5 files changed, 279 insertions, 0 deletions
diff --git a/devtools/shared/jsinspector/moz.build b/devtools/shared/jsinspector/moz.build
new file mode 100644
index 000000000..fc81f7e1e
--- /dev/null
+++ b/devtools/shared/jsinspector/moz.build
@@ -0,0 +1,17 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+XPIDL_SOURCES += [
+    'nsIJSInspector.idl',
+]
+
+XPIDL_MODULE = 'jsinspector'
+
+SOURCES += [
+    'nsJSInspector.cpp',
+]
+
+FINAL_LIBRARY = 'xul'
diff --git a/devtools/shared/jsinspector/nsIJSInspector.idl b/devtools/shared/jsinspector/nsIJSInspector.idl
new file mode 100644
index 000000000..40ad49523
--- /dev/null
+++ b/devtools/shared/jsinspector/nsIJSInspector.idl
@@ -0,0 +1,75 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+/**
+ * Utilities for running nested event loops, asking them to return, and
+ * keeping track of which ones are still running.
+ */
+[scriptable, uuid(6758d0d7-e96a-4c5c-bca8-3bcbe5a15943)]
+interface nsIJSInspector : nsISupports
+{
+  /**
+   * Process the current thread's event queue, calling event handlers until
+   * a call to exitNestedEventLoop, below, asks us to return.
+   *
+   * The name 'enterNestedEventLoop' may be misleading if read too literally.
+   * This method loops calling event handlers until one asks it to stop, and
+   * then returns. So by that point, the nested event loop has been not only
+   * entered, but also run and exited.
+   *
+   * When enterNestedEventLoop calls an event handler, that handler may itself
+   * call enterNestedEventLoop, and so on, so that there may be arbitrarily
+   * many such calls on the stack at the same time.
+   *
+   * We say an enterNestedEventLoop call is "running" if it has not yet been
+   * asked to return, or "stopped" if it has been asked to return once it has
+   * finished processing the current event.
+   *
+   * @param requestor   A token of the caller's choice to identify this event
+   *                    loop.
+   *
+   * @return depth      The number of running enterNestedEventLoop calls
+   *                    remaining, now that this one has returned.
+   *
+   *                    (Note that not all calls still on the stack are
+   *                    necessary running; exitNestedEventLoop can ask any
+   *                    number of enterNestedEventLoop calls to return.)
+   */
+  unsigned long enterNestedEventLoop(in jsval requestor);
+
+  /**
+   * Stop the youngest running enterNestedEventLoop call, asking it to return
+   * once it has finished processing the current event.
+   *
+   * The name 'exitNestedEventLoop' may be misleading if read too literally.
+   * The affected event loop does not return immediately when this method is
+   * called. Rather, this method simply returns to its caller; the affected
+   * loop's current event handler is allowed to run to completion; and then
+   * that loop returns without processing any more events.
+   *
+   * This method ignores loops that have already been stopped, and operates on
+   * the youngest loop that is still running. Each call to this method stops
+   * another running loop.
+   *
+   * @return depth      The number of running enterNestedEventLoop calls
+   *                    remaining, now that one has been stopped.
+   *
+   * @throws NS_ERROR_FAILURE if there are no running enterNestedEventLoop calls.
+   */
+  unsigned long exitNestedEventLoop();
+
+  /**
+    * The number of running enterNestedEventLoop calls on the stack.
+    * This count does not include stopped enterNestedEventLoop calls.
+    */
+  readonly attribute unsigned long eventLoopNestLevel;
+
+  /**
+   * The |requestor| value that was passed to the youngest running
+   * enterNestedEventLoop call.
+   */
+  readonly attribute jsval lastNestRequestor;
+};
diff --git a/devtools/shared/jsinspector/nsJSInspector.cpp b/devtools/shared/jsinspector/nsJSInspector.cpp
new file mode 100644
index 000000000..6d717af5b
--- /dev/null
+++ b/devtools/shared/jsinspector/nsJSInspector.cpp
@@ -0,0 +1,147 @@
+/* -*-  Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsJSInspector.h"
+#include "nsIXPConnect.h"
+#include "nsThreadUtils.h"
+#include "jsfriendapi.h"
+#include "mozilla/HoldDropJSObjects.h"
+#include "mozilla/ModuleUtils.h"
+#include "mozilla/dom/ScriptSettings.h"
+#include "nsServiceManagerUtils.h"
+#include "nsMemory.h"
+#include "nsArray.h"
+#include "nsTArray.h"
+
+#define JSINSPECTOR_CONTRACTID \
+  "@mozilla.org/jsinspector;1"
+
+#define JSINSPECTOR_CID \
+{ 0xec5aa99c, 0x7abb, 0x4142, { 0xac, 0x5f, 0xaa, 0xb2, 0x41, 0x9e, 0x38, 0xe2 } }
