Polish GUI design

python_app/gui/trace_png_export.py

@@ -17,12 +17,10 @@ from PyQt6.QtCore import QRectF
 from pyqtgraph.exporters import ImageExporter
 
 from python_app.models.dataset_model import TraceData
+from python_app.gui.theme import PLOT_BACKGROUND
 
 logger = logging.getLogger(__name__)
 
-# Matches the preview pane styling in preprocess_dialog so saved PNGs and the
-# on-screen preview look the same.
-_BACKGROUND = "#101418"
 _MAGNITUDE_PEN = pg.mkPen("#4cc9f0", width=1.8)
 _PHASE_PEN = pg.mkPen("#f48c06", width=1.8)
 _EXPORT_SIZE = (1400, 520)
@@ -45,7 +43,7 @@ def export_trace_png(
     phase_deg = np.degrees(np.angle(samples))
 
     layout = pg.GraphicsLayoutWidget(show=False, size=_EXPORT_SIZE)
-    layout.setBackground(_BACKGROUND)
+    layout.setBackground(PLOT_BACKGROUND)
     try:
         layout.ci.addLabel(title, row=0, col=0, colspan=2)