QR Encoder refactor + fountain encoder restart()

src/seedsigner/gui/screens/screen.py

@@ -10,6 +10,7 @@
 from seedsigner.gui.keyboard import Keyboard, TextEntryDisplay
 from seedsigner.gui.renderer import Renderer
 from seedsigner.hardware.buttons import HardwareButtonsConstants, HardwareButtons
+from seedsigner.models.encode_qr import BaseQrEncoder
 from seedsigner.models.settings import SettingsConstants
 from seedsigner.models.threads import BaseThread, ThreadsafeCounter
 
@@ -657,10 +658,10 @@ def swap_selected_button(new_selected_button: int):
 
 @dataclass
 class QRDisplayScreen(BaseScreen):
-    qr_encoder: 'EncodeQR' = None
+    qr_encoder: BaseQrEncoder = None
 
     class QRDisplayThread(BaseThread):
-        def __init__(self, qr_encoder: 'EncodeQR', qr_brightness: ThreadsafeCounter, renderer: Renderer,
+        def __init__(self, qr_encoder: BaseQrEncoder, qr_brightness: ThreadsafeCounter, renderer: Renderer,
                      tips_start_time: ThreadsafeCounter):
             super().__init__()
             self.qr_encoder = qr_encoder

src/seedsigner/helpers/ur2/fountain_encoder.py

@@ -90,6 +90,7 @@ def __init__(self, message, max_fragment_len, first_seq_num = 0, min_fragment_le
         self.fragment_len = FountainEncoder.find_nominal_fragment_length(self.message_len, min_fragment_len, max_fragment_len)
         self.fragments = FountainEncoder.partition_message(message, self.fragment_len)
         self.seq_num = first_seq_num
+        self.current_part: Part = None
 
     @staticmethod
     def find_nominal_fragment_length(message_len, min_fragment_len, max_fragment_len):
@@ -143,7 +144,17 @@ def next_part(self):
         indexes = choose_fragments(self.seq_num, self.seq_len(), self.checksum)
         mixed = self.mix(indexes)
         data = bytes(mixed)
-        return Part(self.seq_num, self.seq_len(), self.message_len, self.checksum, data)
+        self.current_part = Part(self.seq_num, self.seq_len(), self.message_len, self.checksum, data)
+        return self.current_part
+
+
+    def restart(self):
+        """
+        Restart from the beginning; each cycle's first n frames are full data frames
+        (not XOR composites).
+        """
+        self.seq_num = 0
+
 
     def mix(self, indexes):
         result = [0] * self.fragment_len

src/seedsigner/helpers/ur2/ur_encoder.py

@@ -34,12 +34,26 @@ def is_complete(self):
     def is_single_part(self):
         return self.fountain_encoder.is_single_part()
 
-    def next_part(self):
-        part = self.fountain_encoder.next_part()
+    def next_part(self) -> str:
         if self.is_single_part():
             return UREncoder.encode(self.ur)
         else:
+            part = self.fountain_encoder.next_part()
             return UREncoder.encode_part(self.ur.type, part)
+
+    def current_part(self) -> str:
+        if self.is_single_part():
+            return UREncoder.encode(self.ur)
+        else:
+            part = self.fountain_encoder.current_part
+            if not part:
+                part = self.fountain_encoder.next_part()
+            return UREncoder.encode_part(self.ur.type, part)
+
+
+    def restart(self):
+        self.fountain_encoder.restart()
+
 
     @staticmethod
     def encode_part(type, part):