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.so man.macros

.TH Tk_CreateItemType 3 4.0 Tk "Tk Library Procedures"

.BS

.SH NAME

Tk_CreateItemType, Tk_GetItemTypes \- define new kind of canvas item

.SH SYNOPSIS

.nf

\fB#include \fR

.sp

\fBTk_CreateItemType\fR(\fItypePtr\fR)

.sp

Tk_ItemType *

\fBTk_GetItemTypes\fR()

.SH ARGUMENTS

.AS Tk_ItemType *typePtr

.AP Tk_ItemType *typePtr in

Structure that defines the new type of canvas item.

.BE

.SH INTRODUCTION

.PP

\fBTk_CreateItemType\fR is invoked to define a new kind of canvas item

described by the \fItypePtr\fR argument.

An item type corresponds to a particular value of the \fItype\fR

argument to the \fBcreate\fR widget command for canvases, and

the code that implements a canvas item type is called a \fItype manager\fR.

Tk defines several built-in item types, such as \fBrectangle\fR

and \fBtext\fR and \fBimage\fR, but \fBTk_CreateItemType\fR

allows additional item types to be defined.

Once \fBTk_CreateItemType\fR returns, the new item type may be used

in new or existing canvas widgets just like the built-in item

types.

.PP

\fBTk_GetItemTypes\fR returns a pointer to the first in the list

of all item types currently defined for canvases.

The entries in the list are linked together through their

\fInextPtr\fR fields, with the end of the list marked by a

NULL \fInextPtr\fR.

.PP

You may find it easier to understand the rest of this manual entry

by looking at the code for an existing canvas item type such as

bitmap (file tkCanvBmap.c) or text (tkCanvText.c).

The easiest way to create a new type manager is to copy the code

for an existing type and modify it for the new type.

.PP

Tk provides a number of utility procedures for the use of canvas

type managers, such as \fBTk_CanvasCoords\fR and \fBTk_CanvasPsColor\fR;

these are described in separate manual entries.

.SH "DATA STRUCTURES"

.PP

A type manager consists of a collection of procedures that provide a

standard set of operations on items of that type.

The type manager deals with three kinds of data

structures.

The first data structure is a Tk_ItemType; it contains

information such as the name of the type and pointers to

the standard procedures implemented by the type manager:

.CS

typedef struct Tk_ItemType {

        char *\fIname\fR;

        int \fIitemSize\fR;

        Tk_ItemCreateProc *\fIcreateProc\fR;

        Tk_ConfigSpec *\fIconfigSpecs\fR;

        Tk_ItemConfigureProc *\fIconfigProc\fR;

        Tk_ItemCoordProc *\fIcoordProc\fR;

        Tk_ItemDeleteProc *\fIdeleteProc\fR;

        Tk_ItemDisplayProc *\fIdisplayProc\fR;

        int \fIalwaysRedraw\fR;

        Tk_ItemPointProc *\fIpointProc\fR;

        Tk_ItemAreaProc *\fIareaProc\fR;

        Tk_ItemPostscriptProc *\fIpostscriptProc\fR;

        Tk_ItemScaleProc *\fIscaleProc\fR;

        Tk_ItemTranslateProc *\fItranslateProc\fR;

        Tk_ItemIndexProc *\fIindexProc\fR;

        Tk_ItemCursorProc *\fIicursorProc\fR;

        Tk_ItemSelectionProc *\fIselectionProc\fR;

        Tk_ItemInsertProc *\fIinsertProc\fR;

        Tk_ItemDCharsProc *\fIdCharsProc\fR;

        Tk_ItemType *\fInextPtr\fR;

} Tk_ItemType;

.CE

.PP

The fields of a Tk_ItemType structure are described in more detail

later in this manual entry.

When \fBTk_CreateItemType\fR is called, its \fItypePtr\fR

argument must point to a structure with all of the fields initialized

except \fInextPtr\fR, which Tk sets to link all the types together

into a list.

The structure must be in permanent memory (either statically

allocated or dynamically allocated but never freed);  Tk retains

a pointer to this structure.

.PP

The second data structure manipulated by a type manager is an

\fIitem record\fR.

For each item in a canvas there exists one item record.

All of the items of a given type generally have item records with

the same structure, but different types usually have different

formats for their item records.

The first part of each item record is a header with a standard structure

defined by Tk via the type Tk_Item;  the rest of the item

record is defined by the type manager.

