fix: read the aareDB transmission as the percentage it is

DataCollectionParameters.transmission is a StrictInt documented as
"positive, between 0 and 100" (aareDB's own API description of the
spreadsheet payload), while every model that consumes it wants a 0-to-1
fraction. The old "divide by 100 only when above 1.0" guess therefore
turned a spreadsheet asking for 1% into a scan at 100% transmission -
a hundredfold dose on the sample. A fraction cannot be stored in that
column at all: the model rejects 0.2.

The mapping test now builds a real DataCollectionParameters instead of a
stand-in namespace, so a renamed column fails the test rather than the
beamline. That is what let 'totalrange' through.

daq.py's spreadsheet_params and get_auto_raster_params still carry both
the old column name and the same transmission guess.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JHoUkj66jxByS2ypY5h9Mn

src/aare/gui/panels/scan_settings_panel.py

@@ -86,9 +86,11 @@ class SampleParameters:
         params = None if sample is None else sample.aaredb_params
         if params is None:
             return cls()
+        # aareDB holds transmission as a percentage (DataCollectionParameters
+        # .transmission is an int, 0 to 100); everything here works in the
+        # 0-to-1 fraction the scan requests are built from.
         transmission = _spreadsheet_float(params, "transmission")
-        if transmission is not None and transmission > 1.0:
-            # aareDB holds transmission either as a fraction or as a percentage
+        if transmission is not None:
             transmission = transmission / 100.0
         return cls(
             resolution_a=_spreadsheet_float(params, "targetresolution"),

src/aare/gui/threads/prediction_subscriber.py

@@ -1,5 +1,6 @@
 import json
 import time
+from threading import Lock
 
 import cv2
 import numpy as np
@@ -14,6 +15,17 @@ from aare.gui.constants import LOGGER_NAME
 
 logger = setup_logger(LOGGER_NAME)
 
+# Frames handed to the GUI thread but not painted yet. The image signal is a
+# queued connection, so without a cap the subscriber hands over frames faster
+# than they can be painted and the Qt event queue grows without bound - lag
+# that no amount of draining on the socket can fix.
+MAX_FRAMES_IN_FLIGHT = 1
+
+# The socket's own queue. Only a memory bound: _recv_latest() drops whatever
+# piled up behind the newest frame anyway. Has to stay above the number of
+# parts in a frame, or the pipe cannot assemble a multipart message.
+RCV_QUEUE_MESSAGES = 10
+
 
 class PredictionSubscriber(QThread):
     prediction = Signal(dict)
@@ -30,6 +42,14 @@ class PredictionSubscriber(QThread):
         self._sock = self._ctx.socket(zmq.SUB)
         self._sock.setsockopt(zmq.RCVTIMEO, 500)
         self._sock.setsockopt(zmq.LINGER, 0)
+        self._sock.setsockopt(zmq.RCVHWM, RCV_QUEUE_MESSAGES)
+
+        # Delivery of an image frees the slot for the next one. Queued back to
+        # the thread this object lives in (the GUI thread), like the painting
+        # slots, so it runs once the GUI has worked through the frame.
+        self._frames_in_flight = 0
+        self._frames_in_flight_lock = Lock()
+        self.image.connect(self._on_image_delivered)
 
         self._emit_images = True
         self.running = True
@@ -62,6 +82,37 @@ class PredictionSubscriber(QThread):
     def set_emit_images(self, enabled: bool) -> None:
         self._emit_images = enabled
 
+    def _recv_latest(self) -> tuple[list[bytes], int]:
+        """The newest frame on the socket, plus how many older ones were
+        dropped to get to it. This is what CONFLATE would do, except that
+        CONFLATE keeps a single message *part* and every frame here is
+        multipart (header, image, detections), so it cannot be used."""
+        sock = self._sock
+        if sock is None:  # run() has already torn the socket down
+            raise zmq.Again
+        parts = sock.recv_multipart()
+        dropped = 0
+        while True:
+            try:
+                parts = sock.recv_multipart(zmq.NOBLOCK)
+            except zmq.Again:
+                return parts, dropped
+            dropped += 1
+
+    @Slot(QPixmap)
+    def _on_image_delivered(self, _pixmap: QPixmap) -> None:
+        with self._frames_in_flight_lock:
+            self._frames_in_flight = max(0, self._frames_in_flight - 1)
+
+    def _gui_ready_for_frame(self) -> bool:
+        with self._frames_in_flight_lock:
+            return self._frames_in_flight < MAX_FRAMES_IN_FLIGHT
+
+    def _emit_image(self, pixmap: QPixmap) -> None:
+        with self._frames_in_flight_lock:
+            self._frames_in_flight += 1
+        self.image.emit(pixmap)
+
     def _set_camera_available(self, available: bool, error: str | None = None) -> None:
         if available != self._camera_available:
             self._camera_available = available
@@ -152,12 +203,10 @@ class PredictionSubscriber(QThread):
         self.focus_measure.emit(sharpness)
 
     def run(self):
-        self._debug_last_log_ts = time.perf_counter()
-        self._debug_msg_count = 0
         try:
             while self.running:
                 try:
-                    parts = self._sock.recv_multipart()
+                    parts, dropped = self._recv_latest()
                 except zmq.Again:
                     now = time.perf_counter()
                     elapsed = now - self._fps_window_start
@@ -179,7 +228,8 @@ class PredictionSubscriber(QThread):
 
                 now = time.perf_counter()
                 self._last_frame_time = now
-                self._fps_frame_count += 1
+                # dropped frames count too: this is the camera's rate, not ours
+                self._fps_frame_count += 1 + dropped
 
                 elapsed = now - self._fps_window_start
                 if elapsed >= self._fps_emit_period_s:
@@ -211,7 +261,12 @@ class PredictionSubscriber(QThread):
                 target = next((d for d in json_dicts if "target_point" in d), None)
                 image_bytes = max(non_json_parts, key=len) if non_json_parts else None
 
-                if self._emit_images and header and image_bytes:
+                # The decode is skipped along with the emit: a frame the GUI
+                # is too busy to paint is not worth decoding. The sharpness
+                # read-out is the exception, it works on the decoded image.
+                emit_image = self._emit_images and self._gui_ready_for_frame()
+
+                if header and image_bytes and (emit_image or self._measure_focus):
                     rgb = self._decode_rgb_image(header, image_bytes)
                     if rgb is None:
                         self._set_camera_available(
@@ -220,9 +275,9 @@ class PredictionSubscriber(QThread):
                     else:
                         self._set_camera_available(True)
                         self._emit_focus_measure_if_enabled(rgb)
-                        if self.running:
-                            self.image.emit(self._rgb_to_pixmap(rgb))
-                elif self._emit_images:
+                        if emit_image and self.running:
+                            self._emit_image(self._rgb_to_pixmap(rgb))
+                elif self._emit_images and not (header and image_bytes):
                     self._set_camera_available(
                         False, "Sample camera feed unavailable: no frame header in zmq stream"
                     )

tests/unit/gui/test_data_collection_settings.py

@@ -13,7 +13,12 @@ from typing import Any, cast
 import pytest
 from aarecommon.math.coordinate import Coordinate, SmargonCoordinate
 from aarecommon.math.diffraction_geometry import DiffractionGeometry
-from aarecommon.models.models import BeamlineStateEnum, SampleGeometryModel
+from aarecommon.models.models import (
+    BeamlineStateEnum,
+    DataCollectionParameters,
+    SampleGeometryModel,
+    SampleShortInfo,
+)
 from PySide6.QtCore import Qt
 
 from aare.gui.panels.data_collection_settings import DataCollectionSettings
@@ -43,14 +48,23 @@ def _mount(panel, **params):
 
 
 def test_sample_parameters_translate_the_spreadsheet_row():
-    params = types.SimpleNamespace(
-        targetresolution=1.5,
-        transmission=20.0,  # percent
-        totalangle="180",  # spreadsheet cells can arrive as text
-        oscillation=0.1,
-        exposure=0.02,
+    # The real model, so the column names are checked against aareDB and not
+    # against a stand-in that agrees with whatever this file happens to say.
+    sample = SampleShortInfo(
+        db_id=1,
+        puck_name="puck1",
+        dewar_name="dewar1",
+        sample_name="sample1",
+        run_number=1,
+        pin=1,
+        aaredb_params=DataCollectionParameters(
+            targetresolution=1.5,
+            transmission=20,  # aareDB stores a percentage
+            totalangle=180,
+            oscillation=0.1,
+            exposure=0.02,
+        ),
     )
-    sample = cast(Any, types.SimpleNamespace(aaredb_params=params))
     assert SampleParameters.from_sample(sample) == SampleParameters(
         resolution_a=1.5,
         transmission=0.2,