Polish the image gestures example.

- Add a command line parser to properly evaluate help option and
  directory argument, add options to disable gestures.
- Add logging category so that the user can actually see what is
  happening.
- Scale large images.
- Use qreal instead of float.
- Minor polishing: set window title, position file dialog at
  pictures location.

Task-number: QTBUG-37759
Task-number: QTBUG-37203

Change-Id: Ibaf54a13034b150386a8aee476f83a9eba298298
Reviewed-by: Indrajit Tapadar <indrajit.tapadar@digia.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>

examples/widgets/gestures/imagegestures/imagewidget.cpp

@@ -1,7 +1,7 @@
 
 /****************************************************************************
 **
-** 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.
@@ -43,6 +43,8 @@
 
 #include <QtWidgets>
 
+Q_LOGGING_CATEGORY(lcExample, "qt.examples.imagegestures")
+
 //! [constructor]
 ImageWidget::ImageWidget(QWidget *parent)
     : QWidget(parent),
@@ -55,15 +57,17 @@ ImageWidget::ImageWidget(QWidget *parent)
 
 {
     setMinimumSize(QSize(100,100));
-
-//! [enable gestures]
-    grabGesture(Qt::PanGesture);
-    grabGesture(Qt::PinchGesture);
-    grabGesture(Qt::SwipeGesture);
-//! [enable gestures]
 }
 //! [constructor]
 
+void ImageWidget::grabGestures(const QList<Qt::GestureType> &gestures)
+{
+    //! [enable gestures]
+    foreach (Qt::GestureType gesture, gestures)
+        grabGesture(gesture);
+    //! [enable gestures]
+}
+
 //! [event handler]
 bool ImageWidget::event(QEvent *event)
 {
@@ -77,10 +81,10 @@ void ImageWidget::paintEvent(QPaintEvent*)
 {
     QPainter p(this);
 
-    float iw = currentImage.width();
-    float ih = currentImage.height();
-    float wh = height();
-    float ww = width();
+    const qreal iw = currentImage.width();
+    const qreal ih = currentImage.height();
+    const qreal wh = height();
+    const qreal ww = width();
 
     p.translate(ww/2, wh/2);
     p.translate(horizontalOffset, verticalOffset);
@@ -98,11 +102,13 @@ void ImageWidget::mouseDoubleClickEvent(QMouseEvent *)
     verticalOffset = 0;
     horizontalOffset = 0;
     update();
+    qCDebug(lcExample) << "reset on mouse double click";
 }
 
 //! [gesture event handler]
 bool ImageWidget::gestureEvent(QGestureEvent *event)
 {
+    qCDebug(lcExample) << "gestureEvent():" << event->gestures().size();
     if (QGesture *swipe = event->gesture(Qt::SwipeGesture))
         swipeTriggered(static_cast<QSwipeGesture *>(swipe));
     else if (QGesture *pan = event->gesture(Qt::PanGesture))
@@ -126,6 +132,7 @@ void ImageWidget::panTriggered(QPanGesture *gesture)
     }
 #endif
     QPointF delta = gesture->delta();
+    qCDebug(lcExample) << "panTriggered():" << delta;
     horizontalOffset += delta.x();
     verticalOffset += delta.y();
     update();
@@ -135,13 +142,16 @@ void ImageWidget::pinchTriggered(QPinchGesture *gesture)
 {
     QPinchGesture::ChangeFlags changeFlags = gesture->changeFlags();
     if (changeFlags & QPinchGesture::RotationAngleChanged) {
-        qreal value = gesture->property("rotationAngle").toReal();
-        qreal lastValue = gesture->property("lastRotationAngle").toReal();
-        rotationAngle += value - lastValue;
+        const qreal value = gesture->property("rotationAngle").toReal();
+        const qreal lastValue = gesture->property("lastRotationAngle").toReal();
+        const qreal rotationAngleDelta = value - lastValue;
+        rotationAngle += rotationAngleDelta;
+        qCDebug(lcExample) << "pinchTriggered(): rotation by" << rotationAngleDelta << rotationAngle;
     }
     if (changeFlags & QPinchGesture::ScaleFactorChanged) {
         qreal value = gesture->property("scaleFactor").toReal();
         currentStepScaleFactor = value;
+        qCDebug(lcExample) << "pinchTriggered(): " << currentStepScaleFactor;
     }
     if (gesture->state() == Qt::GestureFinished) {
         scaleFactor *= currentStepScaleFactor;
@@ -155,10 +165,13 @@ void ImageWidget::swipeTriggered(QSwipeGesture *gesture)
 {
     if (gesture->state() == Qt::GestureFinished) {
         if (gesture->horizontalDirection() == QSwipeGesture::Left
-            || gesture->verticalDirection() == QSwipeGesture::Up)
+            || gesture->verticalDirection() == QSwipeGesture::Up) {
+            qCDebug(lcExample) << "swipeTriggered(): swipe to previous";
             goPrevImage();
-        else
+        } else {
+            qCDebug(lcExample) << "swipeTriggered(): swipe to next";
             goNextImage();
+        }
         update();
     }
 }
@@ -184,17 +197,22 @@ void ImageWidget::openDirectory(const QString &path)
 
