QtWidget docs: small fixes

Apply some minor fixes to the widget docs
 - use nullptr
 - use c++11 initializer list
 - properly delete widget when cleaning the layout (QTBUG-29471)
 - rework CardLayout example to make it work with Qt5

Fixes: QTBUG-29471
Change-Id: Ie2ee9f75eb8faf97d2bbd2c25e7013d4f30d8dd0
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

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

@@ -53,14 +53,15 @@
 #define CARD_H
 
 #include <QtWidgets>
-#include <QList>
+#include <QVector>
 
 class CardLayout : public QLayout
 {
 public:
-    CardLayout(QWidget *parent, int dist): QLayout(parent, 0, dist) {}
-    CardLayout(QLayout *parent, int dist): QLayout(parent, dist) {}
-    CardLayout(int dist): QLayout(dist) {}
+    CardLayout(int spacing): QLayout()
+    { setSpacing(spacing); }
+    CardLayout(int spacing, QWidget *parent): QLayout(parent)
+    { setSpacing(spacing); }
     ~CardLayout();
 
     void addItem(QLayoutItem *item) override;
@@ -72,7 +73,7 @@ public:
     void setGeometry(const QRect &rect) override;
 
 private:
-    QList<QLayoutItem*> list;
+    QVector<QLayoutItem*> m_items;
 };
 #endif
 //! [0]
@@ -85,23 +86,23 @@ private:
 //! [2]
 int CardLayout::count() const
 {
-    // QList::size() returns the number of QLayoutItems in the list
-    return list.size();
+    // QVector::size() returns the number of QLayoutItems in m_items
+    return m_items.size();
 }
 //! [2]
 
 //! [3]
 QLayoutItem *CardLayout::itemAt(int idx) const
 {
-    // QList::value() performs index checking, and returns 0 if we are
+    // QVector::value() performs index checking, and returns nullptr if we are
     // outside the valid range
-    return list.value(idx);
+    return m_items.value(idx);
 }
 
 QLayoutItem *CardLayout::takeAt(int idx)
 {
-    // QList::take does not do index checking
-    return idx >= 0 && idx < list.size() ? list.takeAt(idx) : 0;
+    // QVector::take does not do index checking
+    return idx >= 0 && idx < m_items.size() ? m_items.takeAt(idx) : 0;
 }
 //! [3]
 
@@ -109,7 +110,7 @@ QLayoutItem *CardLayout::takeAt(int idx)
 //! [4]
 void CardLayout::addItem(QLayoutItem *item)
 {
-    list.append(item);
+    m_items.append(item);
 }
 //! [4]
 
@@ -129,14 +130,14 @@ void CardLayout::setGeometry(const QRect &r)
 {
     QLayout::setGeometry(r);
 
-    if (list.size() == 0)
+    if (m_items.size() == 0)
         return;
 
-    int w = r.width() - (list.count() - 1) * spacing();
-    int h = r.height() - (list.count() - 1) * spacing();
+    int w = r.width() - (m_items.count() - 1) * spacing();
+    int h = r.height() - (m_items.count() - 1) * spacing();
     int i = 0;
-    while (i < list.size()) {
-        QLayoutItem *o = list.at(i);
+    while (i < m_items.size()) {
+        QLayoutItem *o = m_items.at(i);
         QRect geom(r.x() + i * spacing(), r.y() + i * spacing(), w, h);
         o->setGeometry(geom);
         ++i;
@@ -148,29 +149,29 @@ void CardLayout::setGeometry(const QRect &r)
 //! [7]
 QSize CardLayout::sizeHint() const
 {
-    QSize s(0,0);
-    int n = list.count();
+    QSize s(0, 0);
+    int n = m_items.count();
     if (n > 0)
-        s = QSize(100,70); //start with a nice default size
+        s = QSize(100, 70); //start with a nice default size
     int i = 0;
     while (i < n) {
-        QLayoutItem *o = list.at(i);
+        QLayoutItem *o = m_items.at(i);
         s = s.expandedTo(o->sizeHint());
         ++i;
     }
-    return s + n*QSize(spacing(), spacing());
+    return s + n * QSize(spacing(), spacing());
 }
 
 QSize CardLayout::minimumSize() const
 {
-    QSize s(0,0);
-    int n = list.count();
+    QSize s(0, 0);
+    int n = m_items.count();
     int i = 0;
     while (i < n) {
-        QLayoutItem *o = list.at(i);
+        QLayoutItem *o = m_items.at(i);
         s = s.expandedTo(o->minimumSize());
         ++i;
     }
-    return s + n*QSize(spacing(), spacing());
+    return s + n * QSize(spacing(), spacing());
 }
 //! [7]

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

@@ -89,11 +89,10 @@ dialog.setNameFilter("*.cpp *.cc *.C *.cxx *.c++");
 
 
 //! [7]
-QStringList filters;
-filters << "Image files (*.png *.xpm *.jpg)"
-        << "Text files (*.txt)"
-        << "Any files (*)";
-
+const QStringList filters({"Image files (*.png *.xpm *.jpg)",
+                           "Text files (*.txt)",
+                           "Any files (*)"
+                          });
 QFileDialog dialog(this);
 dialog.setNameFilters(filters);
 dialog.exec();
@@ -131,10 +130,10 @@ QString dir = QFileDialog::getExistingDirectory(this, tr("Open Directory"),
 //! [12]
 
