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Tk_GetPixelsFromObj(3)       Tk Library Procedures      Tk_GetPixelsFromObj(3)




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

       Interpreter to use for error reporting.  Window whose  screen  geometry
       determines  the  conversion  between absolute units and pixels.  String
       value specifies a distance on the screen; internal rep will be modified
       to  cache  converted  distance.  Same as objPtr except specification of
       distance is passed as a string.  Pointer to location in which to  store
       converted  distance  in  pixels.  Pointer to location in which to store
       converted distance in millimeters.



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_GetPix-
       elsFromObj 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 pre-
       vents 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)

GetPixels 8.5.4 - Generated Sat Aug 23 18:14:54 CDT 2008
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