Manual Pages for UNIX Darwin command on man canvas

canvas(n) Tk Built-In Commands canvas(n)

NAME

canvas - Create and manipulate canvas widgets

SYNOPSIS

ccaannvvaass pathName ?options? SSTTAANNDDAARRDD OOPPTTIIOONNSS

-bbaacckkggrroouunndd -iinnsseerrttbboorrddeerrwwiiddtthh -sseelleeccttbboorrddeerrwwiiddtthh

-bboorrddeerrwwiiddtthh -iinnsseerrttooffffttiimmee -sseelleeccttffoorreeggrroouunndd

-ccuurrssoorr -iinnsseerrttoonnttiimmee -ttaakkeeffooccuuss

-hhiigghhlliigghhttbbaacckkggrroouunndd -iinnsseerrttwwiiddtthh -xxssccrroollllccoommmmaanndd

-hhiigghhlliigghhttccoolloorr -rreelliieeff -yyssccrroollllccoommmmaanndd

-hhiigghhlliigghhtttthhiicckknneessss -ssttaattee

-iinnsseerrttbbaacckkggrroouunndd -sseelleeccttbbaacckkggrroouunndd

See the ooppttiioonnss manual entry for details on the standard options.

WWIIDDGGEETT-SSPPEECCIIFFIICC OOPPTTIIOONNSS

Command-Line Name:-cclloosseeeennoouugghh

Database Name: cclloosseeEEnnoouugghh Database Class: CClloosseeEEnnoouugghh

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.

Command-Line Name:-ccoonnffiinnee

Database Name: ccoonnffiinnee Database Class: CCoonnffiinnee 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 ssccrroollllRReeggiioonn argument. Defaults to true, which means that the view will be constrained within the scroll region.

Command-Line Name:-hheeiigghhtt

Database Name: hheeiigghhtt Database Class: HHeeiigghhtt

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.

Command-Line Name:-ssccrroollllrreeggiioonn

Database Name: ssccrroollllRReeggiioonn Database Class: SSccrroollllRReeggiioonn 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.

Command-Line Name:-ssttaattee

Database Name: ssttaattee Database Class: SSttaattee

Modifies the default state of the canvas where state may be set

to one of: nnoorrmmaall, ddiissaabblleedd, or hhiiddddeenn. Individual canvas

objects all have their own state option which may override the default state. Many options can take separate specifications

such that the appearance of the item can be different in differ-

ent situations. The options that start with aaccttiivvee control the appearence when the mouse pointer is over it, while the option starting with ddiissaabblleedd controls the appearence when the state is disabled. Canvas items which are ddiissaabblleedd will not react to

canvas bindings.

Command-Line Name:-wwiiddtthh

Database Name: wwiiddtthh Database Class: wwiiddtthh

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.

Command-Line Name:-xxssccrroolllliinnccrreemmeenntt

Database Name: xxSSccrroollllIInnccrreemmeenntt Database Class: SSccrroollllIInnccrreemmeenntt 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 xxSSccrroollllIInnccrreemmeenntt; 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 xxSSccrroollllIInnccrreemmeenntt. If the value of this option is less than or equal to zero, then horizontal scrolling is unconstrained.

Command-Line Name:-yyssccrroolllliinnccrreemmeenntt

Database Name: yySSccrroollllIInnccrreemmeenntt Database Class: SSccrroollllIInnccrreemmeenntt 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 win-

dow will be constrained so that the canvas y coordinate at the

top edge of the window is always an even multiple of yySSccrroollllIInnccrreemmeenntt; 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 yySSccrroollllIInnccrreemmeenntt. If the value of this option is less than or equal to zero, then vertical scrolling is unconstrained. IINNTTRROODDUUCCTTIIOONN

The ccaannvvaass command creates a new window (given by the pathName argu-

ment) 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 ccaannvvaass command returns its pathName argument. At the time this command is invoked, there must not exist a window named pathName, but pathName's parent must exist.

Canvas widgets implement structured graphics. A canvas displays any

number of items, which may be things like rectangles, circles, lines,

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

mands may be associated with items in much the same way that the bbiinndd

command allows commands to be bound to widgets. For example, a partic-

ular 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. DDIISSPPLLAAYY LLIISSTT

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 every-

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

display list.

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

dow 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 rraaiissee and lloowweerr Tk com-

mands instead. IITTEEMM IIDDSS AANNDD TTAAGGSS

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.

Each item may also have any number of tags 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''.

The tag aallll is implicitly associated with every item in the canvas; it

may be used to invoke operations on all the items in the canvas.

The tag ccuurrrreenntt is managed automatically by Tk; it applies to the cur-

rent item, which is the topmost item whose drawn area covers the posi-

tion of the mouse cursor. If the mouse is not in the canvas widget or

is not over an item, then no item has the ccuurrrreenntt tag.

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 tagOrId 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. tagOrId may contain a logical expressions of tags by using operators: '&&', '||', '^' '!', and parenthezised subexpressions. For example: .c find withtag {(a&&!b)||(!a&&b)} or equivalently: .c find withtag {a^b} will find only those items with either "a" or "b" tags, but not both. Some widget commands only operate on a single item at a time; if

tagOrId is specified in a way that names multiple items, then the nor-

mal 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. CCOOOORRDDIINNAATTEESS

All coordinates related to canvases are stored as floating-point num-

bers. Coordinates and distances are specified in screen units, which

are floating-point numbers optionally followed by one of several let-

ters. If no letter is supplied then the distance is in pixels. If the letter is mm then the distance is in millimeters on the screen; if it is cc then the distance is in centimeters; ii means inches, and pp 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. Coordinates can be specified either as an even number of | parameters, or as a single list parameter containing an even number of | x and y coordinate values. TTRRAANNSSFFOORRMMAATTIIOONNSS

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 ori-

gin of the window using the xxvviieeww and yyvviieeww widget commands; this is

typically used for scrolling. Canvases do not support scaling or rota-

tion of the canvas coordinate system relative to the window coordinate

system. Individual items may be moved or scaled using widget commands described below, but they may not be rotated. IINNDDIICCEESS Text items support the notion of an index for identifying particular positions within the item. In a similar fashion, line and polygon items support index for identifying, inserting and deleting subsets of their coordinates. Indices are used for commands such as inserting or

deleting a range of characters or coordinates, and setting the inser-

tion 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 advis-

able 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. Lines and Polygons don't support the insertion cursor and the selection. Their indixes are supposed to be even always, because coordinates always appear in pairs. number A decimal number giving the position of the desired character within the text item. 0 refers to the first character, 1 to the next character, and so on. If indexes are odd for lines and polygons, they will be automatically decremented by one. 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. For poly-

gons, numbers less than 0 or greater then the length of the coordinate list will be adjusted by adding or substracting the length until the result is between zero and the length, inclusive. eenndd Refers to the character or coordinate just after the last one in the item (same as the number of characters or coordinates in the item).

iinnsseerrtt Refers to the character just before which the insertion cur-

sor is drawn in this item. Not valid for lines and polygons. sseell..ffiirrsstt Refers to the first selected character in the item. If the selection isn't in this item then this form is illegal. sseell..llaasstt Refers to the last selected character in the item. If the selection isn't in this item then this form is illegal. @@x,y Refers to the character or coordinate at the point given by x and y, where x and y are specified in the coordinate system

of the canvas. If x and y lie outside the coordinates cov-

ered by the text item, then they refer to the first or last character in the line that is closest to the given point. DDAASSHH PPAATTTTEERRNNSS Many items support the notion of an dash pattern for outlines.

The first possible syntax is a list of integers. Each element repre-

sents the number of pixels of a line segment. Only the odd segments are drawn using the "outline" color. The other segments are drawn transparant.

The second possible syntax is a character list containing only 5 possi-

ble characters [[..,,- ]]. The space can be used to enlarge the space

between other line elements, and can not occur as the first position in the string. Some examples:

-dash .= -dash {2 4}

-dash - = -dash {6 4}

-dash -. = -dash {6 4 2 4}

-dash -.. = -dash {6 4 2 4 2 4}

-dash {. } = -dash {2 8}

-dash ,= -dash {4 4}

The main difference of this syntax with the previous is that it it

shape-conserving. This means that all values in the dash list will be

multiplied by the line width before display. This assures that "." will

always be displayed as a dot and "-" always as a dash regardless of the

line width. On systems which support only a limited set of dash patterns, the dash

pattern will be displayed as the closest dash pattern that is avail-

able. For example, on Windows only the first 4 of the above examples are available. The last 2 examples will be displayed identically to the first one. WWIIDDGGEETT CCOOMMMMAANNDD The ccaannvvaass command creates a new Tcl command whose name is pathName. This command may be used to invoke various operations on the widget. It has the following general form: pathName option ?arg arg ...? Option and the args determine the exact behavior of the command. The

following widget commands are possible for canvas widgets:

pathName aaddddttaagg tag searchSpec ?arg arg ...? For each item that meets the constraints specified by searchSpec and the args, add tag 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 searchSpec and args, in which case the command has no effect. This command returns an empty string as result. SearchSpec and arg's may take any of the following forms: aabboovvee tagOrId Selects the item just after (above) the one given by tagOrId in the display list. If tagOrId denotes more than one item, then the last (topmost) of these items in the display list is used.

aallll Selects all the items in the canvas.

bbeellooww tagOrId Selects the item just before (below) the one given by tagOrId in the display list. If tagOrId denotes more than one item, then the first (lowest) of these items in the display list is used. cclloosseesstt x y ?halo? ?start? Selects the item closest to the point given by x and y. 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 halo is specified, then it must be a non-negative

value. Any item closer than halo to the point is consid-

ered to overlap it. The start argument may be used to step circularly through all the closest items. If start 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 start in the display list; if no such item

exists, then the selection behaves as if the start argu-

ment had not been specified. eenncclloosseedd x1 y1 x2 y2 Selects all the items completely enclosed within the rectangular region given by x1, y1, x2, and y2. X1 must be no greater then x2 and y1 must be no greater than y2. oovveerrllaappppiinngg x1 y1 x2 y2 Selects all the items that overlap or are enclosed within the rectangular region given by x1, y1, x2, and y2. X1 must be no greater then x2 and y1 must be no greater than y2. wwiitthhttaagg tagOrId Selects all the items given by tagOrId. pathName bbbbooxx tagOrId ?tagOrId tagOrId ...? Returns a list with four elements giving an approximate bounding box for all the items named by the tagOrId arguments. The list has the form ``x1 y1 x2 y2'' such that the drawn areas of all the named elements are within the region bounded by x1 on the left, x2 on the right, y1 on the top, and y2 on the bottom. The return value may overestimate the actual bounding box by a few pixels. If no items match any of the tagOrId arguments or if the matching items have empty bounding boxes (i.e. they have nothing to display) then an empty string is returned. pathName bbiinndd tagOrId ?sequence? ?command? This command associates command with all the items given by tagOrId such that whenever the event sequence given by sequence occurs for one of the items the command will be invoked. This widget command is similar to the bbiinndd command except that it

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

the bbiinndd manual entry for complete details on the syntax of sequence and the substitutions performed on command before invoking it. If all arguments are specified then a new binding is created, replacing any existing binding for the same sequence and tagOrId (if the first character of command is ``+'' then command augments an existing binding rather than replacing it). In this case the return value is an empty string. If command is omitted then the command returns the command associated with

tagOrId and sequence (an error occurs if there is no such bind-

ing). If both command and sequence are omitted then the command returns a list of all the sequences for which bindings have been defined for tagOrId. The only events for which bindings may be specified are those

related to the mouse and keyboard (such as EEnntteerr, LLeeaavvee, BBuuttttoonn-

PPrreessss, MMoottiioonn, and KKeeyyPPrreessss) or virtual events. The handling of

events in canvases uses the current item defined in ITEM IDS AND

TAGS above. EEnntteerr and LLeeaavvee 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 EEnntteerr and LLeeaavvee 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 ffooccuuss widget command below for more on this).

If a virtual event is used in a binding, that binding can trig-

ger only if the virtual event is defined by an underlying mouse-

related or keyboard-related event.

It is possible for multiple bindings to match a particular

event. This could occur, for example, if one binding is associ-

ated 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 aallll 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 ccoonnttiinnuuee command in a

binding script terminates that script, and a bbrreeaakk command ter-

minates that script and skips any remaining scripts for the event, just as for the bbiinndd command.

If bindings have been created for a canvas window using the bbiinndd

command, then they are invoked in addition to bindings created

for the canvas's items using the bbiinndd widget command. The bind-

ings for items will be invoked before any of the bindings for the window as a whole. pathName ccaannvvaassxx screenx ?gridspacing?

Given a window x-coordinate in the canvas screenx, this command

returns the canvas x-coordinate that is displayed at that loca-

tion. If gridspacing is specified, then the canvas coordinate

is rounded to the nearest multiple of gridspacing units. pathName ccaannvvaassyy screeny ?gridspacing?

Given a window y-coordinate in the canvas screeny this command

returns the canvas y-coordinate that is displayed at that loca-

tion. If gridspacing is specified, then the canvas coordinate

is rounded to the nearest multiple of gridspacing units. pathName ccggeett option Returns the current value of the configuration option given by

option. Option may have any of the values accepted by the ccaann-

vvaass command. pathName ccoonnffiigguurree ??option? ?value? ?option value ...? Query or modify the configuration options of the widget. If no

option is specified, returns a list describing all of the avail-

able options for pathName (see TTkkCCoonnffiigguurreeIInnffoo for information on the format of this list). If option is specified with no value, 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 option is specified). If one or

more option-value 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. Option may have any of the values accepted by the ccaannvvaass command. pathName ccoooorrddss tagOrId ?x0 y0 ...? pathName ccoooorrddss tagOrId ?coordList? 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 tagOrId. If

coordinates are specified, then they replace the current coordi-

nates for the named item. If tagOrId refers to multiple items, then the first one in the display list is used. pathName ccrreeaattee type x y ?x y ...? ?option value ...? pathName ccrreeaattee type coordList ?option value ...? Create a new item in pathName of type type. The exact format of

the arguments after ttyyppee depends on ttyyppee, but usually they con-

sist of the coordinates for one or more points, followed by

specifications for zero or more item options. See the subsec-

tions on individual item types below for more on the syntax of this command. This command returns the id for the new item. pathName ddcchhaarrss tagOrId first ?last?

For each item given by tagOrId, delete the characters, or coor-

dinates, in the range given by first and last, inclusive. If

some of the items given by tagOrId don't support indexing opera-

tions then they ignore dchars. Text items interpret first and last as indices to a character, line and polygon items interpret them indices to a coordinate (an x,y pair). Indices are described in INDICES above. If last is omitted, it defaults to first. This command returns an empty string. pathName ddeelleettee ?tagOrId tagOrId ...? Delete each of the items given by each tagOrId, and return an empty string. pathName ddttaagg tagOrId ?tagToDelete? For each of the items given by tagOrId, delete the tag given by tagToDelete from the list of those associated with the item. If

an item doesn't have the tag tagToDelete then the item is unaf-

fected by the command. If tagToDelete is omitted then it defaults to tagOrId. This command returns an empty string. pathName ffiinndd searchCommand ?arg arg ...? This command returns a list consisting of all the items that meet the constraints specified by searchCommand and arg's. SearchCommand and args have any of the forms accepted by the aaddddttaagg command. The items are returned in stacking order, with the lowest item first. pathName ffooccuuss ?tagOrId?

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

by tagOrId. If tagOrId refers to several items, then the focus is set to the first such item in the display list that supports the insertion cursor. If tagOrId doesn't refer to any items, or if none of them support the insertion cursor, then the focus isn't changed. If tagOrId is an empty string, then the focus item is reset so that no item has the focus. If tagOrId is not

specified then the command returns the id for the item that cur-

rently has the focus, or an empty string if no item has the focus. 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 ffooccuuss command) are totally indepen-

dent: 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 ffooccuuss widget command with the ffooccuuss command to set the focus

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

pathName ggeettttaaggss tagOrId Return a list whose elements are the tags associated with the item given by tagOrId. If tagOrId refers to more than one item,

then the tags are returned from the first such item in the dis-

play list. If tagOrId doesn't refer to any items, or if the item contains no tags, then an empty string is returned. pathName iiccuurrssoorr tagOrId index Set the position of the insertion cursor for the item(s) given by tagOrId to just before the character whose position is given by index. If some or all of the items given by tagOrId 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 index. Note: the insertion cursor is only displayed in an

item if that item currently has the keyboard focus (see the wid-

get command ffooccuuss, below), but the cursor position may be set even when the item doesn't have the focus. This command returns an empty string. pathName iinnddeexx tagOrId index This command returns a decimal string giving the numerical index within tagOrId corresponding to index. Index gives a textual description of the desired position as described in INDICES above. Text items interpret index as an index to a character, line and polygon items interpret it as an index to a coordinate (an x,y pair). The return value is guaranteed to lie between 0 and the number of characters, or coordinates, within the item, inclusive. If tagOrId refers to multiple items, then the index is processed in the first of these items that supports indexing operations (in display list order). pathName iinnsseerrtt tagOrId beforeThis string For each of the items given by tagOrId, if the item supports text or coordinate, insertion then string is inserted into the item's text just before the character, or coordinate, whose index is beforeThis. Text items interpret beforethis as an index to a character, line and polygon items interpret it as an index to a coordinate (an x,y pair). For lines and polygons the string must be a valid coordinate sequence. See INDICES above for information about the forms allowed for beforeThis. This command returns an empty string. pathName iitteemmccggeett tagOrId option Returns the current value of the configuration option for the item given by tagOrId whose name is option. This command is similar to the ccggeett widget command except that it applies to a particular item rather than the widget as a whole. Option may have any of the values accepted by the ccrreeaattee widget command when the item was created. If tagOrId is a tag that refers to more than one item, the first (lowest) such item is used. pathName iitteemmccoonnffiigguurree tagOrId ?option? ?value? ?option value ...? This command is similar to the ccoonnffiigguurree widget command except

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

tagOrId instead of modifying options for the overall canvas wid-

get. If no option is specified, returns a list describing all of the available options for the first item given by tagOrId (see TTkkCCoonnffiigguurreeIInnffoo for information on the format of this list). If option is specified with no value, 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 option is specified). If one or more option-value 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 tagOrId; in this case the command returns an empty string. The options and values are the same as those permissible in the ccrreeaattee widget command when the item(s) were created; see the sections describing individual item types below for details on the legal options. pathName lloowweerr tagOrId ?belowThis? Move all of the items given by tagOrId to a new position in the display list just before the item given by belowThis. If tagOrId refers to more than one item then all are moved but the relative order of the moved items will not be changed. BelowThis 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 rraaiissee and lloowweerr commands, not the rraaiissee and

lloowweerr widget commands for canvases. This command returns an

empty string. pathName mmoovvee tagOrId xAmount yAmount

Move each of the items given by tagOrId in the canvas coordinate

space by adding xAmount to the x-coordinate of each point asso-

ciated with the item and yAmount to the y-coordinate of each

point associated with the item. This command returns an empty string. pathName ppoossttssccrriipptt ?option value option value ...?

Generate a Postscript representation for part or all of the can-

vas. If the -ffiillee 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. If the

interpreter that owns the canvas is marked as safe, the opera-

tion will fail because safe interpreters are not allowed to

write files. If the -cchhaannnneell 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. The Post-

script 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 -wwiiddtthh and -hheeiigghhtt options

to specify the area of the canvas to print. The option-value

argument pairs provide additional information to control the generation of Postscript. The following options are supported:

-ccoolloorrmmaapp varName

VarName must be the name of an array variable that speci-

fies a color mapping to use in the Postscript. Each ele-

ment of varName must consist of Postscript code to set a

particular color value (e.g. ``11..00 11..00 00..00 sseettrrggbb-

ccoolloorr''). When outputting color information in the Post-

script, Tk checks to see if there is an element of var-

Name 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 varName for a given color, then Tk uses the red, green, and blue intensities from the X color.

-ccoolloorrmmooddee mode

Specifies how to output color information. Mode must be either ccoolloorr (for full color output), ggrraayy (convert all

colors to their gray-scale equivalents) or mmoonnoo (convert

all colors to black or white).

-ffiillee fileName

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.

-ffoonnttmmaapp varName

VarName must be the name of an array variable that speci-

fies a font mapping to use in the Postscript. Each ele-

ment of varName must consist of a Tcl list with two ele-

ments, which are the name and point size of a Postscript

font. When outputting Postscript commands for a particu-

lar font, Tk checks to see if varName contains an element

with the same name as the font. If there is such an ele-

ment, 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 gener-

ally 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 exam-

ple, -**-CCoouurriieerr-BBoolldd-RR-NNoorrmmaall--**-112200-** will work but

**CCoouurriieerr-BBoolldd-RR-NNoorrmmaall**112200** will not; Tk needs the

dashes to parse the font name).

-hheeiigghhtt size

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

Defaults to the height of the canvas window.

-ppaaggeeaanncchhoorr anchor

Specifies which point of the printed area of the canvas

should appear over the positioning point on the page

(which is given by the -ppaaggeexx and -ppaaggeeyy options). For

example, -ppaaggeeaanncchhoorr nn 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 cceenntteerr.

-ppaaggeehheeiigghhtt size

Specifies that the Postscript should be scaled in both x

and y so that the printed area is size high on the Post-

script page. Size consists of a floating-point number

followed by cc for centimeters, ii for inches, mm for mil-

limeters, or pp or nothing for printer's points (1/72 inch). Defaults to the height of the printed area on the

screen. If both -ppaaggeehheeiigghhtt and -ppaaggeewwiiddtthh are specified

then the scale factor from -ppaaggeewwiiddtthh is used (non-uni-

form scaling is not implemented).

-ppaaggeewwiiddtthh size

Specifies that the Postscript should be scaled in both x

and y so that the printed area is size wide on the Post-

script page. Size has the same form as for -ppaaggeehheeiigghhtt.

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

If both -ppaaggeehheeiigghhtt and -ppaaggeewwiiddtthh are specified then the

scale factor from -ppaaggeewwiiddtthh is used (non-uniform scal-

ing is not implemented).

-ppaaggeexx position

Position gives the x-coordinate of the positioning point

on the Postscript page, using any of the forms allowed

for -ppaaggeehheeiigghhtt. Used in conjunction with the -ppaaggeeyy and

-ppaaggeeaanncchhoorr options to determine where the printed area

appears on the Postscript page. Defaults to the center of the page.

-ppaaggeeyy position

Position gives the y-coordinate of the positioning point

on the Postscript page, using any of the forms allowed

for -ppaaggeehheeiigghhtt. Used in conjunction with the -ppaaggeexx and

-ppaaggeeaanncchhoorr options to determine where the printed area

appears on the Postscript page. Defaults to the center of the page.

-rroottaattee boolean

Boolean 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 (``land-

scape'' orientation). Defaults to non-rotated.

-wwiiddtthh size

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

Defaults to the width of the canvas window.

-xx position

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

of the canvas that is to be printed, in canvas coordi-

nates, not window coordinates. Defaults to the coordi-

nate of the left edge of the window.

-yy position

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. pathName rraaiissee tagOrId ?aboveThis? Move all of the items given by tagOrId to a new position in the display list just after the item given by aboveThis. If tagOrId refers to more than one item then all are moved but the relative order of the moved items will not be changed. AboveThis 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 des-

tination 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 rraaiissee and lloowweerr commands, not the rraaiissee and lloowweerr widget

commands for canvases. This command returns an empty string.

pathName ssccaallee tagOrId xOrigin yOrigin xScale yScale

Rescale all of the items given by tagOrId in canvas coordinate

space. XOrigin and yOrigin identify the origin for the scaling operation and xScale and yScale 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 xOrigin by a factor of xScale. Similarly, each y-

coordinate is adjusted to change the distance from yOrigin by a factor of yScale. This command returns an empty string. pathName ssccaann option args

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

two forms, depending on option: pathName ssccaann mmaarrkk x y

Records x and y and the canvas's current view; used in

conjunction with later ssccaann ddrraaggttoo commands. Typically this command is associated with a mouse button press in the widget and x and y are the coordinates of the mouse. It returns an empty string. pathName ssccaann ddrraaggttoo x y ?gain?. This command computes the difference between its x and y arguments (which are typically mouse coordinates) and the x and y arguments to the last ssccaann mmaarrkk command for the

widget. It then adjusts the view by gain times the dif-

ference in coordinates, where gain defaults to 10. This command is typically associated with mouse motion events

in the widget, to produce the effect of dragging the can-

vas at high speed through its window. The return value is an empty string. pathName sseelleecctt option ?tagOrId arg? Manipulates the selection in one of several ways, depending on option. The command may take any of the forms described below. In all of the descriptions below, tagOrId 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. Index gives a textual description of a posi-

tion within tagOrId, as described in INDICES above. pathName sseelleecctt aaddjjuusstt tagOrId index Locate the end of the selection in tagOrId nearest to the character given by index, and adjust that end of the selection to be at index (i.e. including but not going beyond index). The other end of the selection is made the anchor point for future sseelleecctt ttoo commands. If the selection isn't currently in tagOrId then this command behaves the same as the sseelleecctt ttoo widget command. Returns an empty string. pathName sseelleecctt cclleeaarr 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. pathName sseelleecctt ffrroomm tagOrId index Set the selection anchor point for the widget to be just before the character given by index in the item given by tagOrId. This command doesn't change the selection; it just sets the fixed end of the selection for future sseelleecctt ttoo commands. Returns an empty string. pathName sseelleecctt iitteemm 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.

pathName sseelleecctt ttoo tagOrId index Set the selection to consist of those characters of tagOrId between the selection anchor point and index. The new selection will include the character given by index; it will include the character given by the anchor point only if index is greater than or equal to the anchor point. The anchor point is determined by the most

recent sseelleecctt aaddjjuusstt or sseelleecctt ffrroomm command for this wid-

get. If the selection anchor point for the widget isn't

currently in tagOrId, then it is set to the same charac-

ter given by index. Returns an empty string. pathName ttyyppee tagOrId Returns the type of the item given by tagOrId, such as rreeccttaannggllee or tteexxtt. If tagOrId refers to more than one item, then the type of the first item in the display list is returned. If tagOrId doesn't refer to any items at all then an empty string is returned. pathName xxvviieeww ?args? 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: pathName xxvviieeww 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 ele-

ment is .6, 20% of the canvas's area (as defined by the

-ssccrroollllrreeggiioonn option) is off-screen to the left, the mid-

dle 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 -xxssccrroollllccoommmmaanndd option.

pathName xxvviieeww mmoovveettoo fraction Adjusts the view in the window so that fraction of the

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

Fraction must be a fraction between 0 and 1. pathName xxvviieeww ssccrroollll number what This command shifts the view in the window left or right according to number and what. Number must be an integer. What must be either uunniittss or ppaaggeess or an abbreviation of one of these. If what is uunniittss, the view adjusts left or right in units of the xxSSccrroollllIInnccrreemmeenntt option, if it is

greater than zero, or in units of one-tenth the window's

width otherwise. If what is ppaaggeess then the view adjusts

in units of nine-tenths the window's width. If number is

negative then information farther to the left becomes visible; if it is positive then information farther to the right becomes visible. pathName yyvviieeww ?args? 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: pathName yyvviieeww 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 ele-

ment is 1.0, the lowest 40% of the canvas's area (as

defined by the -ssccrroollllrreeggiioonn option) is visible in the

window. These are the same values passed to scrollbars

via the -yyssccrroollllccoommmmaanndd option.

pathName yyvviieeww mmoovveettoo fraction Adjusts the view in the window so that fraction of the

canvas's area is off-screen to the top. Fraction is a

fraction between 0 and 1. pathName yyvviieeww ssccrroollll number what This command adjusts the view in the window up or down according to number and what. Number must be an integer. What must be either uunniittss or ppaaggeess. If what is uunniittss,

the view adjusts up or down in units of the yySSccrroollllIInnccrree-

mmeenntt option, if it is greater than zero, or in units of

one-tenth the window's height otherwise. If what is

ppaaggeess then the view adjusts in units of nine-tenths the

window's height. If number is negative then higher information becomes visible; if it is positive then lower information becomes visible. OOVVEERRVVIIEEWW OOFF IITTEEMM TTYYPPEESS 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 ccrreeaattee 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 ccrreeaattee and iitteemmccoonnffiigguurree widget commands. Most items don't support indexing or selection or the commands related

to them, such as iinnddeexx and iinnsseerrtt. Where items do support these facil-

ities, it is noted explicitly in the descriptions below. At present,

text, line and polygon items provide this support. For lines and poly-

gons the indexing facility is used to manipulate the coordinates of the item. CCOOMMMMOONN IITTEEMM OOPPTTIIOONNSS Many items share a common set of options. These options are explained here, and then referred to be each widget type for brevity.

-ddaasshh pattern

-aaccttiivveeddaasshh pattern

-ddiissaabblleeddddaasshh pattern

This option specifies dash patterns for the normal, active state, and disabled state of an item. pattern may have any of

the forms accepted by TTkkGGeettDDaasshh. If the dash options are omit-

ted then the default is a solid outline. See "DASH PATTERNS" for more information.

-ddaasshhooffffsseett offset

The starting offset in pixels into the pattern provided by the

-ddaasshh option. -ddaasshhooffffsseett is ignored if there is no -ddaasshh pat-

tern. The offset may have any of the forms described in the COORDINATES section above.

-ffiillll color

-aaccttiivveeffiillll color

-ddiissaabblleeddffiillll color

Specifies the color to be used to fill item's area. in its nor-

mal, active, and disabled states, Color may have any of the forms accepted by TTkkGGeettCCoolloorr. If color is an empty string (the default), then then the item will not be filled. For the line item, it specifies the color of the line drawn. For the text item, it specifies the foreground color of the text.

-oouuttlliinnee color

-aaccttiivveeoouuttlliinnee color

-ddiissaabblleeddoouuttlliinnee color

This option specifies the color that should be used to draw the outline of the item in its normal, active and disabled states. Color may have any of the forms accepted by TTkkGGeettCCoolloorr. This option defaults to bbllaacckk. If color is specified as an empty string then no outline is drawn for the item.

-ooffffsseett offset

Specifies the offset of stipples. The offset value can be of the form xx,,yy or ssiiddee, where side can be nn, nnee, ee, ssee, ss, ssww, ww, nnww, or cceenntteerr. In the first case the origin is the origin of the

toplevel of the current window. For the canvas itself and can-

vas objects the origin is the canvas origin, but putting ## in

front of the coordinate pair indicates using the toplevel origin

instead. For canvas objects, the -ooffffsseett option is used for

stippling as well. For the line and polygon canvas items you

can also specify an index as argument, which connects the stip-

ple origin to one of the coordinate points of the line/polygon.

-oouuttlliinneessttiippppllee bitmap

-aaccttiivveeoouuttlliinneessttiippppllee bitmap

-ddiissaabblleeddoouuttlliinneessttiippppllee bitmap

This option specifies stipple patterns that should be used to draw the outline of the item in its normal, active and disabled states. Indicates that the outline for the item should be drawn with a stipple pattern; bitmap specifies the stipple pattern to

use, in any of the forms accepted by TTkkGGeettBBiittmmaapp. If the -oouutt-

lliinnee option hasn't been specified then this option has no effect. If bitmap is an empty string (the default), then the outline is drawn in a solid fashion.

-ssttiippppllee bitmap

-aaccttiivveessttiippppllee bitmap

-ddiissaabblleeddssttiippppllee bitmap

This option specifies stipple patterns that should be used to fill the the item in its normal, active and disabled states. bitmap specifies the stipple pattern to use, in any of the forms

accepted by TTkkGGeettBBiittmmaapp. If the -ffiillll option hasn't been spec-

ified then this option has no effect. If bitmap is an empty string (the default), then filling is done in a solid fashion. For the text item, it affects the actual text.

-ssttaattee state

This allows an item to override the canvas widget's global state

option. It takes the same values: normal, disabled or hidden.

-ttaaggss tagList

Specifies a set of tags to apply to the item. TagList consists of a list of tag names, which replace any existing tags for the item. TagList may be an empty list.

-wwiiddtthh outlineWidth

-aaccttiivveewwiiddtthh outlineWidth

-ddiissaabblleeddwwiiddtthh outlineWidth

Specifies the width of the outline to be drawn around the item's region, in its normal, active and disabled states. outlineWidth may be in any of the forms described in the COORDINATES section

above. If the -oouuttlliinnee option has been specified as an empty

string then this option has no effect. This option defaults to 1.0. For arcs, wide outlines will be drawn centered on the edges of the arc's region. AARRCC IITTEEMMSS

Items of type aarrcc appear on the display as arc-shaped regions. An arc

is a section of an oval delimited by two angles (specified by the

-ssttaarrtt and -eexxtteenntt options) and displayed in one of several ways (spec-

ified by the -ssttyyllee option). Arcs are created with widget commands of

the following form: pathName ccrreeaattee aarrcc x1 y1 x2 y2 ?option value option value ...? pathName ccrreeaattee aarrcc coordList ?option value option value ...? The arguments x1, y1, x2, and y2 or coordList give the coordinates of two diagonally opposite corners of a rectangular region enclosing the

oval that defines the arc. After the coordinates there may be any num-

ber of option-value pairs, each of which sets one of the configuration

options for the item. These same option-value pairs may be used in

iitteemmccoonnffiigguurree widget commands to change the item's configuration. The following standard options are supported by arcs:

-dash

-activedash

-disableddash

-dashoffset

-fill

-activefill

-disabledfill

-offset

-outline

-activeoutline

-disabledoutline

-outlinestipple

-activeoutlinestipple

-disabledoutlinestipple

-stipple

-activestipple

-disabledstipple

-state

-tags

-width

-activewidth

-disabledwidth

The following extra options are supported for arcs:

-eexxtteenntt degrees

Specifies the size of the angular range occupied by the arc.

The arc's range extends for degrees degrees counter-clockwise

from the starting angle given by the -ssttaarrtt option. Degrees may

be negative. If it is greater than 360 or less than -360, then

degrees modulo 360 is used as the extent.

-ssttaarrtt degrees

Specifies the beginning of the angular range occupied by the

arc. Degrees is given in units of degrees measured counter-

clockwise from the 3-o'clock position; it may be either posi-

tive or negative.

-ssttyyllee type

Specifies how to draw the arc. If type is ppiieesslliiccee (the default) then the arc's region is defined by a section of the oval's perimeter plus two line segments, one between the center of the oval and each end of the perimeter section. If type is cchhoorrdd then the arc's region is defined by a section of the oval's perimeter plus a single line segment connecting the two end points of the perimeter section. If type is aarrcc then the arc's region consists of a section of the perimeter alone. In

this last case the -ffiillll option is ignored.

BBIITTMMAAPP IITTEEMMSS Items of type bbiittmmaapp appear on the display as images with two colors, foreground and background. Bitmaps are created with widget commands of the following form: pathName ccrreeaattee bbiittmmaapp x y ?option value option value ...? pathName ccrreeaattee bbiittmmaapp coordList ?option value option value ...? The arguments x and y or coordList specify the coordinates of a point

used to position the bitmap on the display (see the -aanncchhoorr option

below for more information on how bitmaps are displayed). After the

coordinates there may be any number of option-value pairs, each of

which sets one of the configuration options for the item. These same

option-value pairs may be used in iitteemmccoonnffiigguurree widget commands to

change the item's configuration. The following standard options are supported by bitmaps:

-state

-tags

The following extra options are supported for bitmaps:

-aanncchhoorr anchorPos

AnchorPos tells how to position the bitmap relative to the posi-

tioning point for the item; it may have any of the forms accepted by TTkkGGeettAAnncchhoorr. For example, if anchorPos is cceenntteerr then the bitmap is centered on the point; if anchorPos is nn then the bitmap will be drawn so that its top center point is at the positioning point. This option defaults to cceenntteerr.

-bbaacckkggrroouunndd color

-aaccttiivveebbaacckkggrroouunndd bitmap

-ddiissaabblleeddbbaacckkggrroouunndd bitmap

Specifies the color to use for each of the bitmap's '0' valued pixels in its normal, active and disabled states. Color may have any of the forms accepted by TTkkGGeettCCoolloorr. If this option isn't specified, or if it is specified as an empty string, then

nothing is displayed where the bitmap pixels are 0; this pro-

duces a transparent effect.

-bbiittmmaapp bitmap

-aaccttiivveebbiittmmaapp bitmap

-ddiissaabblleeddbbiittmmaapp bitmap

Specifies the bitmaps to display in the item in its normal, active and disabled states. Bitmap may have any of the forms accepted by TTkkGGeettBBiittmmaapp.

-ffoorreeggrroouunndd color

-aaccttiivveeffoorreeggrroouunndd bitmap

-ddiissaabblleeddffoorreeggrroouunndd bitmap

Specifies the color to use for each of the bitmap's '1' valued pixels in its normal, active and disabled states. Color may have any of the forms accepted by TTkkGGeettCCoolloorr and defaults to bbllaacckk. IIMMAAGGEE IITTEEMMSS

Items of type iimmaaggee are used to display images on a canvas. Images are

created with widget commands of the following form: pathName ccrreeaattee iimmaaggee x y ?option value option value ...? pathName ccrreeaattee iimmaaggee coordList ?option value option value ...? The arguments x and y or coordList specify the coordinates of a point

used to position the image on the display (see the -aanncchhoorr option below

for more information). After the coordinates there may be any number

of option-value pairs, each of which sets one of the configuration

options for the item. These same option-value pairs may be used in

iitteemmccoonnffiigguurree widget commands to change the item's configuration. The following standard options are supported by images:

-state

-tags

The following extra options are supported for images:

-aanncchhoorr anchorPos

AnchorPos tells how to position the image relative to the posi-

tioning point for the item; it may have any of the forms accepted by TTkkGGeettAAnncchhoorr. For example, if anchorPos is cceenntteerr then the image is centered on the point; if anchorPos is nn then the image will be drawn so that its top center point is at the positioning point. This option defaults to cceenntteerr.

