tst_QStaticText: Output verbose message for test failures.

Factor out function to check on the pixel color that
outputs a verbose message on failure.

Change-Id: I2331fe45f35327d1ff8ae547a58d93a2e6fe9184
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>

tests/auto/gui/text/qstatictext/tst_qstatictext.cpp

@@ -610,6 +610,29 @@ void tst_QStaticText::plainTextVsRichText()
     QCOMPARE(imagePlainText, imageRichText);
 }
 
+static bool checkPixels(const QImage &image,
+                        Qt::GlobalColor expectedColor1, Qt::GlobalColor expectedColor2,
+                        QByteArray *errorMessage)
+{
+    const QRgb expectedRgb1 = QColor(expectedColor1).rgba();
+    const QRgb expectedRgb2 = QColor(expectedColor2).rgba();
+
+    for (int x = 0, w = image.width(); x < w; ++x) {
+        for (int y = 0, h = image.height(); y < h; ++y) {
+            const QRgb pixel = image.pixel(x, y);
+            if (pixel != expectedRgb1 && pixel != expectedRgb2) {
+                QString message;
+                QDebug(&message) << "Color mismatch in image" << image
+                    << "at" << x << ',' << y << ':' << showbase << hex << pixel
+                    << "(expected: " << expectedRgb1 << ',' << expectedRgb2 << ')';
+                *errorMessage = message.toLocal8Bit();
+                return false;
+            }
+        }
+    }
+    return true;
+}
+
 void tst_QStaticText::setPenPlainText_data()
 {
     QTest::addColumn<QImage::Format>("format");
@@ -640,13 +663,9 @@ void tst_QStaticText::setPenPlainText()
         p.drawStaticText(0, 0, staticText);
     }
 
-    for (int x=0; x<image.width(); ++x) {
-        for (int y=0; y<image.height(); ++y) {
-            QRgb pixel = image.pixel(x, y);
-            QVERIFY(pixel == QColor(Qt::white).rgba()
-                    || pixel == QColor(Qt::yellow).rgba());
-        }
-    }
+    QByteArray errorMessage;
+    QVERIFY2(checkPixels(image, Qt::yellow, Qt::white, &errorMessage),
+             errorMessage.constData());
 }
 
 void tst_QStaticText::setPenRichText()
@@ -668,14 +687,9 @@ void tst_QStaticText::setPenRichText()
         p.drawStaticText(0, 0, staticText);
     }
 
-    QImage img = image.toImage();
-    for (int x=0; x<img.width(); ++x) {
-        for (int y=0; y<img.height(); ++y) {
-            QRgb pixel = img.pixel(x, y);
-            QVERIFY(pixel == QColor(Qt::white).rgba()
-                    || pixel == QColor(Qt::green).rgba());
-        }
-    }
+    QByteArray errorMessage;
+    QVERIFY2(checkPixels(image.toImage(), Qt::green, Qt::white, &errorMessage),
+             errorMessage.constData());
 }
 
 void tst_QStaticText::richTextOverridesPen()
@@ -697,14 +711,9 @@ void tst_QStaticText::richTextOverridesPen()
         p.drawStaticText(0, 0, staticText);
     }
 
-    QImage img = image.toImage();
-    for (int x=0; x<img.width(); ++x) {
-        for (int y=0; y<img.height(); ++y) {
-            QRgb pixel = img.pixel(x, y);
-            QVERIFY(pixel == QColor(Qt::white).rgba()
-                    || pixel == QColor(Qt::red).rgba());
-        }
-    }
+    QByteArray errorMessage;
+    QVERIFY2(checkPixels(image.toImage(), Qt::red, Qt::white, &errorMessage),
+             errorMessage.constData());
 }
 
 void tst_QStaticText::drawStruckOutText()