[HJG] On Linux, it works correctly: the drawings left and right are drawn with dashed lines.
On Windows, the dash-pattern is ignored when the width is 2 or more.

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 #!/bin/bash
 # the next line restarts using wish \
   exec /usr/bin/wish "$0" "$@"

 #: WinDash.tcl - HaJo Gurt - 2005-07-13
 #: Bug-Demo: On Windows, dash-patterns only work with width 1

 #########1#########2#########3#########4#########5#########6#########7#####

  package require Tk

  grid [canvas .c -width 300 -height 325]

  # Dash-patterns: {2 4}  {2 8}  {6 4}  {6 4 2 4}  {6 4 2 4 2 4}

  .c create oval  25  25  125 125  -width 1 -dash {2 4}  -fill grey60
  .c create oval 175  25  275 125  -width 2 -dash .  

  .c create line  20 150  130 150  -fill grey30  -width 1  -dash {6 4 2 4 2 4} 
  .c create line 170 150  280 150                -width 2  -dash {6 4 2 4} 

  for {set y 170} {$y<=180} {incr y} {   # crude workaround for thick dashed line:
    .c create line  20 $y  280 $y  -fill grey30  -width 1  -dash {2 4 6 4}  ;# -dash .-
  }

  .c create rect  25 200  125 300  -fill grey70  -width 1  -dash {6 4}
  .c create rect 175 200  275 300                -width 2  -dash -

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The tcl-help text says "all values in the dash list will be multiplied by the line width before display. 
This assures that "." will always be displayed as a dot and "-" always as a dash regardless of the line width."

But on Windows, it looks like the dash-pattern is ignored when the width is 2 or more.

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[bch] I am running into this same problem.  I develop a map application on an X11 system (FreeBSD) and deploy it on Windows.  As you say, the dashed lines are drawn as specified on a non-Windows platform, but Windows won't do it "right."  Unfortunately, the end-users of my application won't be moving to a non-Windows platform, thus I'm stuck trying to figure out how to get around this problem.

I did some quick perusing of the Tk code, and I will summarize what I found below.  (Note that I'm not a Tcl/Tk developer which means I could be missing some nuances and details.)

The Windows dash support can be found in the file tk/win/tkWinDraw.c [http://tktoolkit.cvs.sourceforge.net/tktoolkit/tk/win/tkWinDraw.c?revision=1.12.2.2&view=markup&pathrev=core-8-4-14].

The code of interest is in the SetUpGraphicsPort function starting on line 1182.  I couldn't see any reason why this function would cause the problems we are seeing.

Then I did some other searching and found this site [http://msdn.microsoft.com/library/default.asp?url=/library/en-us/gdi/pens_9wha.asp] (MSDN).  It has this to say:

"CreatePen returns a pen with the specified width bit with the PS_SOLID style if you specify a width greater than one for the following styles: PS_DASH, PS_DOT, PS_DASHDOT, PS_DASHDOTDOT."

This is corroborated a little more clearly at this site [http://www.functionx.com/visualc/gdi/pens.htm] where it says:

"This means that, if you specify the style as PS_DASH, PS_DOT, PS_DASHDOT, or PS_DASHDOTDOT but set a width higher than 1, the line would be drawn as PS_SOLID."

The bottom line appears to be this:  This is a Windows-specific problem, and overcoming that using the current methodology is probably not an option.  I suppose one could write their own line drawing routines, etc.  (ouch)

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