gecko/content/xbl/src/nsXBLProtoImpl.cpp

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 * 1.1 (the "License"); you may not use this file except in compliance with
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 *
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 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Mozilla Communicator client code.
 *
 * The Initial Developer of the Original Code is
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 * Portions created by the Initial Developer are Copyright (C) 1998
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   David Hyatt <hyatt@netscape.com> (Original Author)
 *
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#include "nsXBLProtoImpl.h"
#include "nsIContent.h"
#include "nsIDocument.h"
#include "nsContentUtils.h"
#include "nsIScriptGlobalObject.h"
#include "nsIScriptGlobalObjectOwner.h"
#include "nsIScriptContext.h"
#include "nsIXPConnect.h"
#include "nsIServiceManager.h"
#include "nsIDOMNode.h"
#include "nsXBLPrototypeBinding.h"

// Checks that the version is not modified in a given scope.
class AutoVersionChecker
{
  JSContext * const cx;
  JSVersion versionBefore;

public:
  explicit AutoVersionChecker(JSContext *cx) : cx(cx) {
#ifdef DEBUG
    versionBefore = JS_GetVersion(cx);
#endif
  }

  ~AutoVersionChecker() {
#ifdef DEBUG
    JSVersion versionAfter = JS_GetVersion(cx);
    NS_ABORT_IF_FALSE(versionAfter == versionBefore, "version must not change");
#endif
  }
};

nsresult
nsXBLProtoImpl::InstallImplementation(nsXBLPrototypeBinding* aBinding, nsIContent* aBoundElement)
{
  // This function is called to install a concrete implementation on a bound element using
  // this prototype implementation as a guide.  The prototype implementation is compiled lazily,
  // so for the first bound element that needs a concrete implementation, we also build the
  // prototype implementation.
  if (!mMembers && !mFields)  // Constructor and destructor also live in mMembers
    return NS_OK; // Nothing to do, so let's not waste time.

  // If the way this gets the script context changes, fix
  // nsXBLProtoImplAnonymousMethod::Execute
  nsIDocument* document = aBoundElement->OwnerDoc();
  if (!document) return NS_OK;

  nsIScriptGlobalObject *global = document->GetScopeObject();
  if (!global) return NS_OK;

  nsCOMPtr<nsIScriptContext> context = global->GetContext();
  if (!context) return NS_OK;

  // InitTarget objects gives us back the JS object that represents the bound element and the
  // class object in the bound document that represents the concrete version of this implementation.
  // This function also has the side effect of building up the prototype implementation if it has
  // not been built already.
  nsCOMPtr<nsIXPConnectJSObjectHolder> holder;
  void * targetClassObject = nsnull;
  nsresult rv = InitTargetObjects(aBinding, context, aBoundElement,
                                  getter_AddRefs(holder), &targetClassObject);
  NS_ENSURE_SUCCESS(rv, rv); // kick out if we were unable to properly intialize our target objects

  JSObject * targetScriptObject;
  holder->GetJSObject(&targetScriptObject);

  JSContext *cx = context->GetNativeContext();

  AutoVersionChecker avc(cx);
  
  // Walk our member list and install each one in turn.
  for (nsXBLProtoImplMember* curr = mMembers;
       curr;
       curr = curr->GetNext())
    curr->InstallMember(context, aBoundElement, targetScriptObject,
                        targetClassObject, mClassName);

  return NS_OK;
}

nsresult 
nsXBLProtoImpl::InitTargetObjects(nsXBLPrototypeBinding* aBinding,
                                  nsIScriptContext* aContext, 
                                  nsIContent* aBoundElement, 
                                  nsIXPConnectJSObjectHolder** aScriptObjectHolder, 
                                  void** aTargetClassObject)
{
  nsresult rv = NS_OK;
  *aScriptObjectHolder = nsnull;
  
  if (!mClassObject) {
    rv = CompilePrototypeMembers(aBinding); // This is the first time we've ever installed this binding on an element.
                                 // We need to go ahead and compile all methods and properties on a class
                                 // in our prototype binding.
    if (NS_FAILED(rv))
      return rv;

    if (!mClassObject)
      return NS_OK; // This can be ok, if all we've got are fields (and no methods/properties).
  }

  nsIDocument *ownerDoc = aBoundElement->OwnerDoc();
  nsIScriptGlobalObject *sgo;

  if (!ownerDoc || !(sgo = ownerDoc->GetScopeObject())) {
    return NS_ERROR_UNEXPECTED;
  }

  // Because our prototype implementation has a class, we need to build up a corresponding
  // class for the concrete implementation in the bound document.
  JSContext* jscontext = aContext->GetNativeContext();
  JSObject* global = sgo->GetGlobalJSObject();
  nsCOMPtr<nsIXPConnectJSObjectHolder> wrapper;
  jsval v;
  rv = nsContentUtils::WrapNative(jscontext, global, aBoundElement, &v,
                                  getter_AddRefs(wrapper));
  NS_ENSURE_SUCCESS(rv, rv);

  // All of the above code was just obtaining the bound element's script object and its immediate
  // concrete base class.  We need to alter the object so that our concrete class is interposed
  // between the object and its base class.  We become the new base class of the object, and the
  // object's old base class becomes the new class' base class.
  rv = aBinding->InitClass(mClassName, jscontext, global, JSVAL_TO_OBJECT(v),
                           aTargetClassObject);
  if (NS_FAILED(rv))
    return rv;

  nsContentUtils::PreserveWrapper(aBoundElement, aBoundElement);

  wrapper.swap(*aScriptObjectHolder);
  
  return rv;
}

nsresult
nsXBLProtoImpl::CompilePrototypeMembers(nsXBLPrototypeBinding* aBinding)
{
  // We want to pre-compile our implementation's members against a "prototype context". Then when we actually 
  // bind the prototype to a real xbl instance, we'll clone the pre-compiled JS into the real instance's 
  // context.
  nsCOMPtr<nsIScriptGlobalObjectOwner> globalOwner(
      do_QueryObject(aBinding->XBLDocumentInfo()));
  nsIScriptGlobalObject* globalObject = globalOwner->GetScriptGlobalObject();
  NS_ENSURE_TRUE(globalObject, NS_ERROR_UNEXPECTED);

  nsIScriptContext *context = globalObject->GetContext();
  NS_ENSURE_TRUE(context, NS_ERROR_OUT_OF_MEMORY);

  JSContext *cx = context->GetNativeContext();
  JSObject *global = globalObject->GetGlobalJSObject();
  

  void* classObject;
  nsresult rv = aBinding->InitClass(mClassName, cx, global, global,
                                    &classObject);
  if (NS_FAILED(rv))
    return rv;

  mClassObject = (JSObject*) classObject;
  if (!mClassObject)
    return NS_ERROR_FAILURE;

  AutoVersionChecker avc(cx);

  // Now that we have a class object installed, we walk our member list and compile each of our
  // properties and methods in turn.
  for (nsXBLProtoImplMember* curr = mMembers;
       curr;
       curr = curr->GetNext()) {
    nsresult rv = curr->CompileMember(context, mClassName, mClassObject);
    if (NS_FAILED(rv)) {
      DestroyMembers();
      return rv;
    }
  }

  return NS_OK;
}

void
nsXBLProtoImpl::Trace(TraceCallback aCallback, void *aClosure) const
{
  // If we don't have a class object then we either didn't compile members
  // or we only have fields, in both cases there are no cycles through our
  // members.
  if (!mClassObject) {
    return;
  }

  nsXBLProtoImplMember *member;
  for (member = mMembers; member; member = member->GetNext()) {
    member->Trace(aCallback, aClosure);
  }
}

void
nsXBLProtoImpl::UnlinkJSObjects()
{
  if (mClassObject) {
    DestroyMembers();
  }
}

nsXBLProtoImplField*
nsXBLProtoImpl::FindField(const nsString& aFieldName) const
{
  for (nsXBLProtoImplField* f = mFields; f; f = f->GetNext()) {
    if (aFieldName.Equals(f->GetName())) {
      return f;
    }
  }

  return nsnull;
}

bool
nsXBLProtoImpl::ResolveAllFields(JSContext *cx, JSObject *obj) const
{
  AutoVersionChecker avc(cx);
  for (nsXBLProtoImplField* f = mFields; f; f = f->GetNext()) {
    // Using OBJ_LOOKUP_PROPERTY is a pain, since what we have is a
    // PRUnichar* for the property name.  Let's just use the public API and
    // all.
    nsDependentString name(f->GetName());
    jsval dummy;
    if (!::JS_LookupUCProperty(cx, obj,
                               reinterpret_cast<const jschar*>(name.get()),
                               name.Length(), &dummy)) {
      return false;
    }
  }

  return true;
}

void
nsXBLProtoImpl::UndefineFields(JSContext *cx, JSObject *obj) const
{
  JSAutoRequest ar(cx);
  for (nsXBLProtoImplField* f = mFields; f; f = f->GetNext()) {
    nsDependentString name(f->GetName());

    const jschar* s = reinterpret_cast<const jschar*>(name.get());
    JSBool hasProp;
    if (::JS_AlreadyHasOwnUCProperty(cx, obj, s, name.Length(), &hasProp) &&
        hasProp) {
      jsval dummy;
      ::JS_DeleteUCProperty2(cx, obj, s, name.Length(), &dummy);
    }
  }
}

void
nsXBLProtoImpl::DestroyMembers()
{
  NS_ASSERTION(mClassObject, "This should never be called when there is no class object");

  delete mMembers;
  mMembers = nsnull;
  mConstructor = nsnull;
  mDestructor = nsnull;
}

nsresult
NS_NewXBLProtoImpl(nsXBLPrototypeBinding* aBinding, 
                   const PRUnichar* aClassName, 
                   nsXBLProtoImpl** aResult)
{
  nsXBLProtoImpl* impl = new nsXBLProtoImpl();
  if (!impl)
    return NS_ERROR_OUT_OF_MEMORY;
  if (aClassName)
    impl->mClassName.AssignWithConversion(aClassName);
  else
    aBinding->BindingURI()->GetSpec(impl->mClassName);
  aBinding->SetImplementation(impl);
  *aResult = impl;

  return NS_OK;
}