InputDispatcher: Add InputTracerInterface for tracing input events
The interface documents how the tracer will interact with
InputDispatcher.
Bug: 210460522
Test: Build
Change-Id: Id97f9b0851f1248956b95e8b18b2302ecff1bff5
diff --git a/services/inputflinger/dispatcher/trace/InputTracerInterface.h b/services/inputflinger/dispatcher/trace/InputTracerInterface.h
new file mode 100644
index 0000000..c6cd7de
--- /dev/null
+++ b/services/inputflinger/dispatcher/trace/InputTracerInterface.h
@@ -0,0 +1,87 @@
+/*
+ * Copyright 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include "../Entry.h"
+#include "../InputTarget.h"
+#include "EventTrackerInterface.h"
+
+namespace android::inputdispatcher::trace {
+
+/**
+ * InputTracerInterface is the tracing interface for InputDispatcher.
+ *
+ * The tracer is responsible for tracing information about input events and where they are
+ * dispatched. The trace is logged to the backend using the InputTracingBackendInterface.
+ *
+ * A normal traced event should have the following lifecycle:
+ * - The EventTracker is obtained from traceInboundEvent(), after which point the event
+ * should not change.
+ * - While the event is being processed, dispatchToTargetHint() is called for each target that
+ * the event will be eventually sent to.
+ * - Once all targets have been determined, eventProcessingComplete() is called, at which point
+ * the tracer will have enough information to commit the event to the trace.
+ * - For each event that is dispatched to the client, traceEventDispatch() is called, and the
+ * tracer will record that the event was sent to the client.
+ */
+class InputTracerInterface {
+public:
+ InputTracerInterface() = default;
+ virtual ~InputTracerInterface() = default;
+ InputTracerInterface(const InputTracerInterface&) = delete;
+ InputTracerInterface& operator=(const InputTracerInterface&) = delete;
+
+ /**
+ * Trace an input event that is being processed by InputDispatcher. The event must not be
+ * modified after it is traced to keep the traced event consistent with the event that is
+ * eventually dispatched. An EventTracker is returned for each traced event that should be used
+ * to track the event's lifecycle inside InputDispatcher.
+ */
+ virtual std::unique_ptr<EventTrackerInterface> traceInboundEvent(const EventEntry&) = 0;
+
+ /**
+ * Notify the tracer that the traced event will be sent to the given InputTarget.
+ * The tracer may change how the event is logged depending on the target. For example,
+ * events targeting certain UIDs may be logged as sensitive events.
+ * This may be called 0 or more times for each tracked event before event processing is
+ * completed.
+ */
+ virtual void dispatchToTargetHint(const EventTrackerInterface&, const InputTarget&) = 0;
+
+ /**
+ * Notify the tracer that the event processing is complete. This may be called at most once
+ * for each traced event. If a tracked event is dropped before it can be processed, it is
+ * possible that this is never called before the EventTracker is destroyed.
+ *
+ * This is used to commit the event to the trace in a timely manner, rather than always
+ * waiting for the event to go out of scope (and thus for the EventTracker to be destroyed)
+ * before committing. The point at which the event is destroyed can depend on several factors
+ * outside of our control, such as how long apps take to respond, so we don't want to depend on
+ * that.
+ */
+ virtual void eventProcessingComplete(const EventTrackerInterface&) = 0;
+
+ /**
+ * Trace an input event being successfully dispatched to a window. The dispatched event may
+ * be a previously traced inbound event, or it may be a synthesized event that has not been
+ * previously traced. For inbound events that were previously traced, the EventTracker cookie
+ * must be provided. For events that were not previously traced, the cookie must be null.
+ */
+ virtual void traceEventDispatch(const DispatchEntry&, const EventTrackerInterface*) = 0;
+};
+
+} // namespace android::inputdispatcher::trace