Add notes about how to do mkts "trimming"

Which is basically just "deleting" rows from a column series.
You can only use the trim command from the `.cmd` cli and only with a so
called `LocalClient` currently; it's also sketchy af and caused
a machine to hang due to mem usage..

Ideally we can patch in this functionality for use by the rpc api
and have it not hang like this XD

Pertains to https://github.com/alpacahq/marketstore/issues/264

piker/brokers/ib.py

@@ -1791,7 +1791,7 @@ async def _setup_quote_stream(
     to_trio.send_nowait(None)
 
     async with load_aio_clients() as accts2clients:
-        client = get_preferred_data_client(accts2clients)
+        caccount_name, client = get_preferred_data_client(accts2clients)
         contract = contract or (await client.find_contract(symbol))
         ticker: Ticker = client.ib.reqMktData(contract, ','.join(opts))
 

piker/data/_source.py

@@ -33,7 +33,7 @@ ohlc_fields = [
     ('high', float),
     ('low', float),
     ('close', float),
-    ('volume', int),
+    ('volume', float),
     ('bar_wap', float),
 ]
 

piker/data/marketstore.py

@@ -230,8 +230,8 @@ _ohlcv_dt = [
     # ohlcv sampling
     ('Open', 'f4'),
     ('High', 'f4'),
-    ('Low', 'i8'),
-    ('Close', 'i8'),
+    ('Low', 'f4'),
+    ('Close', 'f4'),
     ('Volume', 'f4'),
 ]
 
@@ -547,6 +547,17 @@ class Storage:
                 if err:
                     raise MarketStoreError(err)
 
+    # XXX: currently the only way to do this is through the CLI:
+
+    # sudo ./marketstore connect --dir ~/.config/piker/data
+    # >> \show mnq.globex.20220617.ib/1Sec/OHLCV 2022-05-15
+    # and this seems to block and use up mem..
+    # >> \trim mnq.globex.20220617.ib/1Sec/OHLCV 2022-05-15
+
+    # relevant source code for this is here:
+    # https://github.com/alpacahq/marketstore/blob/master/cmd/connect/session/trim.go#L14
+    # def delete_range(self, start_dt, end_dt) -> None:
+    #     ...
 
 @acm
 async def open_storage_client(

piker/ui/_curve.py

@@ -34,10 +34,11 @@ from PyQt5.QtCore import (
 
 from .._profile import pg_profile_enabled, ms_slower_then
 from ._style import hcolor
-from ._compression import (
-    # ohlc_to_m4_line,
-    ds_m4,
-)
+# from ._compression import (
+#     # ohlc_to_m4_line,
+#     ds_m4,
+# )
+from ._pathops import xy_downsample
 from ..log import get_logger
 
 
@@ -174,32 +175,6 @@ class FastAppendCurve(pg.GraphicsObject):
             QLineF(lbar, 0, rbar, 0)
         ).length()
 
-    def downsample(
-        self,
-        x,
-        y,
-        px_width,
-        uppx,
-
-    ) -> tuple[np.ndarray, np.ndarray]:
-
-        # downsample whenever more then 1 pixels per datum can be shown.
-        # always refresh data bounds until we get diffing
-        # working properly, see above..
-        bins, x, y = ds_m4(
-            x,
-            y,
-            px_width=px_width,
-            uppx=uppx,
-            # log_scale=bool(uppx)
-        )
-        x = np.broadcast_to(x[:, None], y.shape)
-        # x = (x + np.array([-0.43, 0, 0, 0.43])).flatten()
-        x = (x + np.array([-0.5, 0, 0, 0.5])).flatten()
-        y = y.flatten()
-
-        return x, y
-
     def update_from_array(
         self,
 
@@ -396,7 +371,8 @@ class FastAppendCurve(pg.GraphicsObject):
                 self._in_ds = False
 
             elif should_ds and uppx and px_width > 1:
-                x_out, y_out = self.downsample(
+
+                x_out, y_out = xy_downsample(
                     x_out,
                     y_out,
                     px_width,
@@ -461,7 +437,7 @@ class FastAppendCurve(pg.GraphicsObject):
             )
 
