Implement Qt.alpha()

Introduces an easy way to get a version of a color with transparency
(e.g. Qt.alpha("red", 0.5)).

[ChangeLog][QML][General] Added Qt.alpha for easily modifying a color's alpha value

Task-number: QTBUG-77635
Change-Id: Ic724e5fa503ca2ae5157a99eed1b5c913a39239f
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

2 files changed, 48 insertions, 0 deletions

diff --git a/tests/auto/qml/qqmlqt/data/alpha.qml b/tests/auto/qml/qqmlqt/data/alpha.qml
new file mode 100644
index 0000000000..0587f60bc6
--- /dev/null
+++ b/tests/auto/qml/qqmlqt/data/alpha.qml
@@ -0,0 +1,16 @@
+import QtQuick 2.0
+
+QtObject {
+    property variant test1: Qt.alpha(Qt.rgba(1, 0.8, 0.3), 0.5)
+    property variant test2: Qt.alpha()
+    property variant test3: Qt.alpha(Qt.rgba(1, 0.8, 0.3), 0.7)
+    property variant test4: Qt.alpha("red", 0.5);
+    property variant test5: Qt.alpha("perfectred", 0.5); // Non-existent color
+    property variant test6: Qt.alpha(1, 0.5);
+    property variant test7: Qt.alpha(Qt.rgba(1, 0.8, 0.3), 2.8, 10)
+
+    property variant testColor1: Qt.rgba(1, 0.8, 0.3).alpha(0.5)
+    property variant testColor3: Qt.rgba(1, 0.8, 0.3).alpha(0.7)
+    property variant testColor4: Qt.color("red").alpha(0.5);
+    property variant testColor7: Qt.rgba(1, 0.8, 0.3).alpha(2.8, 10);
+}
diff --git a/tests/auto/qml/qqmlqt/tst_qqmlqt.cpp b/tests/auto/qml/qqmlqt/tst_qqmlqt.cpp
index 6c93b46167..da33a46c68 100644
--- a/tests/auto/qml/qqmlqt/tst_qqmlqt.cpp
+++ b/tests/auto/qml/qqmlqt/tst_qqmlqt.cpp
@@ -79,6 +79,7 @@ private slots:
     void font();
     void lighter();
     void darker();
+    void alpha();
     void tint();
     void color();
     void openUrlExternally();
@@ -543,6 +544,37 @@ void tst_qqmlqt::darker()
     QCOMPARE(qvariant_cast<QColor>(object->property("test6")), QColor());
 }
 
+void tst_qqmlqt::alpha()
+{
+    QQmlComponent component(&engine, testFileUrl("alpha.qml"));
+
+    QString warning1 = component.url().toString() + ":5: Error: Qt.alpha(): Wrong number of arguments provided";
+    QString warning2 = component.url().toString() + ":10: Error: Qt.alpha(): Wrong number of arguments provided";
+    QTest::ignoreMessage(QtWarningMsg, qPrintable(warning1));
+    QTest::ignoreMessage(QtWarningMsg, qPrintable(warning2));
+
+    QScopedPointer<QObject> object(component.create());
+    QVERIFY(object != nullptr);
+
+    QCOMPARE(qvariant_cast<QColor>(object->property("test1")),
+             QColor::fromRgbF(1.0, 0.8, 0.3, 0.5));
+    QCOMPARE(qvariant_cast<QColor>(object->property("testColor1")),
+             QColor::fromRgbF(1, 0.8, 0.3, 0.5));
+    QCOMPARE(qvariant_cast<QColor>(object->property("test2")), QColor());
+    QCOMPARE(qvariant_cast<QColor>(object->property("test3")),
+             QColor::fromRgbF(1.0, 0.8, 0.3, 0.7));
+    QCOMPARE(qvariant_cast<QColor>(object->property("testColor3")),
+             QColor::fromRgbF(1, 0.8, 0.3, 0.7));
+
+    QColor alphaRed = QColor("red");
+    alphaRed.setAlphaF(0.5);
+
+    QCOMPARE(qvariant_cast<QColor>(object->property("test4")), alphaRed);
+    QCOMPARE(qvariant_cast<QColor>(object->property("testColor4")), alphaRed);
+    QCOMPARE(qvariant_cast<QColor>(object->property("test5")), QColor());
+    QCOMPARE(qvariant_cast<QColor>(object->property("test6")), QColor());
+}
+
 void tst_qqmlqt::tint()
 {
     QQmlComponent component(&engine, testFileUrl("tint.qml"));