Refactor motion path logic in VideoEditor for clarity

This commit updates the VideoEditor class to improve the logic for drawing and checking motion paths between tracking points. The comments have been adjusted to clarify the conditions for drawing lines between previous→current and previous→next frames. Additionally, debug statements have been enhanced to provide clearer insights during the snapping process, ensuring better tracking point interactions.

croppa/main.py

@@ -510,7 +510,7 @@ class VideoEditor:
     CROP_SIZE_STEP = 15  # pixels to expand/contract crop
 
     # Motion tracking settings
-    TRACKING_POINT_THRESHOLD = 20  # pixels for delete/snap radius
+    TRACKING_POINT_THRESHOLD = 10  # pixels for delete/snap radius
 
     # Seek frame counts
     SEEK_FRAMES_CTRL = 60  # Ctrl modifier: 60 frames
@@ -2033,35 +2033,42 @@ class VideoEditor:
             prev_result = self._get_previous_tracking_point()
             next_result = self._get_next_tracking_point()
             
-            # Draw motion path if we have both previous and next points
-            if prev_result and next_result:
-                prev_frame, prev_pts = prev_result
-                next_frame, next_pts = next_result
+            # Draw motion path - either previous→current OR previous→next
+            line_to_draw = None
+            if prev_result and self.current_frame in self.tracking_points:
+                # Draw previous→current line (we're on a frame with tracking points)
+                line_to_draw = ("prev_current", prev_result, (self.current_frame, self.tracking_points[self.current_frame]))
+            elif prev_result and next_result:
+                # Draw previous→next line (we're between frames)
+                line_to_draw = ("prev_next", prev_result, next_result)
+            
+            if line_to_draw:
+                line_type, (frame1, pts1), (frame2, pts2) = line_to_draw
                 
                 # Draw lines between corresponding tracking points
-                for i, (prev_rx, prev_ry) in enumerate(prev_pts):
-                    if i < len(next_pts):
-                        next_rx, next_ry = next_pts[i]
-                        prev_sx, prev_sy = self._map_rotated_to_screen(prev_rx, prev_ry)
-                        next_sx, next_sy = self._map_rotated_to_screen(next_rx, next_ry)
+                for i, (px1, py1) in enumerate(pts1):
+                    if i < len(pts2):
+                        px2, py2 = pts2[i]
+                        sx1, sy1 = self._map_rotated_to_screen(px1, py1)
+                        sx2, sy2 = self._map_rotated_to_screen(px2, py2)
                         
                         # Draw motion path line with arrow (thin and transparent)
                         overlay = canvas.copy()
-                        cv2.line(overlay, (prev_sx, prev_sy), (next_sx, next_sy), (255, 255, 0), 1)  # Thin yellow line
+                        cv2.line(overlay, (sx1, sy1), (sx2, sy2), (255, 255, 0), 1)  # Thin yellow line
                         
-                        # Draw arrow head pointing from previous to next
-                        angle = np.arctan2(next_sy - prev_sy, next_sx - prev_sx)
+                        # Draw arrow head pointing from first to second point
+                        angle = np.arctan2(sy2 - sy1, sx2 - sx1)
                         arrow_length = 12
                         arrow_angle = np.pi / 6  # 30 degrees
                         
                         # Calculate arrow head points
-                        arrow_x1 = int(next_sx - arrow_length * np.cos(angle - arrow_angle))
-                        arrow_y1 = int(next_sy - arrow_length * np.sin(angle - arrow_angle))
-                        arrow_x2 = int(next_sx - arrow_length * np.cos(angle + arrow_angle))
-                        arrow_y2 = int(next_sy - arrow_length * np.sin(angle + arrow_angle))
+                        arrow_x1 = int(sx2 - arrow_length * np.cos(angle - arrow_angle))
+                        arrow_y1 = int(sy2 - arrow_length * np.sin(angle - arrow_angle))
+                        arrow_x2 = int(sx2 - arrow_length * np.cos(angle + arrow_angle))
+                        arrow_y2 = int(sy2 - arrow_length * np.sin(angle + arrow_angle))
                         
-                        cv2.line(overlay, (next_sx, next_sy), (arrow_x1, arrow_y1), (255, 255, 0), 1)
-                        cv2.line(overlay, (next_sx, next_sy), (arrow_x2, arrow_y2), (255, 255, 0), 1)
+                        cv2.line(overlay, (sx2, sy2), (arrow_x1, arrow_y1), (255, 255, 0), 1)
+                        cv2.line(overlay, (sx2, sy2), (arrow_x2, arrow_y2), (255, 255, 0), 1)
                         cv2.addWeighted(overlay, 0.3, canvas, 0.7, 0, canvas)  # Very transparent
             
             # Previous tracking point (red) - from the most recent frame with tracking points before current
@@ -2196,22 +2203,30 @@ class VideoEditor:
                                 best_snap_distance = distance
                                 best_snap_point = (int(px), int(py))
                     
-                    # Check for line snapping between previous and next tracking points (the actual cyan arrows)
+                    # Check for line snapping - either previous→next OR previous→current
                     prev_result = self._get_previous_tracking_point()
                     next_result = self._get_next_tracking_point()
                     
                     print(f"DEBUG: Line snapping - prev_result: {prev_result}, next_result: {next_result}")
                     
-                    if prev_result and next_result:
-                        prev_frame, prev_pts = prev_result
-                        next_frame, next_pts = next_result
+                    # Determine which line to check: previous→current OR previous→next
+                    line_to_check = None
+                    if prev_result and self.current_frame in self.tracking_points:
+                        # Check previous→current line (we're on a frame with tracking points)
+                        line_to_check = ("prev_current", prev_result, (self.current_frame, self.tracking_points[self.current_frame]))
+                        print(f"DEBUG: Checking prev->current line")
+                    elif prev_result and next_result:
+                        # Check previous→next line (we're between frames)
+                        line_to_check = ("prev_next", prev_result, next_result)
+                        print(f"DEBUG: Checking prev->next line")
                     
-                        print(f"DEBUG: Checking line between prev frame {prev_frame} and next frame {next_frame}")
+                    if line_to_check:
+                        line_type, (frame1, pts1), (frame2, pts2) = line_to_check
                         
-                        # Check each corresponding pair of points between previous and next
-                        for j in range(min(len(prev_pts), len(next_pts))):
-                            px1, py1 = prev_pts[j]
-                            px2, py2 = next_pts[j]
+                        # Check each corresponding pair of points
+                        for j in range(min(len(pts1), len(pts2))):
+                            px1, py1 = pts1[j]
+                            px2, py2 = pts2[j]
                             
                             # Convert to screen coordinates
                             sx1, sy1 = self._map_rotated_to_screen(px1, py1)
@@ -2220,35 +2235,19 @@ class VideoEditor:
                             # Calculate distance to infinite line and foot of perpendicular
                             line_distance, (foot_x, foot_y) = self._point_to_line_distance_and_foot(x, y, sx1, sy1, sx2, sy2)
                             
-                            print(f"DEBUG: Line {j}: ({sx1},{sy1}) to ({sx2},{sy2}), distance to click ({x},{y}) = {line_distance:.2f}, foot = ({foot_x:.1f}, {foot_y:.1f})")
+                            print(f"DEBUG: {line_type} Line {j}: ({sx1},{sy1}) to ({sx2},{sy2}), distance to click ({x},{y}) = {line_distance:.2f}, foot = ({foot_x:.1f}, {foot_y:.1f})")
                             
                             if line_distance <= threshold and line_distance < best_snap_distance:
                                 print(f"DEBUG: Line snap found! Distance {line_distance:.2f} <= threshold {threshold}")
                                 
-                                # Clamp the foot to the line segment
-                                # Calculate parameter t for the foot point
-                                line_dx = sx2 - sx1
-                                line_dy = sy2 - sy1
-                                line_length_sq = line_dx * line_dx + line_dy * line_dy
-                                
-                                if line_length_sq > 0:
-                                    t = ((foot_x - sx1) * line_dx + (foot_y - sy1) * line_dy) / line_length_sq
-                                    t = max(0, min(1, t))  # Clamp to [0, 1]
-                                    
-                                    # Calculate clamped foot point
-                                    clamped_foot_x = sx1 + t * line_dx
-                                    clamped_foot_y = sy1 + t * line_dy
-                                    
-                                    print(f"DEBUG: Clamped foot from ({foot_x:.1f}, {foot_y:.1f}) to ({clamped_foot_x:.1f}, {clamped_foot_y:.1f})")
-                                    
-                                    # Convert clamped foot back to rotated coordinates
-                                    closest_rx, closest_ry = self._map_screen_to_rotated(int(clamped_foot_x), int(clamped_foot_y))
+                                # Convert foot of perpendicular back to rotated coordinates (no clamping - infinite line)
+                                closest_rx, closest_ry = self._map_screen_to_rotated(int(foot_x), int(foot_y))
                                 
                                 best_snap_distance = line_distance
                                 best_snap_point = (int(closest_rx), int(closest_ry))
                                 print(f"DEBUG: Best line snap point: ({closest_rx}, {closest_ry})")
                     else:
-                        print(f"DEBUG: No prev/next points found for line snapping")
+                        print(f"DEBUG: No line found for snapping")
                     
                     # Apply the best snap if found
                     if best_snap_point:
@@ -2272,6 +2271,9 @@ class VideoEditor:
                 self.clear_transformation_cache()
                 self.save_state()
                 
+                # Force immediate display update to recalculate previous/next points and arrows
+                self.display_current_frame()
+
         # Handle scroll wheel: Ctrl+scroll -> zoom; plain scroll -> seek ±1 frame (independent of multiplier)
         if event == cv2.EVENT_MOUSEWHEEL:
             if flags & cv2.EVENT_FLAG_CTRLKEY: