Fix Incomplete Output File Handling

Core/RenderManager.cs

@@ -226,6 +226,11 @@ internal class RenderManager : MonoBehaviour
     private GameObject? _debugMonitorObj;
     private GameObject? _escapeHandlerObj;
     internal string? CurrentOutPath;
+
+    // Output file of the current render that is not finished yet.
+    // Set just before the encoder opens the file, cleared by the render thread after the encoder finished the file (End).
+    // Only this file is deleted when a render is cancelled, fails or the game exits (DeleteIncompleteOutputFile).
+    private string? _incompleteOutputPath;
     private bool _renderSetup;
 
     private void Awake()
@@ -286,6 +291,32 @@ internal class RenderManager : MonoBehaviour
         {
             RenderThread.Join(200);
         }
+
+        // The encoders are disposed above, which closes the output file. An unfinished file of this render is deleted.
+        DeleteIncompleteOutputFile();
+    }
+
+    /// <summary>
+    /// Deletes the output file of the current render when the render did not finish it (_incompleteOutputPath).
+    /// Files of earlier, finished renders are never deleted.
+    /// Returns true when a file was deleted.
+    /// </summary>
+    private bool DeleteIncompleteOutputFile()
+    {
+        var path = Interlocked.Exchange(ref _incompleteOutputPath, null);
+        if (string.IsNullOrEmpty(path) || !File.Exists(path)) return false;
+
+        try
+        {
+            File.Delete(path);
+            Melon<RenderMod>.Logger.Msg($"[File Cleanup] Deleted incomplete video: {path}");
+            return true;
+        }
+        catch (Exception ex)
+        {
+            Melon<RenderMod>.Logger.Error($"[File Cleanup] Failed to delete incomplete video: {ex.Message}");
+            return false;
+        }
     }
 
     private void Update()
@@ -634,6 +665,7 @@ internal class RenderManager : MonoBehaviour
             {
                 _allVideoFFmpegInstances.Add(videoFFmpeg);
             }
+            Volatile.Write(ref _incompleteOutputPath, CurrentOutPath);
             videoFFmpeg.Start(CurrentOutPath);
         }
         catch (Exception)
@@ -735,7 +767,13 @@ internal class RenderManager : MonoBehaviour
                     FrameAvailableEvent.WaitOne(50);
                 }
 
-                if (!IsRenderAborted) videoFFmpeg.End();
+                if (!IsRenderAborted)
+                {
+                    // End throws when the file cannot be finished (e.g. the trailer cannot be written),
+                    // which is handled as a render failure by the catch block below.
+                    videoFFmpeg.End();
+                    Volatile.Write(ref _incompleteOutputPath, null);
+                }
                 videoFFmpeg.Dispose();
 
                 lock (_allVideoFFmpegInstances)
@@ -862,18 +900,9 @@ internal class RenderManager : MonoBehaviour
                 scrController.instance.noFailInfiniteMargin = false;
             }
 
-            // 6. Immediately delete cancelled incomplete temporary video file
-            if (!string.IsNullOrEmpty(CurrentOutPath) && File.Exists(CurrentOutPath))
+            // 6. Immediately delete the incomplete video file of this render
+            if (DeleteIncompleteOutputFile())
             {
-                try
-                {
-                    File.Delete(CurrentOutPath);
-                    Melon<RenderMod>.Logger.Msg($"[File Cleanup] Deleted incomplete video: {CurrentOutPath}");
-                }
-                catch (Exception ex)
-                {
-                    Melon<RenderMod>.Logger.Error($"[File Cleanup] Failed to delete temporary video: {ex.Message}");
-                }
                 CurrentOutPath = null;
             }