Each `pyqtgraph.PlotItem` uses a `QGraphicsGridLayout` to place its view
box, axes and titles in the traditional graph format. With multiple
overlayed charts we need those axes to not collide with one another and
further allow for an "order" specified by the user. We accomplish this
by adding `QGraphicsLinearLayout`s for each axis "side": `{'left',
'right', 'top', 'bottom'}` such that plot axes can be inserted and moved
easily without having to constantly re-stack/order a grid layout (which
does not have a linked-list style API).
The new type is called `ComposedGridLayout` for now and offers a basic
list-like API with `.insert()`, `.append()`, and eventually a dict-style
`.pop()`. We probably want to also eventually offer a `.focus()` to
allow user switching of *which* main graphics object (aka chart) is "in
use".
This syncs with a dev branch in our `pyqtgraph` fork:
https://github.com/pyqtgraph/pyqtgraph/pull/2162
The main idea is to get mult-yaxis display fully functional with
multiple view boxes running in a "relay mode" where some focussed view
relays signals to overlaid views which may have independent axes. This
preps us for both displaying independent codomain-set FSP output as well
as so called "aggregate" feeds of multiple fins underlyings on the same
chart (eg. options and futures over top of ETFs and underlying stocks).
The eventual desired UX is to support fast switching of instruments for
order mode trading without requiring entirely separate charts as well as
simple real-time anal of associated instruments.
The first effort here is to display vlm and $_vlm alongside each other
as a built-in FSP subchart.
We can instead use the god widget's nursery to schedule all the feed
pause/resume requests and be even more concurrent during a view (of
symbols) switch.
Use `tractor.trionics.gather_contexts()` to start up the fsp and volume
chart-displays (for an additional conc speedup). Drop `dolla_vlm` again for
now until we figure out how we can display it *and* vlm on the same
sub-chart? It would be nice to avoid having to spawn an fsp process
before showing the volume curve.
Call the resize method only after all FSP subcharts have rendered
such that the main OHLC chart's final width is read.
Further tweaks:
- drop rsi by default
- drop the stream drain stuff
- fix failed-to-read shm logging
This fixes a weird re-render bug/slowdown/artifact that was introduced
with the order mode sidepane work. Prior to the sidepane addition, chart
switching was immediate with zero noticeable widget rendering steps.
The slow down was caused by 2 things:
- not yielding back to the Qt loop asap after re-showing/focussing
a linked split chart that was already in memory.
- pausing/resuming feeds only after a Qt loop render cycle has
completed.
This now restores the near zero latency UX.
There was a lingering issue where the fsp daemon would sync its shm
array with the source data and we'd set the start/end indices to the
same value. Under some races a reader would then read an empty `.array`
which it wasn't expecting. This fixes that as well as tidies up the
`ShmArray.push()` logic and adds a temporary check in `.array` for zero
length if the array hasn't been written yet.
We can now start removing read array length checks in consumer code
and hopefully no more races will show up.
Revert to old shm "last" meaning last row
It can now be declared inside an fsp config dict under the name
`dolla_vlm`. We still need to offer an engine control that zeros
the newest sample value instead of copying from the previous.
This also litters the engine code with `pyqtgraph` profiling to see if
we can improve startup times - likely it'll mean pre-allocating a small
fsp daemon cluster at startup.
Tyler Goodlet
goodboy
wattygetlood