Tests: Un-crash image comparison tests

When (naively) running the tests with High-DPI scaling active, the
test would assert on mismatching image sizes caused by the scaling.
Add an error message parameter to
QQuickVisualTestUtil::compareImages() for use with QVERIFY2, return
false instead of asserting on format/size mismatches and adapt the
usages. Remove duplicate code in tst_qquickwindow.

Change-Id: I76564f4125798fa1e065a0202b686bc7f5ec5680
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

1 files changed, 3 insertions, 39 deletions

diff --git a/tests/auto/quick/qquickwindow/tst_qquickwindow.cpp b/tests/auto/quick/qquickwindow/tst_qquickwindow.cpp
index 578ae56cca..ab101dc1be 100644
--- a/tests/auto/quick/qquickwindow/tst_qquickwindow.cpp
+++ b/tests/auto/quick/qquickwindow/tst_qquickwindow.cpp
@@ -1506,44 +1506,6 @@ void tst_qquickwindow::animationsWhileHidden()
     QTRY_VERIFY(window->isVisible());
 }
 
-// When running on native Nvidia graphics cards on linux, the
-// distance field glyph pixels have a measurable, but not visible
-// pixel error. Use a custom compare function to avoid
-//
-// This was GT-216 with the ubuntu "nvidia-319" driver package.
-// llvmpipe does not show the same issue.
-//
-bool compareImages(const QImage &ia, const QImage &ib)
-{
-    if (ia.size() != ib.size())
-        qDebug() << "images are of different size" << ia.size() << ib.size();
-    Q_ASSERT(ia.size() == ib.size());
-    Q_ASSERT(ia.format() == ib.format());
-
-    int w = ia.width();
-    int h = ia.height();
-    const int tolerance = 5;
-    for (int y=0; y<h; ++y) {
-        const uint *as= (const uint *) ia.constScanLine(y);
-        const uint *bs= (const uint *) ib.constScanLine(y);
-        for (int x=0; x<w; ++x) {
-            uint a = as[x];
-            uint b = bs[x];
-
-            // No tolerance for error in the alpha.
-            if ((a & 0xff000000) != (b & 0xff000000))
-                return false;
-            if (qAbs(qRed(a) - qRed(b)) > tolerance)
-                return false;
-            if (qAbs(qRed(a) - qRed(b)) > tolerance)
-                return false;
-            if (qAbs(qRed(a) - qRed(b)) > tolerance)
-                return false;
-        }
-    }
-    return true;
-}
-
 void tst_qquickwindow::headless()
 {
     QQmlEngine engine;
@@ -1597,7 +1559,9 @@ void tst_qquickwindow::headless()
 
     // Verify that the visual output is the same
     QImage newContent = window->grabWindow();
-    QVERIFY(compareImages(newContent, originalContent));
+    QString errorMessage;
+    QVERIFY2(QQuickVisualTestUtil::compareImages(newContent, originalContent, &errorMessage),
+             qPrintable(errorMessage));
 }
 
 void tst_qquickwindow::noUpdateWhenNothingChanges()