-iimmaaggee name

-aaccttiivveeiimmaaggee name

-ddiissaabblleeddiimmaaggee name

Specifies the name of the images to display in the item in is normal, active and disabled states. This image must have been created previously with the iimmaaggee ccrreeaattee command. LLIINNEE IITTEEMMSS Items of type lliinnee appear on the display as one or more connected line segments or curves. Line items support coordinate indexing operations

using the canvas widget commands: ddcchhaarrss,, iinnddeexx,, iinnsseerrtt.. Lines are

created with widget commands of the following form: pathName ccrreeaattee lliinnee x1 y1... xn yn ?option value option value ...? pathName ccrreeaattee lliinnee coordList ?option value option value ...? The arguments x1 through yn or coordList give the coordinates for a series of two or more points that describe a series of connected line segments. After the coordinates there may be any number of

option-value pairs, each of which sets one of the configuration options

for the item. These same option-value pairs may be used in iitteemmccoonnffiigg-

uurree widget commands to change the item's configuration. The following standard options are supported by lines:

-dash

-activedash

-disableddash

-dashoffset

-fill

-activefill

-disabledfill

-stipple

-activestipple

-disabledstipple

-state

-tags

-width

-activewidth

-disabledwidth

The following extra options are supported for lines:

-aarrrrooww where

Indicates whether or not arrowheads are to be drawn at one or both ends of the line. Where must have one of the values nnoonnee (for no arrowheads), ffiirrsstt (for an arrowhead at the first point of the line), llaasstt (for an arrowhead at the last point of the line), or bbootthh (for arrowheads at both ends). This option defaults to nnoonnee.

-aarrrroowwsshhaappee shape

This option indicates how to draw arrowheads. The shape argu-

ment must be a list with three elements, each specifying a dis-

tance in any of the forms described in the COORDINATES section above. The first element of the list gives the distance along the line from the neck of the arrowhead to its tip. The second element gives the distance along the line from the trailing points of the arrowhead to the tip, and the third element gives the distance from the outside edge of the line to the trailing

points. If this option isn't specified then Tk picks a ``rea-

sonable'' shape.

-ccaappssttyyllee style

Specifies the ways in which caps are to be drawn at the end-

points of the line. Style may have any of the forms accepted by TTkkGGeettCCaappSSttyyllee (bbuutttt, pprroojjeeccttiinngg, or rroouunndd). If this option isn't specified then it defaults to bbuutttt. Where arrowheads are drawn the cap style is ignored.

-jjooiinnssttyyllee style

Specifies the ways in which joints are to be drawn at the ver-

tices of the line. Style may have any of the forms accepted by TTkkGGeettCCaappSSttyyllee (bbeevveell, mmiitteerr, or rroouunndd). If this option isn't specified then it defaults to mmiitteerr. If the line only contains two points then this option is irrelevant.

-ssmmooootthh smoothMethod

smoothMethod must have one of the forms accepted by TTkkGGeett-

BBoooolleeaann or a line smoothing method. Only bbeezziieerr is supported in the core, but more can be added at runtime. If a boolean false value or empty string is given, no smoothing is applied. A boolean truth value assume bbeezziieerr smoothing. It indicates whether or not the line should be drawn as a curve. If so, the line is rendered as a set of parabolic splines: one spline is drawn for the first and second line segments, one for the second

and third, and so on. Straight-line segments can be generated

within a curve by duplicating the end-points of the desired line

segment.

-sspplliinneesstteeppss number

Specifies the degree of smoothness desired for curves: each spline will be approximated with number line segments. This

option is ignored unless the -ssmmooootthh option is true.

OOVVAALL IITTEEMMSS Items of type oovvaall appear as circular or oval regions on the display. Each oval may have an outline, a fill, or both. Ovals are created with widget commands of the following form: pathName ccrreeaattee oovvaall x1 y1 x2 y2 ?option value option value ...? pathName ccrreeaattee oovvaall coordList ?option value option value ...? The arguments x1, y1, x2, and y2 or coordList give the coordinates of two diagonally opposite corners of a rectangular region enclosing the oval. The oval will include the top and left edges of the rectangle

not the lower or right edges. If the region is square then the result-

ing oval is circular; otherwise it is elongated in shape. After the

coordinates there may be any number of option-value pairs, each of

which sets one of the configuration options for the item. These same

option-value pairs may be used in iitteemmccoonnffiigguurree widget commands to

change the item's configuration. The following standard options are supported by ovals:

-dash

-activedash

-disableddash

-dashoffset

-fill

-activefill

-disabledfill

-offset

-outline

-activeoutline

-disabledoutline

-outlinestipple

-activeoutlinestipple

-disabledoutlinestipple

-stipple

-activestipple

-disabledstipple

-state

-tags

-width

-activewidth

-disabledwidth

PPOOLLYYGGOONN IITTEEMMSS Items of type ppoollyyggoonn appear as polygonal or curved filled regions on the display. Polygon items support coordinate indexing operations

using the canvas widget commands: ddcchhaarrss,, iinnddeexx,, iinnsseerrtt.. Polygons are

created with widget commands of the following form: pathName ccrreeaattee ppoollyyggoonn x1 y1 ... xn yn ?option value option value ...? pathName ccrreeaattee ppoollyyggoonn coordList ?option value option value ...? The arguments x1 through yn or coordList specify the coordinates for three or more points that define a polygon. The first point should not be repeated as the last to close the shape; Tk will automatically close the periphery between the first and last points. After the coordinates

there may be any number of option-value pairs, each of which sets one

of the configuration options for the item. These same option-value

pairs may be used in iitteemmccoonnffiigguurree widget commands to change the item's configuration. The following standard options are supported by polygons:

-dash

-activedash

-disableddash

-dashoffset

-fill

-activefill

-disabledfill

-offset

-outline

-activeoutline

-disabledoutline

-outlinestipple

-activeoutlinestipple

-disabledoutlinestipple

-stipple

-activestipple

-disabledstipple

-state

-tags

-width

-activewidth

-disabledwidth

The following extra options are supported for polygons:

-jjooiinnssttyyllee style

Specifies the ways in which joints are to be drawn at the ver-

tices of the outline. Style may have any of the forms accepted by TTkkGGeettCCaappSSttyyllee (bbeevveell, mmiitteerr, or rroouunndd). If this option isn't specified then it defaults to mmiitteerr.

-ssmmooootthh boolean

Boolean must have one of the forms accepted by TTkkGGeettBBoooolleeaann It indicates whether or not the polygon should be drawn with a curved perimeter. If so, the outline of the polygon becomes a set of parabolic splines, one spline for the first and second line segments, one for the second and third, and so on.

Straight-line segments can be generated in a smoothed polygon by

duplicating the end-points of the desired line segment.

-sspplliinneesstteeppss number

Specifies the degree of smoothness desired for curves: each spline will be approximated with number line segments. This

option is ignored unless the -ssmmooootthh option is true.

