Fix silent printing and shorten printer display names

- Print directly via win32print API without opening PDF viewer
- Shorten printer names to 20 chars in dropdown (strip server prefix for network printers)
- Map display names back to full names for printing
- PDF backup saved silently without launching viewer

label_printer_gui.py

@@ -38,15 +38,42 @@ class LabelPrinterApp(App):
     
     def __init__(self, **kwargs):
         super().__init__(**kwargs)
-        self.available_printers = self.get_available_printers()
+        # Build printer display names and mapping to full names
+        full_printers = get_available_printers()
+        self.printer_display_map = {}  # display_name -> full_name
+        self.available_printers = []
+        for full_name in full_printers:
+            display_name = self._shorten_printer_name(full_name)
+            # Ensure unique display names
+            if display_name in self.printer_display_map:
+                display_name = full_name[:20]
+            self.printer_display_map[display_name] = full_name
+            self.available_printers.append(display_name)
         # Clean old PDF backup files on startup
         self.cleanup_old_pdfs()
         # Clean old log files on startup
         self.cleanup_old_logs()
     
-    def get_available_printers(self):
-        """Get list of available printers (cross-platform)"""
-        return get_available_printers()
+    def _shorten_printer_name(self, name, max_len=20):
+        """Shorten printer name for display (max 20 chars).
+        For network printers like \\\\server\\printer, show just the printer part."""
+        if name.startswith('\\\\'):
+            # Network printer: \\server\printer -> extract printer name
+            parts = name.strip('\\').split('\\')
+            if len(parts) >= 2:
+                short = parts[-1]  # Just the printer name
+            else:
+                short = name
+        else:
+            short = name
+        # Truncate to max_len
+        if len(short) > max_len:
+            short = short[:max_len]
+        return short
+    
+    def _get_full_printer_name(self, display_name):
+        """Resolve display name back to full printer name for printing."""
+        return self.printer_display_map.get(display_name, display_name)
     
     def cleanup_old_pdfs(self, days=5):
         """
@@ -278,7 +305,8 @@ class LabelPrinterApp(App):
             values=self.available_printers,
             size_hint_y=None,
             height=45,
-            font_size='12sp'
+            font_size='12sp',
+            sync_height=True,
         )
         self.printer_spinner = printer_spinner
         form_layout.add_widget(printer_spinner)
@@ -320,7 +348,8 @@ class LabelPrinterApp(App):
         sap_nr = self.sap_input.text.strip()
         quantity = self.qty_input.text.strip()
         cable_id = self.cable_id_input.text.strip()
-        printer = self.printer_spinner.text
+        # Resolve display name to full printer name
+        printer = self._get_full_printer_name(self.printer_spinner.text)
         
         # Validate input
         if not sap_nr and not quantity and not cable_id: