Return xy data from `Curve.draw_last_datum()` methods

piker/ui/_curve.py

@@ -383,17 +383,16 @@ class Curve(pg.GraphicsObject):
             x = render_data['index']
             y = render_data[array_key]
 
-            x_last = x[-1]
-            y_last = y[-1]
-
             # draw the "current" step graphic segment so it
             # lines up with the "middle" of the current
             # (OHLC) sample.
             self._last_line = QLineF(
                 x[-2], y[-2],
-                x_last, y_last
+                x[-1], y[-1],
             )
 
+        return x, y
+
 
 # TODO: this should probably be a "downsampled" curve type
 # that draws a bar-style (but for the px column) last graphics
@@ -421,6 +420,7 @@ class FlattenedOHLC(Curve):
             x[-2], y[-2],
             x[-1], y[-1]
         )
+        return x, y
 
 
 class StepCurve(Curve):
@@ -461,6 +461,7 @@ class StepCurve(Curve):
             x_last - w, 0,
             x_last + w, y_last,
         )
+        return x, y
 
     def sub_paint(
         self,

piker/ui/_ohlc.py

@@ -200,16 +200,26 @@ class BarItems(pg.GraphicsObject):
         reset: bool,
         array_key: str,
 
+        fields: list[str] = [
+            'index',
+            'open',
+            'high',
+            'low',
+            'close',
+        ],
+
     ) -> None:
-        last = src_data[-1]
+
+        # relevant fields
+        ohlc = src_data[fields]
+        last_row = ohlc[-1:]
+
+        # individual values
+        last_row = i, o, h, l, last = ohlc[-1]
 
         # generate new lines objects for updatable "current bar"
-        self._last_bar_lines = bar_from_ohlc_row(last)
+        self._last_bar_lines = bar_from_ohlc_row(last_row)
 
-        # last bar update
-        i, o, h, l, last, v = last[
-            ['index', 'open', 'high', 'low', 'close', 'volume']
-        ]
         # assert i == graphics.start_index - 1
         # assert i == last_index
         body, larm, rarm = self._last_bar_lines
@@ -236,3 +246,5 @@ class BarItems(pg.GraphicsObject):
             # removal of the body for a bar index that is now out of
             # date / from some previous sample. It's weird though
             # because i've seen it do this to bars i - 3 back?
+
+        return ohlc['index'], ohlc['close']