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'\" Copyright (c) 1990 The Regents of the University of California.

'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.

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'\" RCS: @(#) $Id: GetCursor.3,v 1.1.1.1 2002-01-16 10:25:48 markom Exp $

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.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