Created a function called css2-fallback($value, $css2-value) that will use the $css2-value in a css2 context and the $value in other contexts.

doc-src/content/CHANGELOG.markdown

@@ -14,7 +14,11 @@ The Documentation for the [latest stable release](http://compass-style.org/docs/
 
 The Documentation for the [latest preview release](http://beta.compass-style.org/)
 
-0.11.beta.5 (UNRELEASED)
+0.11.beta.6 (3/27/2011)
+------------------------
+* Added opera prefix support for linear and radial gradients.
+
+0.11.beta.5 (03/27/2011)
 ------------------------
 
 ### Compass Sprites

doc-src/content/reference/compass/helpers.haml

@@ -24,6 +24,7 @@ layout: core
   * [append-selector()](/reference/compass/helpers/selectors/#append-selector)
   * [color-stops()](/reference/compass/helpers/color-stops/)
   * [cos()](/reference/compass/helpers/trig/#cos)
+  * [css2-fallback()](/reference/compass/helpers/cross-browser/#css2-fallback)
   * [elements-of-type()](/reference/compass/helpers/display/)
   * [enumerate()](/reference/compass/helpers/selectors/#enumerate)
   * [font-files()](/reference/compass/helpers/font-files/)

doc-src/content/reference/compass/helpers/cross-browser.haml

@@ -112,3 +112,14 @@ documented_functions:
       It is a kind of hack to sanitize the output of experimental code
       into a form that can be parsed by a css2.1 compliant parser.
       Usually this results in causing some functions to be omitted.
+#css2-fallback.helper
+  %h3
+    %a(href="#css2-fallback")
+      css2-fallback(<span class="arg">$value</span>, <span class="arg">$css2-value</span>)
+  .details
+    %p
+      This function returns a value that is normally <code>$value<code>,
+      but is <code>$css2-value</code> when passed through the <code>-css2()</code>
+      helper function. Many of the compass css3 mixins will create a css2 fallback
+      value if the arguments have a css2 representation (gradients have a null css2
+      representation).

lib/compass/sass_extensions/functions/cross_browser_support.rb

@@ -1,4 +1,31 @@
 module Compass::SassExtensions::Functions::CrossBrowserSupport
+
+  class CSS2FallbackValue < Sass::Script::Literal
+    attr_accessor :value, :css2_value
+    def children
+      [value, css2_value]
+    end
+    def initialize(value, css2_value)
+      self.value = value
+      self.css2_value = css2_value
+    end
+    def inspect
+      to_s
+    end
+    def to_s(options = self.options)
+      value.to_s(options)
+    end
+    def supports?(aspect)
+      aspect == "css2"
+    end
+    def has_aspect?
+      true
+    end
+    def to_css2(options = self.options)
+      css2_value
+    end
+  end
+
   # Check if any of the arguments passed require a vendor prefix.
   def prefixed(prefix, *args)
     aspect = prefix.value.sub(/^-/,"")
@@ -36,4 +63,8 @@ module Compass::SassExtensions::Functions::CrossBrowserSupport
     end
   end
 
+  def css2_fallback(value, css2_value)
+    CSS2FallbackValue.new(value, css2_value)
+  end
+
 end

test/sass_extensions_test.rb

@@ -89,6 +89,12 @@ class SassExtensionsTest < Test::Unit::TestCase
     assert_equal "true", evaluate("blank(-compass-space-list(' '))")
   end
 
+  def test_css2_fallback
+    assert_equal "css3", evaluate("css2-fallback(css3, css2)")
+    assert_equal "css2", evaluate("-css2(css2-fallback(css3, css2))")
+    assert_equal "true", evaluate("prefixed(-css2, css2-fallback(css3, css2))")
+  end
+
 protected
   def evaluate(value)
     Sass::Script::Parser.parse(value, 0, 0).perform(Sass::Environment.new).to_s