Add onChange event to preference extension APIs.

chrome/browser/extensions/extension_preference_api.cc

Index: chrome/browser/extensions/extension_preference_api.cc
diff --git a/chrome/browser/extensions/extension_preference_api.cc b/chrome/browser/extensions/extension_preference_api.cc
index 088c8cfc9392d09bf400b192d0ddd134c099707c..8fa0ac23f6d5a039f49d30edccf095530ff8da93 100644
--- a/chrome/browser/extensions/extension_preference_api.cc
+++ b/chrome/browser/extensions/extension_preference_api.cc
@@ -4,22 +4,20 @@
 
 #include "chrome/browser/extensions/extension_preference_api.h"
 
+#include "base/json/json_writer.h"
 #include "base/singleton.h"
 #include "base/stringprintf.h"
 #include "base/values.h"
+#include "chrome/browser/extensions/extension_event_router.h"
 #include "chrome/browser/extensions/extension_prefs.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/profiles/profile.h"
+#include "chrome/common/notification_type.h"
+#include "chrome/common/notification_service.h"
 #include "chrome/common/pref_names.h"
 
 namespace {
 
-struct PrefMappingEntry {
-  const char* extension_pref;
-  const char* browser_pref;
-  const char* permission;
-};
-
 const char kNotControllable[] = "NotControllable";
 const char kControlledByOtherExtensions[] = "ControlledByOtherExtensions";
 const char kControllableByThisExtension[] = "ControllableByThisExtension";
@@ -30,10 +28,22 @@ const char kIncognitoSpecific[] = "incognitoSpecific";
 const char kLevelOfControl[] = "levelOfControl";
 const char kValue[] = "value";
 
+const char kOnPrefChangeFormat[] = "experimental.preferences.%s.onChange";
+
+const char kPermissionErrorMessage[] =
+    "You do not have permission to access the preference '%s'. "
+    "Be sure to declare in your manifest what permissions you need.";
+
 const char kIncognitoErrorMessage[] =
     "You do not have permission to access incognito preferences.";
 
-PrefMappingEntry pref_mapping[] = {
+struct PrefMappingEntry {
+  const char* extension_pref;
+  const char* browser_pref;
+  const char* permission;
+};
+
+PrefMappingEntry kPrefMapping[] = {
   { "blockThirdPartyCookies",
     prefs::kBlockThirdPartyCookies,
     Extension::kContentSettingsPermission
@@ -63,52 +73,156 @@ class PrefMapping {
     return false;
   }
 
+  bool FindEventForBrowserPref(const std::string& browser_pref,
+                               std::string* event_name,
+                               std::string* permission) {
+    std::map<std::string, std::pair<std::string, std::string> >::iterator it =
+        event_mapping_.find(browser_pref);
+    if (it != event_mapping_.end()) {
+      *event_name = it->second.first;
+      *permission = it->second.second;
+      return true;
+    }
+    return false;
+  }
+
  private:
   friend struct DefaultSingletonTraits<PrefMapping>;
 
+  // Mapping from extension pref keys to browser pref keys.

[battre, 2011/03/10 13:07:28]

Thanks you :-)

   std::map<std::string, std::pair<std::string, std::string> > mapping_;
 
+  // Mapping from browser pref keys to extension event names.
+  std::map<std::string, std::pair<std::string, std::string> > event_mapping_;
+
   PrefMapping() {
-    for (size_t i = 0; i < arraysize(pref_mapping); ++i) {
-      mapping_[pref_mapping[i].extension_pref] =
-          std::make_pair(pref_mapping[i].browser_pref,
-                         pref_mapping[i].permission);
+    for (size_t i = 0; i < arraysize(kPrefMapping); ++i) {
+      mapping_[kPrefMapping[i].extension_pref] =
+          std::make_pair(kPrefMapping[i].browser_pref,
+                         kPrefMapping[i].permission);
+      std::string event_name =
+          base::StringPrintf(kOnPrefChangeFormat,
+                             kPrefMapping[i].extension_pref);
+      event_mapping_[kPrefMapping[i].browser_pref] =
+          std::make_pair(event_name, kPrefMapping[i].permission);
     }

[battre, 2011/03/10 13:07:28]

DCHECK(mapping_.size()==arraysize(kPrefMapping) &&
event_mapping_.size()==arraysize(kPrefMapping)) to be sure that all entries are
unique?

[Bernhard Bauer, 2011/03/10 14:51:15]

Done.

   }
 };
 
-const char kPermissionErrorMessage[] =
-    "You do not have permission to access the preference '%s'. "
-    "Be sure to declare in your manifest what permissions you need.";
-
-}  // namespace
-
-// TODO(battre): Factor out common parts once this is stable.
-
-GetPreferenceFunction::~GetPreferenceFunction() { }
-
-const char* GetPreferenceFunction::GetLevelOfControl(
+// Returns a string constant (defined in the API) indicating the level of
+// control this extension has over the specified preference.
+const char* GetLevelOfControl(
+    Profile* profile,
+    const std::string& extension_id,
     const std::string& browser_pref,
-    bool incognito) const {
-  PrefService* prefs = incognito ? profile_->GetOffTheRecordPrefs()
-                                 : profile_->GetPrefs();
+    bool incognito) {
+  PrefService* prefs = incognito ? profile->GetOffTheRecordPrefs()
+                                 : profile->GetPrefs();
   const PrefService::Preference* pref =
       prefs->FindPreference(browser_pref.c_str());
   CHECK(pref);
-  ExtensionPrefs* ep = profile_->GetExtensionService()->extension_prefs();
+  ExtensionPrefs* ep = profile->GetExtensionService()->extension_prefs();
 
   if (!pref->IsExtensionModifiable())
     return kNotControllable;
 
