Refactor border detection logic in crop functionality to target nearest edge instead of whatever the fuck random one

Enhance the border detection mechanism in the VideoEditor class by calculating distances to each border and identifying the closest one. This change ensures that the closest border is returned only if within the specified threshold, improving user interaction during crop adjustments.

croppa/main.py

@@ -3773,23 +3773,35 @@ class VideoEditor:
 
         # Handle crop border dragging (only when Shift and Ctrl are NOT pressed)
         if not (flags & cv2.EVENT_FLAG_SHIFTKEY) and not (flags & cv2.EVENT_FLAG_CTRLKEY) and self.crop_rect:
-            border_threshold = 800  # pixels
+            border_threshold = 800  # pixels - maximum distance to consider
             
             # Get effective crop in rotated coords and map to screen
             eff_x, eff_y, eff_w, eff_h = self._get_effective_crop_rect_for_frame(getattr(self, 'current_frame', 0))
             sx1, sy1 = self._map_rotated_to_screen(eff_x, eff_y)
             sx2, sy2 = self._map_rotated_to_screen(eff_x + eff_w, eff_y + eff_h)
             
-            # Detect which border is near
+            # Detect which border is closest to cursor
             def detect_border():
-                if abs(x - sx1) < border_threshold and sy1 <= y <= sy2:
-                    return 'left'
-                elif abs(x - sx2) < border_threshold and sy1 <= y <= sy2:
-                    return 'right'
-                elif abs(y - sy1) < border_threshold and sx1 <= x <= sx2:
-                    return 'top'
-                elif abs(y - sy2) < border_threshold and sx1 <= x <= sx2:
-                    return 'bottom'
+                # Calculate distances to each border
+                dist_left = abs(x - sx1) if sy1 <= y <= sy2 else float('inf')
+                dist_right = abs(x - sx2) if sy1 <= y <= sy2 else float('inf')
+                dist_top = abs(y - sy1) if sx1 <= x <= sx2 else float('inf')
+                dist_bottom = abs(y - sy2) if sx1 <= x <= sx2 else float('inf')
+                
+                # Find closest border
+                distances = {
+                    'left': dist_left,
+                    'right': dist_right,
+                    'top': dist_top,
+                    'bottom': dist_bottom
+                }
+                
+                closest_edge = min(distances, key=distances.get)
+                closest_dist = distances[closest_edge]
+                
+                # Only return if within threshold
+                if closest_dist < border_threshold:
+                    return closest_edge
                 return None
             
             if event == cv2.EVENT_LBUTTONDOWN: