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 <[email protected]>
Reviewed-by: Shawn Rutledge <[email protected]>

9 files changed, 98 insertions, 1 deletions

diff --git a/src/qml/qml/qqmlglobal.cpp b/src/qml/qml/qqmlglobal.cpp
index acebb6bac3..b6a1075c67 100644
--- a/src/qml/qml/qqmlglobal.cpp
+++ b/src/qml/qml/qqmlglobal.cpp
@@ -283,6 +283,10 @@ QVariant QQmlColorProvider::fromHslF(double, double, double, double) { return QV
 QVariant QQmlColorProvider::fromHsvF(double, double, double, double) { return QVariant(); }
 QVariant QQmlColorProvider::lighter(const QVariant &, qreal) { return QVariant(); }
 QVariant QQmlColorProvider::darker(const QVariant &, qreal) { return QVariant(); }
+QVariant QQmlColorProvider::alpha(const QVariant &, qreal)
+{
+    return QVariant();
+}
 QVariant QQmlColorProvider::tint(const QVariant &, const QVariant &) { return QVariant(); }
 
 static QQmlColorProvider *colorProvider = nullptr;
diff --git a/src/qml/qml/qqmlglobal_p.h b/src/qml/qml/qqmlglobal_p.h
index 3c540a6124..b0f239e398 100644
--- a/src/qml/qml/qqmlglobal_p.h
+++ b/src/qml/qml/qqmlglobal_p.h
@@ -278,6 +278,7 @@ public:
     virtual QVariant fromHsvF(double, double, double, double);
     virtual QVariant lighter(const QVariant &, qreal);
     virtual QVariant darker(const QVariant &, qreal);
+    virtual QVariant alpha(const QVariant &, qreal);
     virtual QVariant tint(const QVariant &, const QVariant &);
 };
 
diff --git a/src/qml/qml/v8/qqmlbuiltinfunctions.cpp b/src/qml/qml/v8/qqmlbuiltinfunctions.cpp
index 158f05c743..1123949cfa 100644
--- a/src/qml/qml/v8/qqmlbuiltinfunctions.cpp
+++ b/src/qml/qml/v8/qqmlbuiltinfunctions.cpp
@@ -142,6 +142,7 @@ void Heap::QtObject::init(QQmlEngine *qmlEngine)
     o->defineDefaultProperty(QStringLiteral("binding"), QV4::QtObject::method_binding);
 
     if (qmlEngine) {
+        o->defineDefaultProperty(QStringLiteral("alpha"), QV4::QtObject::method_alpha);
         o->defineDefaultProperty(QStringLiteral("lighter"), QV4::QtObject::method_lighter);
         o->defineDefaultProperty(QStringLiteral("darker"), QV4::QtObject::method_darker);
         o->defineDefaultProperty(QStringLiteral("tint"), QV4::QtObject::method_tint);
@@ -692,6 +693,35 @@ ReturnedValue QtObject::method_darker(const FunctionObject *b, const Value *, co
 }
 
 /*!
+    \qmlmethod color Qt::alpha(color baseColor, real value)
+
+    Returns \a baseColor with an alpha value of \a value.
+
+    \a value is a real ranging from 0 (completely transparent) to 1 (completely opaque).
+*/
+ReturnedValue QtObject::method_alpha(const FunctionObject *b, const Value *, const Value *argv,
+                                     int argc)
+{
+    QV4::Scope scope(b);
+    if (argc != 2)
+        THROW_GENERIC_ERROR("Qt.alpha(): Wrong number of arguments provided");
+
+    QVariant v = scope.engine->toVariant(argv[0], -1);
+    if (v.userType() == QMetaType::QString) {
+        bool ok = false;
+        v = QQmlStringConverters::colorFromString(v.toString(), &ok);
+        if (!ok)
+            return QV4::Encode::null();
+    } else if (v.userType() != QMetaType::QColor) {
+        return QV4::Encode::null();
+    }
+
+    qreal value = argv[1].toNumber();
+
+    return scope.engine->fromVariant(QQml_colorProvider()->alpha(v, value));
+}
+
+/*!
     \qmlmethod color Qt::tint(color baseColor, color tintColor)
 
     This function allows tinting one color (\a baseColor) with another (\a tintColor).
@@ -2258,4 +2288,3 @@ ReturnedValue QtObject::method_callLater(const FunctionObject *b, const Value *t
 }
 
 QT_END_NAMESPACE
-
diff --git a/src/qml/qml/v8/qqmlbuiltinfunctions_p.h b/src/qml/qml/v8/qqmlbuiltinfunctions_p.h
index 0e6d815457..8c64e5b1d8 100644
--- a/src/qml/qml/v8/qqmlbuiltinfunctions_p.h
+++ b/src/qml/qml/v8/qqmlbuiltinfunctions_p.h
@@ -114,6 +114,8 @@ struct QtObject : Object
     static ReturnedValue method_matrix4x4(const FunctionObject *b, const Value *thisObject, const Value *argv, int argc);
     static ReturnedValue method_lighter(const FunctionObject *b, const Value *thisObject, const Value *argv, int argc);
     static ReturnedValue method_darker(const FunctionObject *b, const Value *thisObject, const Value *argv, int argc);
+    static ReturnedValue method_alpha(const FunctionObject *b, const Value *thisObject,
+                                      const Value *argv, int argc);
     static ReturnedValue method_tint(const FunctionObject *b, const Value *thisObject, const Value *argv, int argc);
     static ReturnedValue method_formatDate(const FunctionObject *b, const Value *thisObject, const Value *argv, int argc);
     static ReturnedValue method_formatTime(const FunctionObject *b, const Value *thisObject, const Value *argv, int argc);
diff --git a/src/quick/util/qquickglobal.cpp b/src/quick/util/qquickglobal.cpp
index 3ea2f88712..e8439121ca 100644
--- a/src/quick/util/qquickglobal.cpp
+++ b/src/quick/util/qquickglobal.cpp
@@ -123,6 +123,13 @@ public:
         return QVariant::fromValue(color);
     }
 
+    QVariant alpha(const QVariant &var, qreal value) override
+    {
+        QColor color = var.value<QColor>();
+        color.setAlphaF(value);
+        return QVariant::fromValue(color);
+    }
+
     QVariant tint(const QVariant &baseVar, const QVariant &tintVar) override
     {
         QColor tintColor = tintVar.value<QColor>();
diff --git a/src/quick/util/qquickvaluetypes.cpp b/src/quick/util/qquickvaluetypes.cpp
index 2b86fe5ceb..d836946214 100644
--- a/src/quick/util/qquickvaluetypes.cpp
+++ b/src/quick/util/qquickvaluetypes.cpp
@@ -68,6 +68,11 @@ QVariant QQuickColorValueType::darker(qreal factor) const
     return QQml_colorProvider()->darker(this->v, factor);
 }
 
+QVariant QQuickColorValueType::alpha(qreal value) const
+{
+    return QQml_colorProvider()->alpha(this->v, value);
+}
+
 QVariant QQuickColorValueType::tint(QVariant tintColor) const
 {
     return QQml_colorProvider()->tint(this->v, tintColor);
diff --git a/src/quick/util/qquickvaluetypes_p.h b/src/quick/util/qquickvaluetypes_p.h
index b20fc6c0e3..6ddb51b5de 100644
--- a/src/quick/util/qquickvaluetypes_p.h
+++ b/src/quick/util/qquickvaluetypes_p.h
@@ -90,6 +90,7 @@ class QQuickColorValueType
 public:
     Q_INVOKABLE QString toString() const;
 
+    Q_INVOKABLE QVariant alpha(qreal value) const;
     Q_INVOKABLE QVariant lighter(qreal factor = 1.5) const;
     Q_INVOKABLE QVariant darker(qreal factor = 2.0) const;
     Q_INVOKABLE QVariant tint(QVariant factor) const;
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"));