Rewrite the fetchmore example

- Start in root folder so that large directories (/bin/, Windows)
  are easily reachable
- Remove the line edit and navigate by double clicking instead
  since this is more in line with expectations
- Use a QPlainTextEdit for logging
- Make the log message more informative
- Add icons

Change-Id: Ia3cd7fc143efef80772923291f0b711913aa47be
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
(cherry picked from commit 2393a40ccd455cc2dca410e8a1830856dbfde12d)

examples/widgets/doc/src/fetchmore.qdoc

@@ -34,15 +34,9 @@
 
     \image fetchmore-example.png
 
-
-    This example consists of a dialog where you can enter a directory
-    name in the \uicontrol Directory edit field. The application loads and
-    visualizes all files it finds as you are typing. It is not required
-    to press [Enter] to launch the search.
-
     When you have large - or perhaps even infinite - data sets, you
     will need to add items to the model in batches, and preferably only
-    when the items are needed by the view (i.e., when they are visible
+    when the items are needed by the view (i.e., when they become visible
     in the view).
 
     In this example, we implement \c FileListModel - an item view
@@ -50,6 +44,15 @@
     Window, which sets up the GUI and feeds the model with
     directories.
 
+    The UI consists of a dialog with a list showing the contents
+    of the root directory. Directories can be navigated by double-clicking.
+
+    At the bottom, there is a log window displaying messages when the view
+    asks the model for more data.
+
+    To exercise it, navigate to a large directory (say \c /bin), and scroll
+    to the bottom. Log messages appear showing the data being retrieved.
+
     Let's take a tour of \c {FileListModel}'s code.
 
     \section1 FileListModel Class Definition

examples/widgets/itemviews/fetchmore/filelistmodel.cpp

@@ -54,8 +54,10 @@
 #include <QDir>
 #include <QPalette>
 
+static const int batchSize = 100;
+
 FileListModel::FileListModel(QObject *parent)
-    : QAbstractListModel(parent), fileCount(0)
+    : QAbstractListModel(parent)
 {}
 
 //![4]
@@ -67,24 +69,33 @@ int FileListModel::rowCount(const QModelIndex &parent) const
 QVariant FileListModel::data(const QModelIndex &index, int role) const
 {
     if (!index.isValid())
-        return QVariant();
+        return {};
 
-    if (index.row() >= fileList.size() || index.row() < 0)
+    const int row = index.row();
-        return QVariant();
+    if (row >= fileList.size() || row < 0)
+        return {};
 
-    if (role == Qt::DisplayRole) {
+    switch (role) {
-        return fileList.at(index.row());
+    case Qt::DisplayRole:
-    } else if (role == Qt::BackgroundRole) {
+        return fileList.at(row).fileName();
-        int batch = (index.row() / 100) % 2;
+    case Qt::BackgroundRole: {
-        if (batch == 0)
+        const int batch = row / batchSize;
-            return qApp->palette().base();
+        const QPalette &palette = QGuiApplication::palette();
-        else
+        return (batch % 2) != 0 ? palette.alternateBase() : palette.base();
-            return qApp->palette().alternateBase();
     }
-    return QVariant();
+    case Qt::DecorationRole:
+        return iconProvider.icon(fileList.at(row));
+    }
+    return {};
 }
+
 //![4]
 
+QFileInfo FileListModel::fileInfoAt(const QModelIndex &index) const
+{
+    return fileList.at(index.row());
+}
+
 //![1]
 bool FileListModel::canFetchMore(const QModelIndex &parent) const
 {
@@ -99,19 +110,20 @@ void FileListModel::fetchMore(const QModelIndex &parent)
 {
     if (parent.isValid())
         return;
-    int remainder = fileList.size() - fileCount;
+    const int start = fileCount;
-    int itemsToFetch = qMin(100, remainder);
+    const int remainder = int(fileList.size()) - start;
+    const int itemsToFetch = qMin(batchSize, remainder);
 
     if (itemsToFetch <= 0)
         return;
 
-    beginInsertRows(QModelIndex(), fileCount, fileCount + itemsToFetch - 1);
+    beginInsertRows(QModelIndex(), start, start + itemsToFetch - 1);
 
     fileCount += itemsToFetch;
 
     endInsertRows();
 
-    emit numberPopulated(itemsToFetch);
+    emit numberPopulated(path, start, itemsToFetch, int(fileList.size()));
 }
 //![2]
 
