 
 /*!

src/gui/doc/snippets/separations/screenwidget.cpp

@@ -61,12 +61,11 @@ ScreenWidget::ScreenWidget(QWidget *parent, QColor initialColor,
     connect(colorButton, &QPushButton::clicked, this, &ScreenWidget::setColor);
     connect(invertButton, &QPushButton::clicked, this, &ScreenWidget::invertImage);
 
-    QGridLayout *gridLayout = new QGridLayout;
+    QGridLayout *gridLayout = new QGridLayout(this);
     gridLayout->addWidget(imageLabel, 0, 0, 1, 2);
     gridLayout->addWidget(nameLabel, 1, 0);
     gridLayout->addWidget(colorButton, 1, 1);
     gridLayout->addWidget(invertButton, 2, 1, 1, 1);
-    setLayout(gridLayout);
 }
 
 /*!

src/gui/doc/snippets/transform/main.cpp

@@ -91,11 +91,10 @@ int main(int argc, char **argv)
     CombinedTransformation *combinedWidget = new CombinedTransformation;
     BasicOperations *basicWidget = new BasicOperations;
 
-    QVBoxLayout *layout = new QVBoxLayout;
+    QVBoxLayout *layout = new QVBoxLayout(&widget);
     layout->addWidget(simpleWidget);
     layout->addWidget(combinedWidget);
     layout->addWidget(basicWidget);
-    widget.setLayout(layout);
 
     widget.show();
     widget.resize(130, 350);

src/widgets/doc/snippets/code/src_gui_graphicsview_qgraphicsgridlayout.cpp

@@ -6,11 +6,10 @@ QGraphicsScene scene;
 QGraphicsWidget *textEdit = scene.addWidget(new QTextEdit);
 QGraphicsWidget *pushButton = scene.addWidget(new QPushButton);
 
-QGraphicsGridLayout *layout = new QGraphicsGridLayout;
+QGraphicsWidget *form = new QGraphicsWidget;
+scene.addItem(form);
+
+QGraphicsGridLayout *layout = new QGraphicsGridLayout(form);
 layout->addItem(textEdit, 0, 0);
 layout->addItem(pushButton, 0, 1);
-
-QGraphicsWidget *form = new QGraphicsWidget;
-form->setLayout(layout);
-scene.addItem(form);
 //! [0]

src/widgets/doc/snippets/code/src_gui_graphicsview_qgraphicslinearlayout.cpp

@@ -6,11 +6,10 @@ QGraphicsScene scene;
 QGraphicsWidget *textEdit = scene.addWidget(new QTextEdit);
 QGraphicsWidget *pushButton = scene.addWidget(new QPushButton);
 
-QGraphicsLinearLayout *layout = new QGraphicsLinearLayout;
+QGraphicsWidget *form = new QGraphicsWidget;
+scene.addItem(form);
+
+QGraphicsLinearLayout *layout = new QGraphicsLinearLayout(form);
 layout->addItem(textEdit);
 layout->addItem(pushButton);
-
-QGraphicsWidget *form = new QGraphicsWidget;
-form->setLayout(layout);
-scene.addItem(form);
 //! [0]

src/widgets/doc/snippets/code/src_gui_graphicsview_qgraphicsproxywidget.cpp

@@ -23,9 +23,8 @@ QGroupBox *groupBox = new QGroupBox("Contact Details");
 QLabel *numberLabel = new QLabel("Telephone number");
 QLineEdit *numberEdit = new QLineEdit;
 
-QFormLayout *layout = new QFormLayout;
+QFormLayout *layout = new QFormLayout(groupBox);
 layout->addRow(numberLabel, numberEdit);
-groupBox->setLayout(layout);
 
 QGraphicsScene scene;
 QGraphicsProxyWidget *proxy = scene.addWidget(groupBox);

src/widgets/doc/snippets/code/src_gui_kernel_qformlayout.cpp

@@ -2,15 +2,16 @@
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
 //! [0]
-QFormLayout *formLayout = new QFormLayout;
+QFormLayout *formLayout = new QFormLayout(this);
 formLayout->addRow(tr("&Name:"), nameLineEdit);
 formLayout->addRow(tr("&Email:"), emailLineEdit);
 formLayout->addRow(tr("&Age:"), ageSpinBox);
-setLayout(formLayout);
 //! [0]
 
 
 //! [1]
+QGridLayout *gridLayout = new QGridLayout(this);
+
 nameLabel = new QLabel(tr("&Name:"));
 nameLabel->setBuddy(nameLineEdit);
 
@@ -20,14 +21,12 @@ emailLabel->setBuddy(emailLineEdit);
 ageLabel = new QLabel(tr("&Name:"));
 ageLabel->setBuddy(ageSpinBox);
 
-QGridLayout *gridLayout = new QGridLayout;
 gridLayout->addWidget(nameLabel, 0, 0);
 gridLayout->addWidget(nameLineEdit, 0, 1);
 gridLayout->addWidget(emailLabel, 1, 0);
 gridLayout->addWidget(emailLineEdit, 1, 1);
 gridLayout->addWidget(ageLabel, 2, 0);
 gridLayout->addWidget(ageSpinBox, 2, 1);
-setLayout(gridLayout);
 //! [1]
 
 

src/widgets/doc/snippets/mainwindowsnippet.cpp

@@ -41,9 +41,8 @@ void MainWindow::createToolBars()
 void MainWindow::createDockWidgets()
 {
     QWidget *dockWidgetContents = new QWidget;
-    QVBoxLayout *layout = new QVBoxLayout;
+    QVBoxLayout *layout = new QVBoxLayout(dockWidgetContents);
     layout->addWidget(new QPushButton("My Button."));
-    dockWidgetContents->setLayout(layout);
 
 //! [0]
     QDockWidget *dockWidget = new QDockWidget(tr("Dock Widget"), this);

src/widgets/graphicsview/qgraphicsgridlayout.cpp

@@ -11,13 +11,16 @@
     \inmodule QtWidgets
 
     The most common way to use QGraphicsGridLayout is to construct an object
-    on the heap with no parent, add widgets and layouts by calling addItem(),
-    and finally assign the layout to a widget by calling
-    QGraphicsWidget::setLayout(). QGraphicsGridLayout automatically computes
+    on the heap, passing a parent widget to the constructor, then add widgets
+    and layouts by calling addItem(). QGraphicsGridLayout automatically computes
     the dimensions of the grid as you add items.
 
     \snippet code/src_gui_graphicsview_qgraphicsgridlayout.cpp 0
 
+    Alternatively, if you do not pass a parent widget to the layout's constructor,
+    you will need to call QGraphicsWidget::setLayout() to set this layout as the
+    top-level layout for that widget, the widget will take ownership of the layout.
+
     The layout takes ownership of the items. In some cases when the layout
     item also inherits from QGraphicsItem (such as QGraphicsWidget) there will be a
     ambiguity in ownership because the layout item belongs to two ownership hierarchies.

src/widgets/graphicsview/qgraphicslinearlayout.cpp

@@ -14,12 +14,16 @@
     passing Qt::Vertical to QGraphicsLinearLayout's constructor.
 
     The most common way to use QGraphicsLinearLayout is to construct an object
-    on the heap with no parent, add widgets and layouts by calling addItem(),
-    and finally assign the layout to a widget by calling
-    QGraphicsWidget::setLayout().
+    on the heap, passing a parent widget to the constructor, then add widgets
+    and layouts by calling addItem().
 
     \snippet code/src_gui_graphicsview_qgraphicslinearlayout.cpp 0
 
+    Alternatively, if you do not pass a parent widget to the layout's constructor,
+    you will need to call QGraphicsWidget::setLayout() to set this layout as the
+    top-level layout for that widget, the widget will take ownership of
+    the layout.
+
     You can add widgets, layouts, stretches (addStretch(), insertStretch() or
     setStretchFactor()), and spacings (setItemSpacing()) to a linear
     layout. The layout takes ownership of the items. In some cases when the layout