Merge changes from topic "shell-transition-bugreport" into udc-dev

* changes:
  Add shell side transition trace to bug reports
  Add transition trace on shell side

7 files changed, 476 insertions, 5 deletions

diff --git a/core/java/com/android/internal/util/TraceBuffer.java b/core/java/com/android/internal/util/TraceBuffer.java
index bfcd65d4f277..fcc77bd4f043 100644
--- a/core/java/com/android/internal/util/TraceBuffer.java
+++ b/core/java/com/android/internal/util/TraceBuffer.java
@@ -103,6 +103,10 @@ public class TraceBuffer<P, S extends P, T extends P> {
         this(bufferCapacity, new ProtoOutputStreamProvider(), null);
     }
 
+    public TraceBuffer(int bufferCapacity, Consumer<T> protoDequeuedCallback) {
+        this(bufferCapacity, new ProtoOutputStreamProvider(), protoDequeuedCallback);
+    }
+
     public TraceBuffer(int bufferCapacity, ProtoProvider protoProvider,
             Consumer<T> protoDequeuedCallback) {
         mBufferCapacity = bufferCapacity;
diff --git a/core/tests/bugreports/src/com/android/os/bugreports/tests/BugreportManagerTest.java b/core/tests/bugreports/src/com/android/os/bugreports/tests/BugreportManagerTest.java
index bf8c7c63590f..72969f7d8b96 100644
--- a/core/tests/bugreports/src/com/android/os/bugreports/tests/BugreportManagerTest.java
+++ b/core/tests/bugreports/src/com/android/os/bugreports/tests/BugreportManagerTest.java
@@ -112,6 +112,7 @@ public class BugreportManagerTest {
             Paths.get("/data/misc/wmtrace/layers_trace.winscope"),
             Paths.get("/data/misc/wmtrace/transactions_trace.winscope"),
             Paths.get("/data/misc/wmtrace/transition_trace.winscope"),
+            Paths.get("/data/misc/wmtrace/shell_transition_trace.winscope"),
     };
     private static final Path[] UI_TRACES_GENERATED_DURING_BUGREPORT = {
             Paths.get("/data/misc/wmtrace/layers_trace_from_transactions.winscope"),
diff --git a/libs/WindowManager/Shell/Android.bp b/libs/WindowManager/Shell/Android.bp
index 54978bd4496d..6a79bc1f46c2 100644
--- a/libs/WindowManager/Shell/Android.bp
+++ b/libs/WindowManager/Shell/Android.bp
@@ -125,6 +125,34 @@ prebuilt_etc {
 
 // End ProtoLog
 
+gensrcs {
+    name: "wm-shell-protos",
+
+    tools: [
+        "aprotoc",
+        "protoc-gen-javastream",
+        "soong_zip",
+    ],
+
+    tool_files: [
+        ":libprotobuf-internal-protos",
+    ],
+
+    cmd: "mkdir -p $(genDir)/$(in) " +
+        "&& $(location aprotoc) " +
+        "  --plugin=$(location protoc-gen-javastream) " +
+        "  --javastream_out=$(genDir)/$(in) " +
+        "  -Iexternal/protobuf/src " +
+        "  -I . " +
+        "  $(in) " +
+        "&& $(location soong_zip) -jar -o $(out) -C $(genDir)/$(in) -D $(genDir)/$(in)",
+
+    srcs: [
+        "proto/**/*.proto",
+    ],
+    output_extension: "srcjar",
+}
+
 java_library {
     name: "WindowManager-Shell-proto",
 
