Fix conversion between JavaScript Date and QDateTime

Use JavaScriptCore's conversion functions rather than our own
(incomplete) implementation.
Specifically, this means daylight saving time is finally
handled correctly on Windows.

Task-number: QTBUG-9770
Reviewed-by: Olivier Goffart

2 files changed, 53 insertions, 4 deletions

diff --git a/src/script/api/qscriptengine.cpp b/src/script/api/qscriptengine.cpp
index 655026c..7bccffe 100644
--- a/src/script/api/qscriptengine.cpp
+++ b/src/script/api/qscriptengine.cpp
@@ -438,6 +438,53 @@ qsreal ToNumber(const QString &value)
 
 #endif
 
+static const qsreal MsPerSecond = 1000.0;
+
+static inline int MsFromTime(qsreal t)
+{
+    int r = int(::fmod(t, MsPerSecond));
+    return (r >= 0) ? r : r + int(MsPerSecond);
+}
+
+/*!
+  \internal
+  Converts a JS date value (milliseconds) to a QDateTime (local time).
+*/
+QDateTime MsToDateTime(JSC::ExecState *exec, qsreal t)
+{
+    if (qIsNaN(t))
+        return QDateTime();
+    JSC::GregorianDateTime tm;
+    JSC::msToGregorianDateTime(exec, t, /*output UTC=*/true, tm);
+    int ms = MsFromTime(t);
+    QDateTime convertedUTC = QDateTime(QDate(tm.year + 1900, tm.month + 1, tm.monthDay),
+                                       QTime(tm.hour, tm.minute, tm.second, ms), Qt::UTC);
+    return convertedUTC.toLocalTime();
+}
+
+/*!
+  \internal
+  Converts a QDateTime to a JS date value (milliseconds).
+*/
+qsreal DateTimeToMs(JSC::ExecState *exec, const QDateTime &dt)
+{
+    if (!dt.isValid())
+        return qSNaN();
+    QDateTime utc = dt.toUTC();
+    QDate date = utc.date();
+    QTime time = utc.time();
+    JSC::GregorianDateTime tm;
+    tm.year = date.year() - 1900;
+    tm.month = date.month() - 1;
+    tm.monthDay = date.day();
+    tm.weekDay = date.dayOfWeek();
+    tm.yearDay = date.dayOfYear();
+    tm.hour = time.hour();
+    tm.minute = time.minute();
+    tm.second = time.second();
+    return JSC::gregorianDateTimeToMS(exec, tm, time.msec(), /*inputIsUTC=*/true);
+}
+
 void GlobalClientData::mark(JSC::MarkStack& markStack)
 {
     engine->mark(markStack);
diff --git a/src/script/api/qscriptengine_p.h b/src/script/api/qscriptengine_p.h
index 1b35704..c71465d 100644
--- a/src/script/api/qscriptengine_p.h
+++ b/src/script/api/qscriptengine_p.h
@@ -50,7 +50,6 @@
 #include "bridge/qscriptobject_p.h"
 #include "bridge/qscriptqobject_p.h"
 #include "bridge/qscriptvariant_p.h"
-#include "utils/qscriptdate_p.h"
 
 #include "DateConstructor.h"
 #include "DateInstance.h"
@@ -119,6 +118,9 @@ namespace QScript
     inline QString ToString(qsreal);
 #endif
 
+    QDateTime MsToDateTime(JSC::ExecState *, qsreal);
+    qsreal DateTimeToMs(JSC::ExecState *, const QDateTime &);
+
     //some conversion helper functions
     inline QScriptEnginePrivate *scriptEngineFromExec(const JSC::ExecState *exec);
     bool isFunction(JSC::JSValue value);
@@ -861,7 +863,7 @@ inline JSC::JSValue QScriptEnginePrivate::newDate(JSC::ExecState *exec, qsreal v
 
 inline JSC::JSValue QScriptEnginePrivate::newDate(JSC::ExecState *exec, const QDateTime &value)
 {
-    return newDate(exec, QScript::FromDateTime(value));
+    return newDate(exec, QScript::DateTimeToMs(exec, value));
 }
 
 inline JSC::JSValue QScriptEnginePrivate::newObject()
@@ -994,12 +996,12 @@ inline JSC::UString QScriptEnginePrivate::toString(JSC::ExecState *exec, JSC::JS
     return str;
 }
 
-inline QDateTime QScriptEnginePrivate::toDateTime(JSC::ExecState *, JSC::JSValue value)
+inline QDateTime QScriptEnginePrivate::toDateTime(JSC::ExecState *exec, JSC::JSValue value)
 {
     if (!isDate(value))
         return QDateTime();
     qsreal t = static_cast<JSC::DateInstance*>(JSC::asObject(value))->internalNumber();
-    return QScript::ToDateTime(t, Qt::LocalTime);
+    return QScript::MsToDateTime(exec, t);
 }
 
 inline QObject *QScriptEnginePrivate::toQObject(JSC::ExecState *exec, JSC::JSValue value)