A type manager must define its item records with a Tk_Item as

the first field.

For example, the item record for bitmap items is defined as follows:

.CS

typedef struct BitmapItem {

        Tk_Item \fIheader\fR;

        double \fIx\fR, \fIy\fR;

        Tk_Anchor \fIanchor\fR;

        Pixmap \fIbitmap\fR;

        XColor *\fIfgColor\fR;

        XColor *\fIbgColor\fR;

        GC \fIgc\fR;

} BitmapItem;

.CE

The \fIheader\fR substructure contains information used by Tk

to manage the item, such as its identifier, its tags, its type,

and its bounding box.

The fields starting with \fIx\fR belong to the type manager:

Tk will never read or write them.

The type manager should not need to read or write any of the

fields in the header except for four fields

whose names are \fIx1\fR, \fIy1\fR, \fIx2\fR, and \fIy2\fR.

These fields give a bounding box for the items using integer

canvas coordinates:  the item should not cover any pixels

with x-coordinate lower than \fIx1\fR or y-coordinate

lower than \fIy1\fR, nor should it cover any pixels with

x-coordinate greater than or equal to \fIx2\fR or y-coordinate

greater than or equal to \fIy2\fR.

It is up to the type manager to keep the bounding box up to

date as the item is moved and reconfigured.

.PP

Whenever Tk calls a procedure in a type manager it passes in a pointer

to an item record.

The argument is always passed as a pointer to a Tk_Item;  the type

manager will typically cast this into a pointer to its own specific

type, such as BitmapItem.

.PP

The third data structure used by type managers has type

Tk_Canvas;  it serves as an opaque handle for the canvas widget

as a whole.

Type managers need not know anything about the contents of this

structure.

A Tk_Canvas handle is typically passed in to the

procedures of a type manager, and the type manager can pass the

handle back to library procedures such as Tk_CanvasTkwin

to fetch information about the canvas.

.SH NAME

.PP

This section and the ones that follow describe each of the fields

in a Tk_ItemType structure in detail.

The \fIname\fR field provides a string name for the item type.

Once \fBTk_CreateImageType\fR returns, this name may be used

in \fBcreate\fR widget commands to create items of the new

type.

If there already existed an item type by this name then

the new item type replaces the old one.

.SH ITEMSIZE

\fItypePtr->itemSize\fR gives the size in bytes of item records

of this type, including the Tk_Item header.

Tk uses this size to allocate memory space for items of the type.

All of the item records for a given type must have the same size.

If variable length fields are needed for an item (such as a list

of points for a polygon), the type manager can allocate a separate

object of variable length and keep a pointer to it in the item record.

.SH CREATEPROC

.PP

\fItypePtr->createProc\fR points to a procedure for

Tk to call whenever a new item of this type is created.

\fItypePtr->createProc\fR must match the following prototype:

.CS

typedef int Tk_ItemCreateProc(

        Tcl_Interp *\fIinterp\fR,

        Tk_Canvas \fIcanvas\fR,

        Tk_Item *\fIitemPtr\fR,

        int \fIargc\fR,

        char **\fIargv\fR);

.CE

The \fIinterp\fR argument is the interpreter in which the canvas's

\fBcreate\fR widget command was invoked, and \fIcanvas\fR is a

handle for the canvas widget.

\fIitemPtr\fR is a pointer to a newly-allocated item of

size \fItypePtr->itemSize\fR.

Tk has already initialized the item's header (the first

\fBsizeof(Tk_ItemType)\fR bytes).

The \fIargc\fR and \fIargv\fR arguments describe all of the

arguments to the \fBcreate\fR command after the \fItype\fR

argument.

For example, in the widget command

.CS

\fB\&.c create rectangle 10 20 50 50 \-fill black\fR

.CE

\fIargc\fR will be \fB6\fR and \fIargv\fR[0] will contain the

string \fB10\fR.

.PP

\fIcreateProc\fR should use \fIargc\fR and \fIargv\fR to initialize

the type-specific parts of the item record and set an initial value

for the bounding box in the item's header.

It should return a standard Tcl completion code and leave an

error message in \fIinterp->result\fR if an error occurs.

If an error occurs Tk will free the item record, so \fIcreateProc\fR

must be sure to leave the item record in a clean state if it returns an error

(e.g., it must free any additional memory that it allocated for

the item).