 QImage ImageWidget::loadImage(const QString &fileName)
 {
+    qDebug() << position << files << fileName;
     QImageReader reader(fileName);
+    qCDebug(lcExample) << "loading" << QDir::toNativeSeparators(fileName) << position << '/' << files.size();
     if (!reader.canRead()) {
-        qDebug() << fileName << ": can't load image";
+        qCWarning(lcExample) << QDir::toNativeSeparators(fileName) << ": can't load image";
         return QImage();
     }
 
     QImage image;
     if (!reader.read(&image)) {
-        qDebug() << fileName << ": corrupted image";
+        qCWarning(lcExample) << QDir::toNativeSeparators(fileName) << ": corrupted image: " << reader.errorString();
         return QImage();
     }
+    const QSize maximumSize(2000, 2000); // Reduce in case someone has large photo images.
+    if (image.size().width() > maximumSize.width() || image.height() > maximumSize.height())
+        image = image.scaled(maximumSize, Qt::KeepAspectRatio, Qt::SmoothTransformation);
     return image;
 }
 
@@ -238,7 +256,7 @@ void ImageWidget::goToImage(int index)
         return;
 
     if (index < 0 || index >= files.size()) {
-        qDebug() << "goToImage: invalid index: " << index;
+        qCWarning(lcExample) << "goToImage: invalid index: " << index;
         return;
     }
 

examples/widgets/gestures/imagegestures/imagewidget.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.
@@ -52,6 +52,8 @@ class QPinchGesture;
 class QSwipeGesture;
 QT_END_NAMESPACE
 
+Q_DECLARE_LOGGING_CATEGORY(lcExample)
+
 //! [class definition begin]
 class ImageWidget : public QWidget
 {
@@ -60,6 +62,7 @@ class ImageWidget : public QWidget
 public:
     ImageWidget(QWidget *parent = 0);
     void openDirectory(const QString &path);
+    void grabGestures(const QList<Qt::GestureType> &gestures);
 
 protected:
     bool event(QEvent *event);
@@ -88,11 +91,11 @@ private:
     QImage prevImage, nextImage;
     QImage currentImage;
 
-    float horizontalOffset;
-    float verticalOffset;
-    float rotationAngle;
-    float scaleFactor;
-    float currentStepScaleFactor;
+    qreal horizontalOffset;
+    qreal verticalOffset;
+    qreal rotationAngle;
+    qreal scaleFactor;
+    qreal currentStepScaleFactor;
 //! [class definition end]
 };
 //! [class definition end]

examples/widgets/gestures/imagegestures/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.
@@ -42,17 +42,86 @@
 
 #include "mainwidget.h"
 
+static void showHelp(QCommandLineParser &parser, const QString errorMessage = QString())
+{
+    QString text;
+    QTextStream str(&text);
+    str << "<html><head/><body>";
+    if (!errorMessage.isEmpty())
+        str << "<p>" << errorMessage << "</p>";
+    str << "<pre>" << parser.helpText() << "</pre></body></html>";
+    QMessageBox box(errorMessage.isEmpty() ? QMessageBox::Information : QMessageBox::Warning,
+                    QGuiApplication::applicationDisplayName(), text,
+                    QMessageBox::Ok);
+    box.setTextInteractionFlags(Qt::TextBrowserInteraction);
+    box.exec();
+}
+
 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
+    QCoreApplication::setApplicationVersion(QT_VERSION_STR);
+    QCoreApplication::setApplicationName(QStringLiteral("imagegestures"));
+    QGuiApplication::setApplicationDisplayName(QStringLiteral("Image Gestures Example"));
+
+    QCommandLineParser commandLineParser;
+    const QCommandLineOption disablePanOption("no-pan", "Disable pan gesture");
+    commandLineParser.addOption(disablePanOption);
+    const QCommandLineOption disablePinchOption("no-pinch", "Disable pinch gesture");
+    commandLineParser.addOption(disablePinchOption);
+    const QCommandLineOption disableSwipeOption("no-swipe", "Disable swipe gesture");
+    commandLineParser.addOption(disableSwipeOption);
+    const QCommandLineOption helpOption = commandLineParser.addHelpOption();
+    commandLineParser.addPositionalArgument(QStringLiteral("Directory"),
+                                            QStringLiteral("Directory to display"));
+
+    const QString description = QGuiApplication::applicationDisplayName()
+        + QLatin1String("\n\nEnable \"debug\" on the logging category \"qt.examples.imagegestures\" in order to\n"
+                        "in order to obtain verbose information about Qt's gesture event processing,\n"
+                        "for example by setting the environment variables QT_LOGGING_RULES to\n"
+                        "qt.examples.imagegestures.debug=true\n");
+    commandLineParser.setApplicationDescription(description);
+
+    if (!commandLineParser.parse(QCoreApplication::arguments())) {
+        showHelp(commandLineParser, commandLineParser.errorText());
+        return -1;
+    }
+    if (commandLineParser.isSet(helpOption)) {
+        showHelp(commandLineParser);
+        return 0;
+    }
+
+    QStringList arguments = commandLineParser.positionalArguments();
+    if (!arguments.isEmpty() && !QFileInfo(arguments.front()).isDir()) {
+        showHelp(commandLineParser,
+                 QLatin1Char('"') + QDir::toNativeSeparators(arguments.front())
+                 + QStringLiteral("\" is not a directory."));
+        return -1;
+    }
+
+    QList<Qt::GestureType> gestures;
+    if (!commandLineParser.isSet(disablePanOption))
+        gestures << Qt::PanGesture;
+    if (!commandLineParser.isSet(disablePinchOption))
+        gestures << Qt::PinchGesture;
+    if (!commandLineParser.isSet(disableSwipeOption))
+        gestures << Qt::SwipeGesture;
 
     MainWidget w;
+    w.grabGestures(gestures);
     w.show();
 
-    if (QApplication::arguments().size() > 1)
-        w.openDirectory(QApplication::arguments().at(1));
-    else
-        w.openDirectory(QFileDialog::getExistingDirectory(0, "Select image folder"));
+    if (arguments.isEmpty()) {
+        const QStringList picturesLocations = QStandardPaths::standardLocations(QStandardPaths::PicturesLocation);
+        const QString directory =
+            QFileDialog::getExistingDirectory(&w, "Select image folder",
+                                              picturesLocations.isEmpty() ? QString() : picturesLocations.front());
+        if (directory.isEmpty())
+            return 0;
+        arguments.append(directory);
+    }
+
+    w.openDirectory(arguments.front());
 
     return app.exec();
 }

examples/widgets/gestures/imagegestures/mainwidget.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.
@@ -41,15 +41,28 @@
 #include "imagewidget.h"
 #include "mainwidget.h"
 
+#include <QScreen>
+#include <QGuiApplication>
+#include <QDir>
+
 MainWidget::MainWidget(QWidget *parent)
     : QMainWindow(parent)
+    , imageWidget(new ImageWidget(this))
 {
-    resize(400, 300);
-    imageWidget = new ImageWidget(this);
     setCentralWidget(imageWidget);
+    const QRect screenGeometry = QGuiApplication::primaryScreen()->availableGeometry();
+    QRect geometry(QPoint(0, 0), QSize(screenGeometry.width() * 3 / 4, screenGeometry.height() * 3 / 4));
+    geometry.moveCenter(screenGeometry.center());
+    setGeometry(geometry);
 }
 
 void MainWidget::openDirectory(const QString &path)
 {
+    setWindowTitle(QDir::toNativeSeparators(path));
     imageWidget->openDirectory(path);
 }
+
+void MainWidget::grabGestures(const QList<Qt::GestureType> &gestures)
+{
+    imageWidget->grabGestures(gestures);
+}

examples/widgets/gestures/imagegestures/mainwidget.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.
@@ -51,6 +51,7 @@ class MainWidget : public QMainWindow
 
 public:
     MainWidget(QWidget *parent = 0);
+    void grabGestures(const QList<Qt::GestureType> &gestures);
 
 public slots:
     void openDirectory(const QString &path);