The switch in the signal list means "do not acquire this", and until now a trace of it
stayed on its plot drawing nothing: a slot that holds one of the four a plot has, reads
`--`, and blocks the drop that would fill it with something live.
`on_signal_switch()` now clears every slot that holds that signal, by the **signal name**
the slot remembers -- never the channel index, which is what the enable change renumbers --
and says what it did: `'sine' is off: 1 trace left the plots`. The follow-ups (a relayout,
the panels' chips, the layout save) happen once rather than per slot.
Re-enabling deliberately does not put the traces back: the arrangement is the user's, and
guessing where they were is worse than leaving them off. Say the word if you want that
direction too.
[enable-all-probe] reads it end to end -- it enables every signal, assigns the channels
across the rows, then switches one off *through its own acquire tick*:
[enable-all-probe] switched 'sine' off: traces_left=0 (want 0) notice=''sine' is off: 1 trace left the plots'
which is also why the notice shares the status line's warning styling from the previous
commit: the trace leaving the plots is something the user should see happen.
The refusal was never silent -- `on_drop_channel()` has always set a notice -- but the
status bar renders `notice + " | " + glance` in one label, so "plot 1 already holds
four signals" arrived looking like part of the routine text a reader skims, which is the
"no clear user feedback" report. The probe's own reading showed it plainly: the label held
`plotting 'sine' on plot 1 | live · 4.44 kS/s · 2 s window`.
Three changes:
- While a notice is fresh the status label carries the stock `.warning` class, so a message
looks like a message and the class goes when the notice does. Every notice benefits, not
just this one.
- The refusal says what to *do*: "plot 1 holds four signals already: drop it on another
plot, or add a row with the layout editor (L)".
- The drop's inline notice now goes through `set_notice()`, the one setter, instead of
writing `app.notice` and its deadline by hand.
[drop-probe] reads the whole path, with the row filled first so the drop under test is the
refusal:
full row refused the drop: 0 (want 0)
refused feedback: notice='plot 1 holds four signals already: ...' warning=1
the status line, composed: warning=1 status='plot 1 holds four signals already: ... | live · 9.97 kS/s · 2 s window'
The label is read in the third line and not the second on purpose: the status line composes
the notice into itself on its own cadence, so a beat after the refusal it may still hold the
previous text -- which the first attempt at this reading mistook for the fix not working.
The row limit is not silent in the same way: the layout editor's `+` is insensitive at
`kMaxRows`, which is a control that says "no" by being unusable rather than a message.
src/ui/signals-panel.ui holds the panel's shape: the box and its margins, the heading,
the hint that says what a signal is for, and the list. The rows stay in code -- one per
signal, carrying that signal's switch, colour, calibration and drop targets, rebuilt
whenever the stream's signals change -- so the file holds the frame, which is the shape
the plan gives this slice.
The list's width-only size request moved with it, comment and all: a height floor there
made the list occupy 120 px whatever it held, which hid the compact rows' height behind
it.
Read back by a new dump line, `signals panel: labels=2 list=1`, where a lost id reads as
`labels=1` or `list=0` instead of a panel quietly missing its hint; `panels: … row_h=26`
still reads the list's geometry and the height a row takes. check_ui is at 10 ok.
Martino Ferrari