docs: shim inkscape -> rsvg-convert in docs build (fixes #4040)

debian/configure

@@ -110,7 +110,7 @@ elif [ -f /etc/lsb-release ]; then
 fi
 
 if [ -n "$ENABLE_BUILD_DOCUMENTATION" ]; then
-    DOC_DEPENDS="dblatex (>= 0.2.12),\n    dvipng,\n    fonts-dejavu,\n    graphviz,\n    groff,\n    inkscape,\n    python3-lxml,\n    source-highlight,\n    texlive-extra-utils,\n    texlive-font-utils,\n    texlive-fonts-recommended,\n    texlive-lang-cyrillic,\n    texlive-lang-european,\n    texlive-lang-french,\n    texlive-lang-german,\n    texlive-lang-polish,\n    texlive-lang-spanish,\n    texlive-latex-recommended,\n    w3c-linkchecker,\n    xsltproc"
+    DOC_DEPENDS="dblatex (>= 0.2.12),\n    dvipng,\n    fonts-dejavu,\n    graphviz,\n    groff,\n    inkscape,\n    librsvg2-bin,\n    python3-lxml,\n    source-highlight,\n    texlive-extra-utils,\n    texlive-font-utils,\n    texlive-fonts-recommended,\n    texlive-lang-cyrillic,\n    texlive-lang-european,\n    texlive-lang-french,\n    texlive-lang-german,\n    texlive-lang-polish,\n    texlive-lang-spanish,\n    texlive-latex-recommended,\n    w3c-linkchecker,\n    xsltproc"
 
 
     case $DISTRIB_NAME in

scripts/inkscape

@@ -0,0 +1,96 @@
+#!/bin/bash
+# Shim that intercepts the inkscape calls made by dblatex during the
+# LinuxCNC docs build and forwards them to rsvg-convert. Avoids the noisy
+# Pango/GtkRecentManager warnings that headless Inkscape prints on every
+# SVG conversion (see issue #4040). Handles both dblatex syntaxes:
+#   new (Inkscape 1.x): inkscape -D --export-filename=OUT IN
+#   old (Inkscape 0.x): inkscape -z -D --export-png=OUT IN
+#                       (also --export-pdf=, --export-eps=)
+# Falls back to the real inkscape whenever the args do not match the
+# expected pattern, when rsvg-convert is missing, or when
+# LINUXCNC_DOCS_NO_RSVG is set.
+
+set -u
+
+real_inkscape() {
+    # Find the next `inkscape` on PATH after stripping the directory holding
+    # this shim, so we do not recurse into ourselves.
+    local self_dir
+    self_dir=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)
+    local stripped_path
+    stripped_path=$(printf '%s' "$PATH" | tr ':' '\n' \
+        | grep -vxF "$self_dir" | paste -sd:)
+    PATH="$stripped_path" exec inkscape "$@"
+}
+
+# Escape hatch.
+if [ -n "${LINUXCNC_DOCS_NO_RSVG:-}" ]; then
+    real_inkscape "$@"
+fi
+
+# rsvg-convert must be available.
+if ! command -v rsvg-convert >/dev/null 2>&1; then
+    real_inkscape "$@"
+fi
+
+# Parse the dblatex call pattern. Accepted flags:
+#   -D, -d, -z, --without-gui   (ignored: pose/area/legacy GUI suppression)
+#   --export-filename=OUT       (Inkscape 1.x)
+#   --export-png=OUT            (Inkscape 0.x)
+#   --export-pdf=OUT            (Inkscape 0.x)
+#   --export-eps=OUT            (Inkscape 0.x)
+# One positional input. Anything else falls through to real inkscape.
+out=""
+in=""
+fmt=""
+saw_unknown=0
+for arg in "$@"; do
+    case "$arg" in
+        -D|-d|-z|--without-gui)
+            ;;
+        --export-filename=*)
+            out="${arg#--export-filename=}"
+            ;;
+        --export-png=*)
+            out="${arg#--export-png=}"
+            fmt=png
+            ;;
+        --export-pdf=*)
+            out="${arg#--export-pdf=}"
+            fmt=pdf
+            ;;
+        --export-eps=*)
+            out="${arg#--export-eps=}"
+            fmt=eps
+            ;;
+        -*)
+            saw_unknown=1
+            ;;
+        *)
+            if [ -n "$in" ]; then
+                saw_unknown=1
+            else
+                in="$arg"
+            fi
+            ;;
+    esac
+done
+
+if [ "$saw_unknown" = 1 ] || [ -z "$in" ] || [ -z "$out" ]; then
+    real_inkscape "$@"
+fi
+
+# If format not yet set (new-syntax --export-filename), infer from extension.
+if [ -z "$fmt" ]; then
+    case "$out" in
+        *.pdf) fmt=pdf ;;
+        *.png) fmt=png ;;
+        *.eps) fmt=eps ;;
+        *.svg) fmt=svg ;;
+        *)     real_inkscape "$@" ;;
+    esac
+fi
+
+if ! rsvg-convert -f "$fmt" -o "$out" "$in"; then
+    real_inkscape "$@"
+fi