rofi: fix displaying hicolor icons

This adds the hicolor theme to XDG_DATA_DIRS for rofi and moves all
wrapping to rofi/wrapper.nix.

The wrapper will now always be generated, even when a theme is not provided.

pkgs/applications/misc/rofi/wrapper.nix

@@ -1,6 +1,5 @@
-{ stdenv, rofi-unwrapped, makeWrapper, theme ? null }:
+{ stdenv, rofi-unwrapped, makeWrapper, hicolor-icon-theme, theme ? null }:
 
-if theme == null then rofi-unwrapped else
 stdenv.mkDerivation {
   pname = "rofi";
   version = rofi-unwrapped.version;
@@ -14,8 +13,15 @@ stdenv.mkDerivation {
     rm $out/bin
     mkdir $out/bin
     ln -s ${rofi-unwrapped}/bin/* $out/bin
+
     rm $out/bin/rofi
-    makeWrapper ${rofi-unwrapped}/bin/rofi $out/bin/rofi --add-flags "-theme ${theme}"
+    makeWrapper ${rofi-unwrapped}/bin/rofi $out/bin/rofi \
+      --prefix XDG_DATA_DIRS : ${hicolor-icon-theme}/share \
+      ${if theme != null then ''--add-flags "-theme ${theme}"'' else ""}
+
+    rm $out/bin/rofi-theme-selector
+    makeWrapper ${rofi-unwrapped}/bin/rofi-theme-selector $out/bin/rofi-theme-selector \
+      --prefix XDG_DATA_DIRS : $out/share
   '';
 
   meta = rofi-unwrapped.meta // {