Fix three GUI runtime errors surfaced while browsing

probeflow/gui/convert/__init__.py

@@ -2,7 +2,7 @@
 
 from __future__ import annotations
 
-from probeflow.gui.typography import ui_font
+from probeflow.gui.typography import mono_font, ui_font
 from PySide6.QtCore import Qt
 from PySide6.QtGui import QCursor, QFont
 from PySide6.QtWidgets import (
@@ -95,7 +95,7 @@ def __init__(self, t: dict, cfg: dict, parent=None):
 
         self.log_text = QTextEdit()
         self.log_text.setReadOnly(True)
-        self.log_text.setFont(QFont("Courier", 11))
+        self.log_text.setFont(mono_font(11))
         lay.addWidget(self.log_text, 1)
 
         if cfg.get("input_dir"):

probeflow/gui/dialogs/fft_viewer.py

@@ -5,7 +5,7 @@
 
 from matplotlib.backends.backend_qtagg import FigureCanvasQTAgg
 from matplotlib.figure import Figure
-from probeflow.gui.typography import ui_font
+from probeflow.gui.typography import mono_font, ui_font
 from PySide6.QtCore import Qt, QTimer
 from PySide6.QtGui import QAction, QActionGroup, QFont
 from PySide6.QtWidgets import (
@@ -456,7 +456,7 @@ def _build_fft_column(self) -> QVBoxLayout:
         cursor_title = QLabel("Cursor")
         cursor_title.setFont(ui_font(9, weight=QFont.Bold))
         self._cursor_readout_lbl = QLabel("Move over the FFT")
-        self._cursor_readout_lbl.setFont(QFont("Courier", 8))
+        self._cursor_readout_lbl.setFont(mono_font(8))
         self._cursor_readout_lbl.setWordWrap(True)
         side_lay.addWidget(cursor_title)
         side_lay.addWidget(self._cursor_readout_lbl)
@@ -507,7 +507,7 @@ def _build_fft_column(self) -> QVBoxLayout:
 
         # Measurement summary — always visible at the top
         self._grid_measure_lbl = QLabel("No grid — click Draw Grid to start")
-        self._grid_measure_lbl.setFont(QFont("Courier", 9))
+        self._grid_measure_lbl.setFont(mono_font(9))
         self._grid_measure_lbl.setWordWrap(True)
         self._grid_measure_lbl.setTextInteractionFlags(Qt.TextSelectableByMouse)
         grid_outer_lay.addWidget(self._grid_measure_lbl)
@@ -648,7 +648,7 @@ def _build_fft_column(self) -> QVBoxLayout:
         ref_grid.setColumnStretch(1, 1)
         ref_grid.setColumnStretch(3, 1)
         self._bragg_radius_lbl = QLabel("Shells: —")
-        self._bragg_radius_lbl.setFont(QFont("Courier", 8))
+        self._bragg_radius_lbl.setFont(mono_font(8))
         self._bragg_radius_lbl.setWordWrap(True)
         self._bragg_radius_lbl.setMaximumHeight(34)
         self._bragg_radius_lbl.setTextInteractionFlags(Qt.TextSelectableByMouse)
@@ -665,7 +665,7 @@ def _build_fft_column(self) -> QVBoxLayout:
         self._fft_measured_lbl = QLabel(
             "Draw a grid and select a known structure to see the comparison."
         )
-        self._fft_measured_lbl.setFont(QFont("Courier", 8))
+        self._fft_measured_lbl.setFont(mono_font(8))
         self._fft_measured_lbl.setWordWrap(True)
         self._fft_measured_lbl.setMinimumHeight(32)
         self._fft_measured_lbl.setMaximumHeight(54)
@@ -728,7 +728,7 @@ def _build_fft_column(self) -> QVBoxLayout:
         self._fft_fill_combo.addItems(["NaN", "Background", "Zero"])
 
         self._fft_correction_lbl = QLabel("Align a reciprocal grid to compute correction factors.")
-        self._fft_correction_lbl.setFont(QFont("Courier", 8))
+        self._fft_correction_lbl.setFont(mono_font(8))
         self._fft_correction_lbl.setWordWrap(True)
         self._fft_correction_lbl.setMinimumHeight(34)
         self._fft_correction_lbl.setMaximumHeight(60)
@@ -880,7 +880,7 @@ def _build(self):
         info_lay.setContentsMargins(8, 6, 8, 4)
         info_lay.setSpacing(2)
         self._info_lbl = QLabel("")
-        self._info_lbl.setFont(QFont("Courier", 9))
+        self._info_lbl.setFont(mono_font(9))
         self._info_lbl.setAlignment(Qt.AlignTop | Qt.AlignLeft)
         info_lay.addWidget(self._info_lbl)
         left_col.addWidget(info_frame)

probeflow/gui/dialogs/fft_viewer_reconstruct_mixin.py

@@ -95,7 +95,11 @@ def _build_reconstruct_tab(self) -> QWidget:
             "Remove selected: suppress the selected Fourier features and rebuild "
             "the corrected image. Keep selected: rebuild only the selected "
             "periodic component (everything else removed)."))
-        self._recon_mode_combo.currentIndexChanged.connect(self._update_reconstruct_status)
+        # Drop the combo's int index — _update_reconstruct_status treats its
+        # first positional arg as a reconstruction result, so passing the index
+        # straight through made it call res.imag_residual_norm on an int.
+        self._recon_mode_combo.currentIndexChanged.connect(
+            lambda _idx: self._update_reconstruct_status())
         self._recon_mode_combo.setMaximumWidth(140)
         mode_row.addWidget(self._recon_mode_combo)
         mode_row.addStretch(1)

probeflow/gui/dialogs/image_info.py

@@ -2,11 +2,9 @@
 
 from __future__ import annotations
 
-from pathlib import Path
 from typing import TYPE_CHECKING
 
 from PySide6.QtCore import Qt
-from PySide6.QtGui import QFont
 from PySide6.QtWidgets import (
     QDialog,
     QFormLayout,
@@ -19,6 +17,8 @@
     QWidget,
 )
 
+from probeflow.gui.typography import mono_font
+
 if TYPE_CHECKING:
     from probeflow.core.metadata import ScanMetadata
 
@@ -168,9 +168,7 @@ def _row(field: str, text: str) -> None:
         hist_lay.setContentsMargins(4, 4, 4, 4)
         hist_text = QPlainTextEdit()
         hist_text.setReadOnly(True)
-        mono_font = QFont("Menlo" if Path("/System/Library/Fonts/Menlo.ttc").exists() else "Courier")
-        mono_font.setPointSize(9)
-        hist_text.setFont(mono_font)
+        hist_text.setFont(mono_font(9))
         hist_text.setPlainText(processing_history_text or "(No processing history)")
         hist_lay.addWidget(hist_text)
         tabs.addTab(hist_widget, "Processing History")

probeflow/gui/dialogs/periodic_filter.py

@@ -4,9 +4,8 @@
 
 from matplotlib.backends.backend_qtagg import FigureCanvasQTAgg
 from matplotlib.figure import Figure
-from probeflow.gui.typography import ui_font
+from probeflow.gui.typography import mono_font, ui_font
 from PySide6.QtCore import Qt
-from PySide6.QtGui import QFont
 from PySide6.QtWidgets import (
     QFrame, QHBoxLayout, QLabel, QPushButton, QSlider, QVBoxLayout, QWidget,
 )
@@ -97,7 +96,7 @@ def _build(self):
         info_lay.setContentsMargins(8, 6, 8, 4)
         info_lay.setSpacing(2)
         self._info_lbl = QLabel("")
-        self._info_lbl.setFont(QFont("Courier", 9))
+        self._info_lbl.setFont(mono_font(9))
         self._info_lbl.setAlignment(Qt.AlignTop | Qt.AlignLeft)
         info_lay.addWidget(self._info_lbl)
         info_lay.addStretch(1)

