Polish the SimpleTreeModel example

- Fix/silence most clang-tidy/compiler warnings
  * unsigned/int comparison
  * Avoid repeating return / default parameter types
  * Make functions static/use static invocations
  * Use string literals everywhere
  * Use auto * for pointers
  * Streamline code, use ternary operators
  * Move constructor parameters
  * Observe rule of 5 by using Q_DISABLE_COPY_MOVE
- Add some bells && whistles, resize properly, expand all

Complements 25027444a9b53d61a6257dc5f5ce0ffdb3b06f98.

Change-Id: I78f48d187981ecabf69a5d4d42715bad026fa9e6
Reviewed-by: Kai Köhne <kai.koehne@qt.io>
(cherry picked from commit a3e20df03d522bd1b07ac7a85578401f36f290b9)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

examples/widgets/doc/src/simpletreemodel.qdoc

@@ -145,8 +145,9 @@
 
     \snippet itemviews/simpletreemodel/treeitem.cpp 4
 
-    Column data is returned by the \c data() function. The bounds are checked
+    Column data is returned by the \c data() function. We use
-    before accessing the container with the data:
+    the QList::value() convenience function which checks the bounds
+    and returns a default-constructed QVariant in case they are violated:
 
     \snippet itemviews/simpletreemodel/treeitem.cpp 5
 

examples/widgets/itemviews/simpletreemodel/main.cpp

@@ -5,20 +5,28 @@
 
 #include <QApplication>
 #include <QFile>
+#include <QScreen>
 #include <QTreeView>
 
+using namespace Qt::StringLiterals;
+
 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
 
-    QFile file(":/default.txt");
+    QFile file(":/default.txt"_L1);
-    file.open(QIODevice::ReadOnly);
+    file.open(QIODevice::ReadOnly | QIODevice::Text);
-    TreeModel model(file.readAll());
+    TreeModel model(QString::fromUtf8(file.readAll()));
     file.close();
 
     QTreeView view;
     view.setModel(&model);
-    view.setWindowTitle(QObject::tr("Simple Tree Model"));
+    view.setWindowTitle(TreeModel::tr("Simple Tree Model"));
+    for (int c = 0; c < model.columnCount(); ++c)
+        view.resizeColumnToContents(c);
+    view.expandAll();
+    const auto screenSize = view.screen()->availableSize();
+    view.resize({screenSize.width() / 2, screenSize.height() * 2 / 3});
     view.show();
-    return app.exec();
+    return QCoreApplication::exec();
 }

examples/widgets/itemviews/simpletreemodel/treeitem.cpp

@@ -10,8 +10,8 @@
 #include "treeitem.h"
 
 //! [0]
-TreeItem::TreeItem(const QVariantList &data, TreeItem *parent)
+TreeItem::TreeItem(QVariantList data, TreeItem *parent)
-    : m_itemData(data), m_parentItem(parent)
+    : m_itemData(std::move(data)), m_parentItem(parent)
 {}
 //! [0]
 
@@ -25,32 +25,28 @@ void TreeItem::appendChild(std::unique_ptr<TreeItem> &&child)
 //! [2]
 TreeItem *TreeItem::child(int row)
 {
-    if (row < 0 || row >= m_childItems.size())
+    return row >= 0 && row < childCount() ? m_childItems.at(row).get() : nullptr;
-        return nullptr;
-    return m_childItems.at(row).get();
 }
 //! [2]
 
 //! [3]
 int TreeItem::childCount() const
 {
-    return m_childItems.size();
+    return int(m_childItems.size());
 }
 //! [3]
 
 //! [4]
 int TreeItem::columnCount() const
 {
-    return m_itemData.count();
+    return int(m_itemData.count());
 }
 //! [4]
 
 //! [5]
 QVariant TreeItem::data(int column) const
 {
-    if (column < 0 || column >= m_itemData.size())
+    return m_itemData.value(column);
-        return QVariant();
-    return m_itemData.at(column);
 }
 //! [5]
 
@@ -64,11 +60,11 @@ TreeItem *TreeItem::parentItem()
 //! [7]
 int TreeItem::row() const
 {
-    if (!m_parentItem)
+    if (m_parentItem == nullptr)
         return 0;
     const auto it = std::find_if(m_parentItem->m_childItems.cbegin(), m_parentItem->m_childItems.cend(),
                                  [this](const std::unique_ptr<TreeItem> &treeItem) {
-                                     return treeItem.get() == const_cast<TreeItem *>(this);
+                                     return treeItem.get() == this;
                                  });
 
     if (it != m_parentItem->m_childItems.cend())

examples/widgets/itemviews/simpletreemodel/treeitem.h

@@ -11,7 +11,7 @@
 class TreeItem
 {
 public:
-    explicit TreeItem(const QVariantList &data, TreeItem *parentItem = nullptr);
+    explicit TreeItem(QVariantList data, TreeItem *parentItem = nullptr);
 
     void appendChild(std::unique_ptr<TreeItem> &&child);
 

examples/widgets/itemviews/simpletreemodel/treemodel.cpp

@@ -40,14 +40,10 @@ int TreeModel::columnCount(const QModelIndex &parent) const
 //! [3]
 QVariant TreeModel::data(const QModelIndex &index, int role) const
 {
-    if (!index.isValid())
+    if (!index.isValid() || role != Qt::DisplayRole)
-        return QVariant();
+        return {};
-
-    if (role != Qt::DisplayRole)
-        return QVariant();
-
-    auto item = static_cast<TreeItem*>(index.internalPointer());
 
