feat: add OpenDropZone widget for opening files with default applications via drag-and-drop

src/webdrop_bridge/ui/main_window.py

@@ -200,6 +200,101 @@ DEFAULT_WELCOME_PAGE = """
 """
 
 
+class OpenDropZone(QWidget):
+    """Drop target widget that opens dragged files with their system default application.
+
+    Displays an 'open folder' icon in the navigation toolbar.  When a file is
+    dragged from the web view and dropped here, the file's URL is passed to
+    ``QDesktopServices.openUrl()`` so the OS opens it with the associated
+    programme — exactly the same way double-clicking a file in Explorer/Finder
+    would behave.
+
+    Visual feedback is provided on drag-enter (green border highlight) so the
+    user can see the drop target is active.
+
+    Signals:
+        file_opened (str): Emitted with the local file path when successfully opened.
+        file_open_failed (str, str): Emitted with (path, error_message) on failure.
+    """
+
+    file_opened = Signal(str)
+    file_open_failed = Signal(str, str)
+
+    _NORMAL_STYLE = "QLabel { padding: 4px; border: 2px solid transparent; border-radius: 4px; }"
+    _HOVER_STYLE = (
+        "QLabel { padding: 4px; border: 2px solid #4CAF50; border-radius: 4px;"
+        " background: #E8F5E9; }"
+    )
+
+    def __init__(self, parent: Optional[QWidget] = None) -> None:
+        """Initialize the OpenDropZone widget.
+
+        Args:
+            parent: Parent widget.
+        """
+        super().__init__(parent)
+        self.setAcceptDrops(True)
+
+        layout = QVBoxLayout(self)
+        layout.setContentsMargins(0, 0, 0, 0)
+
+        self._icon_label = QLabel(self)
+        icon = self.style().standardIcon(self.style().StandardPixmap.SP_DirOpenIcon)
+        pixmap = icon.pixmap(QSize(32, 32))
+        self._icon_label.setPixmap(pixmap)
+        self._icon_label.setAlignment(Qt.AlignmentFlag.AlignCenter)
+        self._icon_label.setStyleSheet(self._NORMAL_STYLE)
+        self._icon_label.setToolTip("Drop a file here to open it with its default application")
+        layout.addWidget(self._icon_label)
+
+        self.setMinimumSize(QSize(44, 44))
+        self.setMaximumSize(QSize(48, 48))
+
+    # ------------------------------------------------------------------
+    # Drop handling
+    # ------------------------------------------------------------------
+
+    def dragEnterEvent(self, event) -> None:  # type: ignore[override]
+        """Accept drag events that carry file URLs."""
+        if event.mimeData().hasUrls():
+            event.acceptProposedAction()
+            self._icon_label.setStyleSheet(self._HOVER_STYLE)
+        else:
+            event.ignore()
+
+    def dragLeaveEvent(self, event) -> None:  # type: ignore[override]
+        """Reset appearance when drag leaves the widget."""
+        self._icon_label.setStyleSheet(self._NORMAL_STYLE)
+        super().dragLeaveEvent(event)
+
+    def dropEvent(self, event) -> None:  # type: ignore[override]
+        """Open each dropped file with the system default application.
+
+        Accepts the drop action so that the originating ``QDrag`` reports
+        success (preserving normal drag-started accounting), then immediately
+        opens the file via ``QDesktopServices.openUrl()``.
+        """
+        self._icon_label.setStyleSheet(self._NORMAL_STYLE)
+        mime = event.mimeData()
+        if not mime.hasUrls():
+            event.ignore()
+            return
+
+        event.acceptProposedAction()
+        for url in mime.urls():
+            if url.isLocalFile():
+                file_path = url.toLocalFile()
+                logger.info(f"OpenDropZone: opening '{file_path}' with system default app")
+                if QDesktopServices.openUrl(url):
+                    self.file_opened.emit(file_path)
+                else:
+                    msg = "OS could not open the file"
+                    logger.warning(f"OpenDropZone: {msg}: {file_path}")
+                    self.file_open_failed.emit(file_path, msg)
+            else:
+                logger.debug(f"OpenDropZone: skipping non-local URL {url.toString()}")
+
+
 class _DragBridge(QObject):
     """JavaScript bridge for drag operations via QWebChannel.
 
@@ -899,6 +994,30 @@ class MainWindow(QMainWindow):
             f"Could not complete the drag-and-drop operation.\n\nError: {error}",
         )
 
+    def _on_file_opened_via_drop(self, file_path: str) -> None:
+        """Handle a file successfully opened via the OpenDropZone.
+
+        Args:
+            file_path: Local file path that was opened.
+        """
+        logger.info(f"Opened via drop zone: {file_path}")
+        self.statusBar().showMessage(f"Opened: {Path(file_path).name}", 4000)
+
+    def _on_file_open_failed_via_drop(self, file_path: str, error: str) -> None:
+        """Handle a failure to open a file dropped on the OpenDropZone.
+
+        Args:
+            file_path: Local file path that could not be opened.
+            error: Error description.
+        """
+        logger.warning(f"Failed to open via drop zone '{file_path}': {error}")
+        QMessageBox.warning(
+            self,
+            "Open File Error",
+            f"Could not open the file with its default application.\n\n"
+            f"File: {file_path}\nError: {error}",
+        )
+
     def _on_download_requested(self, download: QWebEngineDownloadRequest) -> None:
         """Handle download requests from the embedded web view.
 
@@ -1102,6 +1221,14 @@ class MainWindow(QMainWindow):
         refresh_action = self.web_view.pageAction(self.web_view.page().WebAction.Reload)
         toolbar.addAction(refresh_action)
 
+        # Open-with-default-app drop zone (right of Reload)
+        self._open_drop_zone = OpenDropZone()
+        self._open_drop_zone.file_opened.connect(self._on_file_opened_via_drop)
+        self._open_drop_zone.file_open_failed.connect(self._on_file_open_failed_via_drop)
+        open_drop_action = QWidgetAction(toolbar)
+        open_drop_action.setDefaultWidget(self._open_drop_zone)
+        toolbar.addAction(open_drop_action)
+
         # Add stretch spacer to push help buttons to the right
         spacer = QWidget()
         spacer.setSizePolicy(QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Minimum)

src/webdrop_bridge/ui/restricted_web_view.py

@@ -204,7 +204,7 @@ class RestrictedWebEngineView(QWebEngineView):
         - Exact domain matches: example.com
         - Wildcard patterns: *.example.com
         - Localhost variations: localhost, 127.0.0.1
-        - File URLs: file://...
+        - Internal/local URLs: file://, data:, about:, blob:, qrc:
 
         Args:
             url: QUrl to check
@@ -216,8 +216,8 @@ class RestrictedWebEngineView(QWebEngineView):
         host = url.host()
         scheme = url.scheme()
 
-        # Allow file:// URLs (local webapp)
-        if scheme == "file":
+        # Allow internal browser/Qt schemes (never send these to the OS)
+        if scheme in ("file", "data", "about", "blob", "qrc"):
             return True
 
         # If no whitelist, allow all URLs