Class: RubyLabs::Canvas::TkObject

Inherits:
Object
  • Object
show all
Defined in:
lib/rubylabs.rb

Overview

TkObject

Base class of all objects defined for RubyLabs::Canvas. Objects derived from this class are proxies for Tk objects in a wish shell, opened when the canvas is initialized.

Applications should not try to instantiate a TkObject directly, but instead should call a constructor of one of the derived classes. For example, to draw a circle on the canvas:

c = Canvas::Circle.new(x, y, r)

Public instance methods defined here are inherited by all objects derived from TkObject, and can be used to manipulate the object. For example, to change the color of the circle:

c.fill = 'green'

The current implementation is very sparse: the only operations defined are the ones needs for the visualizations described in the textbook, which are just the basic methods that create an object or move it around on the screen.

In addition to the usual attributes, these objects have a “pen point”, which is the location of an imaginary pen relative to the object’s base coordinate. The pen point is used by methods that draw a track as an object is moved (e.g. see the methods that control the motion of the robot in SphereLab)

Direct Known Subclasses

Circle, Font, Line, Polygon, Rectangle, Text

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#coords ⇒ Object

Returns the value of attribute coords.



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# File 'lib/rubylabs.rb', line 763

def coords
  @coords
end

#name ⇒ Object

Returns the value of attribute name.



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# File 'lib/rubylabs.rb', line 763

def name
  @name
end

#penpoint ⇒ Object

Returns the value of attribute penpoint.



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# File 'lib/rubylabs.rb', line 763

def penpoint
  @penpoint
end

Class Method Details

.nextId ⇒ Object

Return a unique ID number for a new proxy object.

:call-seq:

TkObject.nextId()



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# File 'lib/rubylabs.rb', line 783

def TkObject.nextId
  @@id += 1
  return "obj" + @@id.to_s
end

.options(h) ⇒ Object

Translate a Ruby hash h into a Tk option string. Example:

>> Canvas::TkObject.options( { :outline => :black, :fill => :red } )
=> "-fill red -outline black"

Note the ordering of the options in the Tk string may not be the same as the order they are listed when the hash object is created.

:call-seq:

TkObject.options(h) => String



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# File 'lib/rubylabs.rb', line 798

def TkObject.options(h)
  a = []
  h.each do |k,v| 
    a << "-#{k} #{v}"
  end
  return a.join(" ")
end

.reset(p) ⇒ Object

Initialization: set the object ID to 0 and save the file descriptor for the connection to the wish shell.

:call-seq:

TkObject.reset(p)



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# File 'lib/rubylabs.rb', line 772

def TkObject.reset(p)
  @@pipe = p
  @@id = 0
end

Instance Method Details

#erase ⇒ Object

Remove an object from the canvas.

:call-seq:

x.erase()



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# File 'lib/rubylabs.rb', line 832

def erase
  @@pipe.puts ".canvas delete $#{@name}"
end

#fill=(x) ⇒ Object

Set the fill color for an object. Example:

>> x.fill = "green"
=> "green"

:call-seq:

x.fill = String



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# File 'lib/rubylabs.rb', line 864

def fill=(x)
  @@pipe.puts ".canvas itemconfigure $#{name} -fill #{x}"
end

#lower ⇒ Object

Put an object in the background (below all other objects on the canvas).

:call-seq:

x.lower()



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# File 'lib/rubylabs.rb', line 822

def lower
  @@pipe.puts ".canvas lower $#{@name}"
end

#raise ⇒ Object

Bring an object to the foreground (on top of all other objects on the canvas).

:call-seq:

x.raise()



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# File 'lib/rubylabs.rb', line 812

def raise
  @@pipe.puts ".canvas raise $#{@name}"
end