wxruby users - Jun 2004 - Tracking Mouse motion

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Hello Shanko

This is a copy of a post that was recently answered for me.

=============================From: alex fenton (alex@delete.pressure.to)
Subject: Re: Comparison of GLs for plotting (x,y,z) pts?


      View this article only
Newsgroups: comp.lang.ruby
Date: 2004-06-20 06:34:10 PST

Todd Gardner wrote:
> My goal is to have my application plot arrays of (x,y) and possibly
> (x,y,z) data points in "real time".  I would also like to write
text
> on the graphs.  I would like to ask for a knowledgeable comparison and
> contrast of the multitudes of graphic utility libraries out there
> capable of doing this seemingly SIMPLE plotting.
...
> WxRuby - I don''t know how to draw lines yet in this library.
In WxRuby you could use a Device Context to draw lines, points, fills,
ellipses, etc, plus text onto a frame. For a full list of methods
available see the WxWidgets docs:

http://www.wxwidgets.org/manuals/2.4.2/wx105.htm#wxdc

I haven''t used these classes in detail, so I don''t know
whether the
bindings are complete, but the following simple example worked for me
using wxruby-0.3.0 (current release is 0.4.0)

chrz
alex

---------------------------

require ''wxruby''

class MyDrawingFrame < Wx::Frame
   def initialize(*args)
     super(*args)
     evt_paint { on_paint }
   end
   def on_paint
     paint do | dc |
       dc.clear
       dc.draw_line( 0, 0, 50, 100)
       dc.draw_line( 50, 100, 100, 75)
       dc.draw_text( ''a label'', 52, 102)
     end
   end
end

class MyApp < Wx::App
   def on_init()
     frame = MyDrawingFrame.new(nil, -1, ''Drawing'')
     frame.set_client_size( Wx::Size.new(200,200))
     frame.show()
   end
end

MyApp.new().main_loop()=============================
Todd
  -----Original Message-----
  From: wxruby-users-bounces@rubyforge.org
[mailto:wxruby-users-bounces@rubyforge.org]On Behalf Of Shashank Date
  Sent: Tuesday, June 22, 2004 6:20 AM
  To: General discussion of wxRuby
  Cc: Shashank Date
  Subject: [Wxruby-users] Tracking Mouse motion


  I am writting a "scribble" like application using wxRuby 0.4.0 on
Win XP
Home.

  I would like to track the movement of the mouse over the canvas ** while
the left button is pressed **. What events should I be looking for ? I have
looked at EVT_MOTION and EVT_LEFT_DOWN and got them working individually.
But I do not know how to look for the _combination_ of those two. DRAG_MOVE
may be ?

  Also, how do I draw a _continuous_ line which tracks the mouse motion? I
got it to draw spots at different (x,y) co-ords, but the result is, umm,
spotty :-)

  See attached code. TIA,
  -- shanko
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Shashank Date wrote:
> I am writting a "scribble" like application using wxRuby 0.4.0 on
Win XP Home.
> 
> I would like to track the movement of the mouse over the canvas 
> ** while the left button is pressed **. What events should I be looking for
?
> I have looked at EVT_MOTION and EVT_LEFT_DOWN and got them working
individually.
> But I do not know how to look for the _combination_ of those two.
I don''t have time to actually try code right now, but the wxMouseEvent 
page of the wxWindows docs suggests that you would want to catch 
EVT_MOTION, and in your handler you would call left_is_down to find out 
whether the user is dragging or not.

Alternatively, you could also catch EVT_LEFT_DOWN and EVT_LEFT_UP and 
set and clear a flag in your class to indicate whether dragging is 
happening.
> Also, how do I draw a _continuous_ line which tracks the mouse motion? 
> I got it to draw spots at different (x,y) co-ords, but the result is, 
> umm, spotty :-)
I would probably remember the previous mouse position, and when a new 
motion event is caught, draw a line between the old point and the new point.

Cheers,

Kevin

Thanks, Todd !
I learnt about draw_text from your example.
  ----- Original Message ----- 
  From: Todd G. Gardner 
  To: General discussion of wxRuby 
  Sent: Tuesday, June 22, 2004 9:02 AM
  Subject: RE: [Wxruby-users] Tracking Mouse motion


  Hello Shanko

  This is a copy of a post that was recently answered for me.

  =============================  From: alex fenton (alex@delete.pressure.to)
  Subject: Re: Comparison of GLs for plotting (x,y,z) pts? 
       
          
        View this article only 
  Newsgroups: comp.lang.ruby
  Date: 2004-06-20 06:34:10 PST 

Todd Gardner wrote:
> My goal is to have my application plot arrays of (x,y) and possibly
> (x,y,z) data points in "real time".  I would also like to write
text
> on the graphs.  I would like to ask for a knowledgeable comparison and
> contrast of the multitudes of graphic utility libraries out there
> capable of doing this seemingly SIMPLE plotting.
...
> WxRuby - I don''t know how to draw lines yet in this library.
In WxRuby you could use a Device Context to draw lines, points, fills, 
ellipses, etc, plus text onto a frame. For a full list of methods 
available see the WxWidgets docs:

http://www.wxwidgets.org/manuals/2.4.2/wx105.htm#wxdc

I haven''t used these classes in detail, so I don''t know
whether the
bindings are complete, but the following simple example worked for me 
using wxruby-0.3.0 (current release is 0.4.0)

chrz
alex

---------------------------

require ''wxruby''

class MyDrawingFrame < Wx::Frame
   def initialize(*args)
     super(*args)
     evt_paint { on_paint }
   end
   def on_paint
     paint do | dc |
       dc.clear
       dc.draw_line( 0, 0, 50, 100)
       dc.draw_line( 50, 100, 100, 75)
       dc.draw_text( ''a label'', 52, 102)
     end
   end
end

class MyApp < Wx::App
   def on_init()
     frame = MyDrawingFrame.new(nil, -1, ''Drawing'')
     frame.set_client_size( Wx::Size.new(200,200))
     frame.show()
   end
end

MyApp.new().main_loop()=============================
  Todd
    -----Original Message-----
    From: wxruby-users-bounces@rubyforge.org
[mailto:wxruby-users-bounces@rubyforge.org]On Behalf Of Shashank Date
    Sent: Tuesday, June 22, 2004 6:20 AM
    To: General discussion of wxRuby
    Cc: Shashank Date
    Subject: [Wxruby-users] Tracking Mouse motion


    I am writting a "scribble" like application using wxRuby 0.4.0 on
Win XP Home.

    I would like to track the movement of the mouse over the canvas ** while the
left button is pressed **. What events should I be looking for ? I have looked
at EVT_MOTION and EVT_LEFT_DOWN and got them working individually. But I do not
know how to look for the _combination_ of those two. DRAG_MOVE may be ?

    Also, how do I draw a _continuous_ line which tracks the mouse motion? I got
it to draw spots at different (x,y) co-ords, but the result is, umm, spotty :-)

    See attached code. TIA,
    -- shanko


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Hi Kevin,

Thanks for responding inspite of your busy schedule (moving and all..)

----- Original Message ----- 
From: "Kevin Smith" <wxruby@qualitycode.com>
To: "General discussion of wxRuby" <wxruby-users@rubyforge.org>
Sent: Tuesday, June 22, 2004 11:13 AM
Subject: Re: [Wxruby-users] Tracking Mouse motion
> Alternatively, you could also catch EVT_LEFT_DOWN and EVT_LEFT_UP and
> set and clear a flag in your class to indicate whether dragging is
> happening.
>
> > Also, how do I draw a _continuous_ line which tracks the mouse motion?
> > I got it to draw spots at different (x,y) co-ords, but the result is,
> > umm, spotty :-)
>
> I would probably remember the previous mouse position, and when a new
> motion event is caught, draw a line between the old point and the new
point.

Yep, that is exactly what I did.

See attached code for a complete working example. Ways to make it
better are always welcome.

-- shanko
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I am trying to understand the use of Wx::Region and cannot find any examples
of usage around.

I want to be able to "rubber-band" a region on Wx::PaintDC and
cut&paste it
some where on the canvas.

Any suggestions?
-- shanko

Shashank Date wrote:
> I am trying to understand the use of Wx::Region and cannot find any
examples
> of usage around.
> 
> I want to be able to "rubber-band" a region on Wx::PaintDC and
cut&paste it
> some where on the canvas.
I have not used regions in wxWindows, but I used them in Windows several 
years ago.... that was Windows 3.1 :-)

It looks like you would construct the region from a polygon. If I 
understand what you want to do, I would next create a destination bitmap 
(you might need to initialize it to be blank), and create a MemoryDC 
pointing to it. Then call MemoryDC#set_clipping_region.

 From that point, any drawing to that dc would be constrained to that 
region. Any attempts to draw outside the region would be ignored. 
Hopefully that applies to blit as well. blit from the PaintDC into the 
MemoryDC.

Now, you can blit the bitmap back into your PaintDC at a different 
location, probably after calling set_clipping_region at the destination 
in your PaintDC.

Good luck,

Kevin

----- Original Message ----- 
From: "Kevin Smith"
<wxruby@qualitycode.com>
> It looks like you would construct the region from a polygon. If I 
> understand what you want to do, I would next create a destination bitmap 
> (you might need to initialize it to be blank), and create a MemoryDC 
> pointing to it. Then call MemoryDC#set_clipping_region.
> 
>  From that point, any drawing to that dc would be constrained to that 
> region. Any attempts to draw outside the region would be ignored. 
> Hopefully that applies to blit as well. blit from the PaintDC into the 
> MemoryDC.
> 
> Now, you can blit the bitmap back into your PaintDC at a different 
> location, probably after calling set_clipping_region at the destination 
> in your PaintDC.
Hmmm... that looks more involved than what I had assumed and I am
not sure I have understood it all. Do you know of any sample code to
go by?

I was able to blit from a source ClientDC to another ClientDC 
easily, like:

# ----------------------------
@source_dc = Wx::ClientDC.new(self) unless @source_dc
if @source_dc
     xdest, ydest, width, height, xsrc,  ysrc = 0,0,100,200,0,0
     dc = Wx::ClientDC.new(@canvas)
     dc.blit(xdest, ydest, width, height,  @source_dc,
                  xsrc,  ysrc, Wx::COPY) 
     dc.free
     @source_dc.free
     @source_dc = nil
end
# ----------------------------

But I could not figure out how to blit when the source and the 
destination ClientDCs were the same (i.e. @canvas in the code
above).

TIA,
-- shanko

----- Original Message ----- 
From: "Shashank Date" <sdate@everestkc.net>
 >
> But I could not figure out how to blit when the source and the 
> destination ClientDCs were the same (i.e. @canvas in the code
> above).
My bad ...I take that back. I was able to do it once I set the 
source, dest co-ords correctly. Sorry for the noise.
-- shanko