'\" '\" Copyright (c) 1990 The Regents of the University of California. '\" Copyright (c) 1994-1996 Sun Microsystems, Inc. '\" '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" '\" SCCS: @(#) GetCursor.3 1.23 96/08/27 13:21:26 '\" .so man.macros .TH Tk_GetCursor 3 4.1 Tk "Tk Library Procedures" .BS .SH NAME Tk_GetCursor, Tk_GetCursorFromData, Tk_NameOfCursor, Tk_FreeCursor \- maintain database of cursors .SH SYNOPSIS .nf \fB#include \fR .sp Tk_Cursor \fBTk_GetCursor(\fIinterp, tkwin, nameId\fB)\fR .sp Tk_Cursor \fBTk_GetCursorFromData(\fIinterp, tkwin, source, mask, width, height, xHot, yHot, fg, bg\fB)\fR .sp char * \fBTk_NameOfCursor(\fIdisplay, cursor\fB)\fR .sp \fBTk_FreeCursor(\fIdisplay, cursor\fB)\fR .SH ARGUMENTS .AS "unsigned long" *pixelPtr .AP Tcl_Interp *interp in Interpreter to use for error reporting. .AP Tk_Window tkwin in Token for window in which the cursor will be used. .AP Tk_Uid nameId in Description of cursor; see below for possible values. .AP char *source in Data for cursor bitmap, in standard bitmap format. .AP char *mask in Data for mask bitmap, in standard bitmap format. .AP "int" width in Width of \fIsource\fR and \fImask\fR. .AP "int" height in Height of \fIsource\fR and \fImask\fR. .AP "int" xHot in X-location of cursor hot-spot. .AP "int" yHot in Y-location of cursor hot-spot. .AP Tk_Uid fg in Textual description of foreground color for cursor. .AP Tk_Uid bg in Textual description of background color for cursor. .AP Display *display in Display for which \fIcursor\fR was allocated. .AP Tk_Cursor cursor in Opaque Tk identifier for cursor. If passed to\fBTk_FreeCursor\fR, must have been returned by some previous call to \fBTk_GetCursor\fR or \fBTk_GetCursorFromData\fR. .BE .SH DESCRIPTION .PP 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 (actually Tk_Uids). .PP \fBTk_GetCursor\fR takes as argument a Tk_Uid describing a cursor, and returns an opaque Tk identifier for a cursor corresponding to the description. It re-uses an existing cursor if possible and creates a new one otherwise. \fINameId\fR must be a standard Tcl list with one of the following forms: .TP \fIname\fR\0[\fIfgColor\fR\0[\fIbgColor\fR]] \fIName\fR is the name of a cursor in the standard X cursor font, i.e., any of the names defined in \fBcursorfont.h\fR, without the \fBXC_\fR. Some example values are \fBX_cursor\fR, \fBhand2\fR, or \fBleft_ptr\fR. Appendix B of ``The X Window System'' by Scheifler & Gettys has illustrations showing what each of these cursors looks like. If \fIfgColor\fR and \fIbgColor\fR are both specified, they give the foreground and background colors to use for the cursor (any of the forms acceptable to \fBTk_GetColor\fR may be used). If only \fIfgColor\fR 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 also supports all of the X cursors. Tk on the Mac will also accept any of the standard Mac cursors including \fBibeam\fR, \fBcrosshair\fR, \fBwatch\fR, \fBplus\fR, and \fBarrow\fR. In addition, Tk will load Macintosh cursor resources of the types \fBcrsr\fR (color) and \fBCURS\fR (black and white) by the name of the 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. .TP \fB@\fIsourceName\0maskName\0fgColor\0bgColor\fR In this form, \fIsourceName\fR and \fImaskName\fR are the names of files describing bitmaps for the cursor's source bits and mask. Each file must be in standard X11 or X10 bitmap format. \fIFgColor\fR and \fIbgColor\fR indicate the colors to use for the cursor, in any of the forms acceptable to \fBTk_GetColor\fR. This form of the command will not work on Macintosh or Windows computers. .TP \fB@\fIsourceName\0fgColor\fR 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. .PP \fBTk_GetCursorFromData\fR allows cursors to be created from in-memory descriptions of their source and mask bitmaps. \fISource\fR points to standard bitmap data for the cursor's source bits, and \fImask\fR points to standard bitmap data describing which pixels of \fIsource\fR are to be drawn and which are to be considered transparent. \fIWidth\fR and \fIheight\fR give the dimensions of the cursor, \fIxHot\fR and \fIyHot\fR indicate the location of the cursor's hot-spot (the point that is reported when an event occurs), and \fIfg\fR and \fIbg\fR describe the cursor's foreground and background colors textually (any of the forms suitable for \fBTk_GetColor\fR may be used). Typically, the arguments to \fBTk_GetCursorFromData\fR are created by including a cursor file directly into the source code for a program, as in the following example: .CS 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")); .CE .PP Under normal conditions, \fBTk_GetCursor\fR and \fBTk_GetCursorFromData\fR will return an identifier for the requested cursor. If an error occurs in creating the cursor, such as when \fInameId\fR refers to a non-existent file, then \fBNone\fR is returned and an error message will be stored in \fIinterp->result\fR. .PP \fBTk_GetCursor\fR and \fBTk_GetCursorFromData\fR maintain a database of all the cursors they have created. Whenever possible, a call to \fBTk_GetCursor\fR or \fBTk_GetCursorFromData\fR will return an existing cursor rather than creating a new one. This approach can substantially reduce server overhead, so the Tk procedures should generally be used in preference to Xlib procedures like \fBXCreateFontCursor\fR or \fBXCreatePixmapCursor\fR, which create a new cursor on each call. .PP The procedure \fBTk_NameOfCursor\fR is roughly the inverse of \fBTk_GetCursor\fR. If its \fIcursor\fR argument was created by \fBTk_GetCursor\fR, then the return value is the \fInameId\fR argument that was passed to \fBTk_GetCursor\fR to create the cursor. If \fIcursor\fR was created by a call to \fBTk_GetCursorFromData\fR, or by any other mechanism, then the return value is a hexadecimal string giving the X identifier for the cursor. Note: the string returned by \fBTk_NameOfCursor\fR is only guaranteed to persist until the next call to \fBTk_NameOfCursor\fR. Also, this call is not portable except for cursors returned by \fBTk_GetCursor\fR. .PP When a cursor returned by \fBTk_GetCursor\fR or \fBTk_GetCursorFromData\fR is no longer needed, \fBTk_FreeCursor\fR should be called to release it. There should be exactly one call to \fBTk_FreeCursor\fR for each call to \fBTk_GetCursor\fR or \fBTk_GetCursorFromData\fR. When a cursor is no longer in use anywhere (i.e. it has been freed as many times as it has been gotten) \fBTk_FreeCursor\fR will release it to the X server and remove it from the database. .SH BUGS In determining whether an existing cursor can be used to satisfy a new request, \fBTk_GetCursor\fR and \fBTk_GetCursorFromData\fR consider only the immediate values of their arguments. For example, when a file name is passed to \fBTk_GetCursor\fR, \fBTk_GetCursor\fR will assume it is safe to re-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, \fBTk_GetCursorFromData\fR assumes that if the same \fIsource\fR 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. .SH KEYWORDS cursor