+
+namespace mozilla {
+namespace jsinspector {
+
+NS_GENERIC_FACTORY_CONSTRUCTOR(nsJSInspector)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsJSInspector)
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+  NS_INTERFACE_MAP_ENTRY(nsIJSInspector)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(nsJSInspector)
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(nsJSInspector)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(nsJSInspector)
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsJSInspector)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsJSInspector)
+  tmp->mRequestors.Clear();
+  tmp->mLastRequestor = JS::NullValue();
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(nsJSInspector)
+  for (uint32_t i = 0; i < tmp->mRequestors.Length(); ++i) {
+    NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mRequestors[i])
+  }
+  NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mLastRequestor)
+NS_IMPL_CYCLE_COLLECTION_TRACE_END
+
+nsJSInspector::nsJSInspector() : mNestedLoopLevel(0), mRequestors(1), mLastRequestor(JS::NullValue())
+{
+}
+
+nsJSInspector::~nsJSInspector()
+{
+  MOZ_ASSERT(mRequestors.Length() == 0);
+  MOZ_ASSERT(mLastRequestor.isNull());
+  mozilla::DropJSObjects(this);
+}
+
+NS_IMETHODIMP
+nsJSInspector::EnterNestedEventLoop(JS::Handle<JS::Value> requestor, uint32_t *out)
+{
+  nsresult rv = NS_OK;
+
+  mLastRequestor = requestor;
+  mRequestors.AppendElement(requestor);
+  mozilla::HoldJSObjects(this);
+
+  mozilla::dom::AutoNoJSAPI nojsapi;
+
+  uint32_t nestLevel = ++mNestedLoopLevel;
+  while (NS_SUCCEEDED(rv) && mNestedLoopLevel >= nestLevel) {
+    if (!NS_ProcessNextEvent())
+      rv = NS_ERROR_UNEXPECTED;
+  }
+
+  NS_ASSERTION(mNestedLoopLevel <= nestLevel,
+               "nested event didn't unwind properly");
+
+  if (mNestedLoopLevel == nestLevel) {
+    mLastRequestor = mRequestors.ElementAt(--mNestedLoopLevel);
+  }
+
+  *out = mNestedLoopLevel;
+  return rv;
+}
+
+NS_IMETHODIMP
+nsJSInspector::ExitNestedEventLoop(uint32_t *out)
+{
+  if (mNestedLoopLevel > 0) {
+    mRequestors.RemoveElementAt(--mNestedLoopLevel);
+    if (mNestedLoopLevel > 0)
+      mLastRequestor = mRequestors.ElementAt(mNestedLoopLevel - 1);
+    else
+      mLastRequestor = JS::NullValue();
+  } else {
+    return NS_ERROR_FAILURE;
+  }
+
+  *out = mNestedLoopLevel;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsJSInspector::GetEventLoopNestLevel(uint32_t *out)
+{
+  *out = mNestedLoopLevel;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsJSInspector::GetLastNestRequestor(JS::MutableHandle<JS::Value> out)
+{
+  out.set(mLastRequestor);
+  return NS_OK;
+}
+
+} // namespace jsinspector
+} // namespace mozilla
+
+NS_DEFINE_NAMED_CID(JSINSPECTOR_CID);
+
+static const mozilla::Module::CIDEntry kJSInspectorCIDs[] = {
+  { &kJSINSPECTOR_CID, false, nullptr, mozilla::jsinspector::nsJSInspectorConstructor },
+  { nullptr }
+};
+
+static const mozilla::Module::ContractIDEntry kJSInspectorContracts[] = {
+  { JSINSPECTOR_CONTRACTID, &kJSINSPECTOR_CID },
+  { nullptr }
+};
+
+static const mozilla::Module kJSInspectorModule = {
+  mozilla::Module::kVersion,
+  kJSInspectorCIDs,
+  kJSInspectorContracts
+};
+
+NSMODULE_DEFN(jsinspector) = &kJSInspectorModule;
diff --git a/devtools/shared/jsinspector/nsJSInspector.h b/devtools/shared/jsinspector/nsJSInspector.h
new file mode 100644
index 000000000..4e60b0428
--- /dev/null
+++ b/devtools/shared/jsinspector/nsJSInspector.h
@@ -0,0 +1,39 @@
+/* -*-  Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef COMPONENTS_JSINSPECTOR_H
+#define COMPONENTS_JSINSPECTOR_H
+
+#include "nsIJSInspector.h"
+#include "mozilla/Attributes.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsTArray.h"
+#include "js/Value.h"
+#include "js/RootingAPI.h"
+
+namespace mozilla {
+namespace jsinspector {
+
+class nsJSInspector final : public nsIJSInspector
+{
+public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(nsJSInspector)
+  NS_DECL_NSIJSINSPECTOR
+
+  nsJSInspector();
+
+private:
+  ~nsJSInspector();
+
+  uint32_t mNestedLoopLevel;
+  nsTArray<JS::Heap<JS::Value> > mRequestors;
+  JS::Heap<JS::Value> mLastRequestor;
+};
+
+} // namespace jsinspector
+} // namespace mozilla
+
+#endif
diff --git a/devtools/shared/moz.build b/devtools/shared/moz.build
index e4de1d84a..6c61206dd 100644
--- a/devtools/shared/moz.build
+++ b/devtools/shared/moz.build
@@ -17,6 +17,7 @@ DIRS += [
     'heapsnapshot',
     'inspector',
     'jsbeautify',
+    'jsinspector',
     'layout',
     'locales',
     'node-properties',