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.so man.macros

.TH canvas n 4.0 Tk "Tk Built-In Commands"

.BS

'\" Note:  do not modify the .SH NAME line immediately below!

.SH NAME

canvas \- Create and manipulate canvas widgets

.SH SYNOPSIS

\fBcanvas\fR \fIpathName \fR?\fIoptions\fR?

.SO

\-background    \-highlightthickness    \-insertwidth   \-takefocus

\-borderwidth   \-insertbackground      \-relief        \-xscrollcommand

\-cursor        \-insertborderwidth     \-selectbackground      \-yscrollcommand

\-highlightbackground   \-insertofftime \-selectborderwidth

\-highlightcolor        \-insertontime  \-selectforeground

.SE

.SH "WIDGET-SPECIFIC OPTIONS"

.OP \-closeenough closeEnough CloseEnough

Specifies a floating-point value indicating how close the mouse cursor

must be to an item before it is considered to be ``inside'' the item.

Defaults to 1.0.

.OP \-confine confine Confine

Specifies a boolean value that indicates whether or not it should be

allowable to set the canvas's view outside the region defined by the

\fBscrollRegion\fR argument.

Defaults to true, which means that the view will

be constrained within the scroll region.

.OP \-height height Height

Specifies a desired window height that the canvas widget should request from

its geometry manager.  The value may be specified in any

of the forms described in the COORDINATES section below.

.OP \-scrollregion scrollRegion ScrollRegion

Specifies a list with four coordinates describing the left, top, right, and

bottom coordinates of a rectangular region.

This region is used for scrolling purposes and is considered to be

the boundary of the information in the canvas.

Each of the coordinates may be specified

in any of the forms given in the COORDINATES section below.

.OP \-width width width

Specifies a desired window width that the canvas widget should request from

its geometry manager.  The value may be specified in any

of the forms described in the COORDINATES section below.

.br

.OP \-xscrollincrement xScrollIncrement ScrollIncrement

Specifies an increment for horizontal scrolling, in any of the usual forms

permitted for screen distances.  If the value of this option is greater

than zero, the horizontal view in the window will be constrained so that

the canvas x coordinate at the left edge of the window is always an even

multiple of \fBxScrollIncrement\fR;  furthermore, the units for scrolling

(e.g., the change in view when the left and right arrows of a scrollbar

are selected) will also be \fBxScrollIncrement\fR.  If the value of

this option is less than or equal to zero, then horizontal scrolling

is unconstrained.

.OP \-yscrollincrement yScrollIncrement ScrollIncrement

Specifies an increment for vertical scrolling, in any of the usual forms

permitted for screen distances.  If the value of this option is greater

than zero, the vertical view in the window will be constrained so that

the canvas y coordinate at the top edge of the window is always an even

multiple of \fByScrollIncrement\fR;  furthermore, the units for scrolling

(e.g., the change in view when the top and bottom arrows of a scrollbar

are selected) will also be \fByScrollIncrement\fR.  If the value of

this option is less than or equal to zero, then vertical scrolling

is unconstrained.

.BE

.SH INTRODUCTION

.PP

The \fBcanvas\fR command creates a new window (given

by the \fIpathName\fR argument) and makes it into a canvas widget.

Additional options, described above, may be specified on the

command line or in the option database

to configure aspects of the canvas such as its colors and 3-D relief.

The \fBcanvas\fR command returns its

\fIpathName\fR argument.  At the time this command is invoked,

there must not exist a window named \fIpathName\fR, but

\fIpathName\fR's parent must exist.

.PP

Canvas widgets implement structured graphics.

A canvas displays any number of \fIitems\fR, which may be things like

rectangles, circles, lines, and text.

Items may be manipulated (e.g. moved or re-colored) and commands may

be associated with items in much the same way that the \fBbind\fR

command allows commands to be bound to widgets.  For example,

a particular command may be associated with the  event

so that the command is invoked whenever button 1 is pressed with

the mouse cursor over an item.

This means that items in a canvas can have behaviors defined by

the Tcl scripts bound to them.

.SH "DISPLAY LIST"

.PP

The items in a canvas are ordered for purposes of display,

with the first item in the display list being displayed

first, followed by the next item in the list, and so on.

Items later in the display list obscure those that are

earlier in the display list and are sometimes referred to

as being ``on top'' of earlier items.

When a new item is created it is placed at the end of the

display list, on top of everything else.

Widget commands may be used to re-arrange the order of the

display list.

.PP

Window items are an exception to the above rules.  The underlying

window systems require them always to be drawn on top of other items.

In addition, the stacking order of window items

is not affected by any of the canvas widget commands; you must use

the \fBraise\fR and \fBlower\fR Tk commands instead.

.SH "ITEM IDS AND TAGS"

.PP

Items in a canvas widget may be named in either of two ways:

by id or by tag.

Each item has a unique identifying number which is assigned to

that item when it is created.  The id of an item never changes

and id numbers are never re-used within the lifetime of a

canvas widget.

.PP

Each item may also have any number of \fItags\fR associated

with it.  A tag is just a string of characters, and it may

take any form except that of an integer.

For example, ``x123'' is OK but ``123'' isn't.

The same tag may be associated with many different items.

This is commonly done to group items in various interesting

ways;  for example, all selected items might be given the

tag ``selected''.

.PP

The tag \fBall\fR is implicitly associated with every item

in the canvas;  it may be used to invoke operations on

all the items in the canvas.

.PP

The tag \fBcurrent\fR is managed automatically by Tk;

it applies to the \fIcurrent item\fR, which is the

topmost item whose drawn area covers the position of

the mouse cursor.

If the mouse is not in the canvas widget or is not over

an item, then no item has the \fBcurrent\fR tag.

.PP

When specifying items in canvas widget commands, if the

specifier is an integer then it is assumed to refer to

the single item with that id.

If the specifier is not an integer, then it is assumed to

refer to all of the items in the canvas that have a tag

matching the specifier.

The symbol \fItagOrId\fR is used below to indicate that

an argument specifies either an id that selects a single

item or a tag that selects zero or more items.

Some widget commands only operate on a single item at a

time;  if \fItagOrId\fR is specified in a way that

names multiple items, then the normal behavior is for

the command to use the first (lowest) of these items in

the display list that is suitable for the command.

Exceptions are noted in the widget command descriptions

below.

.SH "COORDINATES"

.PP

All coordinates related to canvases are stored as floating-point

numbers.

Coordinates and distances are specified in screen units,

which are floating-point numbers optionally followed

by one of several letters.

If no letter is supplied then the distance is in pixels.

If the letter is \fBm\fR then the distance is in millimeters on

the screen;  if it is \fBc\fR then the distance is in centimeters;

\fBi\fR means inches, and \fBp\fR means printers points (1/72 inch).

Larger y-coordinates refer to points lower on the screen;  larger

x-coordinates refer to points farther to the right.

.SH TRANSFORMATIONS

.PP

Normally the origin of the canvas coordinate system is at the

upper-left corner of the window containing the canvas.

It is possible to adjust the origin of the canvas

coordinate system relative to the origin of the window using the

\fBxview\fR and \fByview\fR widget commands;  this is typically used

for scrolling.

Canvases do not support scaling or rotation of the canvas coordinate

system relative to the window coordinate system.

.PP

Individual items may be moved or scaled using widget commands

described below, but they may not be rotated.

.SH "INDICES"

.PP

Text items support the notion of an \fIindex\fR for identifying

particular positions within the item.

Indices are used for commands such as inserting text, deleting

a range of characters, and setting the insertion cursor position.

An index may be specified in any of a number of ways, and

different types of items may support different forms for

specifying indices.

Text items support the following forms for an index;  if you

define new types of text-like items, it would be advisable to

support as many of these forms as practical.

Note that it is possible to refer to the character just after

the last one in the text item;  this is necessary for such

tasks as inserting new text at the end of the item.

.TP 10

\fInumber\fR

A decimal number giving the position of the desired character

within the text item.

so on.

A number less than 0 is treated as if it were zero, and a

number greater than the length of the text item is treated

as if it were equal to the length of the text item.

.TP 10

\fBend\fR

Refers to the character just after the last one in the item

(same as the number of characters in the item).

.TP 10

\fBinsert\fR

Refers to the character just before which the insertion cursor

is drawn in this item.

.TP 10

\fBsel.first\fR

Refers to the first selected character in the item.

If the selection isn't in this item then this form is illegal.

.TP 10

\fBsel.last\fR

Refers to the last selected character in the item.

If the selection isn't in this item then this form is illegal.

.TP 10

\fB@\fIx,y\fR

Refers to the character at the point given by \fIx\fR and

\fIy\fR, where \fIx\fR and \fIy\fR are specified in the coordinate

system of the canvas.

If \fIx\fR and \fIy\fR lie outside the coordinates covered by the

text item, then they refer to the first or last character in the

line that is closest to the given point.

.SH "WIDGET COMMAND"

.PP

The \fBcanvas\fR command creates a new Tcl command whose

name is \fIpathName\fR.  This

command may be used to invoke various

operations on the widget.  It has the following general form:

.CS

\fIpathName option \fR?\fIarg arg ...\fR?

.CE

\fIOption\fR and the \fIarg\fRs

determine the exact behavior of the command.

The following widget commands are possible for canvas widgets:

.TP

\fIpathName \fBaddtag \fItag searchSpec \fR?\fIarg arg ...\fR?

For each item that meets the constraints specified by

\fIsearchSpec\fR and the \fIarg\fRs, add

\fItag\fR to the list of tags associated with the item if it

isn't already present on that list.

It is possible that no items will satisfy the constraints

given by \fIsearchSpec\fR and \fIarg\fRs, in which case the

command has no effect.

This command returns an empty string as result.

\fISearchSpec\fR and \fIarg\fR's may take any of the following

forms:

.RS

.TP

\fBabove \fItagOrId\fR

Selects the item just after (above) the one given by \fItagOrId\fR

in the display list.

