Entrepreneurship: Life Long Learning

John Taber has been trying to use SVG in his Ruby on Rails app.
Unfortunately, Webrick and Rails have been uncooperative.

From railties/lib/webrick_server.rb we see that rails attempts to serve requests from the public directory before dispatching to controllers.

def service(req, res) #:nodoc:
    unless handle_file(req, res)
      begin
        REQUEST_MUTEX.lock unless ActionController::Base.allow_concurrency
        unless handle_dispatch(req, res)
          raise WEBrick::HTTPStatus::NotFound, "`#{req.path}' not found."
        end
      ensure
        unless ActionController::Base.allow_concurrency
          REQUEST_MUTEX.unlock if REQUEST_MUTEX.locked?
        end
      end
    end
end

If you put a svg file in the public directory of a rails app, webrick serves it up, but with the wrong mime type.

$ wget localhost:3000/rect1.svg
--15:54:54--  http://localhost:3000/rect1.svg
           => `rect1.svg.1'
Resolving localhost... 127.0.0.1
Connecting to localhost|127.0.0.1|:3000... connected.
HTTP request sent, awaiting response... 200 OK
Length: 333 [application/octet-stream]

100%[====================================>] 333           --.--K/s

15:54:54 (12.92 MB/s) - `rect1.svg.1' saved [333/333]

Firefox displays a friendly description based on file extension, but doesn’t display the svg because the mime type is wrong.

So add a svg mime type entry to webrick

--- /usr/lib/ruby/1.8/webrick/httputils.rb.orig 2007-04-21 16:00:42.000000000 -0600
+++ /usr/lib/ruby/1.8/webrick/httputils.rb      2007-04-21 16:01:03.000000000 -0600
@@ -86,6 +86,7 @@
       "rtf"   => "application/rtf",
       "sgm"   => "text/sgml",
       "sgml"  => "text/sgml",
+      "svg"   => "image/svg+xml",
       "tif"   => "image/tiff",
       "tiff"  => "image/tiff",
       "txt"   => "text/plain",

And presto

$ wget localhost:3000/rect1.svg
--16:17:22--  http://localhost:3000/rect1.svg
           => `rect1.svg.2'
Resolving localhost... 127.0.0.1
Connecting to localhost|127.0.0.1|:3000... connected.
HTTP request sent, awaiting response... 200 OK
Length: 333 [image/svg+xml]

100%[======================================>] 333           --.--K/s

16:17:22 (22.73 MB/s) - `rect1.svg.2' saved [333/333]

SVG content delivered through a controller works just fine, you just have to set the content disposition to inline.

def index
  data = <<END_D
<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">

<svg width="100%" height="100%" version="1.1"
xmlns="http://www.w3.org/2000/svg">

<rect width="300" height="100"
style="fill:rgb(0,0,255);stroke-width:1;
stroke:rgb(0,0,0)"/>

</svg>
END_D
send_data data, :type => 'image/svg+xml', :disposition => 'inline'
end

Now a DSL for SVG creation would be cool, but that is a completely different project.