app: report whether a recording was actually written

MuxRecorder had a Listener interface that nothing implemented; every
callback fired into a no-op. Delete it. stop() now returns whether a
keyframe ever landed and the muxer ran, so Mirror can stop claiming
"recording saved" when no file was written.

3 files changed, 21 insertions, 36 deletions

diff --git a/app/src/main/java/invalid/lena/scrcpy/Mirror.java b/app/src/main/java/invalid/lena/scrcpy/Mirror.java
index f6e249d..2c361da 100644
--- a/app/src/main/java/invalid/lena/scrcpy/Mirror.java
+++ b/app/src/main/java/invalid/lena/scrcpy/Mirror.java
@@ -260,8 +260,11 @@ public final class Mirror extends Activity {
     private void toggleRecord() {
         if (session == null) return;
         if (session.isRecording()) {
-            session.stopRecording();
-            Toast.makeText(this, "recording saved", Toast.LENGTH_SHORT).show();
+            // stopRecording is false when no keyframe ever landed (still
+            // ARMED) - no file was written, so don't claim one was saved.
+            boolean saved = session.stopRecording();
+            Toast.makeText(this, saved ? "recording saved" : "recording discarded (no video)",
+                    Toast.LENGTH_SHORT).show();
         } else {
             File dir = getExternalFilesDir(null);
             if (dir == null) {
diff --git a/app/src/main/java/invalid/lena/scrcpy/MuxRecorder.java b/app/src/main/java/invalid/lena/scrcpy/MuxRecorder.java
index 457272e..d06551e 100644
--- a/app/src/main/java/invalid/lena/scrcpy/MuxRecorder.java
+++ b/app/src/main/java/invalid/lena/scrcpy/MuxRecorder.java
@@ -26,19 +26,9 @@ import java.nio.ByteBuffer;
 // illegal). User can re-arm; a fresh output gets the new dimensions.
 public final class MuxRecorder implements VideoRecorder {
 
-    public interface Listener {
-        // Fires on the recorder thread; main use is updating the UI's
-        // record button label once writing actually begins (we may be
-        // ARMED for many frames before a keyframe lands).
-        default void onStarted(File out) {}
-        default void onStopped(File out, long bytes) {}
-        default void onError(Throwable t) {}
-    }
-
     private enum State { IDLE, ARMED, RECORDING, ERROR }
 
     private final Object lock = new Object();
-    private final Listener listener;
 
     private State state = State.IDLE;
     private int   fourcc, w, h;
@@ -51,12 +41,6 @@ public final class MuxRecorder implements VideoRecorder {
     private long         firstPtsUs = -1;
     private long         lastPtsUs  = -1;
 
-    public MuxRecorder() { this(null); }
-
-    public MuxRecorder(Listener listener) {
-        this.listener = listener != null ? listener : new Listener() {};
-    }
-
     // Externally-driven controls.
 
     public void arm(File out) {
@@ -74,21 +58,22 @@ public final class MuxRecorder implements VideoRecorder {
         Log.i("rec: armed -> %s", out);
     }
 
-    public void stop() {
-        File out;
+    // Returns true if a recording was actually written (a keyframe landed
+    // and the muxer ran); false if we were still ARMED, so the caller can
+    // tell the user the truth instead of claiming a file was saved.
+    public boolean stop() {
         long bytes;
-        boolean reportStopped;
+        boolean wrote;
         synchronized (lock) {
-            if (state == State.IDLE) return;
-            reportStopped = (state == State.RECORDING);
+            if (state == State.IDLE) return false;
+            wrote = (state == State.RECORDING);
             closeMuxerLocked();
-            out = outFile;
             bytes = bytesWritten;
             state = State.IDLE;
             outFile = null;
         }
         Log.i("rec: stopped (%d bytes)", bytes);
-        if (reportStopped) listener.onStopped(out, bytes);
+        return wrote;
     }
 
     public boolean isActive() {
@@ -102,17 +87,15 @@ public final class MuxRecorder implements VideoRecorder {
     @Override
     public void onMeta(int fcc, int width, int height) {
         synchronized (lock) {
-            // Resize during recording → close, surface as an error so
-            // the UI can re-arm. addTrack after start is illegal; we
-            // don't try to splice tracks together.
+            // Resize during recording → close the file. addTrack after
+            // start is illegal; we don't try to splice tracks together.
+            // The user can re-arm; a fresh output gets the new dimensions.
             if (state == State.RECORDING && (fcc != fourcc || width != w || height != h)) {
-                Log.w("rec: resize/codec change during recording - closing");
-                File out = outFile;
-                long bytes = bytesWritten;
+                Log.w("rec: resize/codec change during recording - closing (%d bytes)",
+                        bytesWritten);
                 closeMuxerLocked();
                 state = State.IDLE;
                 outFile = null;
-                listener.onStopped(out, bytes);
             }
             fourcc = fcc; w = width; h = height;
         }
@@ -142,7 +125,6 @@ public final class MuxRecorder implements VideoRecorder {
                     }
                     writeSampleLocked(data, ptsUs, true);
                     state = State.RECORDING;
-                    listener.onStarted(outFile);
                     return;
                 case RECORDING:
                     writeSampleLocked(data, ptsUs, isKeyframe);
@@ -177,7 +159,6 @@ public final class MuxRecorder implements VideoRecorder {
             try { if (muxer != null) muxer.release(); } catch (Exception ignored) {}
             muxer = null;
             trackIdx = -1;
-            listener.onError(e);
             return false;
         }
     }
diff --git a/app/src/main/java/invalid/lena/scrcpy/Session.java b/app/src/main/java/invalid/lena/scrcpy/Session.java
index 019ce80..774fdc1 100644
--- a/app/src/main/java/invalid/lena/scrcpy/Session.java
+++ b/app/src/main/java/invalid/lena/scrcpy/Session.java
@@ -138,9 +138,10 @@ public final class Session {
         r.arm(out);
     }
 
-    public void stopRecording() {
+    // Returns true if a file was actually written (see MuxRecorder.stop).
+    public boolean stopRecording() {
         MuxRecorder r = recorder;
-        if (r != null) r.stop();
+        return r != null && r.stop();
     }
 
     public boolean isRecording() {