kivy: improve amount dialog

gui/kivy/main.kv

@@ -221,20 +221,11 @@
     background_active: 'atlas://gui/kivy/theming/light/textinput_active'
 
 
-#<ElectrumScreen>
-#    ScrollView:
-#        do_scroll_x: False
-#        do_scroll_y: False if root.fullscreen else (content.height > root.height - dp(16))
-#        AnchorLayout:
-#            size_hint_y: None
-#            height: root.height if root.fullscreen else max(root.height, content.height)
-#            GridLayout:
-#                id: content
-#                cols: 1
-#                spacing: '8dp'
-#                padding: '8dp'
-#                size_hint: (1, 1) if root.fullscreen else (.8, None)
-#                height: self.height if root.fullscreen else self.minimum_height
+<KButton@Button>:
+    size_hint: 1, None
+    height: '48dp'
+    on_release: self.label.amount = app.update_amount(self.label.amount, self.text)
+
 
 <TabbedPanelStrip>:
     on_parent: