Add a pager widget

It's a `ScrollView` but with keyboard controls that allow for paging
just like the classic unix `less` program. Add a search bar widget too!

piker/ui/kb.py

@@ -1,17 +1,22 @@
 """
-VI-like Keyboard controls
+Keyboard controls
 """
+import inspect
+from functools import partial
+
 from kivy.core.window import Window
+from kivy.uix.textinput import TextInput
+from kivy.uix.scrollview import ScrollView
 
 from ..log import get_logger
 log = get_logger('keyboard')
 
 
 async def handle_input(widget, patts2funcs: dict, patt_len_limit=3):
-    """Handle keyboard inputs.
+    """Handle keyboard input.
 
-    For each character pattern in ``patts2funcs`` invoke the corresponding
-    mapped functions.
+    For each character pattern-tuple in ``patts2funcs`` invoke the
+    corresponding mapped function(s) or coro(s).
     """
     def _kb_closed():
         """Teardown handler.
@@ -21,12 +26,11 @@ async def handle_input(widget, patts2funcs: dict, patt_len_limit=3):
         kb.unbind(on_key_down=_kb_closed)
 
     last_patt = []
-
     kb = Window.request_keyboard(_kb_closed, widget, 'text')
-    async for kb, keycode, text, modifiers in kb.async_bind(
-            'on_key_down'
-    ):
-        # log.debug(
+    keyq = kb.async_bind('on_key_down')
+
+    while True:
+        async for kb, keycode, text, modifiers in keyq:
             log.debug(
                 f"Keyboard input received:\n"
                 f"key {keycode}\ntext {text}\nmodifiers {modifiers}"
@@ -42,16 +46,94 @@ async def handle_input(widget, patts2funcs: dict, patt_len_limit=3):
 
             func = patts2funcs.get(tuple(last_patt))
             if not func:
-            func = patts2funcs.get(key)
+                func = patts2funcs.get((key,))
 
-        if func:
-            log.debug(f'invoking func kb {func}')
+            if inspect.iscoroutinefunction(func):
+                # stop kb queue to avoid duplicate input processing
+                keyq.stop()
+
+                log.debug(f'invoking kb coro func {func}')
+                await func()
+                last_patt = []
+                break  # trigger loop restart
+
+            elif func:
+                log.debug(f'invoking kb func {func}')
                 func()
                 last_patt = []
-        elif key == 'q':
-            kb.release()
 
             if len(last_patt) > patt_len_limit:
                 last_patt = []
 
             log.debug(f"last_patt {last_patt}")
+
+        log.debug("Restarting keyboard handling loop")
+        # rebind to avoid capturing keys processed by ^ coro
+        keyq = kb.async_bind('on_key_down')
+
+    log.debug("Exitting keyboard handling loop")
+
+
+class SearchBar(TextInput):
+    def __init__(self, kbctls: dict, parent, **kwargs):
+        super(SearchBar, self).__init__(
+            multiline=False,
+            # text='/',
+            **kwargs
+        )
+        self.kbctls = kbctls
+        self._container = parent
+        # indicate to ``handle_input`` that search is activated on '/'
+        self.kbctls.update({
+            ('/',): self.handle_input
+        })
+
+    def on_text(self, instance, value):
+        # ``scroll.scroll_to()`` looks super awesome here for when we
+        # our interproc-ticker protocol
+        # async for item in self.async_bind('text'):
+        print(value)
+
+    async def handle_input(self):
+        self._container.add_widget(self)  # display it
+        self.focus = True  # focus immediately (doesn't work from __init__)
+        # wait for <enter> to close search bar
+        await self.async_bind('on_text_validate').__aiter__().__anext__()
+
+        log.debug("Closing search bar")
+        self._container.remove_widget(self)  # stop displaying
+        return self.text
+
+
+class PagerView(ScrollView):
+    """Pager view that adds less-like scrolling and search.
+    """
+    def __init__(self, container, nursery, kbctls: dict = None, **kwargs):
+        super(PagerView, self).__init__(**kwargs)
+        self._container = container
+        self.kbctls = kbctls or {}
+        self.kbctls.update({
+            ('g', 'g'): partial(self.move_y, 1),
+            ('shift-g',): partial(self.move_y, 0),
+            ('u',): partial(self.halfpage_y, 'u'),
+            ('d',): partial(self.halfpage_y, 'd'),
+            # ('?',):
+        })
+        self.search = SearchBar(self.kbctls, container)
+        # spawn kb handler task
+        nursery.start_soon(handle_input, self, self.kbctls)
+
+    def move_y(self, val):
+        '''Scroll in the y direction [0, 1].
+        '''
+        self.scroll_y = val
+
+    def halfpage_y(self, direction):
+        """Scroll a half-page up or down.
+        """
+        pxs = (self.height/2)
+        _, yscale = self.convert_distance_to_scroll(0, pxs)
+        new = self.scroll_y + (yscale * {'u': 1, 'd': -1}[direction])
+        # bound to near [0, 1] to avoid "over-scrolling"
+        limited = max(-0.03, min(new, 1.03))
+        self.scroll_y = limited