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  report-
                                         ing.

       Tk_Window    tkwin      (in)      Window  whose  screen geometry deter-
                                         mines the conversion between absolute
                                         units and pixels.

       Tcl_Obj      *objPtr    (in/out)                                        ||
                                         String value specifies a distance  on |
                                         the screen; internal rep will be mod- |
                                         ified 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 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 information about the |
       return  value  in objPtr, which speeds up future calls to Tk_GetPixels- |
       FromObj 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)