.SH CONFIGSPECS

.PP

Each type manager must provide a standard table describing its

configuration options, in a form suitable for use with

\fBTk_ConfigureWidget\fR.

This table will normally be used by \fItypePtr->createProc\fR

and \fItypePtr->configProc\fR, but Tk also uses it directly

to retrieve option information in the \fBitemcget\fR and

\fBitemconfigure\fR widget commands.

\fItypePtr->configSpecs\fR must point to the configuration table

for this type.

Note: Tk provides a custom option type \fBtk_CanvasTagsOption\fR

for implementing the \fB\-tags\fR option;  see an existing type

manager for an example of how to use it in \fIconfigSpecs\fR.

.SH CONFIGPROC

.PP

\fItypePtr->configProc\fR is called by Tk whenever the

\fBitemconfigure\fR widget command is invoked to change the

configuration options for a canvas item.

This procedure must match the following prototype:

.CS

typedef int Tk_ItemConfigureProc(

        Tcl_Interp *\fIinterp\fR,

        Tk_Canvas \fIcanvas\fR,

        Tk_Item *\fIitemPtr\fR,

        int \fIargc\fR,

        char **\fIargv\fR,

        int \fIflags\fR);

.CE

The \fIinterp\fR argument identifies the interpreter in which the

widget command was invoked,  \fIcanvas\fR is a handle for the canvas

widget, and \fIitemPtr\fR is a pointer to the item being configured.

\fIargc\fR and \fIargv\fR contain the configuration options.  For

example, if the following command is invoked:

.CS

\fB\&.c itemconfigure 2 \-fill red \-outline black\fR

.CE

\fIargc\fR is \fB4\fR and \fIargv\fR contains the strings \fB\-fill\fR

through \fBblack\fR.

\fIargc\fR will always be an even value.

The  \fIflags\fR argument contains flags to pass to \fBTk_ConfigureWidget\fR;

currently this value is always TK_CONFIG_ARGV_ONLY when Tk

invokes \fItypePtr->configProc\fR, but the type manager's \fIcreateProc\fR

procedure will usually invoke \fIconfigProc\fR with different flag values.

.PP

\fItypePtr->configProc\fR returns a standard Tcl completion code and

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

It must update the item's bounding box to reflect the new configuration

options.

.SH COORDPROC

.PP

\fItypePtr->coordProc\fR is invoked by Tk to implement the \fBcoords\fR

widget command for an item.

It must match the following prototype:

.CS

typedef int Tk_ItemCoordProc(

        Tcl_Interp *\fIinterp\fR,

        Tk_Canvas \fIcanvas\fR,

        Tk_Item *\fIitemPtr\fR,

        int \fIargc\fR,

        char **\fIargv\fR);

.CE

The arguments \fIinterp\fR, \fIcanvas\fR, and \fIitemPtr\fR

all have the standard meanings, and \fIargc\fR and \fIargv\fR

describe the coordinate arguments.

For example, if the following widget command is invoked:

.CS

\fB\&.c coords 2 30 90\fR

.CE

\fIargc\fR will be \fB2\fR and \fBargv\fR will contain the string values

\fB30\fR and \fB90\fR.

.PP

The \fIcoordProc\fR procedure should process the new coordinates,

update the item appropriately (e.g., it must reset the bounding

box in the item's header), and return a standard Tcl completion

code.

If an error occurs, \fIcoordProc\fR must leave an error message in

\fIinterp->result\fR.

.SH DELETEPROC

.PP

\fItypePtr->deleteProc\fR is invoked by Tk to delete an item

and free any resources allocated to it.

It must match the following prototype:

.CS

typedef void Tk_ItemDeleteProc(

        Tk_Canvas \fIcanvas\fR,

        Tk_Item *\fIitemPtr\fR,

        Display *\fIdisplay\fR);

.CE

The \fIcanvas\fR and \fIitemPtr\fR arguments have the usual

interpretations, and \fIdisplay\fR identifies the X display containing

the canvas.

\fIdeleteProc\fR must free up any resources allocated for the item,

so that Tk can free the item record.

\fIdeleteProc\fR should not actually free the item record;  this will

be done by Tk when \fIdeleteProc\fR returns.

.SH "DISPLAYPROC AND ALWAYSREDRAW"

.PP

\fItypePtr->displayProc\fR is invoked by Tk to redraw an item

on the screen.

It must match the following prototype:

.CS

typedef void Tk_ItemDisplayProc(

        Tk_Canvas \fIcanvas\fR,

        Tk_Item *\fIitemPtr\fR,

        Display *\fIdisplay\fR,

        Drawable \fIdst\fR,

        int \fIx\fR,

        int \fIy\fR,

        int \fIwidth\fR,

        int \fIheight\fR);

.CE

The \fIcanvas\fR and \fIitemPtr\fR arguments have the usual meaning.

\fIdisplay\fR identifies the display containing the canvas, and

\fIdst\fR specifies a drawable in which the item should be rendered;

typically this is an off-screen pixmap, which Tk will copy into

the canvas's window once all relevant items have been drawn.

\fIx\fR, \fIy\fR, \fIwidth\fR, and \fIheight\fR specify a rectangular

region in canvas coordinates, which is the area to be redrawn;

only information that overlaps this area needs to be redrawn.

Tk will not call \fIdisplayProc\fR unless the item's bounding box

overlaps the redraw area, but the type manager may wish to use

the redraw area to optimize the redisplay of the item.

.PP

Because of scrolling and the use of off-screen pixmaps for

double-buffered redisplay, the item's coordinates in \fIdst\fR

will not necessarily be the same as those in the canvas.

\fIdisplayProc\fR should call \fBTk_CanvasDrawableCoords\fR

to transform coordinates from those of the canvas to those

of \fIdst\fR.

.PP

Normally an item's \fIdisplayProc\fR is only invoked if the item

overlaps the area being displayed.

However, if \fItypePtr->alwaysRedraw\fR has a non-zero value, then

\fIdisplayProc\fR is invoked during every redisplay operation,

even if the item doesn't overlap the area of redisplay.

\fIalwaysRedraw\fR should normally be set to 0;  it is only

set to 1 in special cases such as window items that need to be

unmapped when they are off-screen.

.SH POINTPROC

.PP

\fItypePtr->pointProc\fR is invoked by Tk to find out how close

a given point is to a canvas item.

Tk uses this procedure for purposes such as locating the item

under the mouse or finding the closest item to a given point.

The procedure must match the following prototype:

.CS

typedef double Tk_ItemPointProc(

        Tk_Canvas \fIcanvas\fR,

        Tk_Item *\fIitemPtr\fR,

        double *\fIpointPtr\fR);

.CE

\fIcanvas\fR and \fIitemPtr\fR have the usual meaning.

\fIpointPtr\fR points to an array of two numbers giving

the x and y coordinates of a point.

\fIpointProc\fR must return a real value giving the distance

from the point to the item, or 0 if the point lies inside

the item.

.SH AREAPROC

.PP

\fItypePtr->areaProc\fR is invoked by Tk to find out the relationship

between an item and a rectangular area.

It must match the following prototype:

.CS

typedef int Tk_ItemAreaProc(

        Tk_Canvas \fIcanvas\fR,

        Tk_Item *\fIitemPtr\fR,

        double *\fIrectPtr\fR);

.CE

\fIcanvas\fR and \fIitemPtr\fR have the usual meaning.

\fIrectPtr\fR points to an array of four real numbers;

the first two give the x and y coordinates of the upper left

corner of a rectangle, and the second two give the x and y

coordinates of the lower right corner.

\fIareaProc\fR must return \-1 if the item lies entirely outside

the given area, 0 if it lies partially inside and partially

outside the area, and 1 if it lies entirely inside the area.

.SH POSTSCRIPTPROC

.PP

\fItypePtr->postscriptProc\fR is invoked by Tk to generate

Postcript for an item during the \fBpostscript\fR widget command.

If the type manager is not capable of generating Postscript then

\fItypePtr->postscriptProc\fR should be NULL.

The procedure must match the following prototype:

.CS

typedef int Tk_ItemPostscriptProc(

        Tcl_Interp *\fIinterp\fR,

        Tk_Canvas \fIcanvas\fR,

        Tk_Item *\fIitemPtr\fR,

        int \fIprepass\fR);

.CE

The \fIinterp\fR, \fIcanvas\fR, and \fIitemPtr\fR arguments all have

standard meanings;  \fIprepass\fR will be described below.

If \fIpostscriptProc\fR completes successfully, it should append

Postscript for the item to the information in \fIinterp->result\fR

(e.g. by calling \fBTcl_AppendResult\fR, not \fBTcl_SetResult\fR)

and return TCL_OK.

