diff --git a/examples/widgets/doc/src/calculator.qdoc b/examples/widgets/doc/src/calculator.qdoc
index e8f80302070..7d34a86c19c 100644
--- a/examples/widgets/doc/src/calculator.qdoc
+++ b/examples/widgets/doc/src/calculator.qdoc
@@ -142,6 +142,9 @@
     pendingAdditiveOperator and \c pendingMultiplicativeOperator
     variables don't need to be initialized explicitly, because the
     QString constructor initializes them to empty strings.
+    It is also possible to initialize those variable directly in the
+    header. This is called \c member-initializaton and avoids a long
+    initialization list.
 
     \snippet widgets/calculator/calculator.cpp 1
     \snippet widgets/calculator/calculator.cpp 2
diff --git a/examples/widgets/doc/src/tooltips.qdoc b/examples/widgets/doc/src/tooltips.qdoc
index a2782155039..35e3b1e29fe 100644
--- a/examples/widgets/doc/src/tooltips.qdoc
+++ b/examples/widgets/doc/src/tooltips.qdoc
@@ -95,7 +95,7 @@
 
     \snippet widgets/tooltips/sortingbox.h 2
 
-    We keep all the shape items in a QList, and we keep three
+    We keep all the shape items in a QVector, and we keep three
     QPainterPath objects holding the shapes of a circle, a square and
     a triangle. We also need to have a pointer to an item when it is
     moving, and we need to know its previous position.
diff --git a/examples/widgets/widgets/analogclock/analogclock.cpp b/examples/widgets/widgets/analogclock/analogclock.cpp
index c7b3f66cca9..06e298659d4 100644
--- a/examples/widgets/widgets/analogclock/analogclock.cpp
+++ b/examples/widgets/widgets/analogclock/analogclock.cpp
@@ -50,7 +50,9 @@
 
 #include "analogclock.h"
 
-#include <QtWidgets>
+#include <QPainter>
+#include <QTime>
+#include <QTimer>
 
 //! [0] //! [1]
 AnalogClock::AnalogClock(QWidget *parent)
diff --git a/examples/widgets/widgets/calculator/button.cpp b/examples/widgets/widgets/calculator/button.cpp
index a1ce0bf4285..cc370a563ca 100644
--- a/examples/widgets/widgets/calculator/button.cpp
+++ b/examples/widgets/widgets/calculator/button.cpp
@@ -50,8 +50,6 @@
 
 #include "button.h"
 
-#include <QtWidgets>
-
 //! [0]
 Button::Button(const QString &text, QWidget *parent)
     : QToolButton(parent)
diff --git a/examples/widgets/widgets/calculator/calculator.cpp b/examples/widgets/widgets/calculator/calculator.cpp
index dd908cf40a9..2c3669b7a8c 100644
--- a/examples/widgets/widgets/calculator/calculator.cpp
+++ b/examples/widgets/widgets/calculator/calculator.cpp
@@ -48,21 +48,18 @@
 **
 ****************************************************************************/
 
-#include "button.h"
 #include "calculator.h"
+#include "button.h"
 
-#include <QtWidgets>
-
-#include <cmath>
+#include <QGridLayout>
+#include <QLineEdit>
+#include <QtMath>
 
 //! [0]
 Calculator::Calculator(QWidget *parent)
-    : QWidget(parent)
+    : QWidget(parent), sumInMemory(0.0), sumSoFar(0.0)
+    , factorSoFar(0.0), waitingForOperand(true)
 {
-    sumInMemory = 0.0;
-    sumSoFar = 0.0;
-    factorSoFar = 0.0;
-    waitingForOperand = true;
 //! [0]
 
 //! [1]
@@ -78,9 +75,8 @@ Calculator::Calculator(QWidget *parent)
 //! [2]
 
 //! [4]
-    for (int i = 0; i < NumDigitButtons; ++i) {
+    for (int i = 0; i < NumDigitButtons; ++i)
         digitButtons[i] = createButton(QString::number(i), SLOT(digitClicked()));
-    }
 
     Button *pointButton = createButton(tr("."), SLOT(pointClicked()));
     Button *changeSignButton = createButton(tr("\302\261"), SLOT(changeSignClicked()));
@@ -194,6 +190,8 @@ void Calculator::additiveOperatorClicked()
 //! [10] //! [11]
 {
     Button *clickedButton = qobject_cast<Button *>(sender());
+    if (!clickedButton)
+      return;
     QString clickedOperator = clickedButton->text();
     double operand = display->text().toDouble();
 
@@ -233,6 +231,8 @@ void Calculator::additiveOperatorClicked()
 void Calculator::multiplicativeOperatorClicked()
 {
     Button *clickedButton = qobject_cast<Button *>(sender());
+    if (!clickedButton)
+      return;
     QString clickedOperator = clickedButton->text();
     double operand = display->text().toDouble();
 
diff --git a/examples/widgets/widgets/calendarwidget/main.cpp b/examples/widgets/widgets/calendarwidget/main.cpp
index 2622669f327..2582e838413 100644
--- a/examples/widgets/widgets/calendarwidget/main.cpp
+++ b/examples/widgets/widgets/calendarwidget/main.cpp
@@ -48,7 +48,7 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
+#include <QApplication>
 
 #include "window.h"
 
diff --git a/examples/widgets/widgets/calendarwidget/window.cpp b/examples/widgets/widgets/calendarwidget/window.cpp
index 64047aaac97..b8a3d03552f 100644
--- a/examples/widgets/widgets/calendarwidget/window.cpp
+++ b/examples/widgets/widgets/calendarwidget/window.cpp
@@ -48,10 +48,18 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-
 #include "window.h"
 
+#include <QCalendarWidget>
+#include <QCheckBox>
+#include <QComboBox>
+#include <QDateEdit>
+#include <QGridLayout>
+#include <QGroupBox>
+#include <QLabel>
+#include <QLocale>
+#include <QTextCharFormat>
+
 //! [0]
 Window::Window(QWidget *parent)
     : QWidget(parent)
@@ -166,13 +174,12 @@ void Window::reformatHeaders()
     QString text = headerTextFormatCombo->currentText();
     QTextCharFormat format;
 
-    if (text == tr("Bold")) {
+    if (text == tr("Bold"))
         format.setFontWeight(QFont::Bold);
-    } else if (text == tr("Italic")) {
+    else if (text == tr("Italic"))
         format.setFontItalic(true);
-    } else if (text == tr("Green")) {
+    else if (text == tr("Green"))
         format.setForeground(Qt::green);
-    }
     calendar->setHeaderTextFormat(format);
 }
 //! [7]
diff --git a/examples/widgets/widgets/charactermap/characterwidget.cpp b/examples/widgets/widgets/charactermap/characterwidget.cpp
index 061c0164b00..41406b7fb41 100644
--- a/examples/widgets/widgets/charactermap/characterwidget.cpp
+++ b/examples/widgets/widgets/charactermap/characterwidget.cpp
@@ -50,11 +50,14 @@
 
 #include "characterwidget.h"
 
-#include <QtWidgets>
+#include <QFontDatabase>
+#include <QMouseEvent>
+#include <QPainter>
+#include <QToolTip>
 
