Split ScriptRequest in its own header.

We often only need to include ScriptRequest.h and not the full
ScriptInterface.h

Differential Revision: https://code.wildfiregames.com/D3920
This was SVN commit r25366.

source/scriptinterface/ScriptForward.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2020 Wildfire Games.
+/* Copyright (C) 2021 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -36,6 +36,17 @@
 
 #include "js/TypeDecls.h"
 
+// Complete with a few additional ones.
+namespace JS
+{
+class HandleValueArray;
+}
+
+namespace js {
+class BaseProxyHandler;
+}
+
+class ScriptContext;
 class ScriptInterface;
 class ScriptRequest;
 

source/scriptinterface/ScriptInterface.cpp

@@ -71,11 +71,18 @@ struct ScriptInterface_impl
 		JS::PersistentRootedObject m_nativeScope; // native function scope object
 };
 
+/**
+ * Constructor for ScriptRequest - here because it needs access into ScriptInterface_impl.
+ */
 ScriptRequest::ScriptRequest(const ScriptInterface& scriptInterface) :
-	cx(scriptInterface.m->m_cx), nativeScope(scriptInterface.m->m_nativeScope)
+	cx(scriptInterface.m->m_cx), glob(scriptInterface.m->m_glob), nativeScope(scriptInterface.m->m_nativeScope)
 {
 	m_formerRealm = JS::EnterRealm(cx, scriptInterface.m->m_glob);
-	glob = JS::CurrentGlobalOrNull(cx);
+}
+
+ScriptRequest::~ScriptRequest()
+{
+	JS::LeaveRealm(cx, m_formerRealm);
 }
 
 JS::Value ScriptRequest::globalValue() const
@@ -83,10 +90,6 @@ JS::Value ScriptRequest::globalValue() const
 	return JS::ObjectValue(*glob);
 }
 
-ScriptRequest::~ScriptRequest()
-{
-	JS::LeaveRealm(cx, m_formerRealm);
-}
 
 namespace
 {

source/scriptinterface/ScriptInterface.h

@@ -22,6 +22,7 @@
 #include "maths/Fixed.h"
 #include "ps/Errors.h"
 #include "scriptinterface/ScriptExceptions.h"
+#include "scriptinterface/ScriptRequest.h"
 #include "scriptinterface/ScriptTypes.h"
 
 #include <map>
@@ -59,34 +60,6 @@ extern thread_local shared_ptr<ScriptContext> g_ScriptContext;
 
 namespace boost { namespace random { class rand48; } }
 
-/**
- * RAII structure which encapsulates an access to the context and compartment of a ScriptInterface.
- * This struct provides:
- * - a pointer to the context, while acting like JSAutoRequest
- * - a pointer to the global object of the compartment, while acting like JSAutoRealm
- *
- * This way, getting and using those pointers is safe with respect to the GC
- * and to the separation of compartments.
- */
-class ScriptRequest
-{
-public:
-	ScriptRequest() = delete;
-	ScriptRequest(const ScriptRequest& rq) = delete;
-	ScriptRequest& operator=(const ScriptRequest& rq) = delete;
-	ScriptRequest(const ScriptInterface& scriptInterface);
-	ScriptRequest(const ScriptInterface* scriptInterface) : ScriptRequest(*scriptInterface) {}
-	ScriptRequest(shared_ptr<ScriptInterface> scriptInterface) : ScriptRequest(*scriptInterface) {}
-	~ScriptRequest();
-
-	JS::Value globalValue() const;
-	JSContext* cx;
-	JSObject* glob;
-	JS::HandleObject nativeScope;
-private:
-	JS::Realm* m_formerRealm;
-};
-
 /**
  * Abstraction around a SpiderMonkey JS::Realm.
  *

source/scriptinterface/ScriptRequest.h

@@ -0,0 +1,83 @@
+/* Copyright (C) 2021 Wildfire Games.
+ * This file is part of 0 A.D.
+ *
+ * 0 A.D. is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 0 A.D. is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef INCLUDED_SCRIPTREQUEST
+#define INCLUDED_SCRIPTREQUEST
+
+#include "scriptinterface/ScriptForward.h"
+
+// Ignore warnings in SM headers.
+#if GCC_VERSION || CLANG_VERSION
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Wunused-parameter"
+# pragma GCC diagnostic ignored "-Wnon-virtual-dtor"
+#elif MSC_VERSION
+# pragma warning(push, 1)
+#endif
+
+#include "js/RootingAPI.h"
+
+#if GCC_VERSION || CLANG_VERSION
+# pragma GCC diagnostic pop
+#elif MSC_VERSION
+# pragma warning(pop)
+#endif
+
+#include <memory>
+
+class ScriptInterface;
+
+/**
+ * Spidermonkey maintains some 'local' state via the JSContext* object.
+ * This object is an argument to most JSAPI functions.
+ * Furthermore, this state is Realm (~ global) dependent. For many reasons, including GC safety,
+ * The JSContext* Realm must be set up correctly when accessing it.
+ * 'Entering' and 'Leaving' realms must be done in a LIFO manner.
+ * SM recommends using JSAutoRealm, which provides an RAII option.
+ *
+ * ScriptRequest combines both of the above in a single convenient package,
+ * providing safe access to the JSContext*, the global object, and ensuring that the proper realm has been entered.
+ * Most scriptinterface/ functions will take a ScriptRequest, to ensure proper rooting. You may sometimes
+ * have to create one from a ScriptInterface.
+ *
+ * Be particularly careful when manipulating several script interfaces.
+ */
+class ScriptRequest
+{
+	ScriptRequest() = delete;
+	ScriptRequest(const ScriptRequest& rq) = delete;
+	ScriptRequest& operator=(const ScriptRequest& rq) = delete;
+public:
+	/**
+	 * NB: the definitions are in scriptinterface.cpp, because these access members of the PImpled
+	 * implementation of ScriptInterface, and that seemed more convenient.
+	 */
+	ScriptRequest(const ScriptInterface& scriptInterface);
+	ScriptRequest(const ScriptInterface* scriptInterface) : ScriptRequest(*scriptInterface) {}
+	ScriptRequest(std::shared_ptr<ScriptInterface> scriptInterface) : ScriptRequest(*scriptInterface) {}
+	~ScriptRequest();
+
+	JS::Value globalValue() const;
+	JSContext* cx;
+	JS::HandleObject glob;
+	JS::HandleObject nativeScope;
+private:
+	JS::Realm* m_formerRealm;
+};
+
+
+#endif // INCLUDED_SCRIPTREQUEST