             # if should_ds:
-            #     new_x, new_y = self.downsample(
+            #     new_x, new_y = xy_downsample(
             #         new_x,
             #         new_y,
             #         px_width,

piker/ui/_flows.py

@@ -48,19 +48,18 @@ from ..data._sharedmem import (
 )
 from .._profile import (
     pg_profile_enabled,
-    ms_slower_then,
+    # ms_slower_then,
+)
+from ._pathops import (
+    gen_ohlc_qpath,
+    ohlc_to_line,
+    to_step_format,
 )
 from ._ohlc import (
     BarItems,
-    gen_qpath,
 )
 from ._curve import (
     FastAppendCurve,
-    # step_path_arrays_from_1d,
-)
-from ._compression import (
-    # ohlc_flatten,
-    ds_m4,
 )
 from ..log import get_logger
 
@@ -114,32 +113,241 @@ def rowarr_to_path(
     )
 
 
-def mk_ohlc_flat_copy(
-    ohlc_shm: ShmArray,
+def render_baritems(
+    flow: Flow,
+    graphics: BarItems,
+    read: tuple[
+        int, int, np.ndarray,
+        int, int, np.ndarray,
+    ],
+    profiler: pg.debug.Profiler,
+    **kwargs,
 
-    # XXX: we bind this in currently..
-    # x_basis: np.ndarray,
-
-    # vr: Optional[slice] = None,
-
-) -> tuple[np.ndarray, np.ndarray]:
+) -> None:
     '''
-    Return flattened-non-copy view into an OHLC shm array.
+    Graphics management logic for a ``BarItems`` object.
+
+    Mostly just logic to determine when and how to downsample an OHLC
+    lines curve into a flattened line graphic and when to display one
+    graphic or the other.
+
+    TODO: this should likely be moved into some kind of better abstraction
+    layer, if not a `Renderer` then something just above it?
 
     '''
-    ohlc = ohlc_shm._array[['open', 'high', 'low', 'close']]
-    # if vr:
-    #     ohlc = ohlc[vr]
-    #     x = x_basis[vr]
+    (
+        xfirst, xlast, array,
+        ivl, ivr, in_view,
+    ) = read
 