If \fItagOrId\fR denotes more than one item, then the last (topmost)

of these items in the display list is used.

.TP

\fBall\fR

Selects all the items in the canvas.

.TP

\fBbelow \fItagOrId\fR

Selects the item just before (below) the one given by \fItagOrId\fR

in the display list.

If \fItagOrId\fR denotes more than one item, then the first (lowest)

of these items in the display list is used.

.TP

\fBclosest \fIx y \fR?\fIhalo\fR? ?\fIstart\fR?

Selects the item closest to the point given by \fIx\fR and \fIy\fR.

If more than one item is at the same closest distance (e.g. two

items overlap the point), then the top-most of these items (the

last one in the display list) is used.

If \fIhalo\fR is specified, then it must be a non-negative

value.

Any item closer than \fIhalo\fR to the point is considered to

overlap it.

The \fIstart\fR argument may be used to step circularly through

all the closest items.

If \fIstart\fR is specified, it names an item using a tag or id

(if by tag, it selects the first item in the display list with

the given tag).

Instead of selecting the topmost closest item, this form will

select the topmost closest item that is below \fIstart\fR in

the display list;  if no such item exists, then the selection

behaves as if the \fIstart\fR argument had not been specified.

.TP

\fBenclosed\fR \fIx1\fR \fIy1\fR \fIx2\fR \fIy2\fR

Selects all the items completely enclosed within the rectangular

region given by \fIx1\fR, \fIy1\fR, \fIx2\fR, and \fIy2\fR.

\fIX1\fR must be no greater then \fIx2\fR and \fIy1\fR must be

no greater than \fIy2\fR.

.TP

\fBoverlapping\fR \fIx1\fR \fIy1\fR \fIx2\fR \fIy2\fR

Selects all the items that overlap or are enclosed within the

rectangular region given by \fIx1\fR, \fIy1\fR, \fIx2\fR,

and \fIy2\fR.

\fIX1\fR must be no greater then \fIx2\fR and \fIy1\fR must be

no greater than \fIy2\fR.

.TP

\fBwithtag \fItagOrId\fR

Selects all the items given by \fItagOrId\fR.

.RE

.TP

\fIpathName \fBbbox \fItagOrId\fR ?\fItagOrId tagOrId ...\fR?

Returns a list with four elements giving an approximate bounding box

for all the items named by the \fItagOrId\fR arguments.

The list has the form ``\fIx1 y1 x2 y2\fR'' such that the drawn

areas of all the named elements are within the region bounded by

\fIx1\fR on the left, \fIx2\fR on the right, \fIy1\fR on the top,

and \fIy2\fR on the bottom.

The return value may overestimate the actual bounding box by

a few pixels.

If no items match any of the \fItagOrId\fR arguments or if the

matching items have empty bounding boxes (i.e. they have nothing

to display)

then an empty string is returned.

.TP

\fIpathName \fBbind \fItagOrId\fR ?\fIsequence\fR? ?\fIcommand\fR?

This command associates \fIcommand\fR with all the items given by

\fItagOrId\fR such that whenever the event sequence given by

\fIsequence\fR occurs for one of the items the command will

be invoked.

This widget command is similar to the \fBbind\fR command except that

it operates on items in a canvas rather than entire widgets.

See the \fBbind\fR manual entry for complete details

on the syntax of \fIsequence\fR and the substitutions performed

on \fIcommand\fR before invoking it.

If all arguments are specified then a new binding is created, replacing

any existing binding for the same \fIsequence\fR and \fItagOrId\fR

(if the first character of \fIcommand\fR is ``+'' then \fIcommand\fR

augments an existing binding rather than replacing it).

In this case the return value is an empty string.

If \fIcommand\fR is omitted then the command returns the \fIcommand\fR

associated with \fItagOrId\fR and \fIsequence\fR (an error occurs

if there is no such binding).

If both \fIcommand\fR and \fIsequence\fR are omitted then the command

returns a list of all the sequences for which bindings have been

defined for \fItagOrId\fR.

.RS

.PP

.VS

The only events for which bindings may be specified are those related to

the mouse and keyboard (such as \fBEnter\fR, \fBLeave\fR,

\fBButtonPress\fR, \fBMotion\fR, and \fBKeyPress\fR) or virtual events.

The handling of events in canvases uses the current item defined in ITEM

IDS AND TAGS above.  \fBEnter\fR and \fBLeave\fR events trigger for an

item when it becomes the current item or ceases to be the current item;

note that these events are different than \fBEnter\fR and \fBLeave\fR

events for windows.  Mouse-related events are directed to the current

item, if any.  Keyboard-related events are directed to the focus item, if

any (see the \fBfocus\fR widget command below for more on this).  If a

virtual event is used in a binding, that binding can trigger only if the

virtual event is defined by an underlying mouse-related or

keyboard-related event.

.VE

.PP

It is possible for multiple bindings to match a particular event.

This could occur, for example, if one binding is associated with the

item's id and another is associated with one of the item's tags.

When this occurs, all of the matching bindings are invoked.