@@ -142,6 +170,7 @@ android_library {
         // TODO(b/168581922) protologtool do not support kotlin(*.kt)
         ":wm_shell-sources-kt",
         ":wm_shell-aidls",
+        ":wm-shell-protos",
     ],
     resource_dirs: [
         "res",
diff --git a/libs/WindowManager/Shell/proto/wm_shell_transition_trace.proto b/libs/WindowManager/Shell/proto/wm_shell_transition_trace.proto
new file mode 100644
index 000000000000..6e0110193a05
--- /dev/null
+++ b/libs/WindowManager/Shell/proto/wm_shell_transition_trace.proto
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+syntax = "proto2";
+
+package com.android.wm.shell;
+
+option java_multiple_files = true;
+
+/* Represents a file full of transition entries.
+   Encoded, it should start with 0x09 0x57 0x4D 0x53 0x54 0x52 0x41 0x43 0x45 (.WMSTRACE), such
+   that it can be easily identified. */
+message WmShellTransitionTraceProto {
+    /* constant; MAGIC_NUMBER = (long) MAGIC_NUMBER_H << 32 | MagicNumber.MAGIC_NUMBER_L
+   (this is needed because enums have to be 32 bits and there's no nice way to put 64bit
+    constants into .proto files. */
+    enum MagicNumber {
+        INVALID = 0;
+        MAGIC_NUMBER_L = 0x54534D57;  /* WMST (little-endian ASCII) */
+        MAGIC_NUMBER_H = 0x45434152;  /* RACE (little-endian ASCII) */
+    }
+
+    // Must be the first field, set to value in MagicNumber
+    required fixed64 magic_number = 1;
+    repeated Transition transitions = 2;
+    repeated HandlerMapping handlerMappings = 3;
+}
+
+message Transition {
+    required int32 id = 1;
+    optional int64 dispatch_time_ns = 2;
+    optional int32 handler = 3;
+    optional int64 merge_time_ns = 4;
+    optional int64 merge_request_time_ns = 5;
+    optional int32 merged_into = 6;
+    optional int64 abort_time_ns = 7;
+}
+
+message HandlerMapping {
+    required int32 id = 1;
+    required string name = 2;
+}
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/dagger/WMShellBaseModule.java b/libs/WindowManager/Shell/src/com/android/wm/shell/dagger/WMShellBaseModule.java
index 36d941bda663..80e920fefe5f 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/dagger/WMShellBaseModule.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/dagger/WMShellBaseModule.java
@@ -544,13 +544,14 @@ public abstract class WMShellBaseModule {
             DisplayController displayController,
             @ShellMainThread ShellExecutor mainExecutor,
             @ShellMainThread Handler mainHandler,
-            @ShellAnimationThread ShellExecutor animExecutor) {
+            @ShellAnimationThread ShellExecutor animExecutor,
+            ShellCommandHandler shellCommandHandler) {
         if (!context.getResources().getBoolean(R.bool.config_registerShellTransitionsOnInit)) {
             // TODO(b/238217847): Force override shell init if registration is disabled
             shellInit = new ShellInit(mainExecutor);
         }
         return new Transitions(context, shellInit, shellController, organizer, pool,
-                displayController, mainExecutor, mainHandler, animExecutor);
+                displayController, mainExecutor, mainHandler, animExecutor, shellCommandHandler);
     }
 
