From 761b82393977f03397fc9015fb3f8922456be22d Mon Sep 17 00:00:00 2001
From: Tyler Goodlet <jgbt@protonmail.com>
Date: Sun, 6 Mar 2022 17:03:37 -0500
Subject: [PATCH] Always fire a "step/update message" on every fsp history
 update

---
 piker/fsp/_engine.py | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/piker/fsp/_engine.py b/piker/fsp/_engine.py
index 7e75c283..f1904000 100644
--- a/piker/fsp/_engine.py
+++ b/piker/fsp/_engine.py
@@ -127,8 +127,8 @@ async def fsp_compute(
     # each respective field.
     fields = getattr(dst.array.dtype, 'fields', None).copy()
     fields.pop('index')
-    # TODO: nptyping here!
-    history: Optional[np.ndarray] = None
+    history: Optional[np.ndarray] = None  # TODO: nptyping here!
+
     if fields and len(fields) > 1 and fields:
         if not isinstance(history_output, dict):
             raise ValueError(
@@ -209,6 +209,12 @@ async def fsp_compute(
         try:
             # rt stream
             async with ctx.open_stream() as stream:
+
+                # always trigger UI refresh after history update,
+                # see ``piker.ui._fsp.FspAdmin.open_chain()`` and
+                # ``piker.ui._display.trigger_update()``.
+                await stream.send(index)
+
                 async for processed in out_stream:
 
                     log.debug(f"{func_name}: {processed}")