1 files changed, 96 insertions, 0 deletions
diff --git a/devtools/server/actors/resources/jstracer-state.js b/devtools/server/actors/resources/jstracer-state.js
new file mode 100644
index 0000000000..74491a6ced
--- /dev/null
+++ b/devtools/server/actors/resources/jstracer-state.js
@@ -0,0 +1,96 @@
+/* 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/. */
+
+"use strict";
+
+const {
+  TYPES: { JSTRACER_STATE },
+} = require("resource://devtools/server/actors/resources/index.js");
+
+// Bug 1827382, as this module can be used from the worker thread,
+// the following JSM may be loaded by the worker loader until
+// we have proper support for ESM from workers.
+const {
+  addTracingListener,
+  removeTracingListener,
+} = require("resource://devtools/server/tracer/tracer.jsm");
+
+const { LOG_METHODS } = require("resource://devtools/server/actors/tracer.js");
+const Targets = require("resource://devtools/server/actors/targets/index.js");
+
+class TracingStateWatcher {
+  /**
+   * Start watching for tracing state changes for a given target actor.
+   *
+   * @param TargetActor targetActor
+   *        The target actor from which we should observe
+   * @param Object options
+   *        Dictionary object with following attributes:
+   *        - onAvailable: mandatory function
+   *          This will be called for each resource.
+   */
+  async watch(targetActor, { onAvailable }) {
+    // Bug 1874204: tracer doesn't support tracing content process from the browser toolbox just yet
+    if (targetActor.targetType == Targets.TYPES.PROCESS) {
+      return;
+    }
+
+    this.targetActor = targetActor;
+    this.onAvailable = onAvailable;
+
+    this.tracingListener = {
+      onTracingToggled: this.onTracingToggled.bind(this),
+    };
+    addTracingListener(this.tracingListener);
+  }
+
+  /**
+   * Stop watching for tracing state
+   */
+  destroy() {
+    if (!this.tracingListener) {
+      return;
+    }
+    removeTracingListener(this.tracingListener);
+  }
+
+  /**
+   * Be notified by the underlying JavaScriptTracer class
+   * in case it stops by itself, instead of being stopped when the Actor's stopTracing
+   * method is called by the user.
+   *
+   * @param {Boolean} enabled
+   *        True if the tracer starts tracing, false it it stops.
+   * @param {String} reason
+   *        Optional string to justify why the tracer stopped.
+   */
+  onTracingToggled(enabled, reason) {
+    const tracerActor = this.targetActor.getTargetScopedActor("tracer");
+    const logMethod = tracerActor?.getLogMethod();
+
+    // JavascriptTracer only supports recording once in the same process/thread.
+    // If we open another DevTools, on the same process, we would receive notification
+    // about a JavascriptTracer controlled by another toolbox's tracer actor.
+    // Ignore them as our current tracer actor didn't start tracing.
+    if (!logMethod) {
+      return;
+    }
+
+    this.onAvailable([
+      {
+        resourceType: JSTRACER_STATE,
+        enabled,
+        logMethod,
+        profile:
+          logMethod == LOG_METHODS.PROFILER && !enabled
+            ? tracerActor.getProfile()
+            : undefined,
+        timeStamp: ChromeUtils.dateNow(),
+        reason,
+      },
+    ]);
+  }
+}
+
+module.exports = TracingStateWatcher;