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Tk_GetPixelsFromObj(3)	      Tk Library Procedures	  Tk_GetPixelsFromObj(3)

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NAME
     Tk_GetPixelsFromObj, Tk_GetPixels, Tk_GetMMFromObj, Tk_GetScreenMM - trans-
     late 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 absolute units and
				       pixels.

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

     const 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 distance 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  is not one of the ones above) then TCL_ERROR is re-
     turned and an error message is left in interp's result  if  interp  is  not
     NULL.  Tk_GetPixelsFromObj caches information about the return value in ob-
     jPtr, which speeds up future calls to Tk_GetPixelsFromObj with the same ob-
     jPtr.

     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_GetPixels is less effi-
     cient 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 *dou-
     blePtr.

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

Tk				       8.1		  Tk_GetPixelsFromObj(3)

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