Rename Flow -> Viz

The type is better described as a "data visualization":
https://en.wikipedia.org/wiki/Data_and_information_visualization

Add `ChartPlotWidget.get_viz()` to start working towards not accessing
the private table directly XD

We'll probably end up using the name `Flow` for a type that tracks
a collection of composed/cascaded `Flume`s:
https://en.wikipedia.org/wiki/Two-port_network#Cascade_connection

piker/ui/_axes.py

@@ -302,7 +302,7 @@ def _indexes_to_timestrs(
         # XX: ARGGGGG AG:LKSKDJF:LKJSDFD
         chart = self.pi.chart_widget
 
-        flow = chart._flows[chart.name]
+        flow = chart._vizs[chart.name]
         shm = flow.shm
         bars = shm.array
         first = shm._first.value

piker/ui/_chart.py

@@ -72,7 +72,7 @@
 from ._forms import FieldsForm
 from .._profile import pg_profile_enabled, ms_slower_then
 from ._overlay import PlotItemOverlay
-from ._flows import Flow
+from ._flows import Viz
 from ._search import SearchWidget
 from . import _pg_overrides as pgo
 from .._profile import Profiler
@@ -711,7 +711,7 @@ def add_plot(
         if style == 'ohlc_bar':
 
             # graphics, data_key = cpw.draw_ohlc(
-            flow = cpw.draw_ohlc(
+            viz = cpw.draw_ohlc(
                 name,
                 shm,
                 flume=flume,
@@ -727,7 +727,7 @@ def add_plot(
         elif style == 'line':
             add_label = True
             # graphics, data_key = cpw.draw_curve(
-            flow = cpw.draw_curve(
+            viz = cpw.draw_curve(
                 name,
                 shm,
                 flume,
@@ -738,7 +738,7 @@ def add_plot(
         elif style == 'step':
             add_label = True
             # graphics, data_key = cpw.draw_curve(
-            flow = cpw.draw_curve(
+            viz = cpw.draw_curve(
                 name,
                 shm,
                 flume,
@@ -751,8 +751,8 @@ def add_plot(
         else:
             raise ValueError(f"Chart style {style} is currently unsupported")
 
-        graphics = flow.graphics
-        data_key = flow.name
+        graphics = viz.graphics
+        data_key = viz.name
 
         if _is_main:
             assert style == 'ohlc_bar', 'main chart must be OHLC'
@@ -908,7 +908,7 @@ def __init__(
         # self.setViewportMargins(0, 0, 0, 0)
 
         # registry of overlay curve names
-        self._flows: dict[str, Flow] = {}
+        self._vizs: dict[str, Viz] = {}
 
         self.feed: Feed | None = None
 
@@ -974,7 +974,7 @@ def bars_range(self) -> tuple[int, int, int, int]:
         Return a range tuple for the bars present in view.
 
         '''
-        main_flow = self._flows[self.name]
+        main_flow = self._vizs[self.name]
         ifirst, l, lbar, rbar, r, ilast = main_flow.datums_range()
         return l, lbar, rbar, r
 
@@ -1038,9 +1038,9 @@ def default_view(
         Set the view box to the "default" startup view of the scene.
 
         '''
-        flow = self._flows.get(self.name)
+        flow = self._vizs.get(self.name)
         if not flow:
-            log.warning(f'`Flow` for {self.name} not loaded yet?')
+            log.warning(f'`Viz` for {self.name} not loaded yet?')
             return
 
         arr = flow.shm.array
@@ -1220,7 +1220,7 @@ def draw_curve(
 
         **graphics_kwargs,
 
-    ) -> Flow:
+    ) -> Viz:
         '''
         Draw a "curve" (line plot graphics) for the provided data in
         the input shm array ``shm``.
@@ -1254,7 +1254,7 @@ def draw_curve(
                 **graphics_kwargs,
             )
 
-        flow = self._flows[data_key] = Flow(
+        flow = self._vizs[data_key] = Viz(
             data_key,
             pi,
             shm,
@@ -1332,7 +1332,7 @@ def draw_ohlc(
         array_key: Optional[str] = None,
         **draw_curve_kwargs,
 
-    ) -> Flow:
+    ) -> Viz:
         '''
         Draw OHLC datums to chart.
 
@@ -1358,7 +1358,7 @@ def update_graphics_from_flow(
         Update the named internal graphics from ``array``.
 
         '''
-        flow = self._flows[array_key or graphics_name]
+        flow = self._vizs[array_key or graphics_name]
         return flow.update_graphics(
             array_key=array_key,
             **kwargs,
@@ -1426,15 +1426,15 @@ def maxmin(
             delayed=True,
         )
 
-        # TODO: here we should instead look up the ``Flow.shm.array``
+        # TODO: here we should instead look up the ``Viz.shm.array``
         # and read directly from shm to avoid copying to memory first
         # and then reading it again here.
         flow_key = name or self.name
-        flow = self._flows.get(flow_key)
+        viz = self._vizs.get(flow_key)
         if (
-            flow is None
+            viz is None
         ):
-            log.error(f"flow {flow_key} doesn't exist in chart {self.name} !?")
+            log.error(f"viz {flow_key} doesn't exist in chart {self.name} !?")
             key = res = 0, 0
 
         else:
@@ -1445,11 +1445,11 @@ def maxmin(
                 rbar,
                 r,
                 last,
-            ) = bars_range or flow.datums_range()
+            ) = bars_range or viz.datums_range()
             profiler(f'{self.name} got bars range')
 
             key = round(lbar), round(rbar)
-            res = flow.maxmin(*key)
+            res = viz.maxmin(*key)
 
             if (
                 res is None
@@ -1465,3 +1465,9 @@ def maxmin(
         profiler(f'yrange mxmn: {key} -> {res}')
         # print(f'{flow_key} yrange mxmn: {key} -> {res}')
         return res
+
+    def get_viz(
+        self,
+        key: str,
+    ) -> Viz:
+        return self._vizs[key]

piker/ui/_cursor.py

@@ -274,7 +274,7 @@ def update_labels(
     ) -> None:
         for chart, name, label, update in self._labels:
 
-            flow = chart._flows[name]
+            viz = chart.get_viz(name)
             array = flow.shm.array
 
             if not (
@@ -482,25 +482,32 @@ def add_plot(
 
     def add_curve_cursor(
         self,
-        plot: ChartPlotWidget,  # noqa
+        chart: ChartPlotWidget,  # noqa
         curve: 'PlotCurveItem',  # noqa
 
     ) -> LineDot:
-        # if this plot contains curves add line dot "cursors" to denote
+        # if this chart contains curves add line dot "cursors" to denote
         # the current sample under the mouse
-        main_flow = plot._flows[plot.name]
+        main_viz = chart.get_viz(chart.name)
+
         # read out last index
-        i = main_flow.shm.array[-1]['index']
+        i = main_viz.shm.array[-1]['index']
         cursor = LineDot(
             curve,
             index=i,
-            plot=plot
+            plot=chart
         )
-        plot.addItem(cursor)
-        self.graphics[plot].setdefault('cursors', []).append(cursor)
+        chart.addItem(cursor)
+        self.graphics[chart].setdefault('cursors', []).append(cursor)
         return cursor
 
-    def mouseAction(self, action, plot):  # noqa
+    def mouseAction(
+        self,
+        action: str,
+        plot: ChartPlotWidget,
+
+    ) -> None:  # noqa
+
         log.debug(f"{(action, plot.name)}")
         if action == 'Enter':
             self.active_plot = plot