 //! [0]
 CharacterWidget::CharacterWidget(QWidget *parent)
-    : QWidget(parent), columns(16), lastKey(-1)
+    : QWidget(parent)
 {
     calculateSquareSize();
     setMouseTracking(true);
@@ -110,7 +113,7 @@ void CharacterWidget::calculateSquareSize()
 //! [3]
 QSize CharacterWidget::sizeHint() const
 {
-    return QSize(columns*squareSize, (65536/columns)*squareSize);
+    return QSize(columns*squareSize, (65536 / columns) * squareSize);
 }
 //! [3]
 
@@ -118,7 +121,7 @@ QSize CharacterWidget::sizeHint() const
 void CharacterWidget::mouseMoveEvent(QMouseEvent *event)
 {
     QPoint widgetPosition = mapFromGlobal(event->globalPos());
-    uint key = (widgetPosition.y()/squareSize)*columns + widgetPosition.x()/squareSize;
+    uint key = (widgetPosition.y() / squareSize) * columns + widgetPosition.x() / squareSize;
 
     QString text = QString::fromLatin1("<p>Character: <span style=\"font-size: 24pt; font-family: %1\">").arg(displayFont.family())
                   + QChar(key)
@@ -132,7 +135,7 @@ void CharacterWidget::mouseMoveEvent(QMouseEvent *event)
 void CharacterWidget::mousePressEvent(QMouseEvent *event)
 {
     if (event->button() == Qt::LeftButton) {
-        lastKey = (event->y()/squareSize)*columns + event->x()/squareSize;
+        lastKey = (event->y() / squareSize) * columns + event->x() / squareSize;
         if (QChar(lastKey).category() != QChar::Other_NotAssigned)
             emit characterSelected(QString(QChar(lastKey)));
         update();
@@ -152,17 +155,17 @@ void CharacterWidget::paintEvent(QPaintEvent *event)
 
 //! [7]
     QRect redrawRect = event->rect();
-    int beginRow = redrawRect.top()/squareSize;
-    int endRow = redrawRect.bottom()/squareSize;
-    int beginColumn = redrawRect.left()/squareSize;
-    int endColumn = redrawRect.right()/squareSize;
+    int beginRow = redrawRect.top() / squareSize;
+    int endRow = redrawRect.bottom() / squareSize;
+    int beginColumn = redrawRect.left() / squareSize;
+    int endColumn = redrawRect.right() / squareSize;
 //! [7]
 
 //! [8]
     painter.setPen(QPen(Qt::gray));
     for (int row = beginRow; row <= endRow; ++row) {
         for (int column = beginColumn; column <= endColumn; ++column) {
-            painter.drawRect(column*squareSize, row*squareSize, squareSize, squareSize);
+            painter.drawRect(column * squareSize, row * squareSize, squareSize, squareSize);
         }
 //! [8] //! [9]
     }
@@ -172,17 +175,17 @@ void CharacterWidget::paintEvent(QPaintEvent *event)
     QFontMetrics fontMetrics(displayFont);
     painter.setPen(QPen(Qt::black));
     for (int row = beginRow; row <= endRow; ++row) {
-
         for (int column = beginColumn; column <= endColumn; ++column) {
-
-            int key = row*columns + column;
-            painter.setClipRect(column*squareSize, row*squareSize, squareSize, squareSize);
+            int key = row * columns + column;
+            painter.setClipRect(column * squareSize, row * squareSize, squareSize, squareSize);
 
             if (key == lastKey)
-                painter.fillRect(column*squareSize + 1, row*squareSize + 1, squareSize, squareSize, QBrush(Qt::red));
+                painter.fillRect(column * squareSize + 1, row * squareSize + 1,
+                                 squareSize, squareSize, QBrush(Qt::red));
 
-            painter.drawText(column*squareSize + (squareSize / 2) - fontMetrics.horizontalAdvance(QChar(key))/2,
-                             row*squareSize + 4 + fontMetrics.ascent(),
+            painter.drawText(column * squareSize + (squareSize / 2) -
+                                 fontMetrics.horizontalAdvance(QChar(key)) / 2,
+                             row * squareSize + 4 + fontMetrics.ascent(),
                              QString(QChar(key)));
         }
     }
diff --git a/examples/widgets/widgets/charactermap/characterwidget.h b/examples/widgets/widgets/charactermap/characterwidget.h
index d12a46aa15b..67ac8a30bfd 100644
--- a/examples/widgets/widgets/charactermap/characterwidget.h
+++ b/examples/widgets/widgets/charactermap/characterwidget.h
@@ -88,9 +88,9 @@ private:
     void calculateSquareSize();
 
     QFont displayFont;
-    int columns;
-    int lastKey;
-    int squareSize;
+    int columns = 16;
+    int lastKey = -1;
+    int squareSize = 0;
 };
 //! [0]
 
diff --git a/examples/widgets/widgets/charactermap/mainwindow.cpp b/examples/widgets/widgets/charactermap/mainwindow.cpp
index 77aad145e7b..25c4503ddb8 100644
--- a/examples/widgets/widgets/charactermap/mainwindow.cpp
+++ b/examples/widgets/widgets/charactermap/mainwindow.cpp
@@ -48,13 +48,27 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-
-#include "characterwidget.h"
 #include "mainwindow.h"
+#include "characterwidget.h"
+
+#include <QApplication>
+#include <QBoxLayout>
+#include <QCheckBox>
+#include <QClipboard>
+#include <QDesktopWidget>
+#include <QDialog>
+#include <QDialogButtonBox>
+#include <QFontComboBox>
+#include <QLabel>
+#include <QLineEdit>
+#include <QMenuBar>
+#include <QPlainTextEdit>
+#include <QPushButton>
+#include <QScrollArea>
+#include <QStatusBar>
+#include <QTextStream>
 
 //! [0]
-
 Q_DECLARE_METATYPE(QFontComboBox::FontFilter)
 
 MainWindow::MainWindow(QWidget *parent)
diff --git a/examples/widgets/widgets/codeeditor/codeeditor.cpp b/examples/widgets/widgets/codeeditor/codeeditor.cpp
index 8e298606697..e93a0251e55 100644
--- a/examples/widgets/widgets/codeeditor/codeeditor.cpp
+++ b/examples/widgets/widgets/codeeditor/codeeditor.cpp
@@ -48,10 +48,11 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-
 #include "codeeditor.h"
 
+#include <QPainter>
+#include <QTextBlock>
+
 //![constructor]
 
 CodeEditor::CodeEditor(QWidget *parent) : QPlainTextEdit(parent)
@@ -157,8 +158,8 @@ void CodeEditor::lineNumberAreaPaintEvent(QPaintEvent *event)
 //![extraAreaPaintEvent_1]
     QTextBlock block = firstVisibleBlock();
     int blockNumber = block.blockNumber();
-    int top = (int) blockBoundingGeometry(block).translated(contentOffset()).top();
-    int bottom = top + (int) blockBoundingRect(block).height();
+    int top = qRound(blockBoundingGeometry(block).translated(contentOffset()).top());
+    int bottom = top + qRound(blockBoundingRect(block).height());
 //![extraAreaPaintEvent_1]
 