probeflow/gui/lattice_grid/real_space_panel.py

@@ -8,7 +8,7 @@
 
 import numpy as np
 
-from probeflow.gui.typography import ui_font
+from probeflow.gui.typography import mono_font, ui_font
 from PySide6.QtCore import Qt
 from PySide6.QtGui import QFont
 from PySide6.QtWidgets import (
@@ -280,7 +280,7 @@ def _spin_row(
         meas_lay = QVBoxLayout(meas_grp)
         meas_lay.setContentsMargins(6, 6, 6, 4)
         self._meas_lbl = QLabel("")
-        self._meas_lbl.setFont(QFont("Courier", 8))
+        self._meas_lbl.setFont(mono_font(8))
         self._meas_lbl.setAlignment(Qt.AlignTop | Qt.AlignLeft)
         self._meas_lbl.setTextInteractionFlags(Qt.TextSelectableByMouse)
         self._meas_lbl.setWordWrap(True)
@@ -393,7 +393,7 @@ def _spin_row(
         meas_dist_lay = QVBoxLayout(meas_dist_grp)
         meas_dist_lay.setContentsMargins(6, 6, 6, 4)
         self._measured_lbl = QLabel("(tune grid above)")
-        self._measured_lbl.setFont(QFont("Courier", 8))
+        self._measured_lbl.setFont(mono_font(8))
         self._measured_lbl.setAlignment(Qt.AlignTop | Qt.AlignLeft)
         self._measured_lbl.setTextInteractionFlags(Qt.TextSelectableByMouse)
         meas_dist_lay.addWidget(self._measured_lbl)
@@ -405,7 +405,7 @@ def _spin_row(
         corr_lay = QVBoxLayout(corr_grp)
         corr_lay.setContentsMargins(6, 6, 6, 4)
         self._correction_lbl = QLabel("(enter ideal lattice above)")
-        self._correction_lbl.setFont(QFont("Courier", 8))
+        self._correction_lbl.setFont(mono_font(8))
         self._correction_lbl.setAlignment(Qt.AlignTop | Qt.AlignLeft)
         self._correction_lbl.setTextInteractionFlags(Qt.TextSelectableByMouse)
         self._correction_lbl.setWordWrap(True)

probeflow/gui/typography.py

@@ -30,6 +30,7 @@
 }
 
 _UI_FAMILY: str | None = None
+_MONO_FAMILY: str | None = None
 
 
 def ui_family() -> str:
@@ -47,6 +48,27 @@ def ui_family() -> str:
     return _UI_FAMILY
 
 
+def mono_family() -> str:
+    """Return the platform fixed-width font family (Menlo on macOS), cached.
+
+    Asking Qt for the real system monospace family avoids the costly font-alias
+    lookup — and the "missing font family 'Courier'" warning — that an explicit
+    ``QFont("Courier", ...)`` triggers on macOS/Windows, where "Courier" is only
+    an alias rather than an installed family.
+    """
+    global _MONO_FAMILY
+    if _MONO_FAMILY is None:
+        family = ""
+        try:
+            from PySide6.QtGui import QFontDatabase
+
+            family = QFontDatabase.systemFont(QFontDatabase.FixedFont).family()
+        except Exception:
+            family = ""
+        _MONO_FAMILY = family or "Monospace"
+    return _MONO_FAMILY
+
+
 def scaled(pt: int) -> int:
     """Map a legacy point size onto the comfortable scale."""
     return _SIZE_MAP.get(int(pt), int(pt))
@@ -64,4 +86,21 @@ def ui_font(pt: int, *, bold: bool = False, weight=None) -> "QFont":
     return f
 
