2 files changed, 40 insertions, 2 deletions
diff --git a/metapost/context/base/mpiv/mp-chem.mpiv b/metapost/context/base/mpiv/mp-chem.mpiv
index 4ed9eaa8f..c5f79a88c 100644
--- a/metapost/context/base/mpiv/mp-chem.mpiv
+++ b/metapost/context/base/mpiv/mp-chem.mpiv
@@ -513,10 +513,21 @@ def chem_transformed (suffix $) = % not vardef!
     fi
 enddef ;
 
+% vardef chem_draw (expr what, r, c) (text extra) =
+%     draw what
+%         withpen pencircle scaled r
+%         withcolor c
+%         extra ;
+% enddef ;
+
 vardef chem_draw (expr what, r, c) (text extra) =
     draw what
         withpen pencircle scaled r
-        withcolor c
+        if string c :
+            if c <> "" : withcolor c fi
+        else :
+            withcolor c
+        fi
         extra ;
 enddef ;
 
diff --git a/metapost/context/base/mpiv/mp-tool.mpiv b/metapost/context/base/mpiv/mp-tool.mpiv
index cabdf9ab2..f1f31e5f0 100644
--- a/metapost/context/base/mpiv/mp-tool.mpiv
+++ b/metapost/context/base/mpiv/mp-tool.mpiv
@@ -895,9 +895,36 @@ enddef ;
 let normalwithcolor = withcolor ;
 
 def withcolor expr c =
-    normalwithcolor if string c : resolvedcolor(c) else : c fi
+     normalwithcolor if string c : resolvedcolor(c) else : c fi
 enddef ;
 
+% I don't want a "withcolor black" in case of an empty string ... who knows
+% how that can interfere with outer colors. Somehow the next one doesn't
+% always work out ok, but why ... must be some parsing issue. Anyway, when
+% we cannot do that, we need to fix some chem macros instead as empty strings
+% now lead to black while everywhere else in context empty means: leave color
+% untouched.
+
+% def withcolor expr c =
+%     if not string c :
+%         normalwithcolor c
+%     elseif c <> "" :
+%         normalwithcolor resolvedcolor(c)
+%     fi
+% enddef ;
+
+% So why does this work better than the above:
+%
+% def withcolor expr c =
+%     if string c :
+%         if c <> "" :
+%             normalwithcolor resolvedcolor(c)
+%         fi
+%     else :
+%         normalwithcolor c
+%     fi
+% enddef ;
+
 vardef colortype expr c =
         if cmykcolor c : cmykcolor
     elseif rgbcolor  c : rgbcolor