A binding associated with the \fBall\fR tag is invoked first,

followed by one binding for each of the item's tags (in order),

followed by a binding associated with the item's id.

If there are multiple matching bindings for a single tag,

then only the most specific binding is invoked.

A \fBcontinue\fR command in a binding script terminates that

script, and a \fBbreak\fR command terminates that script

and skips any remaining scripts for the event, just as for the

\fBbind\fR command.

.PP

If bindings have been created for a canvas window using the \fBbind\fR

command, then they are invoked in addition to bindings created for

the canvas's items using the \fBbind\fR widget command.

The bindings for items will be invoked before any of the bindings

for the window as a whole.

.RE

.TP

\fIpathName \fBcanvasx \fIscreenx\fR ?\fIgridspacing\fR?

Given a window x-coordinate in the canvas \fIscreenx\fR, this command returns

the canvas x-coordinate that is displayed at that location.

If \fIgridspacing\fR is specified, then the canvas coordinate is

rounded to the nearest multiple of \fIgridspacing\fR units.

.TP

\fIpathName \fBcanvasy \fIscreeny\fR ?\fIgridspacing\fR?

Given a window y-coordinate in the canvas \fIscreeny\fR this command returns

the canvas y-coordinate that is displayed at that location.

If \fIgridspacing\fR is specified, then the canvas coordinate is

rounded to the nearest multiple of \fIgridspacing\fR units.

.TP

\fIpathName \fBcget\fR \fIoption\fR

Returns the current value of the configuration option given

by \fIoption\fR.

\fIOption\fR may have any of the values accepted by the \fBcanvas\fR

command.

.TP

\fIpathName \fBconfigure ?\fIoption\fR? ?\fIvalue\fR? ?\fIoption value ...\fR?

Query or modify the configuration options of the widget.

If no \fIoption\fR is specified, returns a list describing all of

the available options for \fIpathName\fR (see \fBTk_ConfigureInfo\fR for

information on the format of this list).  If \fIoption\fR is specified

with no \fIvalue\fR, then the command returns a list describing the

one named option (this list will be identical to the corresponding

sublist of the value returned if no \fIoption\fR is specified).  If

one or more \fIoption\-value\fR pairs are specified, then the command

modifies the given widget option(s) to have the given value(s);  in

this case the command returns an empty string.

\fIOption\fR may have any of the values accepted by the \fBcanvas\fR

command.

.TP

\fIpathName\fR \fBcoords \fItagOrId \fR?\fIx0 y0 ...\fR?

Query or modify the coordinates that define an item.

If no coordinates are specified, this command returns a list

whose elements are the coordinates of the item named by

\fItagOrId\fR.

If coordinates are specified, then they replace the current

coordinates for the named item.

If \fItagOrId\fR refers to multiple items, then

the first one in the display list is used.

.TP

\fIpathName \fBcreate \fItype x y \fR?\fIx y ...\fR? ?\fIoption value ...\fR?

Create a new item in \fIpathName\fR of type \fItype\fR.

The exact format of the arguments after \fBtype\fR depends

on \fBtype\fR, but usually they consist of the coordinates for

one or more points, followed by specifications for zero or

more item options.

See the subsections on individual item types below for more

on the syntax of this command.

This command returns the id for the new item.

.TP

\fIpathName \fBdchars \fItagOrId first \fR?\fIlast\fR?

For each item given by \fItagOrId\fR, delete the characters

in the range given by \fIfirst\fR and \fIlast\fR,

inclusive.

If some of the items given by \fItagOrId\fR don't support

text operations, then they are ignored.

\fIFirst\fR and \fIlast\fR are indices of characters

within the item(s) as described in INDICES above.

If \fIlast\fR is omitted, it defaults to \fIfirst\fR.

This command returns an empty string.

.TP

\fIpathName \fBdelete \fR?\fItagOrId tagOrId ...\fR?

Delete each of the items given by each \fItagOrId\fR, and return

an empty string.

.TP

\fIpathName \fBdtag \fItagOrId \fR?\fItagToDelete\fR?

For each of the items given by \fItagOrId\fR, delete the

tag given by \fItagToDelete\fR from the list of those

associated with the item.

If an item doesn't have the tag \fItagToDelete\fR then

the item is unaffected by the command.

If \fItagToDelete\fR is omitted then it defaults to \fItagOrId\fR.

This command returns an empty string.

.TP

\fIpathName \fBfind \fIsearchCommand \fR?\fIarg arg ...\fR?

This command returns a list consisting of all the items that

meet the constraints specified by \fIsearchCommand\fR and

\fIarg\fR's.

\fISearchCommand\fR and \fIargs\fR have any of the forms

accepted by the \fBaddtag\fR command.

The items are returned in stacking order, with the lowest item first.

.TP

\fIpathName \fBfocus \fR?\fItagOrId\fR?

Set the keyboard focus for the canvas widget to the item given by

\fItagOrId\fR.

If \fItagOrId\fR refers to several items, then the focus is set

to the first such item in the display list that supports the

insertion cursor.

If \fItagOrId\fR doesn't refer to any items, or if none of them

support the insertion cursor, then the focus isn't changed.

If \fItagOrId\fR is an empty

string, then the focus item is reset so that no item has the focus.

If \fItagOrId\fR is not specified then the command returns the

id for the item that currently has the focus, or an empty string

if no item has the focus.

.RS

.PP

Once the focus has been set to an item, the item will display

the insertion cursor and all keyboard events will be directed

to that item.

The focus item within a canvas and the focus window on the

screen (set with the \fBfocus\fR command) are totally independent:

a given item doesn't actually have the input focus unless (a)

its canvas is the focus window and (b) the item is the focus item

within the canvas.

In most cases it is advisable to follow the \fBfocus\fR widget

command with the \fBfocus\fR command to set the focus window to

the canvas (if it wasn't there already).

.RE

.TP

\fIpathName \fBgettags\fR \fItagOrId\fR

Return a list whose elements are the tags associated with the

item given by \fItagOrId\fR.

If \fItagOrId\fR refers to more than one item, then the tags

are returned from the first such item in the display list.

If \fItagOrId\fR doesn't refer to any items, or if the item

contains no tags, then an empty string is returned.

.TP

\fIpathName \fBicursor \fItagOrId index\fR

Set the position of the insertion cursor for the item(s)

given by \fItagOrId\fR

to just before the character whose position is given by \fIindex\fR.

If some or all of the items given by \fItagOrId\fR don't support

an insertion cursor then this command has no effect on them.

See INDICES above for a description of the

legal forms for \fIindex\fR.

Note:  the insertion cursor is only displayed in an item if

that item currently has the keyboard focus (see the widget

command \fBfocus\fR, below), but the cursor position may

be set even when the item doesn't have the focus.

This command returns an empty string.

.TP

\fIpathName \fBindex \fItagOrId index\fR

This command returns a decimal string giving the numerical index

within \fItagOrId\fR corresponding to \fIindex\fR.

\fIIndex\fR gives a textual description of the desired position

as described in INDICES above.

The return value is guaranteed to lie between 0 and the number

of characters within the item, inclusive.

If \fItagOrId\fR refers to multiple items, then the index

is processed in the first of these items that supports indexing

operations (in display list order).

.TP

\fIpathName \fBinsert \fItagOrId beforeThis string\fR

For each of the items given by \fItagOrId\fR, if the item supports

text insertion then \fIstring\fR is inserted into the item's

text just before the character whose index is \fIbeforeThis\fR.

See INDICES above for information about the forms allowed

for \fIbeforeThis\fR.

This command returns an empty string.

.TP

\fIpathName \fBitemcget\fR \fItagOrId\fR \fIoption\fR

Returns the current value of the configuration option for the

item given by \fItagOrId\fR whose name is \fIoption\fR.

This command is similar to the \fBcget\fR widget command except that

it applies to a particular item rather than the widget as a whole.

\fIOption\fR may have any of the values accepted by the \fBcreate\fR

widget command when the item was created.

If \fItagOrId\fR is a tag that refers to more than one item,

the first (lowest) such item is used.

.TP

\fIpathName \fBitemconfigure \fItagOrId\fR ?\fIoption\fR? ?\fIvalue\fR? ?\fIoption value ...\fR?

This command is similar to the \fBconfigure\fR widget command except

that it modifies item-specific options for the items given by

\fItagOrId\fR instead of modifying options for the overall

canvas widget.

If no \fIoption\fR is specified, returns a list describing all of

the available options for the first item given by \fItagOrId\fR

(see \fBTk_ConfigureInfo\fR for

information on the format of this list).  If \fIoption\fR is specified

with no \fIvalue\fR, then the command returns a list describing the

one named option (this list will be identical to the corresponding

sublist of the value returned if no \fIoption\fR is specified).  If

one or more \fIoption\-value\fR pairs are specified, then the command

modifies the given widget option(s) to have the given value(s) in

each of the items given by \fItagOrId\fR;  in

this case the command returns an empty string.

The \fIoption\fRs and \fIvalue\fRs are the same as those permissible

in the \fBcreate\fR widget command when the item(s) were created;

see the sections describing individual item types below for details

on the legal options.

.TP

\fIpathName \fBlower \fItagOrId \fR?\fIbelowThis\fR?

Move all of the items given by \fItagOrId\fR to a new position

in the display list just before the item given by \fIbelowThis\fR.

If \fItagOrId\fR refers to more than one item then all are moved

but the relative order of the moved items will not be changed.

\fIBelowThis\fR is a tag or id;  if it refers to more than one

item then the first (lowest) of these items in the display list is used

as the destination location for the moved items.

Note: this command has no effect on window items.  Window items always

obscure other item types, and the stacking order of window items is

determined by the \fBraise\fR and \fBlower\fR commands, not the

\fBraise\fR and \fBlower\fR widget commands for canvases.

This command returns an empty string.

.TP

\fIpathName \fBmove \fItagOrId xAmount yAmount\fR

Move each of the items given by \fItagOrId\fR in the canvas coordinate

space by adding \fIxAmount\fR to the x-coordinate of each point

associated with the item and \fIyAmount\fR to the y-coordinate of

each point associated with the item.

This command returns an empty string.

.TP

\fIpathName \fBpostscript \fR?\fIoption value option value ...\fR?

Generate a Postscript representation for part or all of the canvas.

If the \fB\-file\fR option is specified then the Postscript is written

to a file and an empty string is returned;  otherwise the Postscript

is returned as the result of the command.

.VS

If the interpreter that owns the canvas is marked as safe, the operation

will fail because safe interpreters are not allowed to write files.

If the \fB\-channel\fR option is specified, the argument denotes the name

of a channel already opened for writing. The Postscript is written to

that channel, and the channel is left open for further writing at the end

of the operation.

.VE

The Postscript is created in Encapsulated Postscript form using

version 3.0 of the Document Structuring Conventions.

Note: by default Postscript is only generated for information that

appears in the canvas's window on the screen.  If the canvas is

freshly created it may still have its initial size of 1x1 pixel

so nothing will appear in the Postscript.  To get around this problem

either invoke the "update" command to wait for the canvas window

to reach its final size, or else use the \fB\-width\fR and \fB\-height\fR

options to specify the area of the canvas to print.

The \fIoption\fR\-\fIvalue\fR argument pairs provide additional

information to control the generation of Postscript.  The following

options are supported:

.RS

.TP

\fB\-colormap \fIvarName\fR

\fIVarName\fR must be the name of an array variable

that specifies a color mapping to use in the Postscript.

Each element of \fIvarName\fR must consist of Postscript

code to set a particular color value (e.g. ``\fB1.0 1.0 0.0 setrgbcolor\fR'').

When outputting color information in the Postscript, Tk checks

to see if there is an element of \fIvarName\fR with the same

name as the color.

If so, Tk uses the value of the element as the Postscript command

to set the color.

If this option hasn't been specified, or if there isn't an entry

in \fIvarName\fR for a given color, then Tk uses the red, green,

and blue intensities from the X color.

.TP

\fB\-colormode \fImode\fR

Specifies how to output color information.  \fIMode\fR must be either

\fBcolor\fR (for full color output), \fBgray\fR (convert all colors

to their gray-scale equivalents) or \fBmono\fR (convert all colors

to black or white).

.TP

\fB\-file \fIfileName\fR

Specifies the name of the file in which to write the Postscript.

If this option isn't specified then the Postscript is returned as the

result of the command instead of being written to a file.

.TP

\fB\-fontmap \fIvarName\fR

\fIVarName\fR must be the name of an array variable

that specifies a font mapping to use in the Postscript.

Each element of \fIvarName\fR must consist of a Tcl list with

two elements, which are the name and point size of a Postscript font.

When outputting Postscript commands for a particular font, Tk

checks to see if \fIvarName\fR contains an element with the same

name as the font.

If there is such an element, then the font information contained in

that element is used in the Postscript.

Otherwise Tk attempts to guess what Postscript font to use.

Tk's guesses generally only work for well-known fonts such as

Times and Helvetica and Courier, and only if the X font name does not

omit any dashes up through the point size.

For example, \fB\-*\-Courier\-Bold\-R\-Normal\-\-*\-120\-*\fR will work but

\fB*Courier\-Bold\-R\-Normal*120*\fR will not;  Tk needs the dashes to

parse the font name).

.TP

\fB\-height \fIsize\fR

Specifies the height of the area of the canvas to print.

Defaults to the height of the canvas window.

.TP

\fB\-pageanchor \fIanchor\fR

Specifies which point of the printed area of the canvas should appear over

the positioning point on the page (which is given by the \fB\-pagex\fR

and \fB\-pagey\fR options).

For example, \fB\-pageanchor n\fR means that the top center of the

area of the canvas being printed (as it appears in the canvas window)

should be over the positioning point. Defaults to \fBcenter\fR.

.TP

\fB\-pageheight \fIsize\fR

Specifies that the Postscript should be scaled in both x and y so

that the printed area is \fIsize\fR high on the Postscript page.

\fISize\fR consists of a floating-point number followed by

\fBc\fR for centimeters, \fBi\fR for inches, \fBm\fR for millimeters,

or \fBp\fR or nothing for printer's points (1/72 inch).

Defaults to the height of the printed area on the screen.

If both \fB\-pageheight\fR and \fB\-pagewidth\fR are specified then

the scale factor from \fB\-pagewidth\fR is used (non-uniform scaling

is not implemented).

.TP

\fB\-pagewidth \fIsize\fR

Specifies that the Postscript should be scaled in both x and y so

that the printed area is \fIsize\fR wide on the Postscript page.

\fISize\fR has the same form as for \fB\-pageheight\fR.

Defaults to the width of the printed area on the screen.

If both \fB\-pageheight\fR and \fB\-pagewidth\fR are specified then

the scale factor from \fB\-pagewidth\fR  is used (non-uniform scaling

is not implemented).

.TP

\fB\-pagex \fIposition\fR

\fIPosition\fR gives the x-coordinate of the positioning point on

the Postscript page, using any of the forms allowed for \fB\-pageheight\fR.

