Add `get_godw()` singleton getter for `GodWidget`

Expose `get_godw()` helper to retrieve the central `GodWidget`
instance from anywhere in the UI code. Set the singleton in
`_async_main()` on startup.

Also,
- add docstring to `run_qtractor()` explaining trio guest mode
- type annotate `instance: GodWidget` in `run_qtractor()`
- import reorg in `._app` for cleaner grouping
- whitespace cleanup: `Type | None` -> `Type|None` throughout
- fix bitwise-or alignment: `Flag | Other` -> `Flag|Other`

(this commit-msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code

piker/ui/_app.py

@@ -27,15 +27,15 @@ import trio
 from piker.ui.qt import (
     QEvent,
 )
-from ..service import maybe_spawn_brokerd
+from . import _chart
 from . import _event
-from ._exec import run_qtractor
-from ..data.feed import install_brokerd_search
-from ..data._symcache import open_symcache
-from ..accounting import unpack_fqme
 from . import _search
-from ._chart import GodWidget
+from ..accounting import unpack_fqme
+from ..data._symcache import open_symcache
+from ..data.feed import install_brokerd_search
 from ..log import get_logger
+from ..service import maybe_spawn_brokerd
+from ._exec import run_qtractor
 
 log = get_logger(__name__)
 
@@ -73,8 +73,8 @@ async def load_provider_search(
 
 async def _async_main(
 
-    # implicit required argument provided by ``qtractor_run()``
+    # implicit required argument provided by `qtractor_run()`
-    main_widget: GodWidget,
+    main_widget: _chart.GodWidget,
 
     syms: list[str],
     brokers: dict[str, ModuleType],
@@ -87,6 +87,9 @@ async def _async_main(
     Provision the "main" widget with initial symbol data and root nursery.
 
     """
+    # set as singleton
+    _chart._godw = main_widget
+
     from . import _display
     from ._pg_overrides import _do_overrides
     _do_overrides()
@@ -201,6 +204,6 @@ def _main(
             brokermods,
             piker_loglevel,
         ),
-        main_widget_type=GodWidget,
+        main_widget_type=_chart.GodWidget,
         tractor_kwargs=tractor_kwargs,
     )

piker/ui/_chart.py

@@ -82,6 +82,25 @@ if TYPE_CHECKING:
 log = get_logger(__name__)
 
 
+_godw: GodWidget|None = None
+
+def get_godw() -> GodWidget:
+    '''
+    Get the top level "god widget", the root/central-most Qt
+    widget-object set as `QMainWindow.setCentralWidget(_godw)`.
+
+    See `piker.ui._exec` for the runtime init details and all the
+    machinery for running `trio` on the Qt event loop in guest mode.
+
+    '''
+    if _godw is None:
+        raise RuntimeError(
+            'No god-widget initialized ??\n'
+            'Have you called `run_qtractor()` yet?\n'
+        )
+    return _godw
+
+
 class GodWidget(QWidget):
     '''
     "Our lord and savior, the holy child of window-shua, there is no
@@ -567,8 +586,8 @@ class LinkedSplits(QWidget):
 
         # style?
         self.chart.setFrameStyle(
-            QFrame.Shape.StyledPanel |
+            QFrame.Shape.StyledPanel
-            QFrame.Shadow.Plain
+            |QFrame.Shadow.Plain
         )
 
         return self.chart

piker/ui/_exec.py

@@ -91,6 +91,10 @@ def run_qtractor(
     window_type: QMainWindow = None,
 
 ) -> None:
+    '''
+    Run the Qt event loop and embed `trio` via guest mode on it.
+
+    '''
     # avoids annoying message when entering debugger from qt loop
     pyqtRemoveInputHook()
 
@@ -170,7 +174,7 @@ def run_qtractor(
     # hook into app focus change events
     app.focusChanged.connect(window.on_focus_change)
 
-    instance = main_widget_type()
+    instance: GodWidget = main_widget_type()
     instance.window = window
 
     # override tractor's defaults