     @WMSingleton
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Tracer.java b/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Tracer.java
new file mode 100644
index 000000000000..9d7c39f1c90e
--- /dev/null
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Tracer.java
@@ -0,0 +1,327 @@
+/*
+ * Copyright (C) 2023 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.
+ */
+
+package com.android.wm.shell.transition;
+
+import static android.os.Build.IS_USER;
+
+import static com.android.wm.shell.WmShellTransitionTraceProto.MAGIC_NUMBER;
+import static com.android.wm.shell.WmShellTransitionTraceProto.MAGIC_NUMBER_H;
+import static com.android.wm.shell.WmShellTransitionTraceProto.MAGIC_NUMBER_L;
+
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.os.SystemClock;
+import android.os.Trace;
+import android.util.Log;
+import android.util.proto.ProtoOutputStream;
+
+import com.android.internal.util.TraceBuffer;
+import com.android.wm.shell.sysui.ShellCommandHandler;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Helper class to collect and dump transition traces.
+ */
+public class Tracer implements ShellCommandHandler.ShellCommandActionHandler {
+    private static final int ALWAYS_ON_TRACING_CAPACITY = 15 * 1024; // 15 KB
+    private static final int ACTIVE_TRACING_BUFFER_CAPACITY = 5000 * 1024; // 5 MB
+
+    private static final long MAGIC_NUMBER_VALUE = ((long) MAGIC_NUMBER_H << 32) | MAGIC_NUMBER_L;
+
+    static final String WINSCOPE_EXT = ".winscope";
+    private static final String TRACE_FILE =
+            "/data/misc/wmtrace/shell_transition_trace" + WINSCOPE_EXT;
+
+    private final Object mEnabledLock = new Object();
+    private boolean mActiveTracingEnabled = false;
+
+    private final TraceBuffer mTraceBuffer = new TraceBuffer(ALWAYS_ON_TRACING_CAPACITY,
+            (proto) -> handleOnEntryRemovedFromTrace(proto));
+    private final Map<Object, Runnable> mRemovedFromTraceCallbacks = new HashMap<>();
+
+    private final Map<Transitions.TransitionHandler, Integer> mHandlerIds = new HashMap<>();
+    private final Map<Transitions.TransitionHandler, Integer> mHandlerUseCountInTrace =
+            new HashMap<>();
+
+    /**
+     * Adds an entry in the trace to log that a transition has been dispatched to a handler.
+     *
+     * @param transitionId The id of the transition being dispatched.
+     * @param handler The handler the transition is being dispatched to.
+     */
+    public void logDispatched(int transitionId, Transitions.TransitionHandler handler) {
+        final int handlerId;
+        if (mHandlerIds.containsKey(handler)) {
+            handlerId = mHandlerIds.get(handler);
+        } else {
+            handlerId = mHandlerIds.size();
+            mHandlerIds.put(handler, handlerId);
+        }
+
+        ProtoOutputStream outputStream = new ProtoOutputStream();
+        final long protoToken =
+                outputStream.start(com.android.wm.shell.WmShellTransitionTraceProto.TRANSITIONS);
+
+        outputStream.write(com.android.wm.shell.Transition.ID, transitionId);
+        outputStream.write(com.android.wm.shell.Transition.DISPATCH_TIME_NS,
+                SystemClock.elapsedRealtimeNanos());
+        outputStream.write(com.android.wm.shell.Transition.HANDLER, handlerId);
+
+        outputStream.end(protoToken);
+
+        final int useCountAfterAdd = mHandlerUseCountInTrace.getOrDefault(handler, 0) + 1;
+        mHandlerUseCountInTrace.put(handler, useCountAfterAdd);
+
+        mRemovedFromTraceCallbacks.put(outputStream, () -> {
+            final int useCountAfterRemove = mHandlerUseCountInTrace.get(handler) - 1;
+            mHandlerUseCountInTrace.put(handler, useCountAfterRemove);
+        });
+
+        mTraceBuffer.add(outputStream);
+    }
+
+    /**
+     * Adds an entry in the trace to log that a request to merge a transition was made.
+     *
+     * @param mergeRequestedTransitionId The id of the transition we are requesting to be merged.
+     * @param playingTransitionId The id of the transition we was to merge the transition into.
+     */
+    public void logMergeRequested(int mergeRequestedTransitionId, int playingTransitionId) {
+        ProtoOutputStream outputStream = new ProtoOutputStream();
+        final long protoToken =
+                outputStream.start(com.android.wm.shell.WmShellTransitionTraceProto.TRANSITIONS);
+
+        outputStream.write(com.android.wm.shell.Transition.ID, mergeRequestedTransitionId);
+        outputStream.write(com.android.wm.shell.Transition.MERGE_REQUEST_TIME_NS,
+                SystemClock.elapsedRealtimeNanos());
+        outputStream.write(com.android.wm.shell.Transition.MERGED_INTO, playingTransitionId);
+
+        outputStream.end(protoToken);
+
+        mTraceBuffer.add(outputStream);
+    }
+
+    /**
+     * Adds an entry in the trace to log that a transition was merged by the handler.
+     *
+     * @param mergedTransitionId The id of the transition that was merged.
+     * @param playingTransitionId The id of the transition the transition was merged into.
+     */
+    public void logMerged(int mergedTransitionId, int playingTransitionId) {
+        ProtoOutputStream outputStream = new ProtoOutputStream();
+        final long protoToken =
+                outputStream.start(com.android.wm.shell.WmShellTransitionTraceProto.TRANSITIONS);
+
+        outputStream.write(com.android.wm.shell.Transition.ID, mergedTransitionId);
+        outputStream.write(
+                com.android.wm.shell.Transition.MERGE_TIME_NS, SystemClock.elapsedRealtimeNanos());
+        outputStream.write(com.android.wm.shell.Transition.MERGED_INTO, playingTransitionId);
+
+        outputStream.end(protoToken);
+
+        mTraceBuffer.add(outputStream);
+    }
+
+    /**
+     * Adds an entry in the trace to log that a transition was aborted.
+     *
+     * @param transitionId The id of the transition that was aborted.
+     */
+    public void logAborted(int transitionId) {
+        ProtoOutputStream outputStream = new ProtoOutputStream();
+        final long protoToken =
+                outputStream.start(com.android.wm.shell.WmShellTransitionTraceProto.TRANSITIONS);
+
+        outputStream.write(com.android.wm.shell.Transition.ID, transitionId);
+        outputStream.write(
+                com.android.wm.shell.Transition.ABORT_TIME_NS, SystemClock.elapsedRealtimeNanos());
+
+        outputStream.end(protoToken);
+
+        mTraceBuffer.add(outputStream);
+    }
+
+    /**
+     * Starts collecting transitions for the trace.
+     * If called while a trace is already running, this will reset the trace.
+     */
+    public void startTrace(@Nullable PrintWriter pw) {
+        if (IS_USER) {
+            LogAndPrintln.e(pw, "Tracing is not supported on user builds.");
+            return;
+        }
+        Trace.beginSection("Tracer#startTrace");
+        LogAndPrintln.i(pw, "Starting shell transition trace.");
+        synchronized (mEnabledLock) {
+            mActiveTracingEnabled = true;
+            mTraceBuffer.resetBuffer();
+            mTraceBuffer.setCapacity(ACTIVE_TRACING_BUFFER_CAPACITY);
+        }
+        Trace.endSection();
+    }
+
+    /**
+     * Stops collecting the transition trace and dump to trace to file.
+     *
+     * Dumps the trace to @link{TRACE_FILE}.
+     */
+    public void stopTrace(@Nullable PrintWriter pw) {
+        stopTrace(pw, new File(TRACE_FILE));
+    }
+
+    /**
+     * Stops collecting the transition trace and dump to trace to file.
+     * @param outputFile The file to dump the transition trace to.
+     */
+    public void stopTrace(@Nullable PrintWriter pw, File outputFile) {
+        if (IS_USER) {
+            LogAndPrintln.e(pw, "Tracing is not supported on user builds.");
+            return;
+        }
+        Trace.beginSection("Tracer#stopTrace");
+        LogAndPrintln.i(pw, "Stopping shell transition trace.");
+        synchronized (mEnabledLock) {
+            mActiveTracingEnabled = false;
+            writeTraceToFileLocked(pw, outputFile);
+            mTraceBuffer.resetBuffer();
+            mTraceBuffer.setCapacity(ALWAYS_ON_TRACING_CAPACITY);
+        }
+        Trace.endSection();
+    }
+
+    /**
+     * Being called while taking a bugreport so that tracing files can be included in the bugreport.
+     *
+     * @param pw Print writer
+     */
+    public void saveForBugreport(@Nullable PrintWriter pw) {
+        if (IS_USER) {
+            LogAndPrintln.e(pw, "Tracing is not supported on user builds.");
+            return;
+        }
+        Trace.beginSection("TransitionTracer#saveForBugreport");
+        synchronized (mEnabledLock) {
+            final File outputFile = new File(TRACE_FILE);
+            writeTraceToFileLocked(pw, outputFile);
+        }
+        Trace.endSection();
+    }
+
+    private void writeTraceToFileLocked(@Nullable PrintWriter pw, File file) {
+        Trace.beginSection("TransitionTracer#writeTraceToFileLocked");
+        try {
+            ProtoOutputStream proto = new ProtoOutputStream();
+            proto.write(MAGIC_NUMBER, MAGIC_NUMBER_VALUE);
+            writeHandlerMappingToProto(proto);
+            int pid = android.os.Process.myPid();
+            LogAndPrintln.i(pw, "Writing file to " + file.getAbsolutePath()
+                    + " from process " + pid);
+            mTraceBuffer.writeTraceToFile(file, proto);
+        } catch (IOException e) {
+            LogAndPrintln.e(pw, "Unable to write buffer to file", e);
+        }
+        Trace.endSection();
+    }
+
+    private void writeHandlerMappingToProto(ProtoOutputStream outputStream) {
+        for (Transitions.TransitionHandler handler : mHandlerUseCountInTrace.keySet()) {
+            final int count = mHandlerUseCountInTrace.get(handler);
+            if (count > 0) {
+                final long protoToken = outputStream.start(
+                        com.android.wm.shell.WmShellTransitionTraceProto.HANDLER_MAPPINGS);
+                outputStream.write(com.android.wm.shell.HandlerMapping.ID,
+                        mHandlerIds.get(handler));
+                outputStream.write(com.android.wm.shell.HandlerMapping.NAME,
+                        handler.getClass().getName());
+                outputStream.end(protoToken);
+            }
+        }
+    }
+
+    private void handleOnEntryRemovedFromTrace(Object proto) {
+        if (mRemovedFromTraceCallbacks.containsKey(proto)) {
+            mRemovedFromTraceCallbacks.get(proto).run();
+            mRemovedFromTraceCallbacks.remove(proto);
+        }
+    }
+
+    @Override
+    public boolean onShellCommand(String[] args, PrintWriter pw) {
+        switch (args[0]) {
+            case "start": {
+                startTrace(pw);
+                return true;
+            }
+            case "stop": {
+                stopTrace(pw);
+                return true;
+            }
+            case "save-for-bugreport": {
+                saveForBugreport(pw);
+                return true;
+            }
+            default: {
+                pw.println("Invalid command: " + args[0]);
+                printShellCommandHelp(pw, "");
+                return false;
+            }
+        }
+    }
+
+    @Override
+    public void printShellCommandHelp(PrintWriter pw, String prefix) {
+        pw.println(prefix + "start");
+        pw.println(prefix + "  Start tracing the transitions.");
+        pw.println(prefix + "stop");
+        pw.println(prefix + "  Stop tracing the transitions.");
+        pw.println(prefix + "save-for-bugreport");
+        pw.println(prefix + "  Flush in memory transition trace to file.");
+    }
+
+    private static class LogAndPrintln {
+        private static final String LOG_TAG = "ShellTransitionTracer";
+
+        private static void i(@Nullable PrintWriter pw, String msg) {
+            Log.i(LOG_TAG, msg);
+            if (pw != null) {
+                pw.println(msg);
+                pw.flush();
+            }
+        }
+
+        private static void e(@Nullable PrintWriter pw, String msg) {
+            Log.e(LOG_TAG, msg);
+            if (pw != null) {
+                pw.println("ERROR: " + msg);
+                pw.flush();
+            }
+        }
+
+        private static void e(@Nullable PrintWriter pw, String msg, @NonNull Exception e) {
+            Log.e(LOG_TAG, msg, e);
+            if (pw != null) {
+                pw.println("ERROR: " + msg + " ::\n " + e);
+                pw.flush();
+            }
+        }
+    }
+}
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Transitions.java b/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Transitions.java
index a4057b1328f4..f79f1f7a27b1 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Transitions.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Transitions.java
@@ -74,10 +74,12 @@ import com.android.wm.shell.common.ShellExecutor;
 import com.android.wm.shell.common.TransactionPool;
 import com.android.wm.shell.common.annotations.ExternalThread;
 import com.android.wm.shell.protolog.ShellProtoLogGroup;
+import com.android.wm.shell.sysui.ShellCommandHandler;
 import com.android.wm.shell.sysui.ShellController;
 import com.android.wm.shell.sysui.ShellInit;
 import com.android.wm.shell.util.TransitionUtil;
 