If an error occurs, \fIpostscriptProc\fR should clear the result

and replace its contents with an error message;  then it should

return TCL_ERROR.

.PP

Tk provides a collection of utility procedures to simplify

\fIpostscriptProc\fR.

For example, \fBTk_CanvasPsColor\fR will generate Postscript to set

the current color to a given Tk color and \fBTk_CanvasPsFont\fR will

set up font information.

When generating Postscript, the type manager is free to change the

graphics state of the Postscript interpreter, since Tk places

\fBgsave\fR and \fBgrestore\fR commands around the Postscript for

the item.

The type manager can use canvas x coordinates directly in its Postscript,

but it must call \fBTk_CanvasPsY\fR to convert y coordinates from

the space of the canvas (where the origin is at the

upper left) to the space of Postscript (where the origin is at the

lower left).

.PP

In order to generate Postscript that complies with the Adobe Document

Structuring Conventions, Tk actually generates Postscript in two passes.

It calls each item's \fIpostscriptProc\fR in each pass.

The only purpose of the first pass is to collect font information

(which is done by \fBTk_CanvPsFont\fR);  the actual Postscript is

discarded.

Tk sets the \fIprepass\fR argument to \fIpostscriptProc\fR to 1

during the first pass;  the type manager can use \fIprepass\fR to skip

all Postscript generation except for calls to \fBTk_CanvasPsFont\fR.

During the second pass \fIprepass\fR will be 0, so the type manager

must generate complete Postscript.

.SH SCALEPROC

\fItypePtr->scaleProc\fR is invoked by Tk to rescale a canvas item

during the \fBscale\fR widget command.

The procedure must match the following prototype:

.CS

typedef void Tk_ItemScaleProc(

        Tk_Canvas \fIcanvas\fR,

        Tk_Item *\fIitemPtr\fR,

        double \fIoriginX\fR,

        double \fIoriginY\fR,

        double \fIscaleX\fR,

        double \fIscaleY\fR);

.CE

The \fIcanvas\fR and \fIitemPtr\fR arguments have the usual meaning.

\fIoriginX\fR and \fIoriginY\fR specify an origin relative to which

the item is to be scaled, and \fIscaleX\fR and \fIscaleY\fR give the

x and y scale factors.

The item should adjust its coordinates so that a point in the item

that used to have coordinates \fIx\fR and \fIy\fR will have new

coordinates \fIx'\fR and \fIy'\fR, where

.CS

\fIx' = originX  + scaleX*(x-originX)

y' = originY + scaleY*(y-originY)\fR

.CE

\fIscaleProc\fR must also update the bounding box in the item's

header.

.SH TRANSLATEPROC

\fItypePtr->translateProc\fR is invoked by Tk to translate a canvas item

during the \fBmove\fR widget command.

The procedure must match the following prototype:

.CS

typedef void Tk_ItemTranslateProc(

        Tk_Canvas \fIcanvas\fR,

        Tk_Item *\fIitemPtr\fR,

        double \fIdeltaX\fR,

        double \fIdeltaY\fR);

.CE

The \fIcanvas\fR and \fIitemPtr\fR arguments have the usual meaning,

and \fIdeltaX\fR and \fIdeltaY\fR give the amounts that should be

added to each x and y coordinate within the item.

The type manager should adjust the item's coordinates and

update the bounding box in the item's header.

.SH INDEXPROC

\fItypePtr->indexProc\fR is invoked by Tk to translate a string

index specification into a numerical index, for example during the

\fBindex\fR widget command.

It is only relevant for item types that support indexable text;

\fItypePtr->indexProc\fR may be specified as NULL for non-textual

item types.

The procedure must match the following prototype:

.CS

typedef int Tk_ItemIndexProc(

        Tcl_Interp *\fIinterp\fR,

        Tk_Canvas \fIcanvas\fR,

        Tk_Item *\fIitemPtr\fR,

        char \fIindexString\fR,

        int *\fIindexPtr\fR);

.CE

The \fIinterp\fR, \fIcanvas\fR, and \fIitemPtr\fR arguments all

have the usual meaning.

\fIindexString\fR contains a textual description of an index,

and \fIindexPtr\fR points to an integer value that should be

filled in with a numerical index.

It is up to the type manager to decide what forms of index

are supported (e.g., numbers, \fBinsert\fR,  \fBsel.first\fR,

\fBend\fR, etc.).

\fIindexProc\fR should return a Tcl completion code and set

\fIinterp->result\fR in the event of an error.

.SH ICURSORPROC

.PP

\fItypePtr->icursorProc\fR is invoked by Tk during

the \fBicursor\fR widget command to set the position of the

insertion cursor in a textual item.

It is only relevant for item types that support an insertion cursor;

\fItypePtr->icursorProc\fR may be specified as NULL for item types

that don't support an insertion cursor.

The procedure must match the following prototype:

.CS

typedef void Tk_ItemIndexProc(

        Tk_Canvas \fIcanvas\fR,

        Tk_Item *\fIitemPtr\fR,

        int \fIindex\fR);

.CE

\fIcanvas\fR and \fIitemPtr\fR have the usual meanings, and

\fIindex\fR is an index into the item's text, as returned by a

previous call to \fItypePtr->insertProc\fR.

The type manager should position the insertion cursor in the

item just before the character given by \fIindex\fR.

Whether or not to actually display the insertion cursor is

determined by other information provided by \fBTk_CanvasGetTextInfo\fR.

.SH SELECTIONPROC

.PP

\fItypePtr->selectionProc\fR is invoked by Tk during selection

retrievals;  it must return part or all of the selected text in

the item (if any).

It is only relevant for item types that support text;

\fItypePtr->selectionProc\fR may be specified as NULL for non-textual

item types.

The procedure must match the following prototype:

.CS

typedef int Tk_ItemSelectionProc(

        Tk_Canvas \fIcanvas\fR,

        Tk_Item *\fIitemPtr\fR,

        int \fIoffset\fR,

        char *\fIbuffer\fR,

        int \fImaxBytes\fR);

.CE

\fIcanvas\fR and \fIitemPtr\fR have the usual meanings.

\fIoffset\fR is an offset in bytes into the selection where 0 refers

to the first byte of the selection;  it identifies

the first character that is to be returned in this call.

\fIbuffer\fR points to an area of memory in which to store the

requested bytes, and \fImaxBytes\fR specifies the maximum number

of bytes to return.

\fIselectionProc\fR should extract up to \fImaxBytes\fR characters

from the selection and copy them to \fImaxBytes\fR;  it should

return a count of the number of bytes actually copied, which may

be less than \fImaxBytes\fR if there aren't \fIoffset+maxBytes\fR bytes

in the selection.

.SH INSERTPROC

.PP

\fItypePtr->insertProc\fR is invoked by Tk during

the \fBinsert\fR widget command to insert new text into a

canvas item.

It is only relevant for item types that support text;

\fItypePtr->insertProc\fR may be specified as NULL for non-textual

item types.

The procedure must match the following prototype:

.CS

typedef void Tk_ItemInsertProc(

        Tk_Canvas \fIcanvas\fR,

        Tk_Item *\fIitemPtr\fR,

        int \fIindex\fR,

        char *\fIstring\fR);

.CE

\fIcanvas\fR and \fIitemPtr\fR have the usual meanings.

\fIindex\fR is an index into the item's text, as returned by a

previous call to \fItypePtr->insertProc\fR, and \fIstring\fR

contains new text to insert just before the character given

by \fIindex\fR.

The type manager should insert the text and recompute the bounding

box in the item's header.

.SH DCHARSPROC

.PP

\fItypePtr->dCharsProc\fR is invoked by Tk during the \fBdchars\fR

widget command to delete a range of text from a canvas item.

It is only relevant for item types that support text;

\fItypePtr->dCharsProc\fR may be specified as NULL for non-textual

item types.

The procedure must match the following prototype:

.CS

typedef void Tk_ItemDCharsProc(

        Tk_Canvas \fIcanvas\fR,

        Tk_Item *\fIitemPtr\fR,

        int \fIfirst\fR,

        int \fIlast\fR);

.CE

\fIcanvas\fR and \fIitemPtr\fR have the usual meanings.

\fIfirst\fR and \fIlast\fR give the indices of the first and last bytes

to be deleted, as returned by previous calls to \fItypePtr->indexProc\fR.

The type manager should delete the specified characters and update

the bounding box in the item's header.

.SH "SEE ALSO"

Tk_CanvasPsY, Tk_CanvasTextInfo, Tk_CanvasTkwin

.SH KEYWORDS

canvas, focus, item type, selection, type manager