Bindings layer for declarative events API

chrome/renderer/resources/extensions/event.js

Index: chrome/renderer/resources/extensions/event.js
diff --git a/chrome/renderer/resources/extensions/event.js b/chrome/renderer/resources/extensions/event.js
index dffe20193837e78f2e43db42357e14c9d6799a7d..32db12f58109572b98cb555f845004864e671a18 100644
--- a/chrome/renderer/resources/extensions/event.js
+++ b/chrome/renderer/resources/extensions/event.js
@@ -58,9 +58,14 @@ var chrome = chrome || {};
   //   chrome.tabs.onChanged.addListener(function(data) { alert(data); });
   //   chromeHidden.Event.dispatch("tab-changed", "hi");
   // will result in an alert dialog that says 'hi'.
-  chrome.Event = function(opt_eventName, opt_argSchemas) {
+  //
+  // If opt_eventOptions exists, it is a dictionary that contains the boolean
+  // entries "supportsListeners" and "supportsRules".
+  chrome.Event = function(opt_eventName, opt_argSchemas, opt_eventOptions) {
     this.eventName_ = opt_eventName;
     this.listeners_ = [];
+    this.eventOptions_ = opt_eventOptions ||
+        {"supportsListeners": true, "supportsRules": false};
 
     // Validate event parameters if we are in debug.
     if (opt_argSchemas &&
@@ -75,6 +80,8 @@ var chrome = chrome || {};
                  exception;
         }
       };
+    } else {
+      this.validate_ = function() {}
     }
   };
 
@@ -127,6 +134,8 @@ var chrome = chrome || {};
 
   // Registers a callback to be called when this event is dispatched.
   chrome.Event.prototype.addListener = function(cb) {
+    if (!this.eventOptions_.supportsListeners)
+      throw new Error("This event does not support listeners.");
     if (this.listeners_.length == 0) {
       this.attach_();
     }
@@ -135,6 +144,8 @@ var chrome = chrome || {};
 
   // Unregisters a callback.
   chrome.Event.prototype.removeListener = function(cb) {
+    if (!this.eventOptions_.supportsListeners)
+      throw new Error("This event does not support listeners.");
     var idx = this.findListener_(cb);
     if (idx == -1) {
       return;
@@ -148,11 +159,15 @@ var chrome = chrome || {};
 
   // Test if the given callback is registered for this event.
   chrome.Event.prototype.hasListener = function(cb) {
+    if (!this.eventOptions_.supportsListeners)
+      throw new Error("This event does not support listeners.");
     return this.findListener_(cb) > -1;
   };
 
   // Test if any callbacks are registered for this event.
-  chrome.Event.prototype.hasListeners = function(cb) {
+  chrome.Event.prototype.hasListeners = function() {
+    if (!this.eventOptions_.supportsListeners)
+      throw new Error("This event does not support listeners.");
     return this.listeners_.length > 0;
   };
 
@@ -171,12 +186,12 @@ var chrome = chrome || {};
   // Dispatches this event object to all listeners, passing all supplied
   // arguments to this function each listener.
   chrome.Event.prototype.dispatch = function(varargs) {
+    if (!this.eventOptions_.supportsListeners)
+      throw new Error("This event does not support listeners.");
     var args = Array.prototype.slice.call(arguments);
-    if (this.validate_) {
-      var validationErrors = this.validate_(args);
-      if (validationErrors) {
-        return validationErrors;
-      }
+    var validationErrors = this.validate_(args);
+    if (validationErrors) {
+      return validationErrors;
     }
     for (var i = 0; i < this.listeners_.length; i++) {
       try {
@@ -227,6 +242,26 @@ var chrome = chrome || {};
     this.detach_();
   };
 
+  chrome.Event.prototype.addRules = function(rules, opt_cb) {
+    if (!this.eventOptions_.supportsRules)
+      throw new Error("This event does not support rules.");
+    chrome.experimental.declarative.addRules(this.eventName_, rules, opt_cb);

[not at google - send to devlin, 2012/02/01 23:07:23]

You'll still need to check that the experimental.declarative API exists.

This might be most easily done in the constructor, like

if (this.eventOptions_.supportsRules &&
    (!chrome.experimental || !chrome.experimental.declarative)) {
  throw new Error("You must have access to the experimental.declarative " +
                  "API to support rules in events");
}

Possibly when this API gets taken out of experimental the presence of events
with rules will imply permission to use the API? Or possibly not? Not a decision
that needs to be made right now though, extensions will definitely need the
experimental permission to use this.

[battre, 2012/02/02 13:49:59]

Anticipating that experimental.declarative will become "declarative" and that
you don't need to request permission for "declarative" I have split this into
two if statements.

Done.

+  }
+
+  chrome.Event.prototype.removeRules = function(ruleIdentifiers, opt_cb) {
+    if (!this.eventOptions_.supportsRules)
+      throw new Error("This event does not support rules.");
+    chrome.experimental.declarative.removeRules(
+        this.eventName_, ruleIdentifiers, opt_cb);
+  }
+
+  chrome.Event.prototype.getRules = function(ruleIdentifiers, cb) {
+    if (!this.eventOptions_.supportsRules)
+      throw new Error("This event does not support rules.");
+    chrome.experimental.declarative.getRules(
+        this.eventName_, ruleIdentifiers, cb);
+  }
+
   // Special load events: we don't use the DOM unload because that slows
   // down tab shutdown.  On the other hand, onUnload might not always fire,
   // since Chrome will terminate renderers on shutdown (SuddenTermination).