Underline SGR code support

app/assets/javascripts/terminal.js.coffee

@@ -10,6 +10,7 @@ class AsciiIo.Terminal
     @lineData = @normalBuffer
     @dirtyLines = []
     @fg = @bg = undefined
+    @underline = false
 
     @createChildElements()
     @showCursor true
@@ -104,8 +105,13 @@ class AsciiIo.Terminal
       if n is 0
         @fg = @bg = undefined
         @bright = false
+        @underline = false
       else if n is 1
         @bright = true
+      else if n is 4
+        @underline = true
+      else if n is 24
+        @underline = false
       else if n >= 30 and n <= 37
         @fg = n - 30
       else if n >= 40 and n <= 47
@@ -274,7 +280,7 @@ class AsciiIo.Terminal
     prefix = ""
     postfix = ""
 
-    if @fg isnt undefined or @bg isnt undefined or @bright
+    if @fg isnt undefined or @bg isnt undefined or @bright or @underline
       prefix = "<span class=\""
       brightOffset = (if @bright then 8 else 0)
 
@@ -283,6 +289,9 @@ class AsciiIo.Terminal
       else if @bright
         prefix += " bright"
 
+      if @underline
+        prefix += " underline"
+
       prefix += " bg" + @bg if @bg isnt undefined
       prefix += "\">"
       postfix = "</span>"

app/assets/stylesheets/asciicasts.css.scss

@@ -57,6 +57,7 @@
 }
 
 .bright { font-weight: bold }
+.underline { text-decoration: underline }
 
 /* Foregrounds: */