"focus" widget in list but keep cursor in another - widget

Question

using urwid, I'm trying to separate the highlight/walk and cursor functionality of a Pile widget. How can I use up/down to change which widget is highlighted, while keeping the cursor in a different widget?

Answer 1

The default focus behavior couples the cursor with attribute (highlighting) behavior. The example below shows one way to decouple these, where a list of SelectableIcons retains the highlight feature, while the cursor is moved to a separate Edit widget. It does this via:
overriding the keypress method to update the focus where the cursor is not
wrapping each SelectableIcon in AttrMap that change their attribute based on their Pile's focus_position
after changing the SelectableIcon attributes, the focus (cursor) is set back to the Edit widget via focus_part='body'
self._w = ... is called to update all widgets on screen
There may be more concise ways of doing this, but this should be rather flexible.
import urwid
def main():
my_widget = MyWidget()
palette = [('unselected', 'default', 'default'),
('selected', 'standout', 'default', 'bold')]
urwid.MainLoop(my_widget, palette=palette).run()
class MyWidget(urwid.WidgetWrap):
def __init__(self):
n = 10
labels = ['selection {}'.format(j) for j in range(n)]
self.header = urwid.Pile([urwid.AttrMap(urwid.SelectableIcon(label), 'unselected', focus_map='selected') for label in labels])
self.edit_widgets = [urwid.Edit('', label + ' edit_text') for label in labels]
self.body = urwid.Filler(self.edit_widgets[0])
super().__init__(urwid.Frame(header=self.header, body=self.body, focus_part='body'))
self.update_focus(new_focus_position=0)
def update_focus(self, new_focus_position=None):
self.header.focus_item.set_attr_map({None: 'unselected'})
try:
self.header.focus_position = new_focus_position
self.body = urwid.Filler(self.edit_widgets[new_focus_position])
except IndexError:
pass
self.header.focus_item.set_attr_map({None: 'selected'})
self._w = urwid.Frame(header=self.header, body=self.body, focus_part='body')
def keypress(self, size, key):
if key == 'up':
self.update_focus(new_focus_position=self.header.focus_position - 1)
if key == 'down':
self.update_focus(new_focus_position=self.header.focus_position + 1)
if key in {'Q', 'q'}:
raise urwid.ExitMainLoop()
super().keypress(size, key)
main()

Answer 2

If you really need this, it probably makes sense to write your own widgets -- maybe based on some classes extending urwid.Text and urwid.Button
There is no real "highlight" feature in the widgets that come with urwid, there is only a "focus" feature, and it doesn't seem to be easy to decouple the focus highlight from the focus behavior.
You probably want to implement your own widgets with some sort of secondary highlighting.