Polish the image viewer example.

- Open files passed on the command line.
- Point the file dialog to the pictures location
  and use a filter string for the supported types.
- Set the window title according to file name.

Task-number: QTBUG-37203
Task-number: QTBUG-39287
Change-Id: I4e5e43875c3a7544c862c054181e75942939c1d5
Reviewed-by: David Faure <david.faure@kdab.com>

examples/widgets/doc/src/imageviewer.qdoc

@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
 ** Contact: http://www.qt-project.org/legal
 **
 ** This file is part of the documentation of the Qt Toolkit.
@@ -112,15 +112,19 @@
     {ImageViewer}'s appearance.
 
     \snippet widgets/imageviewer/imageviewer.cpp 1
+
+    In the \c open() slot, we show a file dialog to the user. We compile
+    a list of mime types for use as a filter by querying QImageReader
+    for the available mime type names.
+
+    We show the file dialog until a valid file name is entered or
+    the user cancels.
+
+    The function \c loadFile() is used to load the image.
+
     \snippet widgets/imageviewer/imageviewer.cpp 2
 
-    In the \c open() slot, we show a file dialog to the user. The
-    easiest way to create a QFileDialog is to use the static
-    convenience functions. QFileDialog::getOpenFileName() returns an
-    existing file selected by the user. If the user presses \uicontrol
-    Cancel, QFileDialog returns an empty string.
-
-    Unless the file name is a empty string, we check if the file's
+    In the \c loadFile() function, we check if the file's
     format is an image format by constructing a QImage which tries to
     load the image from the file. If the constructor returns a null
     image, we use a QMessageBox to alert the user.
@@ -135,7 +139,6 @@
     information message with an \uicontrol OK button (the default) is
     sufficient, since the message is part of a normal operation.
 
-    \snippet widgets/imageviewer/imageviewer.cpp 3
     \snippet widgets/imageviewer/imageviewer.cpp 4
 
     If the format is supported, we display the image in \c imageLabel

examples/widgets/widgets/imageviewer/imageviewer.cpp

@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
 ** Contact: http://www.qt-project.org/legal
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -61,38 +61,60 @@ ImageViewer::ImageViewer()
     createActions();
     createMenus();
 
-    setWindowTitle(tr("Image Viewer"));
-    resize(500, 400);
+    resize(QGuiApplication::primaryScreen()->availableSize() * 3 / 5);
 }
+
 //! [0]
+//! [2]
+
+bool ImageViewer::loadFile(const QString &fileName)
+{
+    QImage image(fileName);
+    if (image.isNull()) {
+        QMessageBox::information(this, QGuiApplication::applicationDisplayName(),
+                                 tr("Cannot load %1.").arg(QDir::toNativeSeparators(fileName)));
+        setWindowFilePath(QString());
+        imageLabel->setPixmap(QPixmap());
+        imageLabel->adjustSize();
+        return false;
+    }
+//! [2] //! [3]
+    imageLabel->setPixmap(QPixmap::fromImage(image));
+//! [3] //! [4]
+    scaleFactor = 1.0;
+
+    printAct->setEnabled(true);
+    fitToWindowAct->setEnabled(true);
+    updateActions();
+
+    if (!fitToWindowAct->isChecked())
+        imageLabel->adjustSize();
+
+    setWindowFilePath(fileName);
+    return true;
+}
+
+//! [4]
+
+//! [2]
 
 //! [1]
 void ImageViewer::open()
-//! [1] //! [2]
 {
-    QString fileName = QFileDialog::getOpenFileName(this,
-                                    tr("Open File"), QDir::currentPath());
-    if (!fileName.isEmpty()) {
-        QImage image(fileName);
-        if (image.isNull()) {
-            QMessageBox::information(this, tr("Image Viewer"),
-                                     tr("Cannot load %1.").arg(fileName));
-            return;
-        }
-//! [2] //! [3]
-        imageLabel->setPixmap(QPixmap::fromImage(image));
-//! [3] //! [4]
-        scaleFactor = 1.0;
+    QStringList mimeTypeFilters;
+    foreach (const QByteArray &mimeTypeName, QImageReader::supportedMimeTypes())
+        mimeTypeFilters.append(mimeTypeName);
+    mimeTypeFilters.sort();
+    const QStringList picturesLocations = QStandardPaths::standardLocations(QStandardPaths::PicturesLocation);
+    QFileDialog dialog(this, tr("Open File"),
+                       picturesLocations.isEmpty() ? QDir::currentPath() : picturesLocations.first());
+    dialog.setAcceptMode(QFileDialog::AcceptOpen);
+    dialog.setMimeTypeFilters(mimeTypeFilters);
+    dialog.selectMimeTypeFilter("image/jpeg");
 
-        printAct->setEnabled(true);
-        fitToWindowAct->setEnabled(true);
-        updateActions();
-
-        if (!fitToWindowAct->isChecked())
-            imageLabel->adjustSize();
-    }
+    while (dialog.exec() == QDialog::Accepted && !loadFile(dialog.selectedFiles().first())) {}
 }
-//! [4]
+//! [1]
 
 //! [5]
 void ImageViewer::print()

examples/widgets/widgets/imageviewer/imageviewer.h

@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
 ** Contact: http://www.qt-project.org/legal
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -61,6 +61,7 @@ class ImageViewer : public QMainWindow
 
 public:
     ImageViewer();
+    bool loadFile(const QString &);
 
 private slots:
     void open();

examples/widgets/widgets/imageviewer/main.cpp

@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
 ** Contact: http://www.qt-project.org/legal
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -39,13 +39,23 @@
 ****************************************************************************/
 
 #include <QApplication>
+#include <QCommandLineParser>
 
 #include "imageviewer.h"
 
 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
+    QGuiApplication::setApplicationDisplayName(ImageViewer::tr("Image Viewer"));
+    QCommandLineParser commandLineParser;
+    commandLineParser.addHelpOption();
+    commandLineParser.addPositionalArgument(ImageViewer::tr("[file]"), ImageViewer::tr("Image file to open."));
+    commandLineParser.process(QCoreApplication::arguments());
     ImageViewer imageViewer;
+    if (!commandLineParser.positionalArguments().isEmpty()
+        && !imageViewer.loadFile(commandLineParser.positionalArguments().front())) {
+        return -1;
+    }
     imageViewer.show();
     return app.exec();
 }