Tk_GetPixelsFromObj




NAME
       Tk_GetPixelsFromObj,  Tk_GetPixels,  Tk_GetMMFromObj,  Tk_GetScreenMM Tk_GetScreenMMtranslate
       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 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.


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)