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Manual Pages for UNIX Operating System command usage for man Tk_AllocCursorFromObj

Tk Library Procedures Tk_AllocCursorFromObj(3TK)

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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_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) ||

Tk_Cursor. |

char *name (in) || Same as objPtr except | description of cursor | is passed as a string | and resulting |

Tk_Cursor isn't |

Tk Last change: 8.1 1

Tk Library Procedures Tk_AllocCursorFromObj(3TK)

cached.

CONST char *source (in) Data for cursor cur-

sor, in standard cur-

sor 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 cur-

sor 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 identifier for a cursor |

corresponding to the description. It re-uses an existing |

Tk Last change: 8.1 2

Tk Library Procedures Tk_AllocCursorFromObj(3TK)

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_GetCursorFromObj. 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 | isn't 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 illustra-

tions showing what each of these cursors looks like. If fgColor and bgColor are both specified, they give the foreground 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 cur-

sor will use black for its foreground color and white for its background color.

The Macintosh version of Tk supports all of the X cur-

sors and will also accept any of the standard Mac cur-

sors 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 of the resource. The appli-

cation 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 cursor'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 comput-

ers. Tk Last change: 8.1 3

Tk Library Procedures Tk_AllocCursorFromObj(3TK)

@sourceName

This form only works on Windows, and will load a Win-

dows system cursor (.ani or .cur) from the file speci-

fied in sourceName.

Tk_GetCursor is identical to Tk_AllocCursorFromObj except |

that the description of the cursor is specified with a |

string instead of an object. This prevents Tk_GetCursor |

from caching the return value, so Tk_GetCursor is less effi- |

cient than Tk_AllocCursorFromObj. |

Tk_GetCursorFromObj returns the token for an existing cur- |

sor, given the window and description used to create the |

cursor. Tk_GetCursorFromObj doesn't 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 loca-

tion 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 argu-

ments 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 mes-

sage 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_GetCursorFromData

will return an existing cursor rather than creating a new

one. This approach can substantially reduce server over-

head, so the Tk procedures should generally be used in Tk Last change: 8.1 4

Tk Library Procedures Tk_AllocCursorFromObj(3TK)

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 mechanism, 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_NameOfCursor. 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_FreeCursorFromObj the cursor to release |

is specified with the same information used to create it; |

for Tk_FreeCursor 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_AllocCursorFromObj, 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 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 caus-

ing 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

ATTRIBUTES

See attributes(5) for descriptions of the following attri-

butes: Tk Last change: 8.1 5

Tk Library Procedures Tk_AllocCursorFromObj(3TK)

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| ATTRIBUTE TYPE | ATTRIBUTE VALUE|

|____________________|__________________|_

| Availability | runtime/tk-8 |

|____________________|__________________|_

| Interface Stability| Uncommitted |

|____________________|_________________|

NOTES Source for Tk is available on http://opensolaris.org. Tk Last change: 8.1 6