TestCase: Grow some new functionality on grabImage

Add some meta-information about the image that we can use to do slightly
stronger checks than just blindly poking pixel data (width & height
props).

In addition, when a test of a grabbed image fails (which they certainly do),
it is always nice if we can perform some diagnostics. To this end, add a
save() method to save the grabbed QImage to disk.

Tests for the new functionality are blacklisted on Linux at present, as they do
not yet appear stable, inheriting the other tst_grabImage flakiness.

[ChangeLog][QmlTest] The returned object from TestCase::grabImage now has
'width', 'height', and 'size' properties for additional verification. In
addition, there is a save() method to be able to persist the grabbed
image to disk (for diagnostics purposes, for example).

Change-Id: Ic651e0257102c514c39c3f648c05870f9d9c52e8
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

2 files changed, 62 insertions, 2 deletions

diff --git a/src/imports/testlib/TestCase.qml b/src/imports/testlib/TestCase.qml
index 8c1744a2b2..dbed896c59 100644
--- a/src/imports/testlib/TestCase.qml
+++ b/src/imports/testlib/TestCase.qml
@@ -837,7 +837,14 @@ Item {
 
         Returns a snapshot image object of the given \a item.
 
-        The returned image object has the following methods:
+        The returned image object has the following properties:
+        \list
+        \li width Returns the width of the underlying image (since 5.10)
+        \li height Returns the height of the underlying image (since 5.10)
+        \li size Returns the size of the underlying image (since 5.10)
+        \endlist
+
+        Additionally, the returned image object has the following methods:
         \list
         \li red(x, y) Returns the red channel value of the pixel at \a x, \a y position
         \li green(x, y) Returns the green channel value of the pixel at \a x, \a y position
@@ -858,6 +865,21 @@ Item {
         var newImage = grabImage(rect);
         verify(!newImage.equals(image));
         \endcode
+        \li save(path) Saves the image to the given \a path. If the image cannot
+        be saved, an exception will be thrown. (since 5.10)
+
+        This can be useful to perform postmortem analysis on failing tests, for
+        example:
+
+        \code
+        var image = grabImage(rect);
+        try {
+            compare(image.width, 100);
+        } catch (ex) {
+            image.save("debug.png");
+            throw ex;
+        }
+        \endcode
 
         \endlist
 
diff --git a/src/qmltest/quicktestresult.cpp b/src/qmltest/quicktestresult.cpp
index dc6caf505b..3650df8f3a 100644
--- a/src/qmltest/quicktestresult.cpp
+++ b/src/qmltest/quicktestresult.cpp
@@ -1,5 +1,6 @@
 /****************************************************************************
 **
+** Copyright (C) 2017 Crimson AS <info@crimson.no>
 ** Copyright (C) 2016 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
@@ -61,7 +62,10 @@
 #include <QtCore/QDir>
 #include <QtQuick/qquickwindow.h>
 #include <QtGui/qvector3d.h>
+#include <QtGui/qimagewriter.h>
 #include <QtQml/private/qqmlglobal_p.h>
+#include <QtQml/QQmlEngine>
+#include <QtQml/QQmlContext>
 #include <private/qv4qobjectwrapper_p.h>
 
 #include <algorithm>
@@ -77,6 +81,11 @@ extern bool qWaitForSignal(QObject *obj, const char* signal, int timeout = 5000)
 class Q_QUICK_TEST_EXPORT QuickTestImageObject : public QObject
 {
     Q_OBJECT
+
+    Q_PROPERTY(int width READ width CONSTANT)
+    Q_PROPERTY(int height READ height CONSTANT)
+    Q_PROPERTY(QSize size READ size CONSTANT)
+
 public:
     QuickTestImageObject(const QImage& img, QObject *parent = 0)
         : QObject(parent)
@@ -127,6 +136,33 @@ public Q_SLOTS:
 
         return m_image == other->m_image;
     }
+
+    void save(const QString &filePath)
+    {
+        QImageWriter writer(filePath);
+        if (!writer.write(m_image)) {
+            QQmlEngine *engine = qmlContext(this)->engine();
+            QV4::ExecutionEngine *v4 = QV8Engine::getV4(engine->handle());
+            v4->throwError(QStringLiteral("Can't save to %1: %2").arg(filePath, writer.errorString()));
+        }
+    }
+
+public:
+    int width() const
+    {
+        return m_image.width();
+    }
+
+    int height() const
+    {
+        return m_image.height();
+    }
+
+    QSize size() const
+    {
+        return m_image.size();
+    }
+
 private:
     QImage m_image;
 };
@@ -706,7 +742,9 @@ QObject *QuickTestResult::grabImage(QQuickItem *item)
         QImage grabbed = window->grabWindow();
         QRectF rf(item->x(), item->y(), item->width(), item->height());
         rf = rf.intersected(QRectF(0, 0, grabbed.width(), grabbed.height()));
-        return new QuickTestImageObject(grabbed.copy(rf.toAlignedRect()));
+        QObject *o = new QuickTestImageObject(grabbed.copy(rf.toAlignedRect()));
+        QQmlEngine::setContextForObject(o, qmlContext(this));
+        return o;
     }
     return 0;
 }