fix graph and white background added

README.md

@@ -14,8 +14,9 @@ and a **Python application** for supervision, visualization and control.
 
 The pipeline runs as three independent processes connected by lock-free POSIX
 shared-memory ring buffers. Each stage advances on its own, and a slow consumer
-never blocks a producer — the rings are latest-wins, so a reader that falls behind
-skips overwritten frames and continues from the retained tail:
+never blocks a producer — the rings are latest-wins: a full ring overwrites its oldest
+unread frame, a reader that falls behind continues with the frames still retained, and
+one overtaken during a read resumes at the newest frame:
 
 1. **Acquisition** — Python producers configure the radar, acquire frequency sweeps,
    and publish raw S21 traces. Both single and multi-device LibreVNA use
@@ -65,7 +66,8 @@ controls, processing settings and a copy of the live plot through an embedded we
 ## Processing modes
 
 - **pass_through** — magnitude and phase of S21 for each combo.
-- **bscan** — depth-versus-sweep B-scan heatmap.
+- **bscan** — depth-versus-sweep B-scan heatmap. A band selecting fewer than two
+  sweep points gives no range profile, and such sweeps are left out of the image.
 - **gpr** — coherent back-projection on the ground plane, as in `Horns_motion_4x4_ground.py`,
   with object detection. Radar height and look angle define the slice in radar X/Z axes;
   the wave speed is 3×10⁸ m/s (air).
@@ -100,7 +102,7 @@ peak; its size follows the contiguous half-maximum width along the volume axes
 (FWHM, at least one voxel). This measures the imaged response rather than the
 reflector's physical dimensions.
 
-The desktop uses a light theme with dark plot canvases. **Mode** stays below the
+The desktop uses a light theme with white plot canvases. **Mode** stays below the
 **Actions** buttons while the settings sections scroll; the settings panel and
 runtime log can be collapsed with their arrow buttons. SAR3D status, peak
 coordinates and level appear above the projections.
@@ -522,10 +524,14 @@ Profile loading blocks editor signals until all settings are populated.
 `HistoryController` owns retained acquisitions; `PlotController` selects the view
 and supplies independent B-scan, GPR, trace and SAR renderers with typed settings.
 Renderers own their plots and display caches, without access to the acquisition
-processes. Stopped B-scan replay uses the last run's ring, matches exact acquisition
-keys and the requested settings revision, and cancels when that run changes. With
-no retained preprocessed sweeps (including disabled taps), the processor recomputes
-its own retained history. Capture previews preserve the selected processing view.
+processes. Every plot change passes through `PlotController`, which counts changes
+of the shown image for the browser stream. The display shows the newest acquisition,
+including results read while stopping. Stopped B-scan replay uses the last run's
+ring, matches exact acquisition keys and the requested settings revision, and
+cancels when that run changes; sweeps the processor does not return are left out
+rather than mixing settings in one image. With no retained preprocessed sweeps
+(including disabled taps), the processor recomputes its own retained history.
+Capture previews preserve the selected processing view.
 `PipelineController` owns processes, ring readers, polling/recovery, Single Capture
 and replay. Its pause prevents recovery from starting a producer over a hardware
 capture; Stop or Close cancels any pending resumption, including during a drain.