@@ -121,7 +133,8 @@ void FileListModel::setDirPath(const QString &path)
     QDir dir(path);
 
     beginResetModel();
-    fileList = dir.entryList();
+    this->path = path;
+    fileList = dir.entryInfoList(QDir::NoDot | QDir::AllEntries, QDir::Name);
     fileCount = 0;
     endResetModel();
 }

examples/widgets/itemviews/fetchmore/filelistmodel.h

@@ -52,7 +52,8 @@
 #define FILELISTMODEL_H
 
 #include <QAbstractListModel>
-#include <QStringList>
+#include <QFileInfoList>
+#include <QFileIconProvider>
 
 //![0]
 class FileListModel : public QAbstractListModel
@@ -65,8 +66,10 @@ public:
     int rowCount(const QModelIndex &parent = QModelIndex()) const override;
     QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override;
 
+    QFileInfo fileInfoAt(const QModelIndex &) const;
+
 signals:
-    void numberPopulated(int number);
+    void numberPopulated(const QString &path, int start, int number, int total);
 
 public slots:
     void setDirPath(const QString &path);
@@ -76,8 +79,10 @@ protected:
     void fetchMore(const QModelIndex &parent) override;
 
 private:
-    QStringList fileList;
+    QFileInfoList fileList;
-    int fileCount;
+    QString path;
+    QFileIconProvider iconProvider;
+    int fileCount = 0;
 };
 //![0]
 

examples/widgets/itemviews/fetchmore/window.cpp

@@ -56,37 +56,43 @@
 Window::Window(QWidget *parent)
     : QWidget(parent)
 {
-    FileListModel *model = new FileListModel(this);
+    model = new FileListModel(this);
-    model->setDirPath(QLibraryInfo::path(QLibraryInfo::PrefixPath));
+    model->setDirPath(QDir::rootPath());
 
-    QLabel *label = new QLabel(tr("&Directory:"));
+    view = new QListView;
-    QLineEdit *lineEdit = new QLineEdit;
-    label->setBuddy(lineEdit);
-
-    QListView *view = new QListView;
     view->setModel(model);
 
-    logViewer = new QTextBrowser(this);
+    logViewer = new QPlainTextEdit(this);
-    logViewer->setSizePolicy(QSizePolicy(QSizePolicy::Preferred, QSizePolicy::Preferred));
+    logViewer->setReadOnly(true);
+    logViewer->setSizePolicy(QSizePolicy(QSizePolicy::Preferred,
+                                         QSizePolicy::Preferred));
 
-    connect(lineEdit, &QLineEdit::textChanged,
-            model, &FileListModel::setDirPath);
-    connect(lineEdit, &QLineEdit::textChanged,
-            logViewer, &QTextEdit::clear);
     connect(model, &FileListModel::numberPopulated,
             this, &Window::updateLog);
+    connect(view, &QAbstractItemView::activated,
+            this, &Window::activated);
 
-    QGridLayout *layout = new QGridLayout;
+    auto *layout = new QVBoxLayout(this);
-    layout->addWidget(label, 0, 0);
+    layout->addWidget(view);
-    layout->addWidget(lineEdit, 0, 1);
+    layout->addWidget(logViewer);
-    layout->addWidget(view, 1, 0, 1, 2);
-    layout->addWidget(logViewer, 2, 0, 1, 2);
 
-    setLayout(layout);
     setWindowTitle(tr("Fetch More Example"));
 }
 
-void Window::updateLog(int number)
+void Window::updateLog(const QString &path, int start, int number, int total)
 {
-    logViewer->append(tr("%1 items added.").arg(number));
+    const int last = start + number - 1;
+    const QString nativePath = QDir::toNativeSeparators(path);
+    const QString message = tr("%1..%2/%3 items from \"%4\" added.")
+                            .arg(start).arg(last).arg(total).arg(nativePath);
+    logViewer->appendPlainText(message);
+}
+
+void Window::activated(const QModelIndex &index)
+{
+    const QFileInfo fi = model->fileInfoAt(index);
+    if (fi.isDir()) {
+        logViewer->clear();
+        model->setDirPath(fi.absoluteFilePath());
+    }
 }

examples/widgets/itemviews/fetchmore/window.h

@@ -54,9 +54,13 @@
 #include <QWidget>
 
 QT_BEGIN_NAMESPACE
-class QTextBrowser;
+class QModelIndex;
+class QListView;
+class QPlainTextEdit;
 QT_END_NAMESPACE
 
+class FileListModel;
+
 class Window : public QWidget
 {
     Q_OBJECT
@@ -65,10 +69,13 @@ public:
     Window(QWidget *parent = nullptr);
 
 public slots:
-    void updateLog(int number);
+    void updateLog(const QString &path, int start, int number, int total);
+    void activated(const QModelIndex &);
 
 private:
-    QTextBrowser *logViewer;
+    QPlainTextEdit *logViewer;
+    FileListModel *model;
+    QListView *view;
 };
 
 #endif // WINDOW_H