-    unstructured = rfn.structured_to_unstructured(
-        ohlc,
-        copy=False,
+    # if no source data renderer exists create one.
+    self = flow
+    r = self._src_r
+    if not r:
+        # OHLC bars path renderer
+        r = self._src_r = Renderer(
+            flow=self,
+            # TODO: rename this to something with ohlc
+            draw_path=gen_ohlc_qpath,
+            last_read=read,
         )
-    # breakpoint()
-    y = unstructured.flatten()
-    # x = x_basis[:y.size]
-    return y
+
+        ds_curve_r = Renderer(
+            flow=self,
+
+            # just swap in the flat view
+            # data_t=lambda array: self.gy.array,
+            last_read=read,
+            draw_path=partial(
+                rowarr_to_path,
+                x_basis=None,
+            ),
+
+        )
+        curve = FastAppendCurve(
+            name='OHLC',
+            color=graphics._color,
+        )
+        curve.hide()
+        self.plot.addItem(curve)
+
+        # baseline "line" downsampled OHLC curve that should
+        # kick on only when we reach a certain uppx threshold.
+        self._render_table[0] = (
+            ds_curve_r,
+            curve,
+        )
+
+    dsc_r, curve = self._render_table[0]
+
+    # do checks for whether or not we require downsampling:
+    # - if we're **not** downsampling then we simply want to
+    #   render the bars graphics curve and update..
+    # - if insteam we are in a downsamplig state then we to
+    x_gt = 6
+    uppx = curve.x_uppx()
+    in_line = should_line = curve.isVisible()
+    if (
+        should_line
+        and uppx < x_gt
+    ):
+        print('FLIPPING TO BARS')
+        should_line = False
+
+    elif (
+        not should_line
+        and uppx >= x_gt
+    ):
+        print('FLIPPING TO LINE')
+        should_line = True
+
+    profiler(f'ds logic complete line={should_line}')
+
+    # do graphics updates
+    if should_line:
+
+        fields = ['open', 'high', 'low', 'close']
+        if self.gy is None:
+            # create a flattened view onto the OHLC array
+            # which can be read as a line-style format
+            shm = self.shm
+            (
+                self._iflat_first,
+                self._iflat_last,
+                self.gx,
+                self.gy,
+            ) = ohlc_to_line(
+                shm,
+                fields=fields,
+            )
+
+        # print(f'unstruct diff: {time.time() - start}')
+
+        gy = self.gy
+
+        # update flatted ohlc copy
+        (
+            iflat_first,
+            iflat,
+            ishm_last,
+            ishm_first,
+        ) = (
+            self._iflat_first,
+            self._iflat_last,
+            self.shm._last.value,
+            self.shm._first.value
+        )
+
+        # check for shm prepend updates since last read.
+        if iflat_first != ishm_first:
+
+            # write newly prepended data to flattened copy
+            gy[
+                ishm_first:iflat_first
+            ] = rfn.structured_to_unstructured(
+                self.shm._array[fields][ishm_first:iflat_first]
+            )
+            self._iflat_first = ishm_first
+
+        to_update = rfn.structured_to_unstructured(
+            self.shm._array[iflat:ishm_last][fields]
+        )
+
+        gy[iflat:ishm_last][:] = to_update
+        profiler('updated ustruct OHLC data')
+
+        # slice out up-to-last step contents
+        y_flat = gy[ishm_first:ishm_last]
+        x_flat = self.gx[ishm_first:ishm_last]
+
+        # update local last-index tracking
+        self._iflat_last = ishm_last
+
+        # reshape to 1d for graphics rendering
+        y = y_flat.reshape(-1)
+        x = x_flat.reshape(-1)
+        profiler('flattened ustruct OHLC data')
+
+        # do all the same for only in-view data
+        y_iv_flat = y_flat[ivl:ivr]
+        x_iv_flat = x_flat[ivl:ivr]
+        y_iv = y_iv_flat.reshape(-1)
+        x_iv = x_iv_flat.reshape(-1)
+        profiler('flattened ustruct in-view OHLC data')
+
+        # pass into curve graphics processing
+        curve.update_from_array(
+            x,
+            y,
+            x_iv=x_iv,
+            y_iv=y_iv,
+            view_range=(ivl, ivr),  # hack
+            profiler=profiler,
+            # should_redraw=False,
+
+            # NOTE: already passed through by display loop?
+            # do_append=uppx < 16,
+            **kwargs,
+        )
+        curve.show()
+        profiler('updated ds curve')
+
+    else:
+        # render incremental or in-view update
+        # and apply ouput (path) to graphics.
+        path, last = r.render(
+            read,
+            only_in_view=True,
+        )
+
+        graphics.path = path
+        graphics.draw_last(last)
+
+        # NOTE: on appends we used to have to flip the coords
+        # cache thought it doesn't seem to be required any more?
+        # graphics.setCacheMode(QtWidgets.QGraphicsItem.NoCache)
+        # graphics.setCacheMode(QtWidgets.QGraphicsItem.DeviceCoordinateCache)
+
+        # graphics.prepareGeometryChange()
+        graphics.update()
+
+    if (
+        not in_line
+        and should_line
+    ):
+        # change to line graphic
+
+        log.info(
+            f'downsampling to line graphic {self.name}'
+        )
+        graphics.hide()
+        # graphics.update()
+        curve.show()
+        curve.update()
+
+    elif in_line and not should_line:
+        log.info(f'showing bars graphic {self.name}')
+        curve.hide()
+        graphics.show()
+        graphics.update()
+
+    #   update our pre-downsample-ready data and then pass that
+    #   new data the downsampler algo for incremental update.
+
+        # graphics.update_from_array(
+        #     array,
+        #     in_view,
+        #     view_range=(ivl, ivr) if use_vr else None,
+
+        #     **kwargs,
+        # )
+
+        # generate and apply path to graphics obj
+        # graphics.path, last = r.render(
+        #     read,
+        #     only_in_view=True,
+        # )
+        # graphics.draw_last(last)
 
 
 class Flow(msgspec.Struct):  # , frozen=True):
@@ -357,271 +565,30 @@ class Flow(msgspec.Struct):  # , frozen=True):
 