+    const auto *item = static_cast<const TreeItem*>(index.internalPointer());
     return item->data(index.column());
 }
 //! [3]
@@ -55,10 +51,8 @@ QVariant TreeModel::data(const QModelIndex &index, int role) const
 //! [4]
 Qt::ItemFlags TreeModel::flags(const QModelIndex &index) const
 {
-    if (!index.isValid())
+    return index.isValid()
-        return Qt::NoItemFlags;
+        ? QAbstractItemModel::flags(index) : Qt::ItemFlags(Qt::NoItemFlags);
-
-    return QAbstractItemModel::flags(index);
 }
 //! [4]
 
@@ -66,10 +60,8 @@ Qt::ItemFlags TreeModel::flags(const QModelIndex &index) const
 QVariant TreeModel::headerData(int section, Qt::Orientation orientation,
                                int role) const
 {
-    if (orientation == Qt::Horizontal && role == Qt::DisplayRole)
+    return orientation == Qt::Horizontal && role == Qt::DisplayRole
-        return rootItem->data(section);
+        ? rootItem->data(section) : QVariant{};
-
-    return QVariant();
 }
 //! [5]
 
@@ -77,19 +69,15 @@ QVariant TreeModel::headerData(int section, Qt::Orientation orientation,
 QModelIndex TreeModel::index(int row, int column, const QModelIndex &parent) const
 {
     if (!hasIndex(row, column, parent))
-        return QModelIndex();
+        return {};
 
-    TreeItem *parentItem;
+    TreeItem *parentItem = parent.isValid()
+        ? static_cast<TreeItem*>(parent.internalPointer())
+        : rootItem.get();
 
-    if (!parent.isValid())
+    if (auto *childItem = parentItem->child(row))
-        parentItem = rootItem.get();
-    else
-        parentItem = static_cast<TreeItem*>(parent.internalPointer());
-
-    auto childItem = parentItem->child(row);
-    if (childItem)
         return createIndex(row, column, childItem);
-    return QModelIndex();
+    return {};
 }
 //! [6]
 
@@ -97,29 +85,25 @@ QModelIndex TreeModel::index(int row, int column, const QModelIndex &parent) con
 QModelIndex TreeModel::parent(const QModelIndex &index) const
 {
     if (!index.isValid())
-        return QModelIndex();
+        return {};
 
-    TreeItem *childItem = static_cast<TreeItem*>(index.internalPointer());
+    auto *childItem = static_cast<TreeItem*>(index.internalPointer());
     TreeItem *parentItem = childItem->parentItem();
 
-    if (parentItem == rootItem.get())
+    return parentItem != rootItem.get()
-        return QModelIndex();
+        ? createIndex(parentItem->row(), 0, parentItem) : QModelIndex{};
-
-    return createIndex(parentItem->row(), 0, parentItem);
 }
 //! [7]
 
 //! [8]
 int TreeModel::rowCount(const QModelIndex &parent) const
 {
-    TreeItem *parentItem;
     if (parent.column() > 0)
         return 0;
 
-    if (!parent.isValid())
+    const TreeItem *parentItem = parent.isValid()
-        parentItem = rootItem.get();
+        ? static_cast<const TreeItem*>(parent.internalPointer())
-    else
+        : rootItem.get();
-        parentItem = static_cast<TreeItem*>(parent.internalPointer());
 
     return parentItem->childCount();
 }

examples/widgets/itemviews/simpletreemodel/treemodel.h

@@ -16,21 +16,23 @@ class TreeModel : public QAbstractItemModel
     Q_OBJECT
 
 public:
+    Q_DISABLE_COPY_MOVE(TreeModel)
+
     explicit TreeModel(const QString &data, QObject *parent = nullptr);
-    ~TreeModel();
+    ~TreeModel() override;
 
     QVariant data(const QModelIndex &index, int role) const override;
     Qt::ItemFlags flags(const QModelIndex &index) const override;
     QVariant headerData(int section, Qt::Orientation orientation,
                         int role = Qt::DisplayRole) const override;
     QModelIndex index(int row, int column,
-                      const QModelIndex &parent = QModelIndex()) const override;
+                      const QModelIndex &parent = {}) const override;
     QModelIndex parent(const QModelIndex &index) const override;
-    int rowCount(const QModelIndex &parent = QModelIndex()) const override;
+    int rowCount(const QModelIndex &parent = {}) const override;
-    int columnCount(const QModelIndex &parent = QModelIndex()) const override;
+    int columnCount(const QModelIndex &parent = {}) const override;
 
 private:
-    void setupModelData(const QStringList &lines, TreeItem *parent);
+    static void setupModelData(const QStringList &lines, TreeItem *parent);
 
     std::unique_ptr<TreeItem> rootItem;
 };