+import java.io.PrintWriter;
 import java.util.ArrayList;
 import java.util.Arrays;
 
@@ -106,7 +108,8 @@ import java.util.Arrays;
  * track, it will be marked as SYNC. This means that all currently active tracks must be flushed
  * before the SYNC transition can play.
  */
-public class Transitions implements RemoteCallable<Transitions> {
+public class Transitions implements RemoteCallable<Transitions>,
+        ShellCommandHandler.ShellCommandActionHandler {
     static final String TAG = "ShellTransitions";
 
     /** Set to {@code true} to enable shell transitions. */
@@ -165,12 +168,15 @@ public class Transitions implements RemoteCallable<Transitions> {
     private final ShellController mShellController;
     private final ShellTransitionImpl mImpl = new ShellTransitionImpl();
     private final SleepHandler mSleepHandler = new SleepHandler();
-
+    private final Tracer mTracer = new Tracer();
     private boolean mIsRegistered = false;
 
     /** List of possible handlers. Ordered by specificity (eg. tapped back to front). */
     private final ArrayList<TransitionHandler> mHandlers = new ArrayList<>();
 
+    @Nullable
+    private final ShellCommandHandler mShellCommandHandler;
+
     private final ArrayList<TransitionObserver> mObservers = new ArrayList<>();
 