         graphics = self.graphics
         if isinstance(graphics, BarItems):
-
-            # if no source data renderer exists create one.
-            r = self._src_r
-            if not r:
-                # OHLC bars path renderer
-                r = self._src_r = Renderer(
-                    flow=self,
-                    # TODO: rename this to something with ohlc
-                    draw_path=gen_qpath,
-                    last_read=read,
-                )
-
-                ds_curve_r = Renderer(
-                    flow=self,
-
-                    # just swap in the flat view
-                    # data_t=lambda array: self.gy.array,
-                    last_read=read,
-                    draw_path=partial(
-                        rowarr_to_path,
-                        x_basis=None,
-                    ),
-
-                )
-                curve = FastAppendCurve(
-                    name='OHLC',
-                    color=graphics._color,
-                )
-                curve.hide()
-                self.plot.addItem(curve)
-
-                # baseline "line" downsampled OHLC curve that should
-                # kick on only when we reach a certain uppx threshold.
-                self._render_table[0] = (
-                    ds_curve_r,
-                    curve,
-                )
-
-            dsc_r, curve = self._render_table[0]
-
-            # do checks for whether or not we require downsampling:
-            # - if we're **not** downsampling then we simply want to
-            #   render the bars graphics curve and update..
-            # - if insteam we are in a downsamplig state then we to
-            x_gt = 6
-            uppx = curve.x_uppx()
-            in_line = should_line = curve.isVisible()
-            if (
-                should_line
-                and uppx < x_gt
-            ):
-                print('FLIPPING TO BARS')
-                should_line = False
-
-            elif (
-                not should_line
-                and uppx >= x_gt
-            ):
-                print('FLIPPING TO LINE')
-                should_line = True
-
-            profiler(f'ds logic complete line={should_line}')
-
-            # do graphics updates
-            if should_line:
-
-                fields = ['open', 'high', 'low', 'close']
-                if self.gy is None:
-                    # create a flattened view onto the OHLC array
-                    # which can be read as a line-style format
-                    shm = self.shm
-
-                    # flat = self.gy = self.shm.unstruct_view(fields)
-                    self.gy = self.shm.ustruct(fields)
-                    first = self._iflat_first = self.shm._first.value
-                    last = self._iflat_last = self.shm._last.value
-
-                    # write pushed data to flattened copy
-                    self.gy[first:last] = rfn.structured_to_unstructured(
-                        self.shm.array[fields]
-                    )
-
-                    # generate an flat-interpolated x-domain
-                    self.gx = (
-                        np.broadcast_to(
-                            shm._array['index'][:, None],
-                            (
-                                shm._array.size,
-                                # 4,  # only ohlc
-                                self.gy.shape[1],
-                            ),
-                        ) + np.array([-0.5, 0, 0, 0.5])
-                    )
-                    assert self.gy.any()
-
-                # print(f'unstruct diff: {time.time() - start}')
-                # profiler('read unstr view bars to line')
-                # start = self.gy._first.value
-                # update flatted ohlc copy
-                (
-                    iflat_first,
-                    iflat,
-                    ishm_last,
-                    ishm_first,
-                ) = (
-                    self._iflat_first,
-                    self._iflat_last,
-                    self.shm._last.value,
-                    self.shm._first.value
-                )
-
-                # check for shm prepend updates since last read.
-                if iflat_first != ishm_first:
-
-                    # write newly prepended data to flattened copy
-                    self.gy[
-                        ishm_first:iflat_first
-                    ] = rfn.structured_to_unstructured(