 //![extraAreaPaintEvent_2]
@@ -172,7 +173,7 @@ void CodeEditor::lineNumberAreaPaintEvent(QPaintEvent *event)
 
         block = block.next();
         top = bottom;
-        bottom = top + (int) blockBoundingRect(block).height();
+        bottom = top + qRound(blockBoundingRect(block).height());
         ++blockNumber;
     }
 }
diff --git a/examples/widgets/widgets/codeeditor/codeeditor.h b/examples/widgets/widgets/codeeditor/codeeditor.h
index 5a48abafc4e..283a4e0bdfd 100644
--- a/examples/widgets/widgets/codeeditor/codeeditor.h
+++ b/examples/widgets/widgets/codeeditor/codeeditor.h
@@ -80,7 +80,7 @@ protected:
 private slots:
     void updateLineNumberAreaWidth(int newBlockCount);
     void highlightCurrentLine();
-    void updateLineNumberArea(const QRect &, int);
+    void updateLineNumberArea(const QRect &rect, int dy);
 
 private:
     QWidget *lineNumberArea;
@@ -92,16 +92,17 @@ private:
 class LineNumberArea : public QWidget
 {
 public:
-    LineNumberArea(CodeEditor *editor) : QWidget(editor) {
-        codeEditor = editor;
-    }
+    LineNumberArea(CodeEditor *editor) : QWidget(editor), codeEditor(editor)
+    {}
 
-    QSize sizeHint() const override {
+    QSize sizeHint() const override
+    {
         return QSize(codeEditor->lineNumberAreaWidth(), 0);
     }
 
 protected:
-    void paintEvent(QPaintEvent *event) override {
+    void paintEvent(QPaintEvent *event) override
+    {
         codeEditor->lineNumberAreaPaintEvent(event);
     }
 
diff --git a/examples/widgets/widgets/codeeditor/main.cpp b/examples/widgets/widgets/codeeditor/main.cpp
index e17acb87cdf..72d186553a3 100644
--- a/examples/widgets/widgets/codeeditor/main.cpp
+++ b/examples/widgets/widgets/codeeditor/main.cpp
@@ -48,7 +48,7 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
+#include <QApplication>
 
 #include "codeeditor.h"
 
diff --git a/examples/widgets/widgets/digitalclock/digitalclock.cpp b/examples/widgets/widgets/digitalclock/digitalclock.cpp
index 000334f33bc..2b130ecda69 100644
--- a/examples/widgets/widgets/digitalclock/digitalclock.cpp
+++ b/examples/widgets/widgets/digitalclock/digitalclock.cpp
@@ -50,7 +50,8 @@
 
 #include "digitalclock.h"
 
-#include <QtWidgets>
+#include <QTime>
+#include <QTimer>
 
 //! [0]
 DigitalClock::DigitalClock(QWidget *parent)
diff --git a/examples/widgets/widgets/groupbox/window.cpp b/examples/widgets/widgets/groupbox/window.cpp
index 230d360372b..95c4f216fe4 100644
--- a/examples/widgets/widgets/groupbox/window.cpp
+++ b/examples/widgets/widgets/groupbox/window.cpp
@@ -48,10 +48,15 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-
 #include "window.h"
 
+#include <QCheckBox>
+#include <QGridLayout>
+#include <QGroupBox>
+#include <QMenu>
+#include <QPushButton>
+#include <QRadioButton>
+
 //! [0]
 Window::Window(QWidget *parent)
     : QWidget(parent)
diff --git a/examples/widgets/widgets/icons/iconpreviewarea.cpp b/examples/widgets/widgets/icons/iconpreviewarea.cpp
index 7a73a137cd7..96cb6f008e9 100644
--- a/examples/widgets/widgets/icons/iconpreviewarea.cpp
+++ b/examples/widgets/widgets/icons/iconpreviewarea.cpp
@@ -50,7 +50,8 @@
 
 #include "iconpreviewarea.h"
 
-#include <QtWidgets>
+#include <QGridLayout>
+#include <QLabel>
 
 //! [0]
 IconPreviewArea::IconPreviewArea(QWidget *parent)
diff --git a/examples/widgets/widgets/icons/iconsizespinbox.cpp b/examples/widgets/widgets/icons/iconsizespinbox.cpp
index e94d9439931..8e6c6546869 100644
--- a/examples/widgets/widgets/icons/iconsizespinbox.cpp
+++ b/examples/widgets/widgets/icons/iconsizespinbox.cpp
@@ -50,7 +50,7 @@
 
 #include "iconsizespinbox.h"
 
-#include <QtWidgets>
+#include <QRegularExpression>
 
 //! [0]
 IconSizeSpinBox::IconSizeSpinBox(QWidget *parent)
diff --git a/examples/widgets/widgets/icons/imagedelegate.cpp b/examples/widgets/widgets/icons/imagedelegate.cpp
index 786194bae70..39c2e431349 100644
--- a/examples/widgets/widgets/icons/imagedelegate.cpp
+++ b/examples/widgets/widgets/icons/imagedelegate.cpp
@@ -51,7 +51,7 @@
 #include "imagedelegate.h"
 #include "iconpreviewarea.h"
 
-#include <QtWidgets>
+#include <QComboBox>
 
 //! [0]
 ImageDelegate::ImageDelegate(QObject *parent)
diff --git a/examples/widgets/widgets/icons/mainwindow.cpp b/examples/widgets/widgets/icons/mainwindow.cpp
index 91e98ff8960..f342c18c4ce 100644
--- a/examples/widgets/widgets/icons/mainwindow.cpp
+++ b/examples/widgets/widgets/icons/mainwindow.cpp
@@ -48,14 +48,29 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-
+#include "mainwindow.h"
 #include "iconpreviewarea.h"
 #include "iconsizespinbox.h"
 #include "imagedelegate.h"
-#include "mainwindow.h"
 
-#include <memory>
+#include <QApplication>
+#include <QButtonGroup>
+#include <QCheckBox>
+#include <QFileDialog>
+#include <QHeaderView>
+#include <QFormLayout>
+#include <QGridLayout>
+#include <QGroupBox>
+#include <QImageReader>
+#include <QLabel>
+#include <QMenuBar>
+#include <QMessageBox>
+#include <QRadioButton>
+#include <QScreen>
+#include <QStandardPaths>
+#include <QStyleFactory>
+#include <QTableWidget>
+#include <QWindow>
 
 //! [40]
 enum { OtherSize = QStyle::PM_CustomBase };
diff --git a/examples/widgets/widgets/imageviewer/imageviewer.cpp b/examples/widgets/widgets/imageviewer/imageviewer.cpp
index 2fc8ff63dec..83cf8bb7bca 100644
--- a/examples/widgets/widgets/imageviewer/imageviewer.cpp
+++ b/examples/widgets/widgets/imageviewer/imageviewer.cpp
@@ -50,7 +50,24 @@
 
 #include "imageviewer.h"
 
-#include <QtWidgets>
+#include <QApplication>
+#include <QClipboard>
+#include <QColorSpace>
+#include <QDir>
+#include <QFileDialog>
+#include <QImageReader>
+#include <QImageWriter>
+#include <QLabel>
+#include <QMenuBar>
+#include <QMessageBox>
+#include <QMimeData>
+#include <QPainter>
+#include <QScreen>
+#include <QScrollArea>
+#include <QScrollBar>
+#include <QStandardPaths>
+#include <QStatusBar>
+
 #if defined(QT_PRINTSUPPORT_LIB)
 #include <QtPrintSupport/qtprintsupportglobal.h>
 #if QT_CONFIG(printdialog)
@@ -60,8 +77,8 @@
 
