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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  - 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 absolute units and pixels.

       Tcl_Obj *objPtr (in/out) 	 String  value specifies a distance on the screen; inter-
					 nal 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  returned  and  an error message is left in interp's result if
       interp is not NULL.  Tk_GetPixelsFromObj caches information  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 speci-
       fied 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 *doublePtr.

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

Tk					       8.1			   Tk_GetPixelsFromObj(3)
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