qt: ReceiveTab: fix flickering zeroconf message

The ReceiveTab gets updated regularly (e.g. when syncing headers).
Every time it updates we would first show the invoice and then the
zeroconf confirmation overlay. This caused the overly to appear
flickering when there are updates in higher frequency.

Also we need to keep state if the user has already confirmed the
zeroconf message for this request, otherwise the question
will re-appear each time the user clicked "Accept" and the
ReceiveTab updates again.

Author: f321x

electrum/gui/qt/receive_tab.py

@@ -20,6 +20,7 @@
 
 if TYPE_CHECKING:
     from .main_window import ElectrumWindow
+    from electrum.wallet import Request
 
 
 class ReceiveTab(QWidget, MessageBoxMixin, Logger):
@@ -101,6 +102,9 @@ def __init__(self, window: 'ElectrumWindow'):
         self.receive_zeroconf_button = QPushButton(_('Accept'))
         self.receive_zeroconf_button.clicked.connect(self.on_accept_zeroconf)
 
+        self.previous_request = None  # type: Optional['Request']
+        self.confirmed_zeroconf_for_this_request = False  # type: bool
+
         def on_receive_rebalance():
             if self.receive_rebalance_button.suggestion:
                 chan1, chan2, delta = self.receive_rebalance_button.suggestion
@@ -221,14 +225,17 @@ def toggle_receive_qr(self):
 
     def update_receive_widgets(self):
         b = self.config.GUI_QT_RECEIVE_TAB_QR_VISIBLE
-        self.receive_widget.update_visibility(b)
+        self.receive_widget.update_visibility(b, bool(self.receive_help_text.text()))
 
     def update_current_request(self):
         if len(self.request_list.selectionModel().selectedRows(0)) > 1:
             key = None
         else:
             key = self.request_list.get_current_key()
         req = self.wallet.get_request(key) if key else None
+        if req != self.previous_request:
+            self.previous_request = req
+            self.confirmed_zeroconf_for_this_request = False
         if req is None:
             self.receive_e.setText('')
             self.addr = self.URI = self.lnaddr = ''
@@ -243,7 +250,7 @@ def update_current_request(self):
         self.ln_help = help_texts.ln_help
         can_rebalance = help_texts.can_rebalance()
         can_swap = help_texts.can_swap()
-        can_zeroconf = help_texts.can_zeroconf()
+        can_zeroconf = help_texts.can_zeroconf() if not self.confirmed_zeroconf_for_this_request else False
         self.receive_rebalance_button.suggestion = help_texts.ln_rebalance_suggestion
         self.receive_swap_button.suggestion = help_texts.ln_swap_suggestion
         self.receive_rebalance_button.setVisible(can_rebalance)
@@ -253,25 +260,26 @@ def update_current_request(self):
         self.receive_zeroconf_button.setVisible(can_zeroconf)
         self.receive_zeroconf_button.setEnabled(can_zeroconf)
         text, data, help_text, title = self.get_tab_data()
+        if self.confirmed_zeroconf_for_this_request and help_texts.can_zeroconf():
+            help_text = ''
+        # set help before receive_e so we don't flicker from qr to help
+        self.receive_help_text.setText(help_text)
         self.receive_e.setText(text)
         self.receive_qr.setData(data)
-        self.receive_help_text.setText(help_text)
         for w in [self.receive_e, self.receive_qr]:
             w.setEnabled(bool(text) and (not help_text or can_zeroconf))
             w.setToolTip(help_text)
         # macOS hack (similar to #4777)
         self.receive_e.repaint()
         # always show
-        if can_zeroconf:
-            # show the help message if zeroconf so user can first accept it and still sees the invoice
-            # after accepting
-            self.receive_widget.show_help()
         self.receive_widget.setVisible(True)
         self.toggle_qr_button.setEnabled(True)
         self.update_receive_qr_window()
 
     def on_accept_zeroconf(self):
         self.receive_zeroconf_button.setVisible(False)
+        self.confirmed_zeroconf_for_this_request = True
+        self.receive_help_text.setText('')
         self.update_receive_widgets()
 
     def get_tab_data(self):
@@ -386,8 +394,8 @@ def __init__(self, receive_tab: 'ReceiveTab', textedit: QWidget, qr: QWidget, he
 
         self.setLayout(vbox)
 
-    def update_visibility(self, is_qr):
-        if str(self.textedit.toPlainText()):
+    def update_visibility(self, is_qr: bool, show_help: bool):
+        if str(self.textedit.toPlainText()) and not show_help:
             self.help_widget.setVisible(False)
             self.textedit.setVisible(not is_qr)
             self.qr.setVisible(is_qr)