Cleanup QtWidgets (widgets) examples

Cleanup QtWidgets widgets examples:
 - use member-init (clang-tidy)
 - fix includes/don't include QtWidgets globally
 - include own header first
 - use nullptr (clang-tidy)
 - avoid c-style casts
 - use QVector instead QList

Change-Id: Ib56bb507eb2ef885f1ddc664050d3c7af92adb70
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

3 files changed, 14 insertions, 13 deletions

diff --git a/examples/widgets/widgets/tetrix/tetrixboard.cpp b/examples/widgets/widgets/tetrix/tetrixboard.cpp
index ef3ac4fc38..c1192f264d 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 b1b3ca9a99..9f6f6e863a 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 970a38c1dc..5aa5c3f615 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,