The second windows were read-only by accident: nothing accepted a drop on them, and the
signal page's *Plot on* buttons knew only the main window's rows.
- **Drop target per scope window**: the same string payload a badge drags (the signal index),
handled by `on_scope_drop_channel()` -- the target carries its own window, the row is that
window's cell under the pointer, and `assign_signal_to_scope()` lands the signal in the
window's own row set (enabling an unacquired signal first, exactly as the main drop does).
The rebuild and the area's re-point are the window's next frame in the tick: a drop arrives
from inside the very widget it rearranges, and a synchronous rebuild would reset the drag
controller under it.
- **Plot on, per window**: the signal page carries one named group per scope window ("In
\"plot 2\""), one button per plot of that window, sensitive on that window's own rows. A
window closing refreshes the pages in its destroy handler, before the deferred delete could
dangle a button's scope pointer.
- Probe: `[scope-probe]` drops through the wired handler (`drop=1 slot1='square'`) and counts
the page's groups (`page_groups=2`); the section documents that it must not run with
`UDPSCOPE_ENABLE_ALL_MS` -- the enable-all probe's second leg clears the front plot, which
is the slot this probe copies. README, help and the layout invariant follow.
Martino Ferrari
51b4fad386