ui: the trigger's wave is a full period again

The bold pass had turned the trigger into half a period — a signal rising above its level — and that
lost the thing the glyph is for: the crossings. A crest and a trough read as a wave; a hump reads as a
hill, and a trigger that shows no crossing names the "above the level" half of an event. The full-period
sine with the dashed level through it is restored, exactly as it was, and the Signals pill carries the
same wave again so the pill and the toolbar button stay one picture.

The Measure glyph keeps the bold redesign, which is the part that was better: two cursors (a cap over two
4px dashes) beside a ruler of two bands with three 2x4 marks and no end caps. The Signals pill also keeps
its two bold channel rows.

Verified: `toolbar icons: trigger=udpscope-trigger-symbolic(ok)`;
`page icons: measure=udpscope-tab-measure-symbolic(ok) signals=udpscope-tab-signals-symbolic(ok)`;
`switcher: policy=narrow pills=2 labels=0 names=2 icon=32x32 size=308x36`; `[side-tab-probe] … advanced=4`;
the Preferences dialog opened in the same run with no "not present"; `make test-ui` 14 files; zero
`Gtk-CRITICAL`. The icons' blob is 12352 bytes, still over the C99 limit, so the clean-build warning count
stays four.

README.md

@@ -2394,7 +2394,7 @@ now — they are listed so they are not mistaken for anything else:
   section was short of room, and finding one meant scrolling past the others. The built
   sidebar is a **Measure** tab (the cursors readout and the measurements) and a **Signals**
   tab (the trigger and the channels), **each a pill with its own glyph and no text** — the
-  cursors and the ruler for Measure, a signal rising above its trigger level and the channel list
+  cursors and the ruler for Measure, a sine crossing its trigger level and the channel list
   for Signals (the same picture the toolbar's trigger button carries), drawn as a
   32x16 pair so both motifs are legible at a glance — with the words kept as each pill's tooltip and
   accessible name. The design spec had the switcher showing *titles* and neither page an

docs/claude/invariants-gtk-and-chrome.md

@@ -65,10 +65,14 @@ Part of [CLAUDE.md](../../CLAUDE.md). These are rules that cost a defect to lear
   `udpscope-tab-measure-symbolic` is two cursors beside the ruler they read against — each a cap over two
   bold dashes, beside a ruler of two bands with three marks between them and **no end caps** (a closed
   frame reads as a rectangle, and costs a fifth of the ink on two lines that say nothing) — and
-  `udpscope-tab-signals-symbolic` is a signal rising above its level, beside two bold channel rows. They
+  `udpscope-tab-signals-symbolic` is a sine crossing its dashed level, beside two bold channel rows. They
   are not reuses, because a glyph the toolbar already carries means two things the moment a tab shows it
   too; instead the *trigger's* own icon (`udpscope-trigger-symbolic`) was redrawn to the Signals pill's
   picture, so the pill and the button that turns the trigger on are recognisably about the same thing.
+  The wave is a **full period and not a hump**: a crest and a trough are what make it read as a wave
+  rather than as a hill, and the level's dashes survive between the crossings. (A hump was tried and
+  reverted — it named the "above the level" half of a trigger and lost the crossings, which is the half
+  that matters.)
   Both are **32x16** composites drawn **bold** — one thick band, two thick dashes, few features — because
   at this size a thin wave or a 1px tick reads as *texture* rather than as a shape, which is what "not
   clear" looks like. Wider than tall on purpose: a 16px square cell carries one motif, not a pair. And

docs/claude/verification.md

@@ -16,7 +16,7 @@ xvfb-run -a env UDPSCOPE_EXIT_AFTER_MS=8000 UDPSCOPE_ENABLE_ALL_MS=1000 \
 Two baselines every run is read against. A clean build emits **four** warnings and no more: two
 `-Wmissing-field-initializers` on `MathNode::source` and `-Woverlength-strings` on **both**
 generated GResource `.c` files — the help pages' (**514660** bytes) and the icons', whose blob is
-**11774** against C99's 4095-byte string-literal limit with the seven action icons and the two app icons
+**12352** against C99's 4095-byte string-literal limit with the seven action icons and the two app icons
 that remain (a note about a generated file, which GCC itself supports) -- re-measured when
 the tab work changed the set (that icon left, the two tab glyphs arrived, and this file's
 help page was rewritten), which did not move the count; re-measure by touching each `*.gresource.xml`

