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Tk_AllocCursorFromObj(3)                    Tk Library Procedures                   Tk_AllocCursorFromObj(3)



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NAME
       Tk_AllocCursorFromObj,   Tk_GetCursor,  Tk_GetCursorFromObj,  Tk_GetCursorFromData,  Tk_NameOfCursor,
       Tk_FreeCursorFromObj, Tk_FreeCursor - maintain database of cursors

SYNOPSIS
       #include <tk.h>

       Tk_Cursor
       Tk_AllocCursorFromObj(interp, tkwin, objPtr)

       Tk_Cursor
       Tk_GetCursor(interp, tkwin, name)

       Tk_Cursor
       Tk_GetCursorFromObj(tkwin, objPtr)

       Tk_Cursor
       Tk_GetCursorFromData(interp, tkwin, source, mask, width, height, xHot, yHot, fg, bg)

       const char *
       Tk_NameOfCursor(display, cursor)

       Tk_FreeCursorFromObj(tkwin, objPtr)

       Tk_FreeCursor(display, cursor)

ARGUMENTS
       Tcl_Interp *interp (in)               Interpreter to use for error reporting.

       Tk_Window tkwin (in)                  Token for window in which the cursor will be used.

       Tcl_Obj *objPtr (in/out)              Description of cursor;  see below for possible values.   Inter-nal Internal
                                             nal  rep  will  be  modified  to cache pointer to corresponding
                                             Tk_Cursor.

       char *name (in)                       Same as objPtr except description of  cursor  is  passed  as  a
                                             string and resulting Tk_Cursor is not cached.

       const char *source (in)               Data for cursor cursor, in standard cursor format.

       const char *mask (in)                 Data for mask cursor, in standard cursor format.

       int width (in)                        Width of source and mask.

       int height (in)                       Height of source and mask.

       int xHot (in)                         X-location of cursor hot-spot.

       int yHot (in)                         Y-location of cursor hot-spot.

       Tk_Uid fg (in)                        Textual description of foreground color for cursor.

       Tk_Uid bg (in)                        Textual description of background color for cursor.

       Display *display (in)                 Display for which cursor was allocated.

       Tk_Cursor cursor (in)                 Opaque  Tk  identifier for cursor.  If passed to Tk_FreeCursor,
                                             must have been returned by some previous call  to  Tk_GetCursor
                                             or Tk_GetCursorFromData.
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DESCRIPTION
       These  procedures  manage a collection of cursors being used by an application.  The procedures allow
       cursors to be re-used efficiently, thereby avoiding server overhead, and also  allow  cursors  to  be
       named with character strings.

       Tk_AllocCursorFromObj takes as argument an object describing a cursor, and returns an opaque Tk iden-tifier identifier
       tifier for a cursor corresponding to the description.  It re-uses an existing cursor if possible  and
       creates  a  new  one  otherwise.   Tk_AllocCursorFromObj caches information about the return value in
       objPtr, which speeds up future calls to procedures such as Tk_AllocCursorFromObj and Tk_GetCursorFro-mObj. Tk_GetCursorFromObj.
       mObj.  If  an error occurs in creating the cursor, such as when objPtr refers to a non-existent file,
       then None is returned and an error message will be stored in interp's result if interp is  not  NULL.
       ObjPtr must contain a standard Tcl list with one of the following forms:

       name [fgColor [bgColor]]
              Name  is  the name of a cursor in the standard X cursor cursor, i.e., any of the names defined
              in cursorcursor.h, without the XC_.  Some example values are  X_cursor,  hand2,  or  left_ptr.
              Appendix  B of "The X Window System" by Scheifler & Gettys has illustrations showing what each
              of these cursors looks like.  If fgColor and bgColor are both specified, they give  the  fore-ground foreground
              ground and background colors to use for the cursor (any of the forms acceptable to Tk_GetColor
              may be used).  If only fgColor is specified, then there will  be  no  background  color:   the
              background  will  be  transparent.  If no colors are specified, then the cursor will use black
              for its foreground color and white for its background color.

              The Macintosh version of Tk supports all of the X cursors and will  also  accept  any  of  the
              standard Mac cursors including ibeam, crosshair, watch, plus, and arrow.  In addition, Tk will
              load Macintosh cursor resources of the types crsr (color) and CURS (black and  white)  by  the
              name  of the resource.  The application and all its open dynamic library's resource files will
              be searched for the named cursor.  If there are conflicts color cursors will always be  loaded
              in preference to black and white cursors.

       @sourceName maskName fgColor bgColor
              In  this  form, sourceName and maskName are the names of files describing cursors for the cur-sor's cursor's
              sor's source bits and mask.  Each file must be in standard X11 or X10 cursor format.   FgColor
              and  bgColor  indicate  the  colors  to  use for the cursor, in any of the forms acceptable to
              Tk_GetColor.  This form of the command will not work on Macintosh or Windows computers.

       @sourceName fgColor
              This form is similar to the one above, except that the source is  used  as  mask  also.   This
              means  that the cursor's background is transparent.  This form of the command will not work on
              Macintosh or Windows computers.

