From f3d68cfdd48e1a6ea8633e22e86bb479510e5209 Mon Sep 17 00:00:00 2001
From: Martino Ferrari <martinogiordano.ferrari@iter.org>
Date: Sun, 4 Oct 2026 20:27:07 +0200
Subject: [PATCH] feat: an app icon in colour and symbolic form, validated at
 build time

Both are drawn to the GNOME HIG: a 128px instrument face that leaves its
margins, carries one 4px front profile for depth and no gradients or shadows,
and a 16px symbolic reduction of the same metaphor in fills only. The colour
icon strokes its sine because it is never recoloured; the symbolic one cannot.

Every file in the manifest now preprocesses through xmllint, because a
malformed SVG is the one icon failure no runtime check can see: librsvg refuses
the file while the name still resolves, so the icon draws nothing and
has_icon() says it is fine.
---
 CMakeLists.txt                                |  5 ++-
 .../apps/org.udpscope.app-symbolic.svg        | 24 ++++++++++++
 src/icons/scalable/apps/org.udpscope.app.svg  | 39 +++++++++++++++++++
 src/icons/udpscope.gresource.xml              | 26 +++++++++----
 4 files changed, 84 insertions(+), 10 deletions(-)
 create mode 100644 src/icons/scalable/apps/org.udpscope.app-symbolic.svg
 create mode 100644 src/icons/scalable/apps/org.udpscope.app.svg

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2b43668..ed3aae7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -39,7 +39,7 @@ if(CMAKE_C_COMPILER_ID MATCHES "GNU|Clang")
   target_compile_options(udpsclient PRIVATE -Wall -Wextra)
 endif()
 
