set max fee rate in preferences. fixes #2112

gui/qt/fee_slider.py

@@ -12,7 +12,6 @@ class FeeSlider(QSlider):
     def __init__(self, window, config, callback):
         QSlider.__init__(self, Qt.Horizontal)
         self.config = config
-        self.fee_step = self.config.max_fee_rate() / 10
         self.window = window
         self.callback = callback
         self.dyn = False
@@ -49,6 +48,7 @@ class FeeSlider(QSlider):
                 self.setRange(0, 4)
                 self.setValue(pos)
             else:
+                self.fee_step = self.config.max_fee_rate() / 10
                 fee_rate = self.config.fee_per_kb()
                 pos = min(fee_rate / self.fee_step, 10)
                 self.setRange(1, 10)

gui/qt/main_window.py

@@ -2371,14 +2371,30 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, PrintError):
         nz.valueChanged.connect(on_nz)
         gui_widgets.append((nz_label, nz))
 
-        dynfee_cb = QCheckBox(_('Use dynamic fees'))
-        dynfee_cb.setChecked(self.config.get('dynamic_fees', True))
-        dynfee_cb.setToolTip(_("Use fees recommended by the server."))
         def on_dynfee(x):
             self.config.set_key('dynamic_fees', x == Qt.Checked)
             self.fee_slider.update()
-        dynfee_cb.stateChanged.connect(on_dynfee)
+            update_maxfee()
+        dynfee_cb = QCheckBox(_('Use dynamic fees'))
+        dynfee_cb.setChecked(self.config.is_dynfee())
+        dynfee_cb.setToolTip(_("Use fees recommended by the server."))
         fee_widgets.append((dynfee_cb, None))
+        dynfee_cb.stateChanged.connect(on_dynfee)
+
+        def on_maxfee(x):
+            m = maxfee_e.get_amount()
+            if m: self.config.set_key('max_fee_rate', m)
+            self.fee_slider.update()
+        def update_maxfee():
+            d = self.config.is_dynfee()
+            maxfee_e.setDisabled(d)
+            maxfee_label.setDisabled(d)
+        maxfee_label = HelpLabel(_('Max static fee'), _('Max value of the static fee slider'))
+        maxfee_e = BTCkBEdit(self.get_decimal_point)
+        maxfee_e.setAmount(self.config.max_fee_rate())
+        maxfee_e.textChanged.connect(on_maxfee)
+        update_maxfee()
+        fee_widgets.append((maxfee_label, maxfee_e))
 
         feebox_cb = QCheckBox(_('Edit fees manually'))
         feebox_cb.setChecked(self.config.get('show_fee', False))