trezor pin dialog: only show PIN "strength" when creating/changing

fixes #4832

electrum/plugins/keepkey/clientbase.py

@@ -1,5 +1,6 @@
 import time
 from struct import pack
+from typing import Optional
 
 from electrum import ecc
 from electrum.i18n import _
@@ -7,11 +8,12 @@ from electrum.util import UserCancelled
 from electrum.keystore import bip39_normalize_passphrase
 from electrum.bip32 import BIP32Node, convert_bip32_path_to_list_of_uint32
 from electrum.logging import Logger
-from electrum.plugins.hw_wallet.plugin import HardwareClientBase
+from electrum.plugins.hw_wallet.plugin import HardwareClientBase, HardwareHandlerBase
 
 
 class GuiMixin(object):
     # Requires: self.proto, self.device
+    handler: Optional[HardwareHandlerBase]
 
     messages = {
         3: _("Confirm the transaction output on your {} device"),
@@ -45,6 +47,7 @@ class GuiMixin(object):
         return self.proto.ButtonAck()
 
     def callback_PinMatrixRequest(self, msg):
+        show_strength = True
         if msg.type == 2:
             msg = _("Enter a new PIN for your {}:")
         elif msg.type == 3:
@@ -52,7 +55,8 @@ class GuiMixin(object):
                      "NOTE: the positions of the numbers have changed!"))
         else:
             msg = _("Enter your current {} PIN:")
-        pin = self.handler.get_pin(msg.format(self.device))
+            show_strength = False
+        pin = self.handler.get_pin(msg.format(self.device), show_strength=show_strength)
         if len(pin) > 9:
             self.handler.show_error(_('The PIN cannot be longer than 9 characters.'))
             pin = ''  # to cancel below

electrum/plugins/keepkey/qt.py

@@ -137,7 +137,7 @@ class CharacterDialog(WindowModalDialog):
 class QtHandler(QtHandlerBase):
 
     char_signal = pyqtSignal(object)
-    pin_signal = pyqtSignal(object)
+    pin_signal = pyqtSignal(object, object)
     close_char_dialog_signal = pyqtSignal()
 
     def __init__(self, win, pin_matrix_widget_class, device):
@@ -162,17 +162,17 @@ class QtHandler(QtHandlerBase):
             self.character_dialog.accept()
             self.character_dialog = None
 
-    def get_pin(self, msg):
+    def get_pin(self, msg, *, show_strength=True):
         self.done.clear()
-        self.pin_signal.emit(msg)
+        self.pin_signal.emit(msg, show_strength)
         self.done.wait()
         return self.response
 
-    def pin_dialog(self, msg):
+    def pin_dialog(self, msg, show_strength):
         # Needed e.g. when resetting a device
         self.clear_dialog()
         dialog = WindowModalDialog(self.top_level_window(), _("Enter PIN"))
-        matrix = self.pin_matrix_widget_class()
+        matrix = self.pin_matrix_widget_class(show_strength)
         vbox = QVBoxLayout()
         vbox.addWidget(QLabel(msg))
         vbox.addWidget(matrix)