From: Alex Fenton <aff28@...>
Date: 2008-04-01T01:40:04+09:00
Subject: Re: Displaying gruff graphs

Victor Reyes wrote:

> Once a graph is written to disk, g.write("filename.png"), how can it be
> displayed in Ruby?
> I would like to re-create the graph and re-displayed often enough to give
> the appearance of "real time"

It's not clear whether you meant via a browser or in a desktop app. If 
you want to show it on the desktop, you'll need some sort of GUI toolkit 
to display a window then draw the bitmap in it.

You have a lot of choices: wxRuby, FXRuby, QT/Ruby, Tk, Ruby/GTK etc 
etc. They vary widely in suitability for different platforms, ease of 
installation, features, aesthetics.

I use wxRuby b/c it's easy to install (gem install wxruby) and looks 
good on all the big platforms. A simple 25-line example that would 
regularly redraw an updated graph is below:

hth
alex
__
require 'wx'
require 'tempfile'

# A frame that draws a regularly updated graph from Gruff every X millisecs
class GruffFrame < Wx::Frame
   def initialize(refresh_delay = 5000)
     super(nil, :title => 'Gruff')
     Wx::Timer.every(refresh_delay) { refresh }
     evt_paint :on_paint
   end

   # Writes the gruff graph to a file then reads it back to draw it
   def on_paint
     # Set up your graph here
     graph = Gruff::Lines.new # ....
     # Write to a tempfile and read back
     tmp = Tempfile.new('gruff')
     graph.write(tmp.path)
     bmp = Wx::Bitmap.new(tmp.path, Wx::BITMAP_TYPE_PNG)
     # Draw it on the Frame
     paint do | dc |
       dc.draw_bitmap(bmp, 0, 0, false)
     end
   end
end

Wx::App.run { GruffFrame.new.show }