Enable borderless fullscreen window with custom controls

app/app.py

@@ -21,11 +21,7 @@ class ICRSApp(
     def __init__(self, root: tk.Tk):
         self.root = root
         self.root.title("ICRS — Interactive Color Range Analyzer")
-        try:
+        self._setup_window()
-            self.root.state("zoomed")
-        except Exception:
-            pass
-        self.root.configure(bg="#f2f2f7")
 
         # Theme and styling
         self.init_theme()
@@ -64,6 +60,13 @@ class ICRSApp(
         self._init_copy_menu()
         self.bring_to_front()
 
+    def _setup_window(self) -> None:
+        self.root.overrideredirect(True)
+        screen_width = self.root.winfo_screenwidth()
+        screen_height = self.root.winfo_screenheight()
+        self.root.geometry(f"{screen_width}x{screen_height}+0+0")
+        self.root.configure(bg="#f2f2f7")
+
 
 def start_app() -> None:
     """Entry point used by the CLI script."""

app/gui/ui.py

@@ -11,8 +11,10 @@ class UIBuilderMixin:
     """Constructs the Tkinter UI and common widgets."""
 
     def setup_ui(self) -> None:
+        self._create_titlebar()
+
         toolbar = ttk.Frame(self.root)
-        toolbar.pack(fill=tk.X, padx=12, pady=8)
+        toolbar.pack(fill=tk.X, padx=12, pady=0)
         buttons = [
             ("📂 Bild laden", self.load_image),
             ("📁 Ordner laden", self.load_folder),
@@ -71,11 +73,13 @@ class UIBuilderMixin:
 
         left_column = ttk.Frame(main)
         left_column.pack(side=tk.LEFT, fill=tk.BOTH, expand=True, padx=(0, 6))
+        left_column.grid_columnconfigure(1, weight=1)
+        left_column.grid_rowconfigure(0, weight=1)
 
-        self._create_navigation_button(left_column, "◀", self.show_previous_image)
+        self._create_navigation_button(left_column, "◀", self.show_previous_image, column=0)
 
         self.canvas_orig = tk.Canvas(left_column, bg="#1e1e1e", highlightthickness=0, relief="flat")
-        self.canvas_orig.pack(fill=tk.BOTH, expand=True)
+        self.canvas_orig.grid(row=0, column=1, sticky="nsew")
         self.canvas_orig.bind("<Button-1>", self.on_canvas_click)
         self.canvas_orig.bind("<ButtonPress-3>", self._exclude_start)
         self.canvas_orig.bind("<B3-Motion>", self._exclude_drag)
@@ -83,10 +87,13 @@ class UIBuilderMixin:
 
         right_column = ttk.Frame(main)
         right_column.pack(side=tk.RIGHT, fill=tk.BOTH, expand=True, padx=(6, 0))
+        right_column.grid_columnconfigure(0, weight=1)
+        right_column.grid_rowconfigure(0, weight=1)
 
         self.canvas_overlay = tk.Canvas(right_column, bg="#1e1e1e", highlightthickness=0, relief="flat")
-        self.canvas_overlay.pack(fill=tk.BOTH, expand=True)
+        self.canvas_overlay.grid(row=0, column=0, sticky="nsew")
-        self._create_navigation_button(right_column, "▶", self.show_next_image)
+        self._create_navigation_button(right_column, "▶", self.show_next_image, column=1)
+
 
         info_frame = ttk.Frame(self.root)
         info_frame.pack(fill=tk.X, padx=12, pady=(0, 12))
@@ -113,6 +120,7 @@ class UIBuilderMixin:
         self._attach_copy_menu(self.ratio_label)
 
         self.root.bind("<Escape>", self.disable_pick_mode)
+        self.root.bind("<ButtonPress-1>", self._maybe_focus_window)
 
     def add_slider_with_value(self, parent, text, var, minimum, maximum, column=0):
         cell = ttk.Frame(parent)
@@ -317,24 +325,83 @@ class UIBuilderMixin:
         ]
         return canvas.create_polygon(points, smooth=True, splinesteps=24, **kwargs)
 
-    def _create_navigation_button(self, container, symbol: str, command) -> None:
+    def _create_navigation_button(self, container, symbol: str, command, *, column: int) -> None:
-        wrapper = ttk.Frame(container)
+        bg = self.root.cget("bg") if hasattr(self.root, "cget") else "#f2f2f7"
-        wrapper.pack(fill=tk.Y)
+        container.grid_rowconfigure(0, weight=1)
-
         btn = tk.Button(
-            wrapper,
+            container,
             text=symbol,
             command=command,
-            font=("Segoe UI", 18, "bold"),
+            font=("Segoe UI", 26, "bold"),
             relief="flat",
             borderwidth=0,
-            background="#00000000",
+            background=bg,
-            activebackground="#00000000",
+            activebackground=bg,
             highlightthickness=0,
             cursor="hand2",
+            width=2,
         )
-        btn.pack(side=tk.TOP, pady=12)
+        btn.grid(row=0, column=column, sticky="ns", padx=6)
-        wrapper.pack_propagate(False)
+
+    def _create_titlebar(self) -> None:
+        bar_bg = "#1f1f1f"
+        title_bar = tk.Frame(self.root, bg=bar_bg, relief="flat", height=34)
+        title_bar.pack(fill=tk.X, side=tk.TOP)
+        title_bar.pack_propagate(False)
+
+        title_label = tk.Label(
+            title_bar,
+            text="ICRS — Interactive Color Range Analyzer",
+            bg=bar_bg,
+            fg="#f5f5f5",
+            font=("Segoe UI", 11, "bold"),
+            anchor="w",
+        )
+        title_label.pack(side=tk.LEFT, padx=12)
+
+        close_btn = tk.Button(
+            title_bar,
+            text="✕",
+            command=self._close_app,
+            bg=bar_bg,
+            fg="#f5f5f5",
+            activebackground="#ff3b30",
+            activeforeground="#ffffff",
+            borderwidth=0,
+            highlightthickness=0,
+            relief="flat",
+            font=("Segoe UI", 10, "bold"),
+            cursor="hand2",
+            width=3,
+        )
+        close_btn.pack(side=tk.RIGHT, padx=8, pady=4)
+
+        for widget in (title_bar, title_label):
+            widget.bind("<ButtonPress-1>", self._start_window_drag)
+            widget.bind("<B1-Motion>", self._perform_window_drag)
+
+    def _close_app(self) -> None:
+        try:
+            self.root.destroy()
+        except Exception:
+            pass
+
+    def _start_window_drag(self, event) -> None:
+        self._drag_offset = (event.x_root - self.root.winfo_rootx(), event.y_root - self.root.winfo_rooty())
+
+    def _perform_window_drag(self, event) -> None:
+        offset = getattr(self, "_drag_offset", None)
+        if offset is None:
+            return
+        x = event.x_root - offset[0]
+        y = event.y_root - offset[1]
+        self.root.geometry(f"+{x}+{y}")
+
+    def _maybe_focus_window(self, _event) -> None:
+        try:
+            self.root.focus_set()
+        except Exception:
+            pass
 
     def _toolbar_palette(self) -> dict[str, str]:
         is_dark = getattr(self, "theme", "light") == "dark"