Merge pull request #177 from pikers/update_throttling

Naively throttle graphics updates to 60 FPS

piker/ui/_chart.py

@@ -18,6 +18,7 @@
 High level Qt chart widgets.
 
 """
+import time
 from typing import Tuple, Dict, Any, Optional, Callable
 from types import ModuleType
 from functools import partial
@@ -934,7 +935,9 @@ async def test_bed(
         # txt.setPos(vb_right - w, d_coords.y())
         # txt.setPlainText(f"FUCK YOU {i}")
         i += 1
-        # rlabel.setPos(vb_right - 2*w, d_coords.y())
+
+
+_quote_throttle_rate: int = 60  # Hz
 
 
 async def chart_from_quotes(
@@ -1011,9 +1014,17 @@ async def chart_from_quotes(
     tick_size = chart._lc.symbol.tick_size
     tick_margin = 2 * tick_size
 
+    last = time.time()
     async for quotes in stream:
-        for sym, quote in quotes.items():
 
+        now = time.time()
+        period = now - last
+        if period <= 1/_quote_throttle_rate - 0.001:
+            # faster then display refresh rate
+            # print(f'quote too fast: {1/period}')
+            continue
+
+        for sym, quote in quotes.items():
             for tick in quote.get('ticks', ()):
 
                 # print(f"CHART: {quote['symbol']}: {tick}")
@@ -1099,6 +1110,9 @@ async def chart_from_quotes(
 
                 last_mx, last_mn = mx, mn
 
+        # set time of last graphics update
+        last = now
+
 
 async def spawn_fsps(
     linked_charts: LinkedSplitCharts,
@@ -1272,9 +1286,19 @@ async def run_fsp(
 
         stream = conf['stream']
 
+        last = time.time()
+
         # update chart graphics
         async for value in stream:
 
+            now = time.time()
+            period = now - last
+            # if period <= 1/30:
+            if period <= 1/_quote_throttle_rate - 0.001:
+                # faster then display refresh rate
+                # print(f'quote too fast: {1/period}')
+                continue
+
             # TODO: provide a read sync mechanism to avoid this polling.
             # the underlying issue is that a backfill and subsequent shm
             # array first/last index update could result in an empty array
@@ -1299,6 +1323,9 @@ async def run_fsp(
             # update graphics
             chart.update_curve_from_array(fsp_func_name, array)
 
+            # set time of last graphics update
+            last = now
+
 
 async def check_for_new_bars(feed, ohlcv, linked_charts):
     """Task which updates from new bars in the shared ohlcv buffer every
@@ -1506,10 +1533,22 @@ async def _async_main(
     Provision the "main" widget with initial symbol data and root nursery.
 
     """
+
     chart_app = widgets['main']
 
     # attempt to configure DPI aware font size
-    _font.configure_to_dpi(current_screen())
+    screen = current_screen()
+
+    # configure graphics update throttling based on display refresh rate
+    global _quote_throttle_rate
+    _quote_throttle_rate = min(
+        round(screen.refreshRate()),
+        _quote_throttle_rate,
+    )
+    log.info(f'Set graphics update rate to {_quote_throttle_rate} Hz')
+
+    # configure global DPI aware font size
+    _font.configure_to_dpi(screen)
 
     async with trio.open_nursery() as root_n: