Set = true variable for SCAD

Author: sorki

example-escad/obj.escad

@@ -2,3 +2,5 @@ include <header.escad>;
 $res = 1;
 cube ($size);
 translate([10, 10, 0]) cylinder (r=15, h=2);
+if ($viewer) { cube($size*2); }
+echo($size);

src/Graphics/Implicit/Viewer/Loaders.hs

@@ -144,7 +144,7 @@ loadViaEscad modFile initialResolution renderChan = do
       openScadCompatibility = False
     , importsAllowed = True
     })
-    [] -- defines
+    ["$viewer = true;"] -- defines
     content
 
   case warnings of