 
-__all__ = ["ui_family", "scaled", "ui_font"]
+def mono_font(pt: int, *, bold: bool = False, weight=None) -> "QFont":
+    """Build a fixed-width font in the real platform monospace family.
+
+    The point size is preserved verbatim (not run through ``scaled``): these are
+    compact numeric readouts whose layout depends on the existing size — the fix
+    here is only the font *family*, to silence the "Courier" alias warning.
+    """
+    from PySide6.QtGui import QFont
+
+    f = QFont(mono_family(), pt)
+    if weight is not None:
+        f.setWeight(weight)
+    elif bold:
+        f.setBold(True)
+    return f
+
+
+__all__ = ["ui_family", "mono_family", "scaled", "ui_font", "mono_font"]

probeflow/processing/state.py

@@ -475,10 +475,18 @@ def apply_processing_state(
             )
         elif step.op == "stm_background":
             fit_mask = _resolve_mask_roi_param(p, "fit", a.shape, roi_set)
+            fit_region = str(p.get("fit_region", "whole_image"))
+            if fit_region == "active_roi" and fit_mask is None:
+                # The ROI mask could not be resolved (no roi_set, missing ROI,
+                # or non-area ROI) — _resolve_mask_roi_param already warned and
+                # returned None. Degrade to a whole-image fit instead of letting
+                # the kernel raise (active_roi mandates a mask), so thumbnail /
+                # preview renders without a roi_set don't crash.
+                fit_region = "whole_image"
             a = _proc.apply_stm_background(
                 a,
                 _proc.STMBackgroundParams(
-                    fit_region=str(p.get("fit_region", "whole_image")),
+                    fit_region=fit_region,
                     line_statistic=str(p.get("line_statistic", "median")),
                     model=str(p.get("model", "linear")),
                     linear_x_first=bool(p.get("linear_x_first", False)),

tests/test_fft_phase_gui.py

@@ -40,6 +40,19 @@ def _set_view(dlg, text):
     dlg._fft_view_combo.setCurrentIndex(dlg._fft_view_combo.findText(text))
 
 
+class TestReconstructStatus:
+    def test_changing_reconstruct_mode_does_not_crash(self, qapp):
+        # currentIndexChanged emits the int index; _update_reconstruct_status
+        # treats its first positional arg as a reconstruction result, so the
+        # connection must not pass the index straight through (it used to call
+        # int.imag_residual_norm and raise AttributeError).
+        dlg = _dialog(qapp)
+        other = 1 - dlg._recon_mode_combo.currentIndex()
+        dlg._recon_mode_combo.setCurrentIndex(other)  # fires currentIndexChanged
+        assert dlg._recon_mode_combo.currentIndex() == other
+        dlg.deleteLater()
+
+
 class TestPhaseView:
     def test_default_is_magnitude(self, qapp):
         dlg = _dialog(qapp)

tests/test_processing_state.py

@@ -1039,3 +1039,32 @@ def test_apply_processing_state_to_scan_preserves_extent_after_scale(self):
         )
         assert scan.planes[0].shape == (32, 24)
         np.testing.assert_allclose(scan.scan_range_m, (3e-9, 5e-9))
+
+
+def test_stm_background_active_roi_without_roi_set_degrades_to_whole_image():
+    """A constant-Δf/STM background step fit over an ROI must not crash a
+    thumbnail/preview render that has no roi_set: the unresolved ROI mask
+    degrades to a whole-image fit instead of raising in the kernel."""
+
+    rng = np.random.default_rng(0)
+    arr = rng.standard_normal((24, 24)).astype(np.float64) + np.linspace(0, 5, 24)
+
+    state = ProcessingState(
+        [
+            ProcessingStep(
+                "stm_background",
+                {
+                    "fit_region": "active_roi",
+                    "fit_roi_id": "be8e9cc6-84b2-4e4d-9990-24bdc4476258",
+                    "model": "linear",
+                    "line_statistic": "median",
+                },
+            )
+        ]
+    )
+
+    with pytest.warns(UserWarning, match="ROI fit mask ignored"):
+        out = apply_processing_state(arr, state, roi_set=None)
+
+    assert out.shape == arr.shape
+    assert np.isfinite(out).all()