Polygon items are different from other items such as rectangles, ovals and arcs in that interior points are considered to be ``inside'' a polygon (e.g. for purposes of the ffiinndd cclloosseesstt and ffiinndd oovveerrllaappppiinngg widget commands) even if it is not filled. For most other item types, an interior point is considered to be inside the item only if the item is filled or if it has neither a fill nor an outline. If you would like an unfilled polygon whose interior points are not considered to be inside the polygon, use a line item instead. RREECCTTAANNGGLLEE IITTEEMMSS Items of type rreeccttaannggllee appear as rectangular regions on the display. Each rectangle may have an outline, a fill, or both. Rectangles are created with widget commands of the following form: pathName ccrreeaattee rreeccttaannggllee x1 y1 x2 y2 ?option value option value ...? pathName ccrreeaattee rreeccttaannggllee coordList ?option value option value ...? The arguments x1, y1, x2, and y2 or coordList give the coordinates of two diagonally opposite corners of the rectangle (the rectangle will include its upper and left edges but not its lower or right edges).

After the coordinates there may be any number of option-value pairs,

each of which sets one of the configuration options for the item.

These same option-value pairs may be used in iitteemmccoonnffiigguurree widget com-

mands to change the item's configuration. The following standard options are supported by rectangles:

-dash

-activedash

-disableddash

-dashoffset

-fill

-activefill

-disabledfill

-offset

-outline

-activeoutline

-disabledoutline

-outlinestipple

-activeoutlinestipple

-disabledoutlinestipple

-stipple

-activestipple

-disabledstipple

-state

-tags

-width

-activewidth

-disabledwidth

TTEEXXTT IITTEEMMSS A text item displays a string of characters on the screen in one or more lines. Text items support indexing and selection, along with the

following text-related canvas widget commands: ddcchhaarrss, ffooccuuss, iiccuurrssoorr,

iinnddeexx, iinnsseerrtt, sseelleecctt. Text items are created with widget commands of the following form: pathName ccrreeaattee tteexxtt x y ?option value option value ...? pathName ccrreeaattee tteexxtt coordList ?option value option value ...? The arguments x and y or coordList specify the coordinates of a point used to position the text on the display (see the options below for more information on how text is displayed). After the coordinates

there may be any number of option-value pairs, each of which sets one

of the configuration options for the item. These same option-value

pairs may be used in iitteemmccoonnffiigguurree widget commands to change the item's configuration. The following standard options are supported by text items:

-fill

-activefill

-disabledfill

-stipple

-activestipple

-disabledstipple

-state

-tags

The following extra options are supported for text items:

-aanncchhoorr anchorPos

AnchorPos tells how to position the text relative to the posi-

tioning point for the text; it may have any of the forms accepted by TTkkGGeettAAnncchhoorr. For example, if anchorPos is cceenntteerr then the text is centered on the point; if anchorPos is nn then the text will be drawn such that the top center point of the

rectangular region occupied by the text will be at the position-

ing point. This option defaults to cceenntteerr.

-ffoonntt fontName

Specifies the font to use for the text item. FontName may be

any string acceptable to TTkkGGeettFFoonntt. If this option isn't spec-

ified, it defaults to a system-dependent font.

-jjuussttiiffyy how

Specifies how to justify the text within its bounding region. How must be one of the values lleefftt, rriigghhtt, or cceenntteerr. This option will only matter if the text is displayed as multiple lines. If the option is omitted, it defaults to lleefftt.

-tteexxtt string

String specifies the characters to be displayed in the text item. Newline characters cause line breaks. The characters in the item may also be changed with the iinnsseerrtt and ddeelleettee widget commands. This option defaults to an empty string.

-wwiiddtthh lineLength

Specifies a maximum line length for the text, in any of the forms described in the COORDINATES section above. If this option is zero (the default) the text is broken into lines only

at newline characters. However, if this option is non-zero then

any line that would be longer than lineLength is broken just

before a space character to make the line shorter than line-

Length; the space character is treated as if it were a newline character. WWIINNDDOOWW IITTEEMMSS Items of type wwiinnddooww cause a particular window to be displayed at a

given position on the canvas. Window items are created with widget

commands of the following form: pathName ccrreeaattee wwiinnddooww x y ?option value option value ...? pathName ccrreeaattee wwiinnddooww coordList ?option value option value ...? The arguments x and y or coordList specify the coordinates of a point

used to position the window on the display (see the -aanncchhoorr option

below for more information on how bitmaps are displayed). After the

coordinates there may be any number of option-value pairs, each of

which sets one of the configuration options for the item. These same

option-value pairs may be used in iitteemmccoonnffiigguurree widget commands to

change the item's configuration. The following standard options are supported by window items:

-state

-tags

The following extra options are supported for window items:

-aanncchhoorr anchorPos

AnchorPos tells how to position the window relative to the posi-

tioning point for the item; it may have any of the forms accepted by TTkkGGeettAAnncchhoorr. For example, if anchorPos is cceenntteerr then the window is centered on the point; if anchorPos is nn then the window will be drawn so that its top center point is at the positioning point. This option defaults to cceenntteerr.

-hheeiigghhtt pixels

Specifies the height to assign to the item's window. Pixels may have any of the forms described in the COORDINATES section above. If this option isn't specified, or if it is specified as an empty string, then the window is given whatever height it requests internally.

-wwiiddtthh pixels

Specifies the width to assign to the item's window. Pixels may have any of the forms described in the COORDINATES section above. If this option isn't specified, or if it is specified as an empty string, then the window is given whatever width it requests internally.

-wwiinnddooww pathName

Specifies the window to associate with this item. The window

specified by pathName must either be a child of the canvas wid-

get or a child of some ancestor of the canvas widget. PathName

may not refer to a top-level window.

Note: due to restrictions in the ways that windows are managed, it is not possible to draw other graphical items (such as lines and images) on top of window items. A window item always obscures any graphics that overlap it, regardless of their order in the display list.

AAPPPPLLIICCAATTIIOONN-DDEEFFIINNEEDD IITTEEMM TTYYPPEESS

It is possible for individual applications to define new item types for

canvas widgets using C code. See the documentation for TTkkCCrreeaatteeIItteemm-

TTyyppee. BBIINNDDIINNGGSS

In the current implementation, new canvases are not given any default

behavior: you'll have to execute explicit Tcl commands to give the

canvas its behavior.

CCRREEDDIITTSS

Tk's canvas widget is a blatant ripoff of ideas from Joel Bartlett's

ezd program. Ezd provides structured graphics in a Scheme environment

and preceded canvases by a year or two. Its simple mechanisms for

placing and animating graphical objects inspired the functions of can-

vases. KKEEYYWWOORRDDSS