-                        self.shm._array[fields][ishm_first:iflat_first]
-                    )
-                    self._iflat_first = ishm_first
-
-                #     # flat = self.gy = self.shm.unstruct_view(fields)
-                #     self.gy = self.shm.ustruct(fields)
-                #     # self._iflat_last = self.shm._last.value
-
-                #     # self._iflat_first = self.shm._first.value
-                #     # do an update for the most recent prepend
-                #     # index
-                #     iflat = ishm_first
-
-                to_update = rfn.structured_to_unstructured(
-                    self.shm._array[iflat:ishm_last][fields]
-                )
-
-                self.gy[iflat:ishm_last][:] = to_update
-                profiler('updated ustruct OHLC data')
-
-                # slice out up-to-last step contents
-                y_flat = self.gy[ishm_first:ishm_last]
-                x_flat = self.gx[ishm_first:ishm_last]
-
-                # update local last-index tracking
-                self._iflat_last = ishm_last
-
-                # reshape to 1d for graphics rendering
-                y = y_flat.reshape(-1)
-                x = x_flat.reshape(-1)
-                profiler('flattened ustruct OHLC data')
-
-                # do all the same for only in-view data
-                y_iv_flat = y_flat[ivl:ivr]
-                x_iv_flat = x_flat[ivl:ivr]
-                y_iv = y_iv_flat.reshape(-1)
-                x_iv = x_iv_flat.reshape(-1)
-                profiler('flattened ustruct in-view OHLC data')
-
-                # legacy full-recompute-everytime method
-                # x, y = ohlc_flatten(array)
-                # x_iv, y_iv = ohlc_flatten(in_view)
-                # profiler('flattened OHLC data')
-
-                curve.update_from_array(
-                    x,
-                    y,
-                    x_iv=x_iv,
-                    y_iv=y_iv,
-                    view_range=(ivl, ivr),  # hack
-                    profiler=profiler,
-                    # should_redraw=False,
-
-                    # NOTE: already passed through by display loop?
-                    # do_append=uppx < 16,
+            render_baritems(
+                self,
+                graphics,
+                read,
+                profiler,
                 **kwargs,
             )
-                curve.show()
-                profiler('updated ds curve')
-
-            else:
-                # render incremental or in-view update
-                # and apply ouput (path) to graphics.
-                path, last = r.render(
-                    read,
-                    only_in_view=True,
-                )
-
-                graphics.path = path
-                graphics.draw_last(last)
-
-                # NOTE: on appends we used to have to flip the coords
-                # cache thought it doesn't seem to be required any more?
-                # graphics.setCacheMode(QtWidgets.QGraphicsItem.NoCache)
-                # graphics.setCacheMode(QtWidgets.QGraphicsItem.DeviceCoordinateCache)
-
-                # graphics.prepareGeometryChange()
-                graphics.update()
-
-            if (
-                not in_line
-                and should_line
-            ):
-                # change to line graphic
-
-                log.info(
-                    f'downsampling to line graphic {self.name}'
-                )
-                graphics.hide()
-                # graphics.update()
-                curve.show()
-                curve.update()
-
-            elif in_line and not should_line:
-                log.info(f'showing bars graphic {self.name}')
-                curve.hide()
-                graphics.show()
-                graphics.update()
-
-            #   update our pre-downsample-ready data and then pass that
-            #   new data the downsampler algo for incremental update.
-
-                # graphics.update_from_array(
-                #     array,
-                #     in_view,
-                #     view_range=(ivl, ivr) if use_vr else None,
-
-                #     **kwargs,
-                # )
-
-                # generate and apply path to graphics obj
-                # graphics.path, last = r.render(
-                #     read,
-                #     only_in_view=True,
-                # )
-                # graphics.draw_last(last)
 