       @sourceName
              This form only works on Windows, and will load a Windows system cursor (.ani or .cur) from the
              file specified in sourceName.

       Tk_GetCursor is identical to Tk_AllocCursorFromObj except that the description of the cursor is spec-ified specified
       ified with a string instead of an object.  This prevents Tk_GetCursor from caching the return  value,
       so Tk_GetCursor is less efficient than Tk_AllocCursorFromObj.

       Tk_GetCursorFromObj  returns  the token for an existing cursor, given the window and description used
       to create the cursor.  Tk_GetCursorFromObj does not actually  create  the  cursor;  the  cursor  must
       already  have been created with a previous call to Tk_AllocCursorFromObj or Tk_GetCursor.  The return
       value is cached in objPtr, which speeds up future calls to Tk_GetCursorFromObj with the  same  objPtr
       and tkwin.

       Tk_GetCursorFromData  allows  cursors  to  be created from in-memory descriptions of their source and
       mask cursors.  Source points to standard cursor data for the cursor's source bits, and mask points to
       standard cursor data describing which pixels of source are to be drawn and which are to be considered
       transparent.  Width and height give the dimensions of the cursor, xHot and yHot indicate the location
       of  the  cursor's  hot-spot (the point that is reported when an event occurs), and fg and bg describe
       the cursor's foreground and background colors textually (any of the forms  suitable  for  Tk_GetColor
       may  be  used).   Typically,  the arguments to Tk_GetCursorFromData are created by including a cursor
       file directly into the source code for a program, as in the following example:
              Tk_Cursor cursor;
              #include "source.cursor"
              #include "mask.cursor"
              cursor = Tk_GetCursorFromData(interp, tkwin, source_bits,
                  mask_bits, source_width, source_height, source_x_hot,
                  source_y_hot, Tk_GetUid("red"), Tk_GetUid("blue"));

       Under normal conditions Tk_GetCursorFromData will return an identifier for the requested cursor.   If
       an  error  occurs in creating the cursor then None is returned and an error message will be stored in
       interp's result.

       Tk_AllocCursorFromObj, Tk_GetCursor, and Tk_GetCursorFromData maintain a database of all the  cursors
       they  have  created.  Whenever possible, a call to Tk_AllocCursorFromObj, Tk_GetCursor, or Tk_GetCur-sorFromData Tk_GetCursorFromData
       sorFromData will return an existing cursor rather than creating a new one.  This  approach  can  sub-stantially substantially
       stantially  reduce  server  overhead,  so the Tk procedures should generally be used in preference to
       Xlib procedures like XCreateFontCursor or XCreatePixmapCursor, which create  a  new  cursor  on  each
       call.  The Tk procedures are also more portable than the lower-level X procedures.

       The  procedure  Tk_NameOfCursor  is  roughly the inverse of Tk_GetCursor.  If its cursor argument was
       created by Tk_GetCursor, then the return value is the name argument that was passed  to  Tk_GetCursor
       to create the cursor.  If cursor was created by a call to Tk_GetCursorFromData, or by any other mech-anism, mechanism,
       anism, then the return value is a hexadecimal string giving the X identifier for the  cursor.   Note:
       the  string returned by Tk_NameOfCursor is only guaranteed to persist until the next call to Tk_Name-OfCursor. Tk_NameOfCursor.
       OfCursor.  Also, this call is not portable except for cursors returned by Tk_GetCursor.

       When a cursor returned by Tk_AllocCursorFromObj, Tk_GetCursor, or Tk_GetCursorFromData is  no  longer
       needed,  Tk_FreeCursorFromObj or Tk_FreeCursor should be called to release it.  For Tk_FreeCursorFro-mObj Tk_FreeCursorFromObj
       mObj the cursor to release is specified with the same information used to create it; for  Tk_FreeCur-sor Tk_FreeCursor
       sor the cursor to release is specified with its Tk_Cursor token.  There should be exactly one call to
       Tk_FreeCursor for each call to Tk_AllocCursorFromObj, Tk_GetCursor, or Tk_GetCursorFromData.


BUGS
       In determining whether an existing cursor can be used to satisfy a  new  request,  Tk_AllocCursorFro-mObj, Tk_AllocCursorFromObj,
       mObj,  Tk_GetCursor,  and Tk_GetCursorFromData consider only the immediate values of their arguments.
       For example, when a file name is passed to Tk_GetCursor, Tk_GetCursor will assume it is safe  to  re-use reuse
       use  an  existing  cursor created from the same file name:  it will not check to see whether the file
       itself has changed, or whether the current directory has changed, thereby causing the name  to  refer
       to a different file.  Similarly, Tk_GetCursorFromData assumes that if the same source pointer is used
       in two different calls, then the pointers refer to the same data;  it does not check to  see  if  the
       actual data values have changed.


KEYWORDS
       cursor



Tk                                                   8.1                            Tk_AllocCursorFromObj(3)