-  if (ep->DoesExtensionControlPref(extension_id(), browser_pref, incognito))
+  if (ep->DoesExtensionControlPref(extension_id, browser_pref, incognito))
     return kControlledByThisExtension;
 
-  if (ep->CanExtensionControlPref(extension_id(), browser_pref, incognito))
+  if (ep->CanExtensionControlPref(extension_id, browser_pref, incognito))
     return kControllableByThisExtension;
 
   return kControlledByOtherExtensions;
 }
 
+}  // namespace
+
+ExtensionPreferenceEventRouter::ExtensionPreferenceEventRouter(
+    Profile* profile) : profile_(profile) {
+  registrar_.Init(profile_->GetPrefs());
+  incognito_registrar_.Init(profile_->GetOffTheRecordPrefs());
+  for (size_t i = 0; i < arraysize(kPrefMapping); ++i) {
+    registrar_.Add(kPrefMapping[i].browser_pref, this);
+    incognito_registrar_.Add(kPrefMapping[i].browser_pref, this);
+  }
+}
+
+ExtensionPreferenceEventRouter::~ExtensionPreferenceEventRouter() { }
+
+void ExtensionPreferenceEventRouter::Observe(
+    NotificationType type,
+    const NotificationSource& source,
+    const NotificationDetails& details) {
+  if (type == NotificationType::PREF_CHANGED) {
+    const std::string* pref_key =
+        Details<const std::string>(details).ptr();
+    OnPrefChanged(Source<PrefService>(source).ptr(), *pref_key);

[battre, 2011/03/10 13:07:28]

PREF_CHANGED is only fired when the effective value changes. Should we be
notified if the level of control changes?

[Bernhard Bauer, 2011/03/10 14:51:15]

Oh, I was assuming it is also fired when the level of control changes. Is there
another notification for that?

[battre, 2011/03/11 09:28:36]

This is not implemented, yet.

+  } else {
+    NOTREACHED();
+  }
+}
+
+void ExtensionPreferenceEventRouter::OnPrefChanged(
+    PrefService* pref_service,
+    const std::string& browser_pref) {
+  bool incognito = (pref_service != profile_->GetPrefs());
+
+  std::string event_name;
+  std::string permission;
+  bool rv = PrefMapping::GetInstance()->FindEventForBrowserPref(
+      browser_pref, &event_name, &permission);
+  DCHECK(rv);
+
+  ListValue args;
+  DictionaryValue* dict = new DictionaryValue();
+  args.Append(dict);
+  const PrefService::Preference* pref =
+      pref_service->FindPreference(browser_pref.c_str());
+  CHECK(pref);
+  ExtensionService* extension_service = profile_->GetExtensionService();
+  dict->Set(kValue, pref->GetValue()->DeepCopy());

[battre, 2011/03/10 13:07:28]

The proxy settings API needs a hook to modify this value before it is delivered
to the extension.

[Bernhard Bauer, 2011/03/10 14:51:15]

Hm, I see. I guess we'll need a separate event router for proxy events then, and
we should try to pull out the value transformation for events and the get
function.

[battre, 2011/03/11 09:28:36]

Yes, we could even extract the value transformation the other way around.

+  if (incognito) {
+    ExtensionPrefs* ep = extension_service->extension_prefs();
+    dict->Set(
+        kIncognitoSpecific,
+        Value::CreateBooleanValue(ep->HasIncognitoPrefValue(browser_pref)));
+  }
+
+  ExtensionEventRouter* router = profile_->GetExtensionEventRouter();
+  if (!router || !router->HasEventListener(event_name))
+    return;
+  const ExtensionList* extensions = extension_service->extensions();
+  for (ExtensionList::const_iterator it = extensions->begin();
+       it != extensions->end(); ++it) {
+    std::string extension_id = (*it)->id();
+    // TODO(bauerb): Only iterate over registered event listeners.
+    if (router->ExtensionHasEventListener(extension_id, event_name) &&
+        (*it)->HasApiPermission(permission) &&
+        (!incognito || extension_service->CanCrossIncognito(*it))) {
+      std::string level_of_control =
+          GetLevelOfControl(profile_, extension_id, browser_pref, incognito);
+      dict->Set(kLevelOfControl, Value::CreateStringValue(level_of_control));
+
+      std::string json_args;
+      base::JSONWriter::Write(&args, false, &json_args);
+
+      DispatchEvent(extension_id, event_name, json_args);
+    }
+  }
+}
+
+void ExtensionPreferenceEventRouter::DispatchEvent(
+    const std::string& extension_id,
+    const std::string& event_name,
+    const std::string& json_args) {
+  profile_->GetExtensionEventRouter()->DispatchEventToExtension(
+      extension_id, event_name, json_args, NULL, GURL());
+}
+
+// TODO(battre): Factor out common parts once this is stable.
+
+GetPreferenceFunction::~GetPreferenceFunction() { }
+
 bool GetPreferenceFunction::RunImpl() {
   std::string pref_key;
   EXTENSION_FUNCTION_VALIDATE(args_->GetString(0, &pref_key));
@@ -139,7 +253,8 @@ bool GetPreferenceFunction::RunImpl() {
   const PrefService::Preference* pref =
       prefs->FindPreference(browser_pref.c_str());
   CHECK(pref);
-  std::string level_of_control = GetLevelOfControl(browser_pref, incognito);
+  std::string level_of_control =
+      GetLevelOfControl(profile_, extension_id(), browser_pref, incognito);
 
   scoped_ptr<DictionaryValue> result(new DictionaryValue);
   result->Set(kValue, pref->GetValue()->DeepCopy());