add a menu with bt pairing

frontend/views/bluetooth_pairing.py

@@ -0,0 +1,80 @@
+from typing import Callable, Optional, Tuple
+
+from PIL import ImageDraw, Image
+
+from .base import View
+from .button_interface import ButtonInterface
+from .draw_utils import draw_bluetooth_icon
+
+
+class BluetoothPairingView(View, ButtonInterface):
+    """Shows a 'waiting for connection' screen while BT pairing is active.
+
+    ``start_command`` is called once when the view is first rendered, to
+    trigger pairing mode on the hardware side.
+    ``stop_command`` is called when the user cancels (left long press).
+    ``on_connected(device_name)`` is called by external code when a device
+    has paired; it transitions back by calling ``deactivate_command``.
+    ``deactivate_command`` returns to the previous screen.
+    """
+
+    def __init__(self, parent, im_size, center,
+                 start_command: Optional[Callable] = None,
+                 stop_command: Optional[Callable] = None,
+                 on_connected: Optional[Callable[[str], None]] = None,
+                 deactivate_command: Optional[Callable] = None):
+        self.start_command = start_command
+        self.stop_command = stop_command
+        self.on_connected = on_connected
+        self.deactivate_command = deactivate_command
+        self._frame = 0           # used for the waiting animation
+        self._started = False
+        super().__init__(parent, im_size, center)
+
+    # ------------------------------------------------------------------
+
+    def update_weight(self, weight: float) -> Image.Image:
+        if not self._started:
+            self._started = True
+            if self.start_command:
+                self.start_command()
+
+        im = self.bkg_im.copy()
+        draw = ImageDraw.Draw(im)
+        cx = self.size[0] // 2
+
+        # Large BT icon centred
+        draw_bluetooth_icon(draw, (cx, 52), size=20)
+
+        draw.text((cx - 28, 80), "Pairing", fill='black')
+
+        # Three animated dots
+        self._frame = (self._frame + 1) % 6
+        for i in range(3):
+            r = 3 if i < self._frame // 2 + 1 else 1
+            draw.circle((cx - 8 + i * 8, 100), r, fill='black')
+
+        return im
+
+    def notify_connected(self, device_name: str = ''):
+        """Call this from the outside when a BT device has connected."""
+        if self.on_connected:
+            self.on_connected(device_name)
+        self._cancel()
+
+    # ------------------------------------------------------------------
+
+    def _cancel(self):
+        if self.stop_command:
+            self.stop_command()
+        if self.deactivate_command:
+            self.deactivate_command()
+
+    def left_long_press(self):
+        self._cancel()
+
+    def has_button(self) -> Tuple[bool, bool, bool, bool]:
+        return False, True, False, False
+
+    def render_left_long_press(self, draw, x, y):
+        draw.text((x, y - 5), 'Cancel', fill='black')