Wxruby - painting in device context

ruby-talk
1

Hi.
I'm trying to paint in DC context:

# ---------------------------------------------------

frame = Frame.new(nil, -1, "")

frame.paint { |dc|

    dc.draw_line(50, 50, 100, 100) # for
this I don't see the line

    dc.draw_bitmap(Bitmap.new('c:\img.bmp'),0,0) # and for this
program crashes

}

# -----------------------------------------------------------

Does anyone know why is this happening ?

Thanks.

2

Haris Bogdanovi� wrote:

Hi.
I'm trying to paint in DC context:

# ---------------------------------------------------

frame = Frame.new(nil, -1, "")

frame.paint { |dc|

    dc.draw_line(50, 50, 100, 100) # for
this I don't see the line

    dc.draw_bitmap(Bitmap.new('c:\img.bmp'),0,0) # and for this
program crashes

}

# -----------------------------------------------------------

Does anyone know why is this happening ?

Thanks.

It appears to me that you cannot draw on a DC before the window is
created. The following shows nothing with Ruby 1.9 on my Ubuntu Jaunty
machine:

···

=======================================
#!/usr/bin/env ruby
#Encoding: UTF-8
require "wx"

class GUI < Wx::App
  include Wx

  def on_init
    @mainwindow = Frame.new(nil, -1, "Test", DEFAULT_POSITION,
Size.new(400, 400))

    @mainwindow.paint{|dc| dc.draw_line(0, 0, 100, 100)}

    @mainwindow.show
  end

end

x = GUI.new
x.main_loop

But if you use the #paint method after the window has been created,
everything works fine:

=======================================
#!/usr/bin/env ruby
#Encoding: UTF-8
require "wx"

class GUI < Wx::App
  include Wx

  def on_init
    @mainwindow = Frame.new(nil, -1, "Test", DEFAULT_POSITION,
Size.new(400, 400))

    Timer.after(2000){@mainwindow.paint{|dc| dc.draw_line(0, 0, 100,
100)}}

    @mainwindow.show
  end

end

x = GUI.new
x.main_loop

Marvin
--
Posted via http://www.ruby-forum.com/\.

3

Haris Bogdanovi� wrote:

    dc.draw_bitmap(Bitmap.new('c:\img.bmp'),0,0) # and for this
program crashes

You may want to use a forward slash / instead of the backslash, even on
Windows. An alternative is to escape the backslash by duplicating it:
"C:/img.bmp" or "C:\\img.bmp"

Marvin

···

--
Posted via http://www.ruby-forum.com/\.

4

From: "Haris Bogdanoviæ" <fbogdanovi@xnet.hr>
Newsgroups: comp.lang.ruby
Sent: Friday, September 25, 2009 7:13 PM
Subject: wxruby - painting in device context

Hi.
I'm trying to paint in DC context:

# ---------------------------------------------------
frame = Frame.new(nil, -1, "")
frame.paint { |dc|
   dc.draw_line(50, 50, 100, 100) # for
this I don't see the line

   dc.draw_bitmap(Bitmap.new('c:\img.bmp'),0,0) # and for this program crashes
}
# -----------------------------------------------------------
Does anyone know why is this happening ?

Thanks.

Hello Haris:

I haven't been able to get a line drawn either but I know it's possible. The WxRuby samples directory contains a files called bitmap.rb and graphics_drawing.rb that draws bitmaps, text and rectangles.

Michael