resolves #429 require space on either side of math operator (PR #433)

- don't evaluate math in theme keys used for content
- short-circuit keys for font catalog and fallbacks earlier
- minor optimizations

lib/asciidoctor-pdf/theme_loader.rb

@@ -15,8 +15,8 @@ class ThemeLoader
   LoneVariableRx = /^\$([a-z0-9_]+)$/
   HexColorEntryRx = /^(?<k>[[:blank:]]*[[:graph:]]+): +(?<q>["']?)#?(?<v>\w{3,6})\k<q> *(?:#.*)?$/
   MeasurementValueRx = /(?<=^| |\()(-?\d+(?:\.\d+)?)(in|mm|cm|pt)(?=$| |\))/
-  MultiplyDivideOpRx = /(-?\d+(?:\.\d+)?) *([*\/]) *(-?\d+(?:\.\d+)?)/
-  AddSubtractOpRx = /(-?\d+(?:\.\d+)?) *([+\-]) *(-?\d+(?:\.\d+)?)/
+  MultiplyDivideOpRx = /(-?\d+(?:\.\d+)?) +([*\/]) +(-?\d+(?:\.\d+)?)/
+  AddSubtractOpRx = /(-?\d+(?:\.\d+)?) +([+\-]) +(-?\d+(?:\.\d+)?)/
   PrecisionFuncRx = /^(round|floor|ceil)\(/
 
   # TODO implement white? & black? methods
@@ -86,17 +86,23 @@ def load hash, theme_data = nil
   private
 
   def process_entry key, val, data
-    if key.start_with? 'admonition_icon_'
+    if key.start_with? 'font_'
+      data[key] = val
+    elsif key.start_with? 'admonition_icon_'
       data[key] = (val || {}).map do |(key2, val2)|
-        static_val2 = evaluate val2, data
-        [key2.to_sym, (key2.end_with? '_color') ? to_color(static_val2) : static_val2]
+        [key2.to_sym, (key2.end_with? '_color') ? to_color(evaluate val2, data) : (evaluate val2, data)]
       end.to_h
-    elsif key != 'font_catalog' && ::Hash === val
+    elsif ::Hash === val
       val.each do |key2, val2|
         process_entry %(#{key}_#{key2.tr '-', '_'}), val2, data
       end
+    elsif key.end_with? '_color'
+      # QUESTION do we need to evaluate_math in this case?
+      data[key] = to_color(evaluate val, data)
+    elsif %(#{key.chomp '_'}_).include? '_content_'
+      data[key] = expand_vars val, data
     else
-      data[key] = (key.end_with? '_color') ? to_color(evaluate val, data) : (evaluate val, data)
+      data[key] = evaluate val, data
     end
     data
   end