Add "group statuses" support to status bar

Allows for submitting a top level "group status" associated with
a "group key" which eventually resolves once all sub-statuses associated
with that group key (and thus top level status) complete and are also
removed. Also add support for a "final message" for each status such
that once the status clear callback is called a final msg is placed on
the status bar that is then removed when the next status is set.

It's all a questionable bunch of closures/callbacks but it worx.

piker/ui/_window.py

@@ -21,7 +21,8 @@ Qt main window singletons and stuff.
 import os
 import signal
 import time
-from typing import Callable
+from typing import Callable, Optional, Union
+import uuid
 
 from pyqtgraph import QtGui
 from PyQt5 import QtCore
@@ -42,23 +43,97 @@ class MultiStatus:
     def __init__(self, bar, statuses) -> None:
         self.bar = bar
         self.statuses = statuses
+        # self._clear_last: Optional[Callable[..., None]] = None
+        self._to_clear: set = set()
+        self._status_groups: dict[str, (set, Callable)] = {}
 
     def open_status(
+
         self,
         msg: str,
-    ) -> Callable[..., None]:
+        final_msg: Optional[str] = None,
+        clear_on_next: bool = False,
+        group_key: Optional[Union[bool, str]] = False,
+
+    ) -> Union[Callable[..., None], str]:
         '''Add a status to the status bar and return a close callback which
         when called will remove the status ``msg``.
 
         '''
+        for msg in self._to_clear:
+            try:
+                self.statuses.remove(msg)
+            except ValueError:
+                pass
+
         self.statuses.append(msg)
 
         def remove_msg() -> None:
-            self.statuses.remove(msg)
+            try:
-            self.render()
+                self.statuses.remove(msg)
+                self.render()
+            except ValueError:
+                pass
+
+            if final_msg is not None:
+                self.statuses.append(final_msg)
+                self.render()
+                self._to_clear.add(final_msg)
+
+
+        ret = remove_msg
+
+        # create a "status group" such that new `.open_status()`
+        # calls can be made passing in the returned group key.
+        # once all clear callbacks have been called from all statuses
+        # in the group the final status msg to be removed will be the one
+        # the one provided when `group_key=True`, this way you can
+        # create a long living status that completes once all
+        # sub-statuses have finished.
+        if group_key is True:
+            if clear_on_next:
+                ValueError("Can't create group status and clear it on next?")
+
+            # generate a key for a new "status group"
+            new_group_key = str(uuid.uuid4())
+
+            def pop_group_and_clear():
+
+                subs, final_clear = self._status_groups.pop(new_group_key)
+                assert not subs
+                return remove_msg()
+
+            self._status_groups[new_group_key] = (set(), pop_group_and_clear)
+            ret = new_group_key
+
+        elif group_key:
+
+            def pop_from_group_and_maybe_clear_group():
+                # remove the message for this sub-status
+                remove_msg()
+
+                # check to see if all other substatuses have cleared
+                group_tup = self._status_groups.get(group_key)
+
+                if group_tup:
+                    subs, group_clear = group_tup
+                    try:
+                        subs.remove(msg)
+                    except KeyError:
+                        raise KeyError(f'no msg {msg} for group {group_key}!?')
+
+                    if not subs:
+                        group_clear()
+
+            self._status_groups[group_key][0].add(msg)
+            ret = pop_from_group_and_maybe_clear_group
+
+        if clear_on_next:
+            self._to_clear.add(msg)
 
         self.render()
-        return remove_msg
+
+        return ret
 
     def render(self) -> None:
         if self.statuses: