Merge plot-builder-layout-feature: dynamic BSP tiling layout canvas

Replaces layout radio buttons (Stacked/Side-by-Side/Grid) with a
drag-and-drop tiling canvas. Three drop zones per tile edge:
  - squeeze (outer 1/6, amber): insert between two tiles
  - split  (1/6–1/3, blue):    bisect tile 50/50
  - center (green):             swap tile positions

BSP tree stores layout; tree_to_grid() converts to rowspan/colspan for
pyqtgraph. _tree_equalize_ratios ensures all tiles share space equally
after any operation. Backward-compatible with existing .labdaq profiles.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 20 insertions, 13 deletions

diff --git a/ui/strip_chart.py b/ui/strip_chart.py
index 523102d..5a1d1e9 100644
--- a/ui/strip_chart.py
+++ b/ui/strip_chart.py
@@ -42,7 +42,8 @@ if _HAS_PG:
 from devices.device_registry import DeviceRegistry
 from core.acquisition import AcquisitionEngine
 from core.signal_processor import SignalProcessor
-from ui.windows.plot_window import LayoutConfig, PaneSpec, TraceSpec, build_default_layout
+from ui.windows.plot_window import (LayoutConfig, PaneSpec, TraceSpec,
+                                    build_default_layout, tree_to_grid, _tree_grid_size)
 
 _STYLES = {
     "solid": Qt.PenStyle.SolidLine,
@@ -94,25 +95,33 @@ class StripChartWidget(QWidget):
         mf = QFont("IBM Plex Mono", 8)
         n  = len(cfg.panes)
 
-        # Determine row/col for each pane
-        if cfg.layout_mode == "sidebyside":
-            positions = [(0, c) for c in range(n)]
+        # Determine row/col/rowspan/colspan for each pane
+        if cfg.layout_mode == "free" and cfg.tree is not None:
+            gs = _tree_grid_size(cfg.tree)
+            grid_pos: dict = {}
+            tree_to_grid(cfg.tree, 0, 0, gs, gs, grid_pos)
+            # grid_pos[pane_idx] = (row, col, rowspan, colspan)
+        elif cfg.layout_mode == "sidebyside":
+            grid_pos = {i: (0, i, 1, 1) for i in range(n)}
         elif cfg.layout_mode == "grid":
             cols = max(1, cfg.grid_cols)
-            positions = [(i // cols, i % cols) for i in range(n)]
-        else:  # stacked
-            positions = [(r, 0) for r in range(n)]
+            grid_pos = {i: (i // cols, i % cols, 1, 1) for i in range(n)}
+        else:  # stacked (legacy default)
+            grid_pos = {i: (i, 0, 1, 1) for i in range(n)}
 
         ref_plot = None
-        for idx, (spec, (row, col)) in enumerate(zip(cfg.panes, positions)):
-            plot = self._gw.addPlot(row=row, col=col)
+        for idx, spec in enumerate(cfg.panes):
+            if idx not in grid_pos:
+                continue
+            row, col, rowspan, colspan = grid_pos[idx]
+            plot = self._gw.addPlot(row=row, col=col, rowspan=rowspan, colspan=colspan)
             plot.setLabel("left",   spec.y_label or spec.title)
             plot.setLabel("bottom", spec.x_label or "Elapsed (s)")
             plot.showGrid(x=spec.grid, y=spec.grid, alpha=0.12)
             plot.getAxis("left").setStyle(tickFont=mf)
             plot.getAxis("bottom").setStyle(tickFont=mf)
 
-            # Hide bottom axis labels for all but bottom row in stacked
+            # Hide bottom axis labels for non-bottom panes in stacked legacy mode
             if cfg.layout_mode == "stacked" and idx < n - 1:
                 plot.getAxis("bottom").setStyle(showValues=False)
                 plot.getAxis("bottom").setHeight(0)
@@ -133,10 +142,8 @@ class StripChartWidget(QWidget):
             else:
                 plot.enableAutoRange(axis="y")
 
-            # Set column stretch (relative weight)
             self._gw.ci.layout.setColumnStretchFactor(col, spec.weight)
-            if cfg.layout_mode == "stacked":
-                self._gw.ci.layout.setRowStretchFactor(row, spec.weight)
+            self._gw.ci.layout.setRowStretchFactor(row, spec.weight)
 
             for tr in spec.traces:
                 if not tr.visible: continue