 //! [0]
 ImageViewer::ImageViewer(QWidget *parent)
-   : QMainWindow(parent), imageLabel(new QLabel),
-     scrollArea(new QScrollArea), scaleFactor(1)
+   : QMainWindow(parent), imageLabel(new QLabel)
+   , scrollArea(new QScrollArea)
 {
     imageLabel->setBackgroundRole(QPalette::Base);
     imageLabel->setSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored);
diff --git a/examples/widgets/widgets/imageviewer/imageviewer.h b/examples/widgets/widgets/imageviewer/imageviewer.h
index 7e53105b33b..49c7ac205b9 100644
--- a/examples/widgets/widgets/imageviewer/imageviewer.h
+++ b/examples/widgets/widgets/imageviewer/imageviewer.h
@@ -98,7 +98,7 @@ private:
     QImage image;
     QLabel *imageLabel;
     QScrollArea *scrollArea;
-    double scaleFactor;
+    double scaleFactor = 1;
 
 #ifndef QT_NO_PRINTER
     QPrinter printer;
diff --git a/examples/widgets/widgets/lineedits/window.cpp b/examples/widgets/widgets/lineedits/window.cpp
index 33f09d544dc..bb9396411a6 100644
--- a/examples/widgets/widgets/lineedits/window.cpp
+++ b/examples/widgets/widgets/lineedits/window.cpp
@@ -48,10 +48,14 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-
 #include "window.h"
 
+#include <QComboBox>
+#include <QGridLayout>
+#include <QGroupBox>
+#include <QLabel>
+#include <QLineEdit>
+
 //! [0]
 Window::Window(QWidget *parent)
     : QWidget(parent)
@@ -197,6 +201,7 @@ void Window::echoChanged(int index)
         break;
     case 3:
         echoLineEdit->setEchoMode(QLineEdit::NoEcho);
+        break;
     }
 }
 //! [9]
@@ -215,6 +220,7 @@ void Window::validatorChanged(int index)
     case 2:
         validatorLineEdit->setValidator(new QDoubleValidator(-999.0,
             999.0, 2, validatorLineEdit));
+        break;
     }
 
     validatorLineEdit->clear();
@@ -233,6 +239,7 @@ void Window::alignmentChanged(int index)
         break;
     case 2:
         alignmentLineEdit->setAlignment(Qt::AlignRight);
+        break;
     }
 }
 //! [11]
@@ -254,6 +261,7 @@ void Window::inputMaskChanged(int index)
         break;
     case 3:
         inputMaskLineEdit->setInputMask(">AAAAA-AAAAA-AAAAA-AAAAA-AAAAA;#");
+        break;
     }
 }
 //! [12]
@@ -267,6 +275,7 @@ void Window::accessChanged(int index)
         break;
     case 1:
         accessLineEdit->setReadOnly(true);
+        break;
     }
 }
 //! [13]
diff --git a/examples/widgets/widgets/movie/movieplayer.cpp b/examples/widgets/widgets/movie/movieplayer.cpp
index 182b258a829..41cd7923ee3 100644
--- a/examples/widgets/widgets/movie/movieplayer.cpp
+++ b/examples/widgets/widgets/movie/movieplayer.cpp
@@ -50,7 +50,15 @@
 
 #include "movieplayer.h"
 
-#include <QtWidgets>
+#include <QCheckBox>
+#include <QFileDialog>
+#include <QLabel>
+#include <QMovie>
+#include <QSlider>
+#include <QSpinBox>
+#include <QStyle>
+#include <QToolButton>
+#include <QVBoxLayout>
 
 MoviePlayer::MoviePlayer(QWidget *parent)
     : QWidget(parent)
diff --git a/examples/widgets/widgets/scribble/mainwindow.cpp b/examples/widgets/widgets/scribble/mainwindow.cpp
index 44afa64b946..db4f8d3637e 100644
--- a/examples/widgets/widgets/scribble/mainwindow.cpp
+++ b/examples/widgets/widgets/scribble/mainwindow.cpp
@@ -48,11 +48,17 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-
 #include "mainwindow.h"
 #include "scribblearea.h"
 
+#include <QApplication>
+#include <QColorDialog>
+#include <QFileDialog>
+#include <QImageWriter>
+#include <QInputDialog>
+#include <QMenuBar>
+#include <QMessageBox>
+
 //! [0]
 MainWindow::MainWindow(QWidget *parent)
     : QMainWindow(parent), scribbleArea(new ScribbleArea(this))
@@ -71,11 +77,10 @@ MainWindow::MainWindow(QWidget *parent)
 void MainWindow::closeEvent(QCloseEvent *event)
 //! [1] //! [2]
 {
-    if (maybeSave()) {
+    if (maybeSave())
         event->accept();
-    } else {
+    else
         event->ignore();
-    }
 }
 //! [2]
 
@@ -231,11 +236,10 @@ bool MainWindow::maybeSave()
                              "Do you want to save your changes?"),
                           QMessageBox::Save | QMessageBox::Discard
                           | QMessageBox::Cancel);
-        if (ret == QMessageBox::Save) {
+        if (ret == QMessageBox::Save)
             return saveFile("png");
-        } else if (ret == QMessageBox::Cancel) {
+        else if (ret == QMessageBox::Cancel)
             return false;
-        }
     }
     return true;
 }
@@ -252,10 +256,8 @@ bool MainWindow::saveFile(const QByteArray &fileFormat)
                                tr("%1 Files (*.%2);;All Files (*)")
                                .arg(QString::fromLatin1(fileFormat.toUpper()))
                                .arg(QString::fromLatin1(fileFormat)));
-    if (fileName.isEmpty()) {
+    if (fileName.isEmpty())
         return false;
-    } else {
-        return scribbleArea->saveImage(fileName, fileFormat.constData());
-    }
+    return scribbleArea->saveImage(fileName, fileFormat.constData());
 }
 //! [20]
diff --git a/examples/widgets/widgets/scribble/scribblearea.cpp b/examples/widgets/widgets/scribble/scribblearea.cpp
index 13e46f6e1d6..75371b523fe 100644
--- a/examples/widgets/widgets/scribble/scribblearea.cpp
+++ b/examples/widgets/widgets/scribble/scribblearea.cpp
@@ -50,7 +50,9 @@
 
 #include "scribblearea.h"
 
-#include <QtWidgets>
+#include <QMouseEvent>
+#include <QPainter>
+
 #if defined(QT_PRINTSUPPORT_LIB)
 #include <QtPrintSupport/qtprintsupportglobal.h>
 #if QT_CONFIG(printdialog)
@@ -64,10 +66,6 @@ ScribbleArea::ScribbleArea(QWidget *parent)
     : QWidget(parent)
 {
     setAttribute(Qt::WA_StaticContents);
-    modified = false;
-    scribbling = false;
-    myPenWidth = 1;
-    myPenColor = Qt::blue;
 }
 //! [0]
 
@@ -98,9 +96,8 @@ bool ScribbleArea::saveImage(const QString &fileName, const char *fileFormat)
     if (visibleImage.save(fileName, fileFormat)) {
         modified = false;
         return true;
-    } else {
-        return false;
     }
+    return false;
 }
 //! [4]
 
diff --git a/examples/widgets/widgets/scribble/scribblearea.h b/examples/widgets/widgets/scribble/scribblearea.h
index 100c45e1338..ed3c8a2a158 100644
--- a/examples/widgets/widgets/scribble/scribblearea.h
+++ b/examples/widgets/widgets/scribble/scribblearea.h
@@ -88,10 +88,10 @@ private:
     void drawLineTo(const QPoint &endPoint);
     void resizeImage(QImage *image, const QSize &newSize);
 