src/icons/scalable/actions/udpscope-tab-signals-symbolic.svg

@@ -1,25 +1,29 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!-- SPDX-License-Identifier: MIT -->
 <!-- SPDX-FileCopyrightText: 2026 Martino Ferrari -->
-<!-- The Signals tab: the toolbar's trigger picture — a signal above its level — beside the channel
-     list. Sharing that picture is the point: the pill and the button that turns the trigger on should
-     be recognisably about the same thing. Two channel rows on the right, drawn bold for the same
-     reason the wave is, and everything inset two pixels. -->
+<!-- The Signals tab: the toolbar's trigger picture — a sine crossing its dashed level — beside the
+     channel list. Sharing that picture is the point: the pill and the button that turns the trigger on
+     should be recognisably about the same thing. A full period and not a hump: the crest and the trough
+     are what make it read as a wave rather than as a hill, and the level's dashes survive between the
+     crossings. Two channel rows on the right, drawn bold like the wave, and everything inset two
+     pixels, because art flush with the cell edge is what a button or a crop clips. -->
 <svg height="16px" width="32px" viewBox="0 0 32 16" xmlns="http://www.w3.org/2000/svg">
-  <path fill="#2e3436" d="M3 7 H4 V12 H3 Z
-                          M4 6 H5 V11 H4 Z
-                          M5 4 H6 V9 H5 Z
-                          M6 3 H7 V8 H6 Z
-                          M7 2 H8 V7 H7 Z
-                          M8 2 H9 V7 H8 Z
-                          M9 2 H10 V7 H9 Z
-                          M10 2 H11 V7 H10 Z
-                          M11 3 H12 V8 H11 Z
-                          M12 4 H13 V9 H12 Z
-                          M13 6 H14 V11 H13 Z
-                          M14 7 H15 V12 H14 Z
-                          M2 8 H3 V10 H2 Z
-                          M15 8 H17 V10 H15 Z
+  <path fill="#2e3436" d="M2 6 H3 V10 H2 Z
+                          M3 4 H4 V8 H3 Z
+                          M4 3 H5 V7 H4 Z
+                          M5 2 H6 V6 H5 Z
+                          M6 3 H7 V7 H6 Z
+                          M7 4 H8 V8 H7 Z
+                          M8 6 H9 V10 H8 Z
+                          M9 8 H10 V12 H9 Z
+                          M10 9 H11 V13 H10 Z
+                          M11 10 H12 V14 H11 Z
+                          M12 9 H13 V13 H12 Z
+                          M13 8 H14 V12 H13 Z
+                          M14 6 H15 V10 H14 Z
+                          M2 7 H5 V9 H2 Z
+                          M7 7 H10 V9 H7 Z
+                          M12 7 H15 V9 H12 Z
                           M18 3 H23 V8 H18 Z
                           M24 4 H30 V7 H24 Z
                           M18 10 H23 V15 H18 Z

src/icons/scalable/actions/udpscope-trigger-symbolic.svg

@@ -1,22 +1,26 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!-- SPDX-License-Identifier: MIT -->
 <!-- SPDX-FileCopyrightText: 2026 Martino Ferrari -->
-<!-- The trigger: a signal rising above the level it is looked for at, with the level showing on both
-     sides of it. One event, which is what the trigger is for. Bold on purpose: at this size a
-     thinner wave reads as texture, and the level has to survive as two clear marks rather than as a
-     dotted line. Inset two pixels like the tabs' glyphs, so no art sits flush with an edge a button
-     might clip. Whole-pixel stairs, the way the plot rasterises its own traces. -->
+<!-- The trigger: a sine and the dashed level it is looked for at, which is what a trigger *is* on a
+     waveform that is not a step. It used to be a rising edge, and one edge names only one of the four
+     shape triggers the panel offers — a wave crossing a level names the trigger's job instead. One
+     period, one-pixel stairs, the way the plot rasterises its own traces, with the level through the
+     centre so the crest and the trough stand clear and the crossings fall on the steep parts. Inset
+     two pixels, like the tabs' glyphs, so no art is flush with an edge a button might clip. -->
 <svg height="16px" width="16px" viewBox="0 0 16 16" xmlns="http://www.w3.org/2000/svg">
-  <path fill="#2e3436" d="M3 7 H4 V11 H3 Z
-                          M4 5 H5 V9 H4 Z
-                          M5 4 H6 V8 H5 Z
-                          M6 3 H7 V7 H6 Z
-                          M7 2 H8 V6 H7 Z
-                          M8 2 H9 V6 H8 Z
-                          M9 3 H10 V7 H9 Z
-                          M10 4 H11 V8 H10 Z
-                          M11 5 H12 V9 H11 Z
-                          M12 7 H13 V11 H12 Z
-                          M2 8 H3 V10 H2 Z
-                          M13 8 H15 V10 H13 Z"/>
+  <path fill="#2e3436" d="M2 7 H3 V10 H2 Z
+                          M3 5 H4 V8 H3 Z
+                          M4 3 H5 V6 H4 Z
+                          M5 3 H6 V6 H5 Z
+                          M6 4 H7 V7 H6 Z
+                          M7 6 H8 V9 H7 Z
+                          M8 8 H9 V11 H8 Z
+                          M9 10 H10 V13 H9 Z
+                          M10 11 H11 V14 H10 Z
+                          M11 11 H12 V14 H11 Z
+                          M12 9 H13 V12 H12 Z
+                          M13 7 H14 V10 H13 Z
+                          M2 7 H5 V9 H2 Z
+                          M7 7 H10 V9 H7 Z
+                          M11 7 H14 V9 H11 Z"/>
 </svg>