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NAME
     Tk_GetPixelsFromObj,     Tk_GetPixels,      Tk_GetMMFromObj,
     Tk_GetScreenMM - translate between strings and screen units

SYNOPSIS
     #include <tk.h>

     int                                                           |
     Tk_GetPixelsFromObj(interp, tkwin, objPtr, intPtr)            |

     int
     Tk_GetPixels(interp, tkwin, string, intPtr)

     int                                                           |
     Tk_GetMMFromObj(interp, tkwin, objPtr, doublePtr)             |

     int
     Tk_GetScreenMM(interp, tkwin, string, doublePtr)

ARGUMENTS
     Tcl_Interp   *interp    (in)      Interpreter  to  use   for
                                       error reporting.

     Tk_Window    tkwin      (in)      Window    whose     screen
                                       geometry   determines  the
                                       conversion  between  abso-
                                       lute units and pixels.

     Tcl_Obj      *objPtr    (in/out)                                   ||
                                       String  value  specifies a  |
                                       distance  on  the  screen;  |
                                       internal rep will be modi-  |
                                       fied  to  cache  converted  |
                                       distance.                   |

     char         *string    (in)                                       ||
                                       Same   as   objPtr  except  |
                                       specification of  distance  |
                                       is passed as a string.

     int          *intPtr    (out)     Pointer  to  location   in
                                       which  to  store converted
                                       distance in pixels.

     double       *doublePtr (out)     Pointer  to  location   in
                                       which  to  store converted
                                       distance in millimeters.
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DESCRIPTION
     These procedures take as argument a  specification  of  dis-
     tance  on  the  screen  (objPtr  or  string) and compute the  |
     corresponding  distance  either   in   integer   pixels   or
     floating-point  millimeters.   In  either  case,  objPtr  or  |
     string specifies  a  screen  distance  as  a  floating-point
     number  followed  by  one  of  the following characters that
     indicates units:

     <none>
          The number specifies a distance in pixels.

     c    The number specifies a distance in centimeters  on  the
          screen.

     i    The number  specifies  a  distance  in  inches  on  the
          screen.

     m    The number specifies a distance in millimeters  on  the
          screen.

     p    The number specifies a  distance  in  printer's  points
          (1/72 inch) on the screen.

     Tk_GetPixelsFromObj converts the  value  of  objPtr  to  the  |
     nearest  even  number  of  pixels  and  stores that value at  |
     *intPtr.  It returns TCL_OK under normal circumstances.   If  |
     an error occurs (e.g. objPtr contains a number followed by a  |
     character that isn't one of the ones above)  then  TCL_ERROR  |
     is  returned and an error message is left in interp's result  |
     if interp isn't NULL.  Tk_GetPixelsFromObj  caches  informa-  |
     tion  about  the  return  value  in  objPtr, which speeds up  |
     future calls to Tk_GetPixelsFromObj with the same objPtr.     |

     Tk_GetPixels is identical to Tk_GetPixelsFromObj except that  |
     the screen distance is specified with a string instead of an  |
     object.  This prevents Tk_GetPixels from caching the  return  |
     value,    so    Tk_GetAnchor    is   less   efficient   than  |
     Tk_GetPixelsFromObj.                                          |

     Tk_GetMMFromObj   and   Tk_GetScreenMM   are   similar    to  |
     Tk_GetPixelsFromObj  and  Tk_GetPixels (respectively) except  |
     that they convert the screen  distance  to  millimeters  and  |
     store  a  double-precision  floating-point  result at *doub-  |
     lePtr.


KEYWORDS
     centimeters, convert, inches, millimeters,  pixels,  points,
     screen units

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