added automatic minsize of UI to prevent hidden Elements at startup

src/gui.py

@@ -55,7 +55,6 @@ class DHCPApp(tk.Frame):
     def __init__(self, master: tk.Tk) -> None:
         super().__init__(master)
         master.title("Simple DHCP Server (Lab)")
-        master.minsize(700, 500)
         self.pack(fill="both", expand=True, padx=12, pady=12)
 
         # Single server instance
@@ -68,7 +67,7 @@ class DHCPApp(tk.Frame):
         # Zeile 0
         ttk.Label(form, text="Interface:").grid(row=0, column=0, sticky="w")
         self.if_var = tk.StringVar()
-        self.if_menu = ttk.OptionMenu(form, self.if_var, None, *utils.get_network_interfaces(), command=self.on_iface_change)
+        self.if_menu = ttk.OptionMenu(form, self.if_var, None, command=self.on_iface_change)
         self.if_menu.grid(row=0, column=1, sticky="ew", padx=(6, 16))
         form.columnconfigure(1, weight=1)
 
@@ -98,8 +97,10 @@ class DHCPApp(tk.Frame):
         btns.pack(fill="x", pady=(8, 8))
         self.btn_start = ttk.Button(btns, text="Start", command=self.start_server)
         self.btn_stop = ttk.Button(btns, text="Stop", command=self.stop_server, state="disabled")
+        self.btn_rescan = ttk.Button(btns, text="Interfaces neu scannen", command=self.rescan_interfaces)
         self.btn_start.pack(side="left")
         self.btn_stop.pack(side="left", padx=(8, 0))
+        self.btn_rescan.pack(side="left", padx=(8, 0))
 
         # --- Clients & Logs Paned Layout ---
         paned = ttk.Panedwindow(self, orient="horizontal")
@@ -109,24 +110,21 @@ class DHCPApp(tk.Frame):
         left = ttk.Labelframe(paned, text="Aktive Clients / Leases")
         self.clients = tk.Listbox(left, height=12)
         self.clients.pack(fill="both", expand=True, padx=6, pady=6)
-        paned.add(left, weight=1)
+        paned.add(left, weight=1, minsize=240)
 
         # Logs
         right = ttk.Labelframe(paned, text="Log")
         self.log = tk.Text(right, height=12, state="disabled")
         self.log.pack(fill="both", expand=True, padx=6, pady=6)
-        paned.add(right, weight=2)
+        paned.add(right, weight=2, minsize=360)
 
         # --- Status bar ---
         self.status_var = tk.StringVar(value="Bereit.")
         status = ttk.Label(self, textvariable=self.status_var, anchor="w", relief="sunken")
         status.pack(fill="x", side="bottom")
 
-        # initial iface autofill (if any interface exists)
-        ifaces = utils.get_network_interfaces()
-        if ifaces:
-            self.if_var.set(ifaces[0])
-            self.on_iface_change(ifaces[0])
+        self._refresh_interface_list(initial=True)
+        self._apply_min_sizes()
 
         # periodic refresh
         self.after(400, self._refresh)
@@ -134,7 +132,12 @@ class DHCPApp(tk.Frame):
     # -------------------- UI logic --------------------
     def on_iface_change(self, _sel=None):
         iface = self.if_var.get().strip()
+        if not iface:
+            self._clear_iface_fields()
+            return
+
         ip, mask = utils.get_iface_ipv4_config(iface)
+        self._clear_iface_fields()
         if ip:
             self.ip_var.set(ip)
             # sinnvolles Default: Primary DNS = Interface-IP
@@ -150,9 +153,58 @@ class DHCPApp(tk.Frame):
         self.mask_entry.configure(state=state)
         self.dns1_entry.configure(state=state)
         self.dns2_entry.configure(state=state)
+        self.btn_rescan.configure(state=state)
         self.btn_start.configure(state="normal" if enabled else "disabled")
         self.btn_stop.configure(state="disabled" if enabled else "normal")
 
+    def _clear_iface_fields(self) -> None:
+        self.ip_var.set("")
+        self.mask_var.set("")
+        self.dns1_var.set("")
+        self.dns2_var.set("")
+
+    def _select_iface(self, iface: str) -> None:
+        self.if_var.set(iface)
+        self.on_iface_change(iface)
+
+    def _refresh_interface_list(self, initial: bool = False) -> None:
+        interfaces = utils.get_network_interfaces()
+        current = self.if_var.get().strip()
+        menu = self.if_menu["menu"]
+        menu.delete(0, "end")
+        for iface in interfaces:
+            menu.add_command(label=iface, command=lambda val=iface: self._select_iface(val))
+
+        if current in interfaces:
+            selection = current
+        elif interfaces:
+            selection = interfaces[0]
+        else:
+            selection = ""
+
+        if selection:
+            self._select_iface(selection)
+            if not initial:
+                self.status_var.set(f"{len(interfaces)} Interface(s) geladen.")
+        else:
+            self.if_var.set("")
+            self._clear_iface_fields()
+            if not initial:
+                self.status_var.set("Keine Netzwerk-Interfaces gefunden.")
+
+    def _apply_min_sizes(self) -> None:
+        # Ensure window cannot shrink below a comfortable layout
+        self.update_idletasks()
+        min_w = max(self.winfo_reqwidth() + 16, 720)
+        min_h = max(self.winfo_reqheight() + 16, 540)
+        self.master.minsize(min_w, min_h)
+
+    def rescan_interfaces(self) -> None:
+        if self.server and self.server.is_running():
+            messagebox.showinfo("Server läuft", "Stoppe den Server, bevor du Interfaces neu scannst.")
+            return
+        self._refresh_interface_list()
+
     def start_server(self) -> None:
         if self.server and self.server.is_running():
             messagebox.showinfo("Info", "Server läuft bereits.")