-    bool modified;
-    bool scribbling;
-    int myPenWidth;
-    QColor myPenColor;
+    bool modified = false;
+    bool scribbling = false;
+    int myPenWidth = 1;
+    QColor myPenColor = Qt::blue;
     QImage image;
     QPoint lastPoint;
 };
diff --git a/examples/widgets/widgets/shapedclock/shapedclock.cpp b/examples/widgets/widgets/shapedclock/shapedclock.cpp
index 8e7d8319387..3c78f4da89b 100644
--- a/examples/widgets/widgets/shapedclock/shapedclock.cpp
+++ b/examples/widgets/widgets/shapedclock/shapedclock.cpp
@@ -48,10 +48,15 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-
 #include "shapedclock.h"
 
+#include <QAction>
+#include <QCoreApplication>
+#include <QMouseEvent>
+#include <QPainter>
+#include <QTime>
+#include <QTimer>
+
 //! [0]
 ShapedClock::ShapedClock(QWidget *parent)
     : QWidget(parent, Qt::FramelessWindowHint | Qt::WindowSystemMenuHint)
diff --git a/examples/widgets/widgets/sliders/slidersgroup.cpp b/examples/widgets/widgets/sliders/slidersgroup.cpp
index b4eaf9bb3d4..912c9798ce7 100644
--- a/examples/widgets/widgets/sliders/slidersgroup.cpp
+++ b/examples/widgets/widgets/sliders/slidersgroup.cpp
@@ -50,7 +50,10 @@
 
 #include "slidersgroup.h"
 
-#include <QtWidgets>
+#include <QBoxLayout>
+#include <QDial>
+#include <QScrollBar>
+#include <QSlider>
 
 //! [0]
 SlidersGroup::SlidersGroup(Qt::Orientation orientation, const QString &title,
diff --git a/examples/widgets/widgets/sliders/window.cpp b/examples/widgets/widgets/sliders/window.cpp
index d73fafec103..4a28a61f3d0 100644
--- a/examples/widgets/widgets/sliders/window.cpp
+++ b/examples/widgets/widgets/sliders/window.cpp
@@ -48,11 +48,16 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-
 #include "slidersgroup.h"
 #include "window.h"
 
+#include <QCheckBox>
+#include <QComboBox>
+#include <QHBoxLayout>
+#include <QLabel>
+#include <QSpinBox>
+#include <QStackedWidget>
+
 //! [0]
 Window::Window(QWidget *parent)
     : QWidget(parent)
diff --git a/examples/widgets/widgets/spinboxes/window.cpp b/examples/widgets/widgets/spinboxes/window.cpp
index 82e19527a7a..40c02aba70f 100644
--- a/examples/widgets/widgets/spinboxes/window.cpp
+++ b/examples/widgets/widgets/spinboxes/window.cpp
@@ -48,10 +48,16 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-
 #include "window.h"
 
+#include <QCheckBox>
+#include <QComboBox>
+#include <QDateTimeEdit>
+#include <QGroupBox>
+#include <QHBoxLayout>
+#include <QLabel>
+#include <QSpinBox>
+
 //! [0]
 Window::Window(QWidget *parent)
     : QWidget(parent)
diff --git a/examples/widgets/widgets/styles/norwegianwoodstyle.cpp b/examples/widgets/widgets/styles/norwegianwoodstyle.cpp
index a178769bd81..0f614a2e9ae 100644
--- a/examples/widgets/widgets/styles/norwegianwoodstyle.cpp
+++ b/examples/widgets/widgets/styles/norwegianwoodstyle.cpp
@@ -50,7 +50,10 @@
 
 #include "norwegianwoodstyle.h"
 
-#include <QtWidgets>
+#include <QComboBox>
+#include <QPainter>
+#include <QPushButton>
+#include <QStyleFactory>
 
 NorwegianWoodStyle::NorwegianWoodStyle() :
     QProxyStyle(QStyleFactory::create("windows"))
diff --git a/examples/widgets/widgets/styles/widgetgallery.cpp b/examples/widgets/widgets/styles/widgetgallery.cpp
index 34c010df746..fd8f0ec2d16 100644
--- a/examples/widgets/widgets/styles/widgetgallery.cpp
+++ b/examples/widgets/widgets/styles/widgetgallery.cpp
@@ -51,7 +51,24 @@
 #include "widgetgallery.h"
 #include "norwegianwoodstyle.h"
 
-#include <QtWidgets>
+#include <QApplication>
+#include <QCheckBox>
+#include <QComboBox>
+#include <QDateTimeEdit>
+#include <QDial>
+#include <QGridLayout>
+#include <QGroupBox>
+#include <QLabel>
+#include <QLineEdit>
+#include <QProgressBar>
+#include <QPushButton>
+#include <QRadioButton>
+#include <QScrollBar>
+#include <QSpinBox>
+#include <QStyleFactory>
+#include <QTableWidget>
+#include <QTextEdit>
+#include <QTimer>
 
 //! [0]
 WidgetGallery::WidgetGallery(QWidget *parent)
diff --git a/examples/widgets/widgets/stylesheet/main.cpp b/examples/widgets/widgets/stylesheet/main.cpp
index 1874bceb8ca..3b1168398ae 100644
--- a/examples/widgets/widgets/stylesheet/main.cpp
+++ b/examples/widgets/widgets/stylesheet/main.cpp
@@ -48,7 +48,7 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
+#include <QApplication>
 
 #include "mainwindow.h"
 
diff --git a/examples/widgets/widgets/stylesheet/mainwindow.cpp b/examples/widgets/widgets/stylesheet/mainwindow.cpp
index f187c007dd3..a8bd20e964a 100644
--- a/examples/widgets/widgets/stylesheet/mainwindow.cpp
+++ b/examples/widgets/widgets/stylesheet/mainwindow.cpp
@@ -48,11 +48,11 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-
 #include "mainwindow.h"
 #include "stylesheeteditor.h"
 
+#include <QMessageBox>
+
 MainWindow::MainWindow(QWidget *parent)
     : QMainWindow(parent)
 {
diff --git a/examples/widgets/widgets/stylesheet/mainwindow.h b/examples/widgets/widgets/stylesheet/mainwindow.h
index 8af4c01da0b..ba979a38811 100644
--- a/examples/widgets/widgets/stylesheet/mainwindow.h
+++ b/examples/widgets/widgets/stylesheet/mainwindow.h
@@ -51,7 +51,7 @@
 #ifndef MAINWINDOW_H
 #define MAINWINDOW_H
 
-#include <QtWidgets>
+#include <QMainWindow>
 
 #include "ui_mainwindow.h"
 
diff --git a/examples/widgets/widgets/stylesheet/stylesheeteditor.cpp b/examples/widgets/widgets/stylesheet/stylesheeteditor.cpp
index 0874cc35544..2cc0e969e29 100644
--- a/examples/widgets/widgets/stylesheet/stylesheeteditor.cpp
+++ b/examples/widgets/widgets/stylesheet/stylesheeteditor.cpp
@@ -50,7 +50,9 @@
 
 #include "stylesheeteditor.h"
 
-#include <QtWidgets>
+#include <QFile>
+#include <QRegularExpression>
+#include <QStyleFactory>
 
 StyleSheetEditor::StyleSheetEditor(QWidget *parent)
     : QDialog(parent)
diff --git a/examples/widgets/widgets/tablet/main.cpp b/examples/widgets/widgets/tablet/main.cpp
index 5726e791665..0fec526de04 100644
--- a/examples/widgets/widgets/tablet/main.cpp
+++ b/examples/widgets/widgets/tablet/main.cpp
@@ -48,8 +48,6 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-
 #include "mainwindow.h"
 #include "tabletapplication.h"
 #include "tabletcanvas.h"
diff --git a/examples/widgets/widgets/tablet/mainwindow.cpp b/examples/widgets/widgets/tablet/mainwindow.cpp
index a0481195339..8bcb9ada63a 100644
--- a/examples/widgets/widgets/tablet/mainwindow.cpp
+++ b/examples/widgets/widgets/tablet/mainwindow.cpp
@@ -48,14 +48,19 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-
 #include "mainwindow.h"
 #include "tabletcanvas.h"
 
+#include <QApplication>
+#include <QColorDialog>
+#include <QDir>
+#include <QFileDialog>
+#include <QMenuBar>
+#include <QMessageBox>
+
 //! [0]
 MainWindow::MainWindow(TabletCanvas *canvas)
-  : m_canvas(canvas), m_colorDialog(nullptr)
+    : m_canvas(canvas)
 {
     createMenus();
     setWindowTitle(tr("Tablet Example"));
diff --git a/examples/widgets/widgets/tablet/mainwindow.h b/examples/widgets/widgets/tablet/mainwindow.h
index 4be28784b53..3ea9af7ccf5 100644
--- a/examples/widgets/widgets/tablet/mainwindow.h
+++ b/examples/widgets/widgets/tablet/mainwindow.h
@@ -81,7 +81,7 @@ private:
     void createMenus();
 
     TabletCanvas *m_canvas;
-    QColorDialog *m_colorDialog;
+    QColorDialog *m_colorDialog = nullptr;
 };
 //! [0]
 
diff --git a/examples/widgets/widgets/tablet/tabletapplication.cpp b/examples/widgets/widgets/tablet/tabletapplication.cpp
index 37be0182765..a27491a86c2 100644
--- a/examples/widgets/widgets/tablet/tabletapplication.cpp
+++ b/examples/widgets/widgets/tablet/tabletapplication.cpp
@@ -50,8 +50,6 @@
 
 #include "tabletapplication.h"
 
-#include <QtWidgets>
-
 //! [0]
 bool TabletApplication::event(QEvent *event)
 {
diff --git a/examples/widgets/widgets/tablet/tabletcanvas.cpp b/examples/widgets/widgets/tablet/tabletcanvas.cpp
index dc56702142f..9a8029486de 100644
--- a/examples/widgets/widgets/tablet/tabletcanvas.cpp
+++ b/examples/widgets/widgets/tablet/tabletcanvas.cpp
@@ -48,21 +48,16 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-#include <math.h>
-
 #include "tabletcanvas.h"
 
+#include <QCoreApplication>
+#include <QPainter>
+#include <QtMath>
+
 //! [0]
 TabletCanvas::TabletCanvas()
-  : QWidget(nullptr)
-  , m_alphaChannelValuator(TangentialPressureValuator)
-  , m_colorSaturationValuator(NoValuator)
-  , m_lineWidthValuator(PressureValuator)
-  , m_color(Qt::red)
-  , m_brush(m_color)
-  , m_pen(m_brush, 1.0, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin)
-  , m_deviceDown(false)
+    : QWidget(nullptr), m_brush(m_color)
+    , m_pen(m_brush, 1.0, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin)
 {
     resize(500, 500);
     setAutoFillBackground(true);
@@ -138,7 +133,7 @@ void TabletCanvas::tabletEvent(QTabletEvent *event)
 void TabletCanvas::initPixmap()
 {
     qreal dpr = devicePixelRatioF();
-    QPixmap newPixmap = QPixmap(width() * dpr, height() * dpr);
+    QPixmap newPixmap = QPixmap(qRound(width() * dpr), qRound(height() * dpr));
     newPixmap.setDevicePixelRatio(dpr);
     newPixmap.fill(Qt::white);
     QPainter painter(&newPixmap);
@@ -208,7 +203,7 @@ void TabletCanvas::paintPixmap(QPainter &painter, QTabletEvent *event)
                 const QString error(tr("This input device is not supported by the example."));
 #if QT_CONFIG(statustip)
                 QStatusTipEvent status(error);
-                QApplication::sendEvent(this, &status);
+                QCoreApplication::sendEvent(this, &status);
 #else
                 qWarning() << error;
 #endif
@@ -219,7 +214,7 @@ void TabletCanvas::paintPixmap(QPainter &painter, QTabletEvent *event)
                 const QString error(tr("Unknown tablet device - treating as stylus"));
 #if QT_CONFIG(statustip)
                 QStatusTipEvent status(error);
-                QApplication::sendEvent(this, &status);
+                QCoreApplication::sendEvent(this, &status);
 #else
                 qWarning() << error;
 #endif
@@ -261,7 +256,8 @@ void TabletCanvas::updateBrush(const QTabletEvent *event)
                 m_color.setAlpha(255);
             break;
         case TiltValuator:
-            m_color.setAlpha(maximum(abs(vValue - 127), abs(hValue - 127)));
+            m_color.setAlpha(std::max(std::abs(vValue - 127),
+                                      std::abs(hValue - 127)));
             break;
         default:
             m_color.setAlpha(255);
@@ -288,7 +284,8 @@ void TabletCanvas::updateBrush(const QTabletEvent *event)
             m_pen.setWidthF(pressureToWidth(event->pressure()));
             break;
         case TiltValuator:
-            m_pen.setWidthF(maximum(abs(vValue - 127), abs(hValue - 127)) / 12);
+            m_pen.setWidthF(std::max(std::abs(vValue - 127),
+                                     std::abs(hValue - 127)) / 12);
             break;
         default:
             m_pen.setWidthF(1);
diff --git a/examples/widgets/widgets/tablet/tabletcanvas.h b/examples/widgets/widgets/tablet/tabletcanvas.h
index c63ef76893e..4c10731b0fa 100644
--- a/examples/widgets/widgets/tablet/tabletcanvas.h
+++ b/examples/widgets/widgets/tablet/tabletcanvas.h
@@ -51,14 +51,13 @@
 #ifndef TABLETCANVAS_H
 #define TABLETCANVAS_H
 
-#include <QWidget>
+#include <QBrush>
+#include <QColor>
+#include <QPen>
 #include <QPixmap>
 #include <QPoint>
 #include <QTabletEvent>
-#include <QColor>
-#include <QBrush>
-#include <QPen>
-#include <QPoint>
+#include <QWidget>
 
 QT_BEGIN_NAMESPACE
 class QPaintEvent;
@@ -92,8 +91,6 @@ public:
         { return m_color; }
     void setTabletDevice(QTabletEvent *event)
         { updateCursor(event); }
-    int maximum(int a, int b)
-        { return a > b ? a : b; }
 
 protected:
     void tabletEvent(QTabletEvent *event) override;
@@ -108,19 +105,19 @@ private:
     void updateBrush(const QTabletEvent *event);
     void updateCursor(const QTabletEvent *event);
 
-    Valuator m_alphaChannelValuator;
-    Valuator m_colorSaturationValuator;
-    Valuator m_lineWidthValuator;
-    QColor m_color;
+    Valuator m_alphaChannelValuator = TangentialPressureValuator;
+    Valuator m_colorSaturationValuator = NoValuator;
+    Valuator m_lineWidthValuator = PressureValuator;
+    QColor m_color = Qt::red;
     QPixmap m_pixmap;
     QBrush m_brush;
     QPen m_pen;
-    bool m_deviceDown;
+    bool m_deviceDown = false;
 
     struct Point {
         QPointF pos;
-        qreal pressure;
-        qreal rotation;
+        qreal pressure = 0;
+        qreal rotation = 0;
     } lastPoint;
 };
 //! [0]
diff --git a/examples/widgets/widgets/tetrix/tetrixboard.cpp b/examples/widgets/widgets/tetrix/tetrixboard.cpp
index ef3ac4fc385..c1192f264da 100644
--- a/examples/widgets/widgets/tetrix/tetrixboard.cpp
+++ b/examples/widgets/widgets/tetrix/tetrixboard.cpp
@@ -50,16 +50,16 @@
 
 #include "tetrixboard.h"
 
-#include <QtWidgets>
+#include <QKeyEvent>
+#include <QLabel>
+#include <QPainter>
 
 //! [0]
 TetrixBoard::TetrixBoard(QWidget *parent)
-    : QFrame(parent)
+    : QFrame(parent), isStarted(false), isPaused(false)
 {
     setFrameStyle(QFrame::Panel | QFrame::Sunken);
     setFocusPolicy(Qt::StrongFocus);
-    isStarted = false;
-    isPaused = false;
     clearBoard();
 
     nextPiece.setRandomShape();
@@ -396,7 +396,7 @@ bool TetrixBoard::tryMove(const TetrixPiece &newPiece, int newX, int newY)
 //! [36]
 void TetrixBoard::drawSquare(QPainter &painter, int x, int y, TetrixShape shape)
 {
-    static const QRgb colorTable[8] = {
+    static constexpr QRgb colorTable[8] = {
         0x000000, 0xCC6666, 0x66CC66, 0x6666CC,
         0xCCCC66, 0xCC66CC, 0x66CCCC, 0xDAAA00
     };
diff --git a/examples/widgets/widgets/tetrix/tetrixpiece.cpp b/examples/widgets/widgets/tetrix/tetrixpiece.cpp
index b1b3ca9a99b..9f6f6e863a1 100644
--- a/examples/widgets/widgets/tetrix/tetrixpiece.cpp
+++ b/examples/widgets/widgets/tetrix/tetrixpiece.cpp
@@ -62,7 +62,7 @@ void TetrixPiece::setRandomShape()
 //! [1]
 void TetrixPiece::setShape(TetrixShape shape)
 {
-    static const int coordsTable[8][4][2] = {
+    static constexpr int coordsTable[8][4][2] = {
         { { 0, 0 },   { 0, 0 },   { 0, 0 },   { 0, 0 } },
         { { 0, -1 },  { 0, 0 },   { -1, 0 },  { -1, 1 } },
         { { 0, -1 },  { 0, 0 },   { 1, 0 },   { 1, 1 } },
diff --git a/examples/widgets/widgets/tetrix/tetrixwindow.cpp b/examples/widgets/widgets/tetrix/tetrixwindow.cpp
index 970a38c1dc3..5aa5c3f615d 100644
--- a/examples/widgets/widgets/tetrix/tetrixwindow.cpp
+++ b/examples/widgets/widgets/tetrix/tetrixwindow.cpp
@@ -48,23 +48,24 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-
 #include "tetrixboard.h"
 #include "tetrixwindow.h"
 
+#include <QCoreApplication>
+#include <QGridLayout>
+#include <QLabel>
+#include <QLCDNumber>
+#include <QPushButton>
+
 //! [0]
 TetrixWindow::TetrixWindow(QWidget *parent)
-    : QWidget(parent)
+    : QWidget(parent), board(new TetrixBoard)
 {
-    board = new TetrixBoard;
 //! [0]
-
     nextPieceLabel = new QLabel;
     nextPieceLabel->setFrameStyle(QFrame::Box | QFrame::Raised);
     nextPieceLabel->setAlignment(Qt::AlignCenter);
     board->setNextPieceLabel(nextPieceLabel);
-
 //! [1]
     scoreLcd = new QLCDNumber(5);
     scoreLcd->setSegmentStyle(QLCDNumber::Filled);
@@ -86,7 +87,7 @@ TetrixWindow::TetrixWindow(QWidget *parent)
 
     connect(startButton, &QPushButton::clicked, board, &TetrixBoard::start);
 //! [4] //! [5]
-    connect(quitButton , &QPushButton::clicked, qApp, &QApplication::quit);
+    connect(quitButton , &QPushButton::clicked, qApp, &QCoreApplication::quit);
     connect(pauseButton, &QPushButton::clicked, board, &TetrixBoard::pause);
 #if __cplusplus >= 201402L
     connect(board, &TetrixBoard::scoreChanged,
diff --git a/examples/widgets/widgets/tooltips/main.cpp b/examples/widgets/widgets/tooltips/main.cpp
index 8276b3dc8d3..0890020f77c 100644
--- a/examples/widgets/widgets/tooltips/main.cpp
+++ b/examples/widgets/widgets/tooltips/main.cpp
@@ -48,7 +48,7 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
+#include <QApplication>
 
 #include "sortingbox.h"
 
diff --git a/examples/widgets/widgets/tooltips/sortingbox.cpp b/examples/widgets/widgets/tooltips/sortingbox.cpp
index 685eaa7d1d9..f99c38b2335 100644
--- a/examples/widgets/widgets/tooltips/sortingbox.cpp
+++ b/examples/widgets/widgets/tooltips/sortingbox.cpp
@@ -50,7 +50,13 @@
 
 #include "sortingbox.h"
 
-#include <QtWidgets>
+#include <QMouseEvent>
+#include <QIcon>
+#include <QPainter>
+#include <QRandomGenerator>
+#include <QStyle>
+#include <QToolButton>
+#include <QToolTip>
 
 //! [0]
 SortingBox::SortingBox(QWidget *parent)
@@ -277,12 +283,12 @@ QToolButton *SortingBox::createToolButton(const QString &toolTip,
 QPoint SortingBox::initialItemPosition(const QPainterPath &path)
 {
     int x;
-    int y = (height() - (int)path.controlPointRect().height()) / 2;
+    int y = (height() - qRound(path.controlPointRect().height()) / 2);
     if (shapeItems.size() == 0)
-        x = ((3 * width()) / 2 - (int)path.controlPointRect().width()) / 2;
+        x = ((3 * width()) / 2 - qRound(path.controlPointRect().width())) / 2;
     else
         x = (width() / shapeItems.size()
-             - (int)path.controlPointRect().width()) / 2;
+             - qRound(path.controlPointRect().width())) / 2;
 
     return QPoint(x, y);
 }
diff --git a/examples/widgets/widgets/tooltips/sortingbox.h b/examples/widgets/widgets/tooltips/sortingbox.h
index 3d0cecea2bf..785154746e5 100644
--- a/examples/widgets/widgets/tooltips/sortingbox.h
+++ b/examples/widgets/widgets/tooltips/sortingbox.h
@@ -99,7 +99,7 @@ private:
                                   const char *member);
 