     /** List of {@link Runnable} instances to run when the last active transition has finished.  */
@@ -246,8 +252,23 @@ public class Transitions implements RemoteCallable<Transitions> {
             @NonNull WindowOrganizer organizer,
             @NonNull TransactionPool pool,
             @NonNull DisplayController displayController,
-            @NonNull ShellExecutor mainExecutor, @NonNull Handler mainHandler,
+            @NonNull ShellExecutor mainExecutor,
+            @NonNull Handler mainHandler,
             @NonNull ShellExecutor animExecutor) {
+        this(context, shellInit, shellController, organizer, pool, displayController, mainExecutor,
+                mainHandler, animExecutor, null);
+    }
+
+    public Transitions(@NonNull Context context,
+            @NonNull ShellInit shellInit,
+            @NonNull ShellController shellController,
+            @NonNull WindowOrganizer organizer,
+            @NonNull TransactionPool pool,
+            @NonNull DisplayController displayController,
+            @NonNull ShellExecutor mainExecutor,
+            @NonNull Handler mainHandler,
+            @NonNull ShellExecutor animExecutor,
+            @Nullable ShellCommandHandler shellCommandHandler) {
         mOrganizer = organizer;
         mContext = context;
         mMainExecutor = mainExecutor;
@@ -263,6 +284,7 @@ public class Transitions implements RemoteCallable<Transitions> {
         ProtoLog.v(ShellProtoLogGroup.WM_SHELL_TRANSITIONS, "addHandler: Default");
         // Next lowest priority is remote transitions.
         mHandlers.add(mRemoteTransitionHandler);
+        mShellCommandHandler = shellCommandHandler;
         ProtoLog.v(ShellProtoLogGroup.WM_SHELL_TRANSITIONS, "addHandler: Remote");
         shellInit.addInitCallback(this::onInit, this);
     }
@@ -294,6 +316,10 @@ public class Transitions implements RemoteCallable<Transitions> {
             // Pre-load the instance.
             TransitionMetrics.getInstance();
         }
+
+        if (mShellCommandHandler != null) {
+            mShellCommandHandler.addCommandCallback("transitions", this, this);
+        }
     }
 
     public boolean isRegistered() {
@@ -766,6 +792,7 @@ public class Transitions implements RemoteCallable<Transitions> {
         ProtoLog.v(ShellProtoLogGroup.WM_SHELL_TRANSITIONS, "Transition %s ready while"
                 + " %s is still animating. Notify the animating transition"
                 + " in case they can be merged", ready, playing);
+        mTracer.logMergeRequested(ready.mInfo.getDebugId(), playing.mInfo.getDebugId());
         playing.mHandler.mergeAnimation(ready.mToken, ready.mInfo, ready.mStartT,
                 playing.mToken, (wct, cb) -> onMerged(playing, ready));
     }
@@ -799,6 +826,7 @@ public class Transitions implements RemoteCallable<Transitions> {
         for (int i = 0; i < mObservers.size(); ++i) {
             mObservers.get(i).onTransitionMerged(merged.mToken, playing.mToken);
         }
+        mTracer.logMerged(merged.mInfo.getDebugId(), playing.mInfo.getDebugId());
         // See if we should merge another transition.
         processReadyQueue(track);
     }
@@ -825,6 +853,8 @@ public class Transitions implements RemoteCallable<Transitions> {
         // Otherwise give every other handler a chance
         active.mHandler = dispatchTransition(active.mToken, active.mInfo, active.mStartT,
                 active.mFinishT, (wct, cb) -> onFinish(active, wct, cb), active.mHandler);
+
+        mTracer.logDispatched(active.mInfo.getDebugId(), active.mHandler);
     }
 
     /**
@@ -876,6 +906,8 @@ public class Transitions implements RemoteCallable<Transitions> {
         transition.mFinishT.apply();
         transition.mAborted = true;
 
+        mTracer.logAborted(transition.mInfo.getDebugId());
+
         if (transition.mHandler != null) {
             // Notifies to clean-up the aborted transition.
             transition.mHandler.onTransitionConsumed(
@@ -1350,4 +1382,26 @@ public class Transitions implements RemoteCallable<Transitions> {
             mMainExecutor.execute(() -> dispatchAnimScaleSetting(mTransitionAnimationScaleSetting));
         }
     }
+
+
+    @Override
+    public boolean onShellCommand(String[] args, PrintWriter pw) {
+        switch (args[0]) {
+            case "tracing": {
+                mTracer.onShellCommand(Arrays.copyOfRange(args, 1, args.length), pw);
+                return true;
+            }
+            default: {
+                pw.println("Invalid command: " + args[0]);
+                printShellCommandHelp(pw, "");
+                return false;
+            }
+        }
+    }
+
+    @Override
+    public void printShellCommandHelp(PrintWriter pw, String prefix) {
+        pw.println(prefix + "tracing");
+        mTracer.printShellCommandHelp(pw, prefix + "  ");
+    }
 }