Tk Built-In Commands canvas(1T)
NAME
canvas - Create and manipulate canvas widgets
SYNOPSIS
canvas pathName ?options?
STANDARD OPTIONS
-background -insertborderwidth -selectborderwidth
-borderwidth -insertofftime -selectforeground
-cursor -insertontime -takefocus
-highlightbackground -insertwidth -xscrollcommand
-highlightcolor -relief -yscrollcommand
-highlightthickness -state
-insertbackground -selectbackground
See the options manual entry for details on the standard
options.
WIDGET-SPECIFIC OPTIONS
Command-Line Name:-closeenough
Database Name: closeEnough
Database Class: CloseEnough
Specifies a floating-point value indicating how close
the mouse cursor must be to an item before it is con-
sidered to be ``inside'' the item. Defaults to 1.0.
Command-Line Name:-confine
Database Name: confine
Database Class: 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 scrollRegion argument.
Defaults to true, which means that the view will be
constrained within the scroll region.
Command-Line Name:-height
Database Name: height
Database Class: 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 CORDINATES section below.
Command-Line Name:-scrollregion
Database Name: scrollRegion
Database Class: ScrollRegion
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Tk Built-In Commands canvas(1T)
Specifies a list with four coordinates describing the
left, top, right, and bottom coordinates of a rectangu-
lar 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 speci-
fied in any of the forms given in the CORDINATES sec-
tion below.
Command-Line Name:-state
Database Name: state
Database Class: State
Modifies the default state of the canvas where state
may be set to one of: normal, disabled, or hidden.
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 different
situations. The options that start with active control
the appearance when the mouse pointer is over it, while
the option starting with disabled controls the appear-
ance when the state is disabled. Canvas items which
are disabled will not react to canvas bindings.
Command-Line Name:-width
Database Name: width
Database Class: 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
CORDINATES section below.
Command-Line Name:-xscrollincrement
Database Name: xScrollIncrement
Database Class: 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 hor-
izontal 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 xScrollIncrement; furth-
ermore, the units for scrolling (e.g., the change in
view when the left and right arrows of a scrollbar are
selected) will also be xScrollIncrement. If the value
of this option is less than or equal to zero, then hor-
izontal scrolling is unconstrained.
Command-Line Name:-yscrollincrement
Database Name: yScrollIncrement
Database Class: ScrollIncrement
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Tk Built-In Commands canvas(1T)
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 yScrollIncrement; furth-
ermore, the units for scrolling (e.g., the change in
view when the top and bottom arrows of a scrollbar are
selected) will also be yScrollIncrement. If the value
of this option is less than or equal to zero, then
vertical scrolling is unconstrained.
INTRODUCTION
The canvas command creates a new window (given by the path-
Name argument) and makes it into a canvas widget. Addi-
tional 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 canvas
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 rec-
tangles, 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 bind 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 can-
vas can have behaviors defined by the Tcl scripts bound to
them.
DISPLAY LIST
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 ear-
lier 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.
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 win-
dow items is not affected by any of the canvas widget com-
mands; you must use the raise and lower Tk commands instead.
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Tk Built-In Commands canvas(1T)
ITEM IDS AND TAGS
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 all 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 current is managed automatically by Tk; it applies
to the current item, 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 current 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 sym-
bol 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 parenthesized subexpres-
sions. 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 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.
CORDINATES
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Tk Built-In Commands canvas(1T)
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 sup-
plied then the distance is in pixels. If the letter is m
then the distance is in millimeters on the screen; if it is
c then the distance is in centimeters; i means inches, and p
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.
TRANSFORMATIONS
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 xview
and yview widget commands; this is typically used for
scrolling. Canvases do not support scaling or rotation of
the canvas coordinate system relative to the window coordi-
nate system.
Individual items may be moved or scaled using widget com-
mands described below, but they may not be rotated.
Note that the default origin of the canvas's visible area is
coincident with the origin for the whole window as that
makes bindings using the mouse position easier to work with;
you only need to use the canvasx and canvasy widget commands
if you adjust the origin of the visible area. However, this
also means that any focus ring (as controlled by the
-highlightthickness option) and window border (as controlled
by the -borderwidth option) must be taken into account
before you get to the visible area of the canvas.