-# --- icons: four symbolic SVGs compiled into the binary -----------------------
+# --- icons: six SVGs compiled into the binary --------------------------------
 # There is no stock icon for an oscilloscope trigger, a pair of cursors or a measurement
 # ruler, so this app draws its own. They go in a GResource rather than beside the binary
 # because udpscope is run straight out of the build tree and has no install step: a
@@ -48,7 +48,8 @@ endif()
 find_program(GLIB_COMPILE_RESOURCES NAMES glib-compile-resources REQUIRED)
 set(UDPSCOPE_ICON_DIR ${CMAKE_CURRENT_SOURCE_DIR}/src/icons)
 file(GLOB UDPSCOPE_ICON_FILES CONFIGURE_DEPENDS
-     ${UDPSCOPE_ICON_DIR}/scalable/actions/*.svg)
+     ${UDPSCOPE_ICON_DIR}/scalable/actions/*.svg
+     ${UDPSCOPE_ICON_DIR}/scalable/apps/*.svg)
 add_custom_command(
   OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/udpscope_resources.c
   COMMAND ${GLIB_COMPILE_RESOURCES}
diff --git a/src/icons/scalable/apps/org.udpscope.app-symbolic.svg b/src/icons/scalable/apps/org.udpscope.app-symbolic.svg
new file mode 100644
index 0000000..14c6abd
--- /dev/null
+++ b/src/icons/scalable/apps/org.udpscope.app-symbolic.svg
@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- SPDX-License-Identifier: MIT -->
+<!-- SPDX-FileCopyrightText: 2026 Martino Ferrari -->
+<!--
+  The symbolic form of the app icon: the same metaphor reduced to a screen frame with one
+  wave inside it, following the UI-icon rules rather than the app-icon ones.
+
+  Filled paths only, with no stroke anywhere. GTK's symbolic recolour wraps the file in a
+  stylesheet that reaches `fill` on `path`, `rect` and `circle` only, so a stroked line keeps
+  the colour written here and stays dark on a dark theme. The wave is therefore a closed
+  2px band: a sine along its top edge and the same sine 2px lower along its bottom, which is
+  how a stroke's look is had from a fill.
+
+  `fill-rule="evenodd"` over three subpaths. The frame is the outer rect minus the inner one,
+  so the screen's interior is two crossings deep and empty; the wave inside it is three, which
+  is odd, so it fills. Whole-pixel coordinates throughout, because this is drawn at 16px far
+  more often than not and a half-pixel feature is a grey smear at 1x.
+-->
+<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 16 16">
+  <path fill="#2e3436" fill-rule="evenodd"
+        d="M 1 2 H 15 V 14 H 1 Z
+           M 2 3 H 14 V 13 H 2 Z
+           M 3 7 C 5 3 6 3 8 7 C 10 11 11 11 13 7 L 13 9 C 11 13 10 13 8 9 C 6 5 5 5 3 9 Z"/>
+</svg>
diff --git a/src/icons/scalable/apps/org.udpscope.app.svg b/src/icons/scalable/apps/org.udpscope.app.svg
new file mode 100644
index 0000000..cccbacb
--- /dev/null
+++ b/src/icons/scalable/apps/org.udpscope.app.svg
@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- SPDX-License-Identifier: MIT -->
+<!-- SPDX-FileCopyrightText: 2026 Martino Ferrari -->
+<!--
+  The application icon: an oscilloscope's face, which is the clearest metaphor available and
+  the kind of physical object the HIG's top-and-front depth language was written for.
+
+  Drawn to <https://developer.gnome.org/hig/guidelines/app-icons.html>. The artwork spans
+  x 12..116 and y 22..106, so it does not fill the 128px canvas, and every feature sits on
+  the 2px grid. Depth is the 4px front profile along the bottom and nothing else: that is
+  the HIG's maximum of 2 detail units, and since every surface here is straight, the rest
+  is flat colour with no gradients and no shadows.
+
+  The profile is the bottom 4px of the chassis silhouette, clipped to it. A plain rect from
+  (12, 102) to (116, 106) would protrude past the radius-8 corners, which reads as a
+  misdrawn bump at 128px and as a dirty edge at 32px; the clip follows the corners exactly
+  and keeps every coordinate even, which hand-computing the arc would not.
+
+  Two deliberate omissions. There is no graticule: the grid lines a real scope face carries
+  cannot survive 32px, and the trace carries the metaphor without them. And the trace is
+  one cycle, a single crest and a single trough, because at 32px the screen is about
+  22x16 px and anything busier reads as a smudge.
+
+  Colours are the GNOME palette: Dark 3 chassis, Dark 2 profile, Dark 4 screen, Green 1 trace.
+-->
+<svg xmlns="http://www.w3.org/2000/svg" width="128" height="128" viewBox="0 0 128 128">
+  <defs>
+    <clipPath id="chassis-silhouette">
+      <rect x="12" y="22" width="104" height="84" rx="8"/>
+    </clipPath>
+  </defs>
+  <rect x="12" y="22" width="104" height="84" rx="8" fill="#3d3846"/>
+  <g clip-path="url(#chassis-silhouette)">
+    <rect x="12" y="102" width="104" height="4" fill="#5e5c64"/>
+  </g>
+  <rect x="20" y="30" width="88" height="64" rx="4" fill="#241f31"/>
+  <path d="M 24 62 C 37 38 51 38 64 62 C 77 86 91 86 104 62"
+        fill="none" stroke="#8ff0a4" stroke-width="6" stroke-linecap="round"/>
+</svg>
diff --git a/src/icons/udpscope.gresource.xml b/src/icons/udpscope.gresource.xml
index 455e1d1..0a0a3e5 100644
--- a/src/icons/udpscope.gresource.xml
+++ b/src/icons/udpscope.gresource.xml
@@ -2,16 +2,26 @@
 <!-- SPDX-License-Identifier: MIT -->
 <!-- SPDX-FileCopyrightText: 2026 Martino Ferrari -->
 <!--
-  The four icons this app had to draw for itself, compiled into the binary so there is
-  still exactly one file to run. `gtk_icon_theme_add_resource_path()` wants the tree an
-  icon theme has, so the prefix is followed by `<size>/<context>`; `scalable` is the one
-  that means "an SVG, use it at any size".
+  The icons this app had to draw for itself, compiled into the binary so there is still
+  exactly one file to run. `gtk_icon_theme_add_resource_path()` wants the tree an icon theme
+  has, so the prefix is followed by `<size>/<context>`; `scalable` is the one that means
+  "an SVG, use it at any size", and `apps` is where an application icon belongs.
+
+  Every file carries `preprocess="xml-stripblanks"`, which makes glib-compile-resources pipe
+  it through xmllint. That is the only thing that catches a malformed SVG: librsvg refuses
+  such a file outright, but the icon *name* still resolves, so `gtk_icon_theme_has_icon()`
+  returns true and the icon simply draws nothing. No runtime GTK call can tell the two apart
+  (`lookup_icon()` never returns NULL and always reports the size it was asked for), so the
+  check belongs here, where a double hyphen inside a comment fails the build with a file,
+  line and column instead.
 -->
 <gresources>
   <gresource prefix="/org/udpscope/icons">
-    <file>scalable/actions/udpscope-trigger-symbolic.svg</file>
-    <file>scalable/actions/udpscope-cursors-symbolic.svg</file>
-    <file>scalable/actions/udpscope-measure-symbolic.svg</file>
-    <file>scalable/actions/udpscope-math-symbolic.svg</file>
+    <file preprocess="xml-stripblanks">scalable/actions/udpscope-trigger-symbolic.svg</file>
+    <file preprocess="xml-stripblanks">scalable/actions/udpscope-cursors-symbolic.svg</file>
+    <file preprocess="xml-stripblanks">scalable/actions/udpscope-measure-symbolic.svg</file>
+    <file preprocess="xml-stripblanks">scalable/actions/udpscope-math-symbolic.svg</file>
+    <file preprocess="xml-stripblanks">scalable/apps/org.udpscope.app.svg</file>
+    <file preprocess="xml-stripblanks">scalable/apps/org.udpscope.app-symbolic.svg</file>
   </gresource>
 </gresources>