make QScriptEngine::setGlobalObject() work to some extent

JSC requires that the global object is actually a
JSGlobalObject instance, whereas QScriptEngine::setGlobalObject()
allows any object to be set as the global object. The way we
solve this is by proxying from an internal global object to the
custom (user-set) object.

We need to take care that the internal global object is never
actually exposed through our API; a brilliantly named helper
function, toUsableValue(), makes that happen.

Evaluating "var a = 10" with a custom global object doesn't work
yet; the variable always ends up in the internal Global Object.
For variable assignments, JSC appears to bypass the normal
JSObject::put() and instead use
JSGlobalObject::copyGlobals{From,To}(), which means I can't
intercept and proxy the assignments.

This commit enough to get the Context2D example working. There's
another bug with iteration of the built-in Global Object's
properties (non-enumerable properties are always skipped by the
JSC C++ API, whereas with QScriptValueIterator they should not
be), but that's a totally separate issue.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/script/bridge/qscriptvariant.cpp b/src/script/bridge/qscriptvariant.cpp
index 46da70a..752dd09 100644
--- a/src/script/bridge/qscriptvariant.cpp
+++ b/src/script/bridge/qscriptvariant.cpp
@@ -13,6 +13,9 @@
 
 #ifndef QT_NO_SCRIPT
 
+#include "../api/qscriptengine.h"
+#include "../api/qscriptengine_p.h"
+
 #include "Error.h"
 #include "PrototypeFunction.h"
 #include "JSString.h"
@@ -28,6 +31,7 @@ namespace QScript
 {
 
 JSC::UString qtStringToJSCUString(const QString &str);
+QScriptEnginePrivate *scriptEngineFromExec(JSC::ExecState*);
 
 QVariantDelegate::QVariantDelegate(const QVariant &value)
     : m_value(value)
@@ -56,6 +60,8 @@ QScriptObjectDelegate::Type QVariantDelegate::type() const
 static JSC::JSValue JSC_HOST_CALL variantProtoFuncToString(JSC::ExecState *exec, JSC::JSObject*,
                                                            JSC::JSValue thisValue, const JSC::ArgList&)
 {
+    QScriptEnginePrivate *engine = scriptEngineFromExec(exec);
+    thisValue = engine->toUsableValue(thisValue);
     if (!thisValue.isObject(&QScriptObject::info))
         return throwError(exec, JSC::TypeError, "This object is not a QVariant");
     QScriptObjectDelegate *delegate = static_cast<QScriptObject*>(JSC::asObject(thisValue))->delegate();
@@ -69,6 +75,8 @@ static JSC::JSValue JSC_HOST_CALL variantProtoFuncToString(JSC::ExecState *exec,
 static JSC::JSValue JSC_HOST_CALL variantProtoFuncValueOf(JSC::ExecState *exec, JSC::JSObject*,
                                                           JSC::JSValue thisValue, const JSC::ArgList&)
 {
+    QScriptEnginePrivate *engine = scriptEngineFromExec(exec);
+    thisValue = engine->toUsableValue(thisValue);
     if (!thisValue.isObject(&QScriptObject::info))
         return throwError(exec, JSC::TypeError);
     QScriptObjectDelegate *delegate = static_cast<QScriptObject*>(JSC::asObject(thisValue))->delegate();