Qt: disable max button if amount is locked

gui/qt/main_window.py

@@ -894,9 +894,9 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, PrintError):
         grid.addWidget(amount_label, 4, 0)
         grid.addWidget(self.amount_e, 4, 1)
 
-        max_button = EnterButton(_("Max"), self.spend_max)
+        self.max_button = EnterButton(_("Max"), self.spend_max)
         hbox = QHBoxLayout()
-        hbox.addWidget(max_button)
+        hbox.addWidget(self.max_button)
         hbox.addStretch(1)
         grid.addLayout(hbox, 4, 3)
 
@@ -1303,6 +1303,10 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, PrintError):
         dialog.exec_()
         return clayout.selected_index()
 
+    def lock_amount(self, b):
+        self.amount_e.setFrozen(b)
+        self.max_button.setEnabled(not b)
+
     def prepare_for_payment_request(self):
         self.tabs.setCurrentIndex(1)
         self.payto_e.is_pr = True

gui/qt/paytoedit.py

@@ -60,12 +60,6 @@ class PayToEdit(ScanQRTextEdit):
 
         self.previous_payto = ''
 
-    def lock_amount(self):
-        self.amount_edit.setFrozen(True)
-
-    def unlock_amount(self):
-        self.amount_edit.setFrozen(False)
-
     def setFrozen(self, b):
         self.setReadOnly(b)
         self.setStyleSheet(frozen_style if b else normal_style)
@@ -133,7 +127,7 @@ class PayToEdit(ScanQRTextEdit):
             except:
                 pass
             if self.payto_address:
-                self.unlock_amount()
+                self.win.lock_amount(False)
                 return
 
         for i, line in enumerate(lines):
@@ -148,17 +142,8 @@ class PayToEdit(ScanQRTextEdit):
 
         self.outputs = outputs
         self.payto_address = None
-
-        if outputs:
-            self.amount_edit.setAmount(total)
-        else:
-            self.amount_edit.setText("")
-
-        if total or len(lines)>1:
-            self.lock_amount()
-        else:
-            self.unlock_amount()
-
+        self.amount_edit.setAmount(total if outputs else None)
+        self.win.lock_amount(total or len(lines)>1)
 
     def get_errors(self):
         return self.errors