Ruby tk drawing a line

ruby-talk
1

I have a question concerning ruby/tk and drawing lines on a canvas.
I tried to convert from a tcl program.
Everything works fine except that the line when its thickness is large
appears to be a series of short line segments rather than a solid line.

I have binded the "1" mouse button to start the line with the following

canvas.bind( '1', proc { |e|
           
                             $startx = e.x
                             $starty = e.y
                             
                             })

and the motion of the mouse

canvas.bind('B1-Motion', proc { |e|
      $endx = e.x
      $endy = e.y
                        
      $a = TkcLine.new(canvas, $startx, $starty, $endx, $endy)
      $a.width option.value
      $a.fill "#{color}"
      })

Can anyone see why this does not give me a solid line

···

--
Ed Redman
redman@accesswave.ca

2

Ed Redman wrote:

I have a question concerning ruby/tk and drawing lines on a canvas.
I tried to convert from a tcl program. Everything works fine except that the line when its thickness is large appears to be a series of short line segments rather than a solid line.

I have binded the "1" mouse button to start the line with the following

canvas.bind( '1', proc { |e|
                                        $startx = e.x
                             $starty = e.y
                                                          })

and the motion of the mouse

canvas.bind('B1-Motion', proc { |e| $endx = e.x
      $endy = e.y
                              $a = TkcLine.new(canvas, $startx, $starty, $endx, $endy)
      $a.width option.value
      $a.fill "#{color}"
      })

Can anyone see why this does not give me a solid line

Does the same thing happen without the fill param?

A TkcLine has a "dash" parameter, and that might be causing this. But it would be surprising if the default is a dashed line. Anyway, you could try

   $a.dash ""

or

   $a.dash nil

See

   Tk Built-In Commands - canvas manual page

for details.

···

--
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

3

Message-ID: <k7CPi.10981$G25.2545@edtnps89>

canvas.bind('B1-Motion', proc { |e|
      $endx = e.x
      $endy = e.y
                        
      $a = TkcLine.new(canvas, $startx, $starty, $endx, $endy)

You write so many new lines at here.
Each short line is made at each 'B1-Motion' callback.

The following may be an example which you want.

···

From: Ed Redman <redman@accesswave.ca>
Subject: ruby tk drawing a line
Date: Fri, 12 Oct 2007 12:50:10 +0900
-----------------------------------------------------------------
require 'tk'

line = nil
first = nil
last = nil

canvas = TkCanvas.new(:relief=>:ridge, :borderwidth=>3).pack

f = TkFrame.new.pack(:fill=>:x)

color = 'black'
TkButton.new(f, :text=>'color', :command=>proc{
               color = Tk.chooseColor(:initialcolor=>color)
             }).pack(:side=>:right, :padx=>[10,3])

option = TkSpinbox.new(f, :from=>1, :to=>1000,
                       :width=>4).pack(:side=>:right, :padx=>0)
TkLabel.new(f, :text=>'width').pack(:side=>:right, :padx=>[10,0])

canvas.bind('1', '%x', '%y'){|*first|
  line = TkcLine.new(canvas, first, first,
                     :width=>option.value, :fill=>color)
}

canvas.bind('B1-Motion', '%x', '%y'){|*last| line.coords(first, last)}

Tk.mainloop
-----------------------------------------------------------------

Ruby/Tk accepts all of the following coords pattern for a canvas item.

(1) x1, y1, x2, y2, x3, y3, ...

(2) [x1, y1], [x2, y2], [x3, y3], ...

(3) [ [x1, y1], [x2, y2], [x3, y3], ... ]

In my example, I use the pattern (2).
--
Hidetoshi NAGAI (nagai@ai.kyutech.ac.jp)