wxruby users - May 2011 - Device context (get_dc) Question from printing.rb in wxRuby samples

I am using Windows XP SP 3 but want to stay general.

Below is a method within printing.rb.   I have added comments marked by #--.
My question is about get_dc.   The device context is obviously created and
the code works as presented.
It also  works as documented below.   Why does just get_dc satisfy the
linkage?
When does one use the Wx:: or the Wx::PrintOut format?  How does one decide
to use just the short form?

Where could I have found this answer?

<Code>
def on_print_page(page)
    dc = get_dc       #-- don;''t understand where get_dc comes from
                                   #--Wx::get_dc works
                                   #-- Wx::PrintOut.get_dc also works
                                   #--PrintOut.get_dc also works
                                   #-- looks like just get_dc is ok, why and
when
                                   #-- the variable dc is probably a class
or module but
                                   #-- where do I find its definition?


    if dc
        if page == 1
            draw_page_one(dc)   ##-- dc = device context passed in
        elsif (page == 2)
            draw_page_two(dc)  ##-- dc = device context passed in
        end
        dc.set_device_origin(0, 0)
        dc.set_user_scale(1.0, 1.0)

        buf = "PAGE #{page}"
        dc.draw_text(buf, 10, 10)

        return true
    else
        return false
    end
  end   #--end of on_print_page



-- 
Ann Maybury
ann.maybury@gmail.com


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It has a lot to do with scope.

On 09/05/2011 10:38 AM, "Ann Maybury" <ann.maybury at gmail.com>
wrote:

I am using Windows XP SP 3 but want to stay general.

Below is a method within printing.rb.   I have added comments marked by #--.
My question is about get_dc.   The device context is obviously created and
the code works as presented.
It also  works as documented below.   Why does just get_dc satisfy the
linkage?
When does one use the Wx:: or the Wx::PrintOut format?  How does one decide
to use just the short form?

Where could I have found this answer?

<Code>
def on_print_page(page)
    dc = get_dc       #-- don;''t understand where get_dc comes from
                                   #--Wx::get_dc works
                                   #-- Wx::PrintOut.get_dc also works
                                   #--PrintOut.get_dc also works
                                   #-- looks like just get_dc is ok, why and
when
                                   #-- the variable dc is probably a class
or module but
                                   #-- where do I find its definition?


    if dc
        if page == 1
            draw_page_one(dc)   ##-- dc = device context passed in
        elsif (page == 2)
            draw_page_two(dc)  ##-- dc = device context passed in
        end
        dc.set_device_origin(0, 0)
        dc.set_user_scale(1.0, 1.0)

        buf = "PAGE #{page}"
        dc.draw_text(buf, 10, 10)

        return true
    else
        return false
    end
  end   #--end of on_print_page



-- 
Ann Maybury
ann.maybury at gmail.com


_______________________________________________
wxruby-users mailing list
wxruby-users at rubyforge.org
http://rubyforge.org/mailman/listinfo/wxruby-users
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On 09/05/11 00:59, Ann Maybury wrote:
> Below is a method within printing.rb.   I have added comments marked 
> by #--.
> My question is about get_dc.   The device context is obviously created 
> and the code works as presented.
> It also  works as documented below.   Why does just get_dc satisfy the 
> linkage?
> When does one use the Wx:: or the Wx::PrintOut format?  How does one 
> decide to use just the short form?
get_dc is an instance method of Wx::Printout, and in the sample, it''s 
called from within a class that inherits from that.

> Where could I have found this answer?
http://wxruby.rubyforge.org/doc/printout.html#Printout_getdc
> <Code>
> def on_print_page(page)
>     dc = get_dc #-- don;''t understand where get_dc comes from
>                                    #--Wx::get_dc works
>                                    #-- Wx::PrintOut.get_dc also works
>                                    #--PrintOut.get_dc also works
>                                    #-- looks like just get_dc is ok, 
> why and when
>                                    #-- the variable dc is probably a 
> class or module but
>                                    #-- where do I find its definition?
I don''t think PrintOut.get_dc or Wx::get_dc will work? There are no
such
class/module methods in either Wx::Printout or the global Wx:: module.

alex
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