 //! [13]
-QStringList mimeTypeFilters;
-mimeTypeFilters << "image/jpeg" // will show "JPEG image (*.jpeg *.jpg *.jpe)
-            << "image/png"  // will show "PNG image (*.png)"
-            << "application/octet-stream"; // will show "All files (*)"
+QStringList mimeTypeFilters({"image/jpeg", // will show "JPEG image (*.jpeg *.jpg *.jpe)
+                             "image/png",  // will show "PNG image (*.png)"
+                             "application/octet-stream" // will show "All files (*)"
+                            });
 
 QFileDialog dialog(this);
 dialog.setMimeTypeFilters(mimeTypeFilters);

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

@@ -53,6 +53,6 @@ QTreeWidget *treeWidget = new QTreeWidget();
 treeWidget->setColumnCount(1);
 QList<QTreeWidgetItem *> items;
 for (int i = 0; i < 10; ++i)
-    items.append(new QTreeWidgetItem((QTreeWidget*)0, QStringList(QString("item: %1").arg(i))));
+    items.append(new QTreeWidgetItem(static_cast<QTreeWidget *>(nullptr), QStringList(QString("item: %1").arg(i))));
 treeWidget->insertTopLevelItems(0, items);
 //! [0]

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

@@ -51,9 +51,10 @@
 //! [0]
 QCoreApplication* createApplication(int &argc, char *argv[])
 {
-    for (int i = 1; i < argc; ++i)
+    for (int i = 1; i < argc; ++i) {
         if (!qstrcmp(argv[i], "-no-gui"))
             return new QCoreApplication(argc, argv);
+    }
     return new QApplication(argc, argv);
 }
 
@@ -187,14 +188,14 @@ for (const QString &command : commands)
 
 
 //! [12]
-QWidget *widget = qApp->widgetAt(x, y);
+QWidget *widget = QApplication::widgetAt(x, y);
 if (widget)
     widget = widget->window();
 //! [12]
 
 
 //! [13]
-QWidget *widget = qApp->widgetAt(point);
+QWidget *widget = QApplication::widgetAt(point);
 if (widget)
     widget = widget->window();
 //! [13]

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

@@ -70,8 +70,9 @@ void MyWidget::paintEvent(QPaintEvent *)
 
 //! [1]
 QLayoutItem *child;
-while ((child = layout->takeAt(0)) != 0) {
+while ((child = layout->takeAt(0)) != nullptr) {
     ...
-    delete child;
+    delete child->widget(); // delete the widget
+    delete child;   // delete the layout item
 }
 //! [1]

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

@@ -52,8 +52,7 @@
 int MyLayout::heightForWidth(int w) const
 {
     if (cache_dirty || cached_width != w) {
-        // not all C++ compilers support "mutable"
-        MyLayout *that = (MyLayout*)this;
+        MyLayout *that = const_cast<MyLayout *>(this);
         int h = calculateHeightForWidth(w);
         that->cached_hfw = h;
         return h;

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

@@ -53,8 +53,8 @@ class MyProxyStyle : public QProxyStyle
 {
 public:
 
-    int styleHint(StyleHint hint, const QStyleOption *option = 0,
-                  const QWidget *widget = 0, QStyleHintReturn *returnData = 0) const override
+    int styleHint(StyleHint hint, const QStyleOption *option = nullptr,
+                  const QWidget *widget = nullptr, QStyleHintReturn *returnData = nullptr) const override
     {
         if (hint == QStyle::SH_UnderlineShortcut)
             return 1;
@@ -72,8 +72,8 @@ public:
 class MyProxyStyle : public QProxyStyle
 {
   public:
-    int styleHint(StyleHint hint, const QStyleOption *option = 0,
-                  const QWidget *widget = 0, QStyleHintReturn *returnData = 0) const override
+    int styleHint(StyleHint hint, const QStyleOption *option = nullptr,
+                  const QWidget *widget = nullptr, QStyleHintReturn *returnData = nullptr) const override
     {
         if (hint == QStyle::SH_UnderlineShortcut)
             return 0;

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

@@ -54,5 +54,5 @@ menubar->addMenu(fileMenu);
 
 
 //! [1]
-QMenuBar *menuBar = new QMenuBar(0);
+QMenuBar *menuBar = new QMenuBar(nullptr);
 //! [1]

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

@@ -56,10 +56,10 @@ splash->show();
 ... // Loading some items
 splash->showMessage("Loaded modules");
 
-qApp->processEvents();
+QCoreApplication::processEvents();
 
 ... // Establishing connections
 splash->showMessage("Established connections");
 
-qApp->processEvents();
+QCoreApplication::processEvents();
 //! [0]

src/widgets/doc/src/widgets-and-layouts/layout.qdoc

@@ -300,7 +300,7 @@
     \list
         \li  A data structure to store the items handled by the layout. Each
             item is a \l{QLayoutItem}{QLayoutItem}. We will use a
-            QList in this example.
+            QVector in this example.
         \li  \l{QLayout::}{addItem()}, how to add items to the layout.
         \li  \l{QLayout::}{setGeometry()}, how to perform the layout.
         \li  \l{QLayout::}{sizeHint()}, the preferred size of the layout.