feat(main.py): add undo jump functionality with H key

main.py

@@ -87,6 +87,9 @@ class MediaGrader:
         # Bisection navigation tracking
         self.last_jump_position = {}  # Dict[file_path: last_frame] for bisection reference
 
+        # Jump history for H key (undo jump)
+        self.jump_history = {}  # Dict[file_path: List[frame_positions]] for jump undo
+
     def find_media_files(self) -> List[Path]:
         """Find all media files recursively in the directory"""
         media_files = []
@@ -313,6 +316,11 @@ class MediaGrader:
         # Track last position for bisection
         self.last_jump_position[current_file] = self.current_frame
         
+        # Track jump history for H key undo
+        if current_file not in self.jump_history:
+            self.jump_history[current_file] = []
+        self.jump_history[current_file].append(self.current_frame)
+        
         # Jump to the target frame
         self.current_cap.set(cv2.CAP_PROP_POS_FRAMES, target_frame)
         self.load_current_frame()
@@ -415,6 +423,36 @@ class MediaGrader:
         print(f"Bisected forwards to frame {midpoint} ({percentage:.1f}% through video)")
         return True
 
+    def undo_jump(self):
+        """Undo the last L jump by returning to previous position"""
+        if not self.is_video(self.media_files[self.current_index]):
+            return False
+            
+        current_file = str(self.media_files[self.current_index])
+        
+        if current_file not in self.jump_history or not self.jump_history[current_file]:
+            print("No jump history to undo. Use L first to establish jump points.")
+            return False
+        
+        # Get the last position before the most recent jump
+        if len(self.jump_history[current_file]) < 1:
+            print("No previous position to return to.")
+            return False
+        
+        # Remove the current position from history and get the previous one
+        previous_position = self.jump_history[current_file].pop()
+        
+        # Jump back to previous position
+        self.current_cap.set(cv2.CAP_PROP_POS_FRAMES, previous_position)
+        self.load_current_frame()
+        
+        # Update last jump position for bisection reference
+        self.last_jump_position[current_file] = previous_position
+        
+        percentage = (previous_position / self.total_frames) * 100
+        print(f"Undid jump: returned to frame {previous_position} ({percentage:.1f}% through video)")
+        return True
+
     def display_current_frame(self):
         """Display the current cached frame with overlays"""
         if self.current_display_frame is None:
@@ -719,8 +757,9 @@ class MediaGrader:
         print("  P: Previous file")
         print("  U: Undo last grading action")
         print("  L: Sample video at key points (videos only)")
-        print("  K: Bisect backwards from current position (videos only)")
-        print("  J: Bisect forwards toward next sample (videos only)")
+        print("  H: Undo last L jump (videos only)")
+        print("  J: Bisect backwards from current position (videos only)")
+        print("  K: Bisect forwards toward next sample (videos only)")
         print("  Q/ESC: Quit")
 
         cv2.namedWindow("Media Grader", cv2.WINDOW_NORMAL)
@@ -782,6 +821,8 @@ class MediaGrader:
                     self.bisect_backwards()
                 elif key == ord("k"):
                     self.bisect_forwards()
+                elif key == ord("h"): # Changed from "j" to "h" for undo jump
+                    self.undo_jump()
                 elif key in [ord("1"), ord("2"), ord("3"), ord("4"), ord("5")]:
                     grade = int(chr(key))
                     if not self.grade_media(grade):