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'\" Copyright (c) 1994 The Regents of the University of California.

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

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

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.so man.macros

.TH Tk_GetImage 3 4.0 Tk "Tk Library Procedures"

.BS

.SH NAME

Tk_GetImage, Tk_RedrawImage, Tk_SizeOfImage, Tk_FreeImage \- use an image in a widget

.SH SYNOPSIS

.nf

\fB#include \fR

.sp

Tk_Image

\fBTk_GetImage\fR(\fIinterp, tkwin, name, changeProc, clientData\fR)

.sp

\fBTk_RedrawImage\fR(\fIimage, imageX, imageY, width, height, drawable, drawableX, drawableY\fR)

.sp

\fBTk_SizeOfImage\fR(\fIimage, widthPtr, heightPtr\fR)

.sp

\fBTk_FreeImage\fR(\fIimage\fR)

.SH ARGUMENTS

.AS Tk_ImageChangedProc *changeProc

.AP Tcl_Interp *interp in

Place to leave error message.

.AP Tk_Window tkwin in

Window in which image will be used.

.AP char *name in

Name of image.

.AP Tk_ImageChangedProc *changeProc in

Procedure for Tk to invoke whenever image content or size changes.

.AP ClientData clientData in

One-word value for Tk to pass to \fIchangeProc\fR.

.AP Tk_Image image in

Token for image instance;  must have been returned by a previous

call to \fBTk_GetImage\fR.

.AP int imageX in

X-coordinate of upper-left corner of region of image to redisplay

(measured in pixels from the image's upper-left corner).

.AP int imageY in

Y-coordinate of upper-left corner of region of image to redisplay

(measured in pixels from the image's upper-left corner).

.AP "int" width (in)

Width of region of image to redisplay.

.AP "int" height (in)

Height of region of image to redisplay.

.AP Drawable drawable in

Where to display image.  Must either be window specified to

\fBTk_GetImage\fR or a pixmap compatible with that window.

.AP int drawableX in

Where to display image in \fIdrawable\fR: this is the x-coordinate

in \fIdrawable\fR where x-coordinate \fIimageX\fR of the image

should be displayed.

.AP int drawableY in

Where to display image in \fIdrawable\fR: this is the y-coordinate

in \fIdrawable\fR where y-coordinate \fIimageY\fR of the image

should be displayed.

.AP "int" widthPtr out

Store width of \fIimage\fR (in pixels) here.

.AP "int" heightPtr out

Store height of \fIimage\fR (in pixels) here.

.BE

.SH DESCRIPTION

.PP

These procedures are invoked by widgets that wish to display images.

\fBTk_GetImage\fR is invoked by a widget when it first decides to

display an image.

\fIname\fR gives the name of the desired image and \fItkwin\fR

identifies the window where the image will be displayed.

\fBTk_GetImage\fR looks up the image in the table of existing

images and returns a token for a new instance of the image.

If the image doesn't exist then \fBTk_GetImage\fR returns NULL

and leaves an error message in \fIinterp->result\fR.

.PP

When a widget wishes to actually display an image it must

call \fBTk_RedrawWidget\fR, identifying the image (\fIimage\fR),

a region within the image to redisplay (\fIimageX\fR, \fIimageY\fR,

\fIwidth\fR, and \fIheight\fR), and a place to display the

image (\fIdrawable\fR, \fIdrawableX\fR, and \fIdrawableY\fR).

Tk will then invoke the appropriate image manager, which will

display the requested portion of the image before returning.

.PP

A widget can find out the dimensions of an image by calling

\fBTk_SizeOfImage\fR:  the width and height will be stored

in the locations given by \fIwidthPtr\fR and \fIheightPtr\fR,

respectively.

.PP

When a widget is finished with an image (e.g., the widget is

being deleted or it is going to use a different image instead

of the current one), it must call \fBTk_FreeImage\fR to

release the image instance.

The widget should never again use the image token after passing

it to \fBTk_FreeImage\fR.

There must be exactly one call to \fBTk_FreeImage\fR for each

call to \fBTk_GetImage\fR.

.PP

If the contents or size of an image changes, then any widgets

using the image will need to find out about the changes so that

they can redisplay themselves.

The \fIchangeProc\fR and \fIclientData\fR arguments to

\fBTk_GetImage\fR are used for this purpose.

\fIchangeProc\fR will be called by Tk whenever a change occurs

in the image;  it must match the following prototype:

.CS

typedef void Tk_ImageChangedProc(

        ClientData \fIclientData\fR,

        int \fIx\fR,

        int \fIy\fR,

        int \fIwidth\fR,

        int \fIheight\fR,

        int \fIimageWidth\fR,

        int \fIimageHeight\fR);

.CE

The \fIclientData\fR argument to \fIchangeProc\fR is the same as the

\fIclientData\fR argument to \fBTk_GetImage\fR.

It is usually a pointer to the widget record for the widget or

some other data structure managed by the widget.

The arguments \fIx\fR, \fIy\fR, \fIwidth\fR, and \fIheight\fR

identify a region within the image that must be redisplayed;

they are specified in pixels measured from the upper-left

corner of the image.

The arguments \fIimageWidth\fR and \fIimageHeight\fR give

the image's (new) size.

.SH "SEE ALSO"

Tk_CreateImageType

.SH KEYWORDS

images, redisplay