1 files changed, 35 insertions, 0 deletions
diff --git a/tests/auto/quick/shared/visualtestutil.cpp b/tests/auto/quick/shared/visualtestutil.cpp
index 3e18c83ee2..eabfe5368b 100644
--- a/tests/auto/quick/shared/visualtestutil.cpp
+++ b/tests/auto/quick/shared/visualtestutil.cpp
@@ -61,3 +61,38 @@ void QQuickVisualTestUtil::dumpTree(QQuickItem *parent, int depth)
     }
 }
 
+// A custom compare function to avoid issues such as:
+// When running on native Nvidia graphics cards on linux, the
+// distance field glyph pixels have a measurable, but not visible
+// pixel error. This was GT-216 with the ubuntu "nvidia-319" driver package.
+// llvmpipe does not show the same issue.
+bool QQuickVisualTestUtil::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;
+}