         else:
             # ``FastAppendCurve`` case:
             array_key = array_key or self.name
             uppx = graphics.x_uppx()
-            profiler('read uppx')
+            profiler(f'read uppx {uppx}')
 
             if graphics._step_mode and self.gy is None:
-                self._iflat_first = self.shm._first.value
-
-                # create a flattened view onto the OHLC array
-                # which can be read as a line-style format
                 shm = self.shm
-
-                # fields = ['index', array_key]
-                i = shm._array['index'].copy()
-                out = shm._array[array_key].copy()
-
-                self.gx = np.broadcast_to(
-                    i[:, None],
-                    (i.size, 2),
-                ) + np.array([-0.5, 0.5])
-
-                # self.gy = np.broadcast_to(
-                #     out[:, None], (out.size, 2),
-                # )
-                self.gy = np.empty((len(out), 2), dtype=out.dtype)
-                self.gy[:] = out[:, np.newaxis]
-
-                # start y at origin level
-                self.gy[0, 0] = 0
+                (
+                    self._iflat_first,
+                    self.gx,
+                    self.gy,
+                ) = to_step_format(
+                    shm,
+                    array_key,
+                )
                 profiler('generated step mode data')
 
             if graphics._step_mode:
@@ -784,42 +751,11 @@ class Flow(msgspec.Struct):  # , frozen=True):
                     profiler=profiler,
                     **kwargs
                 )
-                profiler(f'`graphics.update_from_array()` complete')
+                profiler('`graphics.update_from_array()` complete')
 
         return graphics
 
 
-def xy_downsample(
-    x,
-    y,
-    px_width,
-    uppx,
-
-    x_spacer: float = 0.5,
-
-) -> tuple[np.ndarray, np.ndarray]:
-
-    # downsample whenever more then 1 pixels per datum can be shown.
-    # always refresh data bounds until we get diffing
-    # working properly, see above..
-    bins, x, y = ds_m4(
-        x,
-        y,
-        px_width=px_width,
-        uppx=uppx,
-        log_scale=bool(uppx)
-    )
-
-    # flatten output to 1d arrays suitable for path-graphics generation.
-    x = np.broadcast_to(x[:, None], y.shape)
-    x = (x + np.array(
-        [-x_spacer, 0, 0, x_spacer]
-    )).flatten()
-    y = y.flatten()
-
-    return x, y
-
-
 class Renderer(msgspec.Struct):
 
     flow: Flow

piker/ui/_ohlc.py

@@ -25,17 +25,15 @@ from typing import (
 
 import numpy as np
 import pyqtgraph as pg
-from numba import njit, float64, int64  # , optional
 from PyQt5 import QtCore, QtGui, QtWidgets
 from PyQt5.QtCore import QLineF, QPointF
-# from numba import types as ntypes
-# from ..data._source import numba_ohlc_dtype
 
 from .._profile import pg_profile_enabled, ms_slower_then
 from ._style import hcolor
 from ..log import get_logger
 from ._curve import FastAppendCurve
 from ._compression import ohlc_flatten
+from ._pathops import gen_ohlc_qpath
 
 if TYPE_CHECKING:
     from ._chart import LinkedSplits
@@ -84,119 +82,6 @@ def bar_from_ohlc_row(
     return [hl, o, c]
 
 
-@njit(
-    # TODO: for now need to construct this manually for readonly arrays, see
-    # https://github.com/numba/numba/issues/4511
-    # ntypes.tuple((float64[:], float64[:], float64[:]))(
-    #     numba_ohlc_dtype[::1],  # contiguous
-    #     int64,
-    #     optional(float64),
-    # ),
-    nogil=True
-)
-def path_arrays_from_ohlc(
-    data: np.ndarray,
-    start: int64,
-    bar_gap: float64 = 0.43,
-
-) -> np.ndarray:
-    '''
-    Generate an array of lines objects from input ohlc data.
-
-    '''
-    size = int(data.shape[0] * 6)
-
-    x = np.zeros(
-        # data,
-        shape=size,
-        dtype=float64,
-    )
-    y, c = x.copy(), x.copy()
-
-    # TODO: report bug for assert @
-    # /home/goodboy/repos/piker/env/lib/python3.8/site-packages/numba/core/typing/builtins.py:991
-    for i, q in enumerate(data[start:], start):
-
-        # TODO: ask numba why this doesn't work..
-        # open, high, low, close, index = q[
-        #     ['open', 'high', 'low', 'close', 'index']]
-
-        open = q['open']
-        high = q['high']
-        low = q['low']
-        close = q['close']
-        index = float64(q['index'])
-
-        istart = i * 6
-        istop = istart + 6
-
-        # x,y detail the 6 points which connect all vertexes of a ohlc bar
-        x[istart:istop] = (
-            index - bar_gap,
-            index,
-            index,
-            index,
-            index,
-            index + bar_gap,
-        )
-        y[istart:istop] = (
-            open,
-            open,
-            low,
-            high,
-            close,
-            close,
-        )
-
-        # specifies that the first edge is never connected to the
-        # prior bars last edge thus providing a small "gap"/"space"
-        # between bars determined by ``bar_gap``.
-        c[istart:istop] = (1, 1, 1, 1, 1, 0)
-
-    return x, y, c
-
-
-def gen_qpath(
-    data: np.ndarray,
-    start: int = 0,  # XXX: do we need this?
-    # 0.5 is no overlap between arms, 1.0 is full overlap
-    w: float = 0.43,
-    path: Optional[QtGui.QPainterPath] = None,
-
-) -> QtGui.QPainterPath:
-
-    path_was_none = path is None
-
-    profiler = pg.debug.Profiler(
-        msg='gen_qpath ohlc',
-        disabled=not pg_profile_enabled(),
-        ms_threshold=ms_slower_then,
-    )
-
-    x, y, c = path_arrays_from_ohlc(
-        data,
-        start,
-        bar_gap=w,
-    )
-    profiler("generate stream with numba")
-
-    # TODO: numba the internals of this!
-    path = pg.functions.arrayToQPath(
-        x,
-        y,
-        connect=c,
-        path=path,
-    )
-
-    # avoid mem allocs if possible
-    if path_was_none:
-        path.reserve(path.capacity())
-
-    profiler("generate path with arrayToQPath")
-
-    return path
-
-
 class BarItems(pg.GraphicsObject):
     '''
     "Price range" bars graphics rendered from a OHLC sampled sequence.
@@ -274,7 +159,7 @@ class BarItems(pg.GraphicsObject):
 
         '''
         hist, last = ohlc[:-1], ohlc[-1]
-        self.path = gen_qpath(hist, start, self.w)
+        self.path = gen_ohlc_qpath(hist, start, self.w)
 
         # save graphics for later reference and keep track
         # of current internal "last index"

piker/ui/_pathops.py

@@ -0,0 +1,256 @@
+# piker: trading gear for hackers
+# Copyright (C) 2018-present  Tyler Goodlet (in stewardship of piker0)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+"""
+Super fast ``QPainterPath`` generation related operator routines.
+
+"""
+from typing import (
+    Optional,
+)
+
+import numpy as np
+from numpy.lib import recfunctions as rfn
+from numba import njit, float64, int64  # , optional
+import pyqtgraph as pg
+from PyQt5 import QtGui
+# from PyQt5.QtCore import QLineF, QPointF
+
+from ..data._sharedmem import (
+    ShmArray,
+)
+from .._profile import pg_profile_enabled, ms_slower_then
+from ._compression import (
+    # ohlc_flatten,
+    ds_m4,
+)
+
+
+def xy_downsample(
+    x,
+    y,
+    px_width,
+    uppx,
+
+    x_spacer: float = 0.5,
+
+) -> tuple[np.ndarray, np.ndarray]:
+
+    # downsample whenever more then 1 pixels per datum can be shown.
+    # always refresh data bounds until we get diffing
+    # working properly, see above..
+    bins, x, y = ds_m4(
+        x,
+        y,
+        px_width=px_width,
+        uppx=uppx,
+        # log_scale=bool(uppx)
+    )
+
+    # flatten output to 1d arrays suitable for path-graphics generation.
+    x = np.broadcast_to(x[:, None], y.shape)
+    x = (x + np.array(
+        [-x_spacer, 0, 0, x_spacer]
+    )).flatten()
+    y = y.flatten()
+
+    return x, y
+
+
+@njit(
+    # TODO: for now need to construct this manually for readonly arrays, see
+    # https://github.com/numba/numba/issues/4511
+    # ntypes.tuple((float64[:], float64[:], float64[:]))(
+    #     numba_ohlc_dtype[::1],  # contiguous
+    #     int64,
+    #     optional(float64),
+    # ),
+    nogil=True
+)
+def path_arrays_from_ohlc(
+    data: np.ndarray,
+    start: int64,
+    bar_gap: float64 = 0.43,
+
+) -> np.ndarray:
+    '''
+    Generate an array of lines objects from input ohlc data.
+
+    '''
+    size = int(data.shape[0] * 6)
+
+    x = np.zeros(
+        # data,
+        shape=size,
+        dtype=float64,
+    )
+    y, c = x.copy(), x.copy()
+
+    # TODO: report bug for assert @
+    # /home/goodboy/repos/piker/env/lib/python3.8/site-packages/numba/core/typing/builtins.py:991
+    for i, q in enumerate(data[start:], start):
+
+        # TODO: ask numba why this doesn't work..
+        # open, high, low, close, index = q[
+        #     ['open', 'high', 'low', 'close', 'index']]
+
+        open = q['open']
+        high = q['high']
+        low = q['low']
+        close = q['close']
+        index = float64(q['index'])
+
+        istart = i * 6
+        istop = istart + 6
+
+        # x,y detail the 6 points which connect all vertexes of a ohlc bar
+        x[istart:istop] = (
+            index - bar_gap,
+            index,
+            index,
+            index,
+            index,
+            index + bar_gap,
+        )
+        y[istart:istop] = (
+            open,
+            open,
+            low,
+            high,
+            close,
+            close,
+        )
+
+        # specifies that the first edge is never connected to the
+        # prior bars last edge thus providing a small "gap"/"space"
+        # between bars determined by ``bar_gap``.
+        c[istart:istop] = (1, 1, 1, 1, 1, 0)
+
+    return x, y, c
+
+
+def gen_ohlc_qpath(
+    data: np.ndarray,
+    start: int = 0,  # XXX: do we need this?
+    # 0.5 is no overlap between arms, 1.0 is full overlap
+    w: float = 0.43,
+    path: Optional[QtGui.QPainterPath] = None,
+
+) -> QtGui.QPainterPath:
+
+    path_was_none = path is None
+
+    profiler = pg.debug.Profiler(
+        msg='gen_qpath ohlc',
+        disabled=not pg_profile_enabled(),
+        ms_threshold=ms_slower_then,
+    )
+
+    x, y, c = path_arrays_from_ohlc(
+        data,
+        start,
+        bar_gap=w,
+    )
+    profiler("generate stream with numba")
+
+    # TODO: numba the internals of this!
+    path = pg.functions.arrayToQPath(
+        x,
+        y,
+        connect=c,
+        path=path,
+    )
+
+    # avoid mem allocs if possible
+    if path_was_none:
+        path.reserve(path.capacity())
+
+    profiler("generate path with arrayToQPath")
+
+    return path
+
+
+def ohlc_to_line(
+    ohlc_shm: ShmArray,
+    fields: list[str] = ['open', 'high', 'low', 'close']
+
+) -> tuple[
+    int,  # flattened first index
+    int,  # flattened last index
+    np.ndarray,
+    np.ndarray,
+]:
+    '''
+    Convert an input struct-array holding OHLC samples into a pair of
+    flattened x, y arrays with the same size (datums wise) as the source
+    data.
+
+    '''
+    y_out = ohlc_shm.ustruct(fields)
+    first = ohlc_shm._first.value
+    last = ohlc_shm._last.value
+
+    # write pushed data to flattened copy
+    y_out[first:last] = rfn.structured_to_unstructured(
+        ohlc_shm.array[fields]
+    )
+
+    # generate an flat-interpolated x-domain
+    x_out = (
+        np.broadcast_to(
+            ohlc_shm._array['index'][:, None],
+            (
+                ohlc_shm._array.size,
+                # 4,  # only ohlc
+                y_out.shape[1],
+            ),
+        ) + np.array([-0.5, 0, 0, 0.5])
+    )
+    assert y_out.any()
+
+    return (
+        first,
+        last,
+        x_out,
+        y_out,
+    )
+
+
+def to_step_format(
+    shm: ShmArray,
+    data_field: str,
+    index_field: str = 'index',
+
+) -> tuple[int, np.ndarray, np.ndarray]:
+    '''
+    Convert an input 1d shm array to a "step array" format
+    for use by path graphics generation.
+
+    '''
+    first = shm._first.value
+    i = shm._array['index'].copy()
+    out = shm._array[data_field].copy()
+
+    x_out = np.broadcast_to(
+        i[:, None],
+        (i.size, 2),
+    ) + np.array([-0.5, 0.5])
+
+    y_out = np.empty((len(out), 2), dtype=out.dtype)
+    y_out[:] = out[:, np.newaxis]
+
+    # start y at origin level
+    y_out[0, 0] = 0
+    return first, x_out, y_out