feat(ui): enable drag-and-drop file loading

.gitignore

@@ -248,3 +248,5 @@ test_results/
 # Keep docs/*.md and tests fixtures tracked; only ignore root-level files
 /AGENTS.md
 /*.txt
+!CubeMain.txt
+!CubeMainWorking.txt

CubeMain.txt

@@ -0,0 +1,2 @@
+col1	col2
+1	2

CubeMainWorking.txt

@@ -0,0 +1,2 @@
+col1	col2
+1	2

README.md

@@ -48,6 +48,7 @@ Diablo2TextEditor/
 - **UI Editor**: Full-featured graphical interface for editing game data
 - **Format Validation**: Comprehensive file format verification
 - **PDF Extraction**: Tools for extracting data from PDF documentation
+- **Drag-and-Drop Loading**: Open any supported `.txt` file by simply dropping it onto the editor window
 
 ## Installation
 

file_bindings.py

@@ -17,7 +17,8 @@ class DataFileBinding:
 
     def __init__(self, json_path: str, txt_path: str = None, metadata: Dict = None):
         self.json_path = json_path
-        self.txt_path = txt_path
+        # Use an empty string for unbound txt paths so os.path functions don't error.
+        self.txt_path = txt_path or ""
         self.metadata = metadata or {}
         self.base_name = Path(json_path).stem
 
@@ -33,7 +34,7 @@ def load_metadata(self) -> Dict:
 
     def load_data(self):
         """Load the actual data from the .txt file."""
-        if self.txt_path is None:
+        if not self.txt_path:
             raise ValueError("No txt file path set for this binding. Use create_dynamic_binding() first.")
         return open_txt_file(self.txt_path)
 

ui.py

@@ -662,25 +662,25 @@ def _load_file_path(self, file_path: str):
 
     # Drag-and-drop support
     def dragEnterEvent(self, event):
+        """Allow drag if payload contains at least one local .txt file."""
         if event.mimeData().hasUrls():
-            # Accept if any of the URLs is a .txt file
-            for url in event.mimeData().urls():
-                if url.isLocalFile() and url.toLocalFile().lower().endswith('.txt'):
-                    event.acceptProposedAction()
-                    return
+            urls = event.mimeData().urls()
+            if any(u.isLocalFile() and u.toLocalFile().lower().endswith(".txt") for u in urls):
+                event.acceptProposedAction()
+                return
         event.ignore()
 
+    def dragMoveEvent(self, event):
+        """Continuously accept drags containing valid .txt files."""
+        self.dragEnterEvent(event)
+
     def dropEvent(self, event):
-        handled = False
+        """Open the first dropped .txt file."""
         for url in event.mimeData().urls():
-            local = url.toLocalFile()
-            if url.isLocalFile() and local.lower().endswith('.txt'):
-                self._load_file_path(local)
-                handled = True
-                # Load only first file for now
+            if url.isLocalFile() and url.toLocalFile().lower().endswith(".txt"):
+                self._load_file_path(url.toLocalFile())
+                event.acceptProposedAction()
                 break
-        if handled:
-            event.acceptProposedAction()
         else:
             event.ignore()