 //! [2]
-    QList<ShapeItem> shapeItems;
+    QVector<ShapeItem> shapeItems;
     QPainterPath circlePath;
     QPainterPath squarePath;
     QPainterPath trianglePath;
diff --git a/examples/widgets/widgets/validators/validatorwidget.cpp b/examples/widgets/widgets/validators/validatorwidget.cpp
index fa0a55aa520..9ddd6409248 100644
--- a/examples/widgets/widgets/validators/validatorwidget.cpp
+++ b/examples/widgets/widgets/validators/validatorwidget.cpp
@@ -50,7 +50,7 @@
 
 #include "validatorwidget.h"
 
-#include <QtWidgets>
+#include <QIntValidator>
 
 ValidatorWidget::ValidatorWidget(QWidget *parent)
     : QWidget(parent)
diff --git a/examples/widgets/widgets/wiggly/wigglywidget.cpp b/examples/widgets/widgets/wiggly/wigglywidget.cpp
index 0399fe90564..ab549ef07c4 100644
--- a/examples/widgets/widgets/wiggly/wigglywidget.cpp
+++ b/examples/widgets/widgets/wiggly/wigglywidget.cpp
@@ -50,11 +50,13 @@
 
 #include "wigglywidget.h"
 
-#include <QtWidgets>
+#include <QFontMetrics>
+#include <QPainter>
+#include <QTimerEvent>
 
 //! [0]
 WigglyWidget::WigglyWidget(QWidget *parent)
-    : QWidget(parent)
+    : QWidget(parent), step(0)
 {
     setBackgroundRole(QPalette::Midlight);
     setAutoFillBackground(true);
@@ -63,7 +65,6 @@ WigglyWidget::WigglyWidget(QWidget *parent)
     newFont.setPointSize(newFont.pointSize() + 20);
     setFont(newFont);
 
-    step = 0;
     timer.start(60, this);
 }
 //! [0]
@@ -72,7 +73,7 @@ WigglyWidget::WigglyWidget(QWidget *parent)
 void WigglyWidget::paintEvent(QPaintEvent * /* event */)
 //! [1] //! [2]
 {
-    static const int sineTable[16] = {
+    static constexpr int sineTable[16] = {
         0, 38, 71, 92, 100, 92, 71, 38, 0, -38, -71, -92, -100, -92, -71, -38
     };
 
diff --git a/examples/widgets/widgets/windowflags/controllerwindow.cpp b/examples/widgets/widgets/windowflags/controllerwindow.cpp
index e2abad89f41..0e9a9169880 100644
--- a/examples/widgets/widgets/windowflags/controllerwindow.cpp
+++ b/examples/widgets/widgets/windowflags/controllerwindow.cpp
@@ -48,10 +48,15 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-
 #include "controllerwindow.h"
 
+#include <QCheckBox>
+#include <QCoreApplication>
+#include <QGroupBox>
+#include <QHBoxLayout>
+#include <QPushButton>
+#include <QRadioButton>
+
 //! [0]
 ControllerWindow::ControllerWindow(QWidget *parent)
     : QWidget(parent)
@@ -63,7 +68,7 @@ ControllerWindow::ControllerWindow(QWidget *parent)
 
     quitButton = new QPushButton(tr("&Quit"));
     connect(quitButton, &QPushButton::clicked,
-            qApp, &QApplication::quit);
+            qApp, &QCoreApplication::quit);
 
     QHBoxLayout *bottomLayout = new QHBoxLayout;
     bottomLayout->addStretch();
@@ -83,26 +88,25 @@ ControllerWindow::ControllerWindow(QWidget *parent)
 //! [1]
 void ControllerWindow::updatePreview()
 {
-    Qt::WindowFlags flags = 0;
+    Qt::WindowFlags flags;
 
-    if (windowRadioButton->isChecked()) {
+    if (windowRadioButton->isChecked())
         flags = Qt::Window;
-    } else if (dialogRadioButton->isChecked()) {
+    else if (dialogRadioButton->isChecked())
         flags = Qt::Dialog;
-    } else if (sheetRadioButton->isChecked()) {
+    else if (sheetRadioButton->isChecked())
         flags = Qt::Sheet;
-    } else if (drawerRadioButton->isChecked()) {
+    else if (drawerRadioButton->isChecked())
         flags = Qt::Drawer;
-    } else if (popupRadioButton->isChecked()) {
+    else if (popupRadioButton->isChecked())
         flags = Qt::Popup;
-    } else if (toolRadioButton->isChecked()) {
+    else if (toolRadioButton->isChecked())
         flags = Qt::Tool;
-    } else if (toolTipRadioButton->isChecked()) {
+    else if (toolTipRadioButton->isChecked())
         flags = Qt::ToolTip;
-    } else if (splashScreenRadioButton->isChecked()) {
+    else if (splashScreenRadioButton->isChecked())
         flags = Qt::SplashScreen;
 //! [1] //! [2]
-    }
 //! [2] //! [3]
 
     if (msWindowsFixedSizeDialogCheckBox->isChecked())
diff --git a/examples/widgets/widgets/windowflags/previewwindow.cpp b/examples/widgets/widgets/windowflags/previewwindow.cpp
index 8773dccb059..d7ebed7b3ca 100644
--- a/examples/widgets/widgets/windowflags/previewwindow.cpp
+++ b/examples/widgets/widgets/windowflags/previewwindow.cpp
@@ -50,7 +50,9 @@
 
 #include "previewwindow.h"
 
-#include <QtWidgets>
+#include <QPushButton>
+#include <QTextEdit>
+#include <QVBoxLayout>
 
 //! [0]
 PreviewWindow::PreviewWindow(QWidget *parent)
@@ -81,23 +83,22 @@ void PreviewWindow::setWindowFlags(Qt::WindowFlags flags)
     QString text;
 
     Qt::WindowFlags type = (flags & Qt::WindowType_Mask);
-    if (type == Qt::Window) {
+    if (type == Qt::Window)
         text = "Qt::Window";
-    } else if (type == Qt::Dialog) {
+    else if (type == Qt::Dialog)
         text = "Qt::Dialog";
-    } else if (type == Qt::Sheet) {
+    else if (type == Qt::Sheet)
         text = "Qt::Sheet";
-    } else if (type == Qt::Drawer) {
+    else if (type == Qt::Drawer)
         text = "Qt::Drawer";
-    } else if (type == Qt::Popup) {
+    else if (type == Qt::Popup)
         text = "Qt::Popup";
-    } else if (type == Qt::Tool) {
+    else if (type == Qt::Tool)
         text = "Qt::Tool";
-    } else if (type == Qt::ToolTip) {
+    else if (type == Qt::ToolTip)
         text = "Qt::ToolTip";
-    } else if (type == Qt::SplashScreen) {
+    else if (type == Qt::SplashScreen)
         text = "Qt::SplashScreen";
-    }
 
     if (flags & Qt::MSWindowsFixedSizeDialogHint)
         text += "\n| Qt::MSWindowsFixedSizeDialogHint";