Used in conjunction with the \fB\-pagey\fR and \fB\-pageanchor\fR options

to determine where the printed area appears on the Postscript page.

Defaults to the center of the page.

.TP

\fB\-pagey \fIposition\fR

\fIPosition\fR gives the y-coordinate of the positioning point on

the Postscript page, using any of the forms allowed for \fB\-pageheight\fR.

Used in conjunction with the \fB\-pagex\fR and \fB\-pageanchor\fR options

to determine where the printed area appears on the Postscript page.

Defaults to the center of the page.

.TP

\fB\-rotate \fIboolean\fR

\fIBoolean\fR specifies whether the printed area is to be rotated 90

degrees.

In non-rotated output the x-axis of the printed area runs along

the short dimension of the page (``portrait'' orientation);

in rotated output the x-axis runs along the long dimension of the

page (``landscape'' orientation).

Defaults to non-rotated.

.TP

\fB\-width \fIsize\fR

Specifies the width of the area of the canvas to print.

Defaults to the width of the canvas window.

.TP

\fB\-x \fIposition\fR

Specifies the x-coordinate of the left edge of the area of the

canvas that is to be printed, in canvas coordinates, not window

coordinates.

Defaults to the coordinate of the left edge of the window.

.TP

\fB\-y \fIposition\fR

Specifies the y-coordinate of the top edge of the area of the

canvas that is to be printed, in canvas coordinates, not window

coordinates.

Defaults to the coordinate of the top edge of the window.

.RE

.TP

\fIpathName \fBraise \fItagOrId \fR?\fIaboveThis\fR?

Move all of the items given by \fItagOrId\fR to a new position

in the display list just after the item given by \fIaboveThis\fR.

If \fItagOrId\fR refers to more than one item then all are moved

but the relative order of the moved items will not be changed.

\fIAboveThis\fR is a tag or id;  if it refers to more than one

item then the last (topmost) of these items in the display list is used

as the destination location for the moved items.

Note: this command has no effect on window items.  Window items always

obscure other item types, and the stacking order of window items is

determined by the \fBraise\fR and \fBlower\fR commands, not the

\fBraise\fR and \fBlower\fR widget commands for canvases.

This command returns an empty string.

.TP

\fIpathName \fBscale \fItagOrId xOrigin yOrigin xScale yScale\fR

Rescale all of the items given by \fItagOrId\fR in canvas coordinate

space.

\fIXOrigin\fR and \fIyOrigin\fR identify the origin for the scaling

operation and \fIxScale\fR and \fIyScale\fR identify the scale

factors for x- and y-coordinates, respectively (a scale factor of

1.0 implies no change to that coordinate).

For each of the points defining each item, the x-coordinate is

adjusted to change the distance from \fIxOrigin\fR by a factor

of \fIxScale\fR.

Similarly, each y-coordinate is adjusted to change the distance

from \fIyOrigin\fR by a factor of \fIyScale\fR.

This command returns an empty string.

.TP

\fIpathName \fBscan\fR \fIoption args\fR

This command is used to implement scanning on canvases.  It has

two forms, depending on \fIoption\fR:

.RS

.TP

\fIpathName \fBscan mark \fIx y\fR

Records \fIx\fR and \fIy\fR and the canvas's current view;  used

in conjunction with later \fBscan dragto\fR commands.

Typically this command is associated with a mouse button press in

the widget and \fIx\fR and \fIy\fR are the coordinates of the

mouse.  It returns an empty string.

.TP

\fIpathName \fBscan dragto \fIx y\fR.

This command computes the difference between its \fIx\fR and \fIy\fR

arguments (which are typically mouse coordinates) and the \fIx\fR and

\fIy\fR arguments to the last \fBscan mark\fR command for the widget.

It then adjusts the view by 10 times the

difference in coordinates.  This command is typically associated

with mouse motion events in the widget, to produce the effect of

dragging the canvas at high speed through its window.  The return

value is an empty string.

.RE

.TP

\fIpathName \fBselect \fIoption\fR ?\fItagOrId arg\fR?

Manipulates the selection in one of several ways, depending on

\fIoption\fR.

The command may take any of the forms described below.

In all of the descriptions below, \fItagOrId\fR must refer to

an item that supports indexing and selection;  if it refers to

multiple items then the first of

these that supports indexing and the selection is used.

\fIIndex\fR gives a textual description of a position

within \fItagOrId\fR, as described in INDICES above.

.RS

.TP

\fIpathName \fBselect adjust \fItagOrId index\fR

Locate the end of the selection in \fItagOrId\fR nearest

to the character given by \fIindex\fR, and adjust that

end of the selection to be at \fIindex\fR (i.e. including

but not going beyond \fIindex\fR).

The other end of the selection is made the anchor point

for future \fBselect to\fR commands.

If the selection isn't currently in \fItagOrId\fR then

this command behaves the same as the \fBselect to\fR widget

command.

Returns an empty string.

.TP

\fIpathName \fBselect clear\fR

Clear the selection if it is in this widget.

If the selection isn't in this widget then the command

has no effect.

Returns an empty string.

.TP

\fIpathName \fBselect from \fItagOrId index\fR

Set the selection anchor point for the widget to be just

before the character

given by \fIindex\fR in the item given by \fItagOrId\fR.

This command doesn't change the selection;  it just sets

the fixed end of the selection for future \fBselect to\fR

commands.

Returns an empty string.

.TP

\fIpathName \fBselect item\fR

Returns the id of the selected item, if the selection is in an

item in this canvas.

If the selection is not in this canvas then an empty string

is returned.

.TP

\fIpathName \fBselect to \fItagOrId index\fR

Set the selection to consist of those characters of \fItagOrId\fR

between the selection anchor point and

\fIindex\fR.

The new selection will include the character given by \fIindex\fR;

it will include the character given by the anchor point only if

\fIindex\fR is greater than or equal to the anchor point.

The anchor point is determined by the most recent \fBselect adjust\fR

or \fBselect from\fR command for this widget.

If the selection anchor point for the widget isn't currently in

\fItagOrId\fR, then it is set to the same character given

by \fIindex\fR.

Returns an empty string.

.RE

.TP

\fIpathName \fBtype\fI tagOrId\fR

Returns the type of the item given by \fItagOrId\fR, such as

\fBrectangle\fR or \fBtext\fR.

If \fItagOrId\fR refers to more than one item, then the type

of the first item in the display list is returned.

If \fItagOrId\fR doesn't refer to any items at all then

an empty string is returned.

.TP

\fIpathName \fBxview  \fR?\fIargs\fR?

This command is used to query and change the horizontal position of the

information displayed in the canvas's window.

It can take any of the following forms:

.RS

.TP

\fIpathName \fBxview\fR

Returns a list containing two elements.

Each element is a real fraction between 0 and 1;  together they describe

the horizontal span that is visible in the window.

For example, if the first element is .2 and the second element is .6,

20% of the canvas's area (as defined by the \fB\-scrollregion\fR option)

is off-screen to the left, the middle 40% is visible

in the window, and 40% of the canvas is off-screen to the right.

These are the same values passed to scrollbars via the \fB\-xscrollcommand\fR

option.

.TP

\fIpathName \fBxview moveto\fI fraction\fR

Adjusts the view in the window so that \fIfraction\fR of the

total width of the canvas is off-screen to the left.

\fIFraction\fR must be a fraction between 0 and 1.

.TP

\fIpathName \fBxview scroll \fInumber what\fR

This command shifts the view in the window left or right according to

\fInumber\fR and \fIwhat\fR.

\fINumber\fR must be an integer.

\fIWhat\fR must be either \fBunits\fR or \fBpages\fR or an abbreviation

of one of these.

If \fIwhat\fR is \fBunits\fR, the view adjusts left or right in units

of the \fBxScrollIncrement\fR option, if it is greater than zero,

or in units of one-tenth the window's width otherwise.

If \fIwhat is \fBpages\fR then the view

adjusts in units of nine-tenths the window's width.

If \fInumber\fR is negative then information farther to the left

becomes visible;  if it is positive then information farther to the right

becomes visible.

.RE

.TP

\fIpathName \fByview \fI?args\fR?

This command is used to query and change the vertical position of the

information displayed in the canvas's window.

It can take any of the following forms:

.RS

.TP

\fIpathName \fByview\fR

Returns a list containing two elements.

Each element is a real fraction between 0 and 1;  together they describe

the vertical span that is visible in the window.

For example, if the first element is .6 and the second element is 1.0,

the lowest 40% of the canvas's area (as defined by the \fB\-scrollregion\fR

option) is visible in the window.

These are the same values passed to scrollbars via the \fB\-yscrollcommand\fR

option.

.TP

\fIpathName \fByview moveto\fI fraction\fR

Adjusts the view in the window so that \fIfraction\fR of the canvas's

area is off-screen to the top.

\fIFraction\fR is a fraction between 0 and 1.

.TP

\fIpathName \fByview scroll \fInumber what\fR

This command adjusts the view in the window up or down according to

\fInumber\fR and \fIwhat\fR.

\fINumber\fR must be an integer.

\fIWhat\fR must be either \fBunits\fR or \fBpages\fR.

If \fIwhat\fR is \fBunits\fR, the view adjusts up or down in units

of the \fByScrollIncrement\fR option, if it is greater than zero,

or in units of one-tenth the window's height otherwise.

If \fIwhat\fR is \fBpages\fR then

the view adjusts in units of nine-tenths the window's height.

If \fInumber\fR is negative then higher information becomes

visible;  if it is positive then lower information

becomes visible.

.RE

.SH "OVERVIEW OF ITEM TYPES"

.PP

The sections below describe the various types of items supported

by canvas widgets.  Each item type is characterized by two things:

first, the form of the \fBcreate\fR command used to create

instances of the type;  and second, a set of configuration options

for items of that type, which may be used in the

\fBcreate\fR and \fBitemconfigure\fR widget commands.

Most items don't support indexing or selection or the commands