QJSEngine: Add efficient conversions for QDateTime and friends

The JavaScript date and time conversions are different from Qt's. Add
them to coerceValue.

Task-number: QTBUG-109380
Change-Id: Ic0d7dd8ff51fb8e29d80d9084d4415becaa76259
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

2 files changed, 50 insertions, 3 deletions

diff --git a/src/qml/jsapi/qjsengine.cpp b/src/qml/jsapi/qjsengine.cpp
index 54efde52d7..add8626691 100644
--- a/src/qml/jsapi/qjsengine.cpp
+++ b/src/qml/jsapi/qjsengine.cpp
@@ -12,6 +12,7 @@
 #include "private/qv4globalobject_p.h"
 #include "private/qv4script_p.h"
 #include "private/qv4runtime_p.h"
+#include <private/qv4dateobject_p.h>
 #include <private/qqmlbuiltinfunctions_p.h>
 #include <private/qqmldebugconnector_p.h>
 #include <private/qv4qobjectwrapper_p.h>
@@ -953,6 +954,16 @@ QString QJSEngine::convertQObjectToString(QObject *object)
                 handle(), object ? object->metaObject() : nullptr, object);
 }
 
+QString QJSEngine::convertDateTimeToString(const QDateTime &dateTime)
+{
+    return QV4::DateObject::dateTimeToString(dateTime, handle());
+}
+
+QDate QJSEngine::convertDateTimeToDate(const QDateTime &dateTime)
+{
+    return QV4::DateObject::dateTimeToDate(dateTime);
+}
+
 /*! \fn template <typename T> QJSValue QJSEngine::toScriptValue(const T &value)
 
     Creates a QJSValue with the given \a value.
diff --git a/src/qml/jsapi/qjsengine.h b/src/qml/jsapi/qjsengine.h
index d5a8eaef15..11f1788701 100644
--- a/src/qml/jsapi/qjsengine.h
+++ b/src/qml/jsapi/qjsengine.h
@@ -9,6 +9,7 @@
 #include <QtCore/qvariant.h>
 #include <QtCore/qsharedpointer.h>
 #include <QtCore/qobject.h>
+#include <QtCore/qtimezone.h>
 #include <QtQml/qjsvalue.h>
 #include <QtQml/qjsmanagedvalue.h>
 #include <QtQml/qqmldebug.h>
@@ -201,9 +202,41 @@ public:
         if constexpr (std::is_same_v<To, QVariant>)
             return QVariant::fromValue(from);
 
-        if constexpr (std::is_same_v<To, QString>
-                && std::is_base_of_v<QObject, std::remove_const_t<std::remove_pointer_t<From>>>) {
-            return convertQObjectToString(from);
+        if constexpr (std::is_same_v<To, QString>) {
+            if constexpr (std::is_base_of_v<QObject, std::remove_const_t<std::remove_pointer_t<From>>>)
+                return convertQObjectToString(from);
+        }
+
+        if constexpr (std::is_same_v<From, QDateTime>) {
+            if constexpr (std::is_same_v<To, QDate>)
+                return convertDateTimeToDate(from.toLocalTime());
+            if constexpr (std::is_same_v<To, QTime>)
+                return from.toLocalTime().time();
+            if constexpr (std::is_same_v<To, QString>)
+                return convertDateTimeToString(from.toLocalTime());
+        }
+
+        if constexpr (std::is_same_v<From, QDate>) {
+            if constexpr (std::is_same_v<To, QDateTime>)
+                return from.startOfDay(QTimeZone::UTC);
+            if constexpr (std::is_same_v<To, QTime>) {
+                // This is the current time zone offset, for better or worse
+                return coerceValue<QDateTime, QTime>(coerceValue<QDate, QDateTime>(from));
+            }
+            if constexpr (std::is_same_v<To, QString>)
+                return convertDateTimeToString(coerceValue<QDate, QDateTime>(from));
+        }
+
+        if constexpr (std::is_same_v<From, QTime>) {
+            if constexpr (std::is_same_v<To, QDate>) {
+                // Yes. April Fools' 1971. See qv4dateobject.cpp.
+                return from.isValid() ? QDate(1971, 4, 1) : QDate();
+            }
+
+            if constexpr (std::is_same_v<To, QDateTime>)
+                return QDateTime(coerceValue<QTime, QDate>(from), from, QTimeZone::LocalTime);
+            if constexpr (std::is_same_v<To, QString>)
+                return convertDateTimeToString(coerceValue<QTime, QDateTime>(from));
         }
 
         if constexpr (std::is_same_v<To, std::remove_const_t<std::remove_pointer_t<To>> const *>) {
@@ -280,7 +313,10 @@ private:
 
     bool convertVariant(const QVariant &value, QMetaType metaType, void *ptr);
     bool convertMetaType(QMetaType fromType, const void *from, QMetaType toType, void *to);
+
     QString convertQObjectToString(QObject *object);
+    QString convertDateTimeToString(const QDateTime &dateTime);
+    static QDate convertDateTimeToDate(const QDateTime &dateTime);
 
     template<typename T>
     friend inline T qjsvalue_cast(const QJSValue &);