Bleh, try a bunch of stuff for step filling

Turns out the performance of updating and refilling step curves > 1k ish
points is super slow :sadkek:. Disabling the fill basically returns
normal performance, so it seems maybe we'll stick with unfilled volume
"bars" for now. The other tricky bit is getting the path to extend and
fill which is particularly slow if you use the `QPainterPath.united()`
(what `+` set op does) operation which seems to require an entire redraw
of the curve each paint iteration. Removing the pixel buffer cache makes
things that much worse too..

One technique i tried was only setting a `._fill` flag when so many
datums are in view (< 1k as determined by the chart widget), and this
helps, but under high load (trade rates) you still see more lag then
without the fill which makes me say screw it and let's stick with
unfilled bars for now. Trying go to get performant filled curves will be
an exercise for an aspiring graphics eng :P

piker/ui/_curve.py

@@ -122,10 +122,12 @@ class FastAppendCurve(pg.PlotCurveItem):
         self._last_line: QLineF = None
         self._xrange: Tuple[int, int] = self.dataBounds(ax=0)
         self._step_mode: bool = step_mode
+        self._fill = False
 
-        self.setBrush(hcolor('bracket'))
+        color = hcolor('davies')
+        self.setBrush(color)
+        self.setPen(color)
 
-        breakpoint()
         # TODO: one question still remaining is if this makes trasform
         # interactions slower (such as zooming) and if so maybe if/when
         # we implement a "history" mode for the view we disable this in
@@ -152,9 +154,6 @@ class FastAppendCurve(pg.PlotCurveItem):
         # over the index space for each datum.
         if self._step_mode:
             x_out, y_out = step_path_arrays_from_1d(x[:-1], y[:-1])
-            # TODO: see ``painter.fillPath()`` call
-            # inside parent's ``.paint()`` to get
-            # a solid brush under the curve.
 
         else:
             # by default we only pull data up to the last (current) index
@@ -164,10 +163,14 @@ class FastAppendCurve(pg.PlotCurveItem):
             self.path = pg.functions.arrayToQPath(
                 x_out,
                 y_out,
-                connect='all'
+                connect='all',
+                finiteCheck=False,
             )
             profiler('generate fresh path')
 
+            if self._step_mode:
+                self.path.closeSubpath()
+
         # TODO: get this working - right now it's giving heck on vwap...
         # if prepend_length:
         #     breakpoint()
@@ -185,25 +188,44 @@ class FastAppendCurve(pg.PlotCurveItem):
         #     self.path.connectPath(old_path)
 
         if append_length:
-            # print(f"append_length: {append_length}")
-            new_x = x[-append_length - 2:-1]
-            new_y = y[-append_length - 2:-1]
-            # print((new_x, new_y))
-
             if self._step_mode:
+                new_x = x[-append_length - 2:-1]
+                new_y = y[-append_length - 2:-1]
                 new_x, new_y = step_path_arrays_from_1d(new_x, new_y)
-                new_x = new_x[2:]
-                new_y = new_y[2:]
+                # new_x = new_x[3:]
+                # new_y = new_y[3:]
+
+            else:
+                # print(f"append_length: {append_length}")
+                new_x = x[-append_length - 2:-1]
+                new_y = y[-append_length - 2:-1]
+                # print((new_x, new_y))
 
             append_path = pg.functions.arrayToQPath(
                 new_x,
                 new_y,
-                connect='all'
+                connect='all',
+                finiteCheck=False,
             )
-            # print(f"append_path br: {append_path.boundingRect()}")
-            # self.path.moveTo(new_x[0], new_y[0])
-            # self.path.connectPath(append_path)
-            self.path.connectPath(append_path)
+
+            if self._step_mode:
+                if self._fill:
+                    path = self.path
+                    # self.path = self.path.united(append_path).simplified()
+                    path.addPath(append_path.simplified())
+                    # path.connectPath(append_path.simplified())
+                    path.closeSubpath()
+                    # path.simplified()
+                else:
+                    self.path.connectPath(append_path.simplified())
+            else:
+                # print(f"append_path br: {append_path.boundingRect()}")
+                # self.path.moveTo(new_x[0], new_y[0])
+                # self.path.connectPath(append_path)
+                self.path.connectPath(append_path.simplified())
+
+            # if self._step_mode:
+            #     self.path.closeSubpath()
             # self.fill_path.connectPath(
 
             # XXX: pretty annoying but, without this there's little
@@ -221,6 +243,7 @@ class FastAppendCurve(pg.PlotCurveItem):
 
         self._xrange = x[0], x[-1]
         if self._step_mode:
+            # TODO: use a ``QRectF`` and ``QPainterPath.addRect()``
             self._last_step_lines = step_lines_from_point(x[-1], y[-1])
         else:
             self._last_line = QLineF(x[-2], y[-2], x[-1], y[-1])
@@ -277,12 +300,18 @@ class FastAppendCurve(pg.PlotCurveItem):
         p.setPen(self.opts['pen'])
 
         if self._step_mode:
+
             p.drawLines(*tuple(filter(bool, self._last_step_lines)))
 
-            # fill_path = QtGui.QPainterPath(self.path)
-            self.path.closeSubpath()
-            p.fillPath(self.path, self.opts['brush'])
             p.drawPath(self.path)
+
+            # fill_path = QtGui.QPainterPath(self.path)
+            # if self._fill:
+            # self.path.closeSubpath()
+            if self._fill:
+                print('FILLED')
+                p.fillPath(self.path, self.opts['brush'])
+
             profiler('.drawPath()')
 
         else: