QSGDefaultRectangleNode: Fix off-by-one color rendering

Implicit conversion from floating-point to int, which simply truncates
the number's fractional part, may have caused the rectangle fill
to be rendered in a color with some of its RGB components different
by ±1 from the specified value.

For example, the actual on-screen color of the following QML item was
#010101 on 32bit Intel (no antialiasing or alpha channel):

  Rectangle {
      width: 100
      height: 100
      color: '#020202'
  }

This commit improves precision of the calculation by applying qRound()
before the conversion to integer.

Change-Id: Ia849c31ba9872e7a92608245406d178051b21917
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>

2 files changed, 25 insertions, 0 deletions

diff --git a/tests/auto/quick/qquickrectangle/data/color.qml b/tests/auto/quick/qquickrectangle/data/color.qml
new file mode 100644
index 0000000000..56b83d11c7
--- /dev/null
+++ b/tests/auto/quick/qquickrectangle/data/color.qml
@@ -0,0 +1,8 @@
+import QtQuick 2.0
+
+Rectangle {
+    width: 100
+    height: 100
+    color: '#020202'
+}
+
diff --git a/tests/auto/quick/qquickrectangle/tst_qquickrectangle.cpp b/tests/auto/quick/qquickrectangle/tst_qquickrectangle.cpp
index d0cb47c1e3..65c7e387a0 100644
--- a/tests/auto/quick/qquickrectangle/tst_qquickrectangle.cpp
+++ b/tests/auto/quick/qquickrectangle/tst_qquickrectangle.cpp
@@ -28,6 +28,7 @@
 #include <qtest.h>
 #include <QtTest/QSignalSpy>
 
+#include <QtGui/qscreen.h>
 #include <QtQml/qqmlengine.h>
 #include <QtQml/qqmlcomponent.h>
 #include <QtQuick/qquickview.h>
@@ -42,6 +43,7 @@ public:
     tst_qquickrectangle();
 
 private slots:
+    void color();
     void gradient();
     void gradient_border();
     void antialiasing();
@@ -54,6 +56,21 @@ tst_qquickrectangle::tst_qquickrectangle()
 {
 }
 
+void tst_qquickrectangle::color()
+{
+    if (QGuiApplication::primaryScreen()->depth() < 24)
+        QSKIP("This test does not work at display depths < 24");
+
+    QQuickView view;
+    view.setSource(testFileUrl("color.qml"));
+    view.show();
+
+    QVERIFY(QTest::qWaitForWindowExposed(&view));
+
+    QImage image = view.grabWindow();
+    QVERIFY(image.pixel(0,0) == QColor("#020202").rgba());
+}
+
 void tst_qquickrectangle::gradient()
 {
     QQmlComponent component(&engine, testFileUrl("gradient.qml"));