tree-wide: Modernize moving gi-docgen-built docs to devdoc output

Since DevHelp 41, it no longer needs to be stored in `share/devhelp`.

pkgs/development/libraries/gdk-pixbuf/default.nix

@@ -111,10 +111,6 @@ stdenv.mkDerivation rec {
     '' + lib.optionalString (stdenv.hostPlatform == stdenv.buildPlatform) ''
       # We need to install 'loaders.cache' in lib/gdk-pixbuf-2.0/2.10.0/
       $dev/bin/gdk-pixbuf-query-loaders --update-cache
-    '' + lib.optionalString withGtkDoc ''
-      # So that devhelp can find this.
-      mkdir -p "$devdoc/share/devhelp"
-      mv "$out/share/doc" "$devdoc/share/devhelp/books"
     '';
 
   # The fixDarwinDylibNames hook doesn't patch binaries.
@@ -124,6 +120,11 @@ stdenv.mkDerivation rec {
     done
   '';
 
+  postFixup = lib.optionalString withGtkDoc ''
+    # Cannot be in postInstall, otherwise _multioutDocs hook in preFixup will move right back.
+    moveToOutput "share/doc" "$devdoc"
+  '';
+
   # The tests take an excessive amount of time (> 1.5 hours) and memory (> 6 GB).
   inherit doCheck;
 

pkgs/development/libraries/gtk/4.x.nix

@@ -202,13 +202,6 @@ stdenv.mkDerivation rec {
     for f in $dev/bin/gtk4-encode-symbolic-svg; do
       wrapProgram $f --prefix XDG_DATA_DIRS : "${shared-mime-info}/share"
     done
-
-  '' + lib.optionalString x11Support ''
-    # So that DevHelp can find this.
-    # TODO: Remove this with DevHelp 41.
-    mkdir -p "$devdoc/share/devhelp/books"
-    mv "$out/share/doc/"* "$devdoc/share/devhelp/books"
-    rmdir -p --ignore-fail-on-non-empty "$out/share/doc"
   '';
 
   # Wrap demos
@@ -219,6 +212,9 @@ stdenv.mkDerivation rec {
       wrapProgram $dev/bin/$program \
         --prefix XDG_DATA_DIRS : "$GSETTINGS_SCHEMAS_PATH:$out/share/gsettings-schemas/${pname}-${version}"
     done
+  '' + lib.optionalString x11Support ''
+    # Cannot be in postInstall, otherwise _multioutDocs hook in preFixup will move right back.
+    moveToOutput "share/doc" "$devdoc"
   '';
 
   passthru = {

pkgs/development/libraries/pango/default.nix

@@ -84,12 +84,9 @@ stdenv.mkDerivation rec {
 
   doCheck = false; # test-font: FAIL
 
-  postInstall = lib.optionalString withDocs ''
-    # So that devhelp can find this.
-    # https://gitlab.gnome.org/GNOME/pango/merge_requests/293/diffs#note_1058448
-    mkdir -p "$devdoc/share/devhelp"
-    mv "$out/share/doc/pango/reference" "$devdoc/share/devhelp/books"
-    rmdir -p --ignore-fail-on-non-empty "$out/share/doc/pango"
+  postFixup = lib.optionalString withDocs ''
+    # Cannot be in postInstall, otherwise _multioutDocs hook in preFixup will move right back.
+    moveToOutput "share/doc" "$devdoc"
   '';
 
   passthru = {