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Internet Message Format  |  2003-01-02  |  4KB
  1. Return-Path: <icon-group-sender>
  2. Received: (from root@localhost)
  3.     by baskerville.CS.Arizona.EDU (8.11.1/8.11.1) id g9OJSmU00911
  4.     for icon-group-addresses; Thu, 24 Oct 2002 12:28:48 -0700 (MST)
  5. Message-Id: <200210241928.g9OJSmU00911@baskerville.CS.Arizona.EDU>
  6. Date: Thu, 24 Oct 2002 08:46:16 -0700
  7. From: Steve Wampler <swampler@noao.edu>
  8. X-Accept-Language: en
  9. To: Trinity Palakkad <tipl2@hotmail.com>,
  10.    icon-group <icon-group@cs.arizona.edu>
  11. Subject: Re: Doubts in programming
  12. Errors-To: icon-group-errors@cs.arizona.edu
  13. Status: RO
  14.  
  15. Trinity Palakkad wrote:
  16. > 
  17. > Program 1
  18. > 
  19. > link wopen
  20. > 
  21. > procedure main()
  22. >         WOpen("size=300,400","pos=100,100")
  23. >         WAttrib("bg=blue","fg=white","canvas=hidden")
  24. >         WDone()
  25. > end
  26. > 
  27. > After executing the program,no other programs can be executed
  28. > due to some linking error.Even the same program cannot be run
  29. > for a second time.What change is to be made to the program?
  30.  
  31. What linking error?  I don't think that's what you're seeing.
  32.  
  33. I think you're seeing the fact that WDone says to wait for
  34. a 'Q' or 'q' to be typed into the window before processing and
  35. you can't do that because you've opened the window as 'hidden',
  36. so you can't see it to type the 'Q' or 'q'.  Try:
  37.  
  38. procedure main()
  39.     WOpen("size=300,400","pos=100,100")
  40.     WAttrib("bg=blue","fg=white","canvas=normal")
  41.     WDone()
  42. end
  43.  
  44. instead and then type Q or q inside the window.  Or consider
  45. using WClose() instead of WDone, depending on what you want to
  46. do...
  47.  
  48. > Program 2
  49. > 
  50. > link wopen
  51. > 
  52. > procedure main()
  53. >         WOpen("size=300,400","pos=100,100","label=W1")
  54. >         WAttrib("bg=blue","fg=white","canvas=normal")
  55. >         WWrite("The window is in the normal state")
  56. >         WOpen("size=300,400","pos=200,200","label=W2")
  57. >         WAttrib("bg=blue","fg=white","canvas=hidden")
  58. >         WDone()
  59. > end
  60. > 
  61. > The program does not produce the desired result.
  62. > W2 has to be closed.Instead,W1 is being closed.
  63. > What change is to be made to the program?
  64.  
  65. Well, it does do what you told it to do, so I guess that
  66. wasn't what you desired...
  67.  
  68. The first WOpen sets &window, which is then used by subsequent
  69. Wxxx() functions that don't specify a window.  So the 2nd
  70. WAttrib() call that sets the canvas to hidden is hiding the
  71. first window, not the second.
  72.  
  73. I've found it to be good practice to use explicit window
  74. names anytime I'm using more than one window.  Doing so,
  75. the above program would be (something like):
  76.  
  77. link wopen
  78.  
  79. procedure main()
  80.         w1 := WOpen("size=300,400","pos=100,100","label=W1")
  81.         WAttrib(w1,"bg=blue","fg=white","canvas=normal")
  82.         WWrite(w1,"The window is in the normal state")
  83.  
  84.         w2 := WOpen("size=300,400","pos=200,200","label=W2")
  85.         WAttrib(w2,"bg=blue","fg=white","canvas=hidden")
  86.         WClose(w2)
  87.  
  88.         WDone(w1)
  89. end
  90.  
  91. Note that I'm using WClose(w2) and not WDone(w2) - since you've
  92. got w2 'hidden', WDone(w2) would be a problem, just as it was
  93. with the hidden window in your first example.
  94.  
  95. If you don't have the "Graphics Programming in Icon" book, you
  96. should get it as an invaluable reference.
  97.  
  98.  
  99.  
  100. > _________________________________________________________________
  101. > Choose an Internet access plan right for you -- try MSN!
  102. > http://resourcecenter.msn.com/access/plans/default.asp
  103.  
  104. -- 
  105. Steve Wampler -- swampler@noao.edu
  106. Quantum materiae materietur marmota monax si marmota
  107.                     monax materiam possit materiari?
  108.