INDICES
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 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
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Tk Built-In Commands canvas(1T)
text at the end of the item. Lines and Polygons don't sup-
port the insertion cursor and the selection. Their indices
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 polygons, numbers
less than 0 or greater then the length of the
coordinate list will be adjusted by adding or sub-
tracting the length until the result is between
zero and the length, inclusive.
end 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).
insert Refers to the character just before which the
insertion cursor is drawn in this item. Not valid
for lines and polygons.
sel.first Refers to the first selected character in the
item. If the selection isn't in this item then
this form is illegal.
sel.last 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 covered by the text
item, then they refer to the first or last charac-
ter in the line that is closest to the given
point.
DASH PATERNS
Many items support the notion of a dash pattern for out-
lines.
The first possible syntax is a list of integers. Each ele-
ment represents the number of pixels of a line segment. Only
the odd segments are drawn using the "outline" color. The
other segments are drawn transparent.
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Tk Built-In Commands canvas(1T)
The second possible syntax is a character list containing
only 5 possible 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 is 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 pat-
terns, the dash pattern will be displayed as the closest
dash pattern that is available. 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.
WIDGET COMAND
The canvas command creates a new Tcl command whose name is
pathName. This command may be used to invoke various opera-
tions on the widget. It has the following general form:
pathName option ?arg arg ...?
Option and the args determine the exact behavior of the com-
mand. The following widget commands are possible for canvas
widgets:
pathName addtag 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:
above 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 (top-
most) of these items in the display list is used.
all Selects all the items in the canvas.
below tagOrId
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Tk Built-In Commands canvas(1T)
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.
closest 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 con-
sidered 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 argument had not been specified.
enclosed 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.
overlapping 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.
withtag tagOrId
Selects all the items given by tagOrId.
pathName bbox 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.
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Tk Built-In Commands canvas(1T)
pathName bind 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 com-
mand will be invoked. This widget command is similar
to the bind command except that it operates on items in
a canvas rather than entire widgets. See the bind
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 associ-
ated with tagOrId and sequence (an error occurs if
there is no such binding). 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 Enter,
Leave, ButtonPress, Motion, and KeyPress) or virtual
events. The handling of events in canvases uses the
current item defined in ITEM IDS AND TAGS above. Enter
and Leave 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 Enter and Leave
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 focus
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.
It is possible for multiple bindings to match a partic-
ular 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 all 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 continue command in a binding script ter-
minates that script, and a break command terminates
that script and skips any remaining scripts for the
event, just as for the bind command.
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Tk Built-In Commands canvas(1T)
If bindings have been created for a canvas window using
the bind command, then they are invoked in addition to
bindings created for the canvas's items using the bind
widget command. The bindings for items will be invoked
before any of the bindings for the window as a whole.
pathName canvasx screenx ?gridspacing?
Given a window x-coordinate in the canvas screenx, this
command returns the canvas x-coordinate that is
displayed at that location. If gridspacing is speci-
fied, then the canvas coordinate is rounded to the
nearest multiple of gridspacing units.
pathName canvasy screeny ?gridspacing?
Given a window y-coordinate in the canvas screeny this
command returns the canvas y-coordinate that is
displayed at that location. If gridspacing is speci-
fied, then the canvas coordinate is rounded to the
nearest multiple of gridspacing units.
pathName cget option
Returns the current value of the configuration option
given by option. Option may have any of the values
accepted by the canvas command.
pathName configure ?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 available options for pathName
(see TkConfigureInfo 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 correspond-
ing 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 canvas command.
pathName coords tagOrId ?x0 y0 ...?
pathName coords 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 coordinates for the named
item. If tagOrId refers to multiple items, then the
first one in the display list is used.
pathName create type x y ?x y ...? ?option value ...?
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Tk Built-In Commands canvas(1T)
pathName create type coordList ?option value ...?
Create a new item in pathName of type type. The exact
format of the arguments after type depends on type, 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.
pathName dchars tagOrId first ?last?
For each item given by tagOrId, delete the characters,
or coordinates, in the range given by first and last,
inclusive. If some of the items given by tagOrId don't
support indexing operations 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 delete ?tagOrId tagOrId ...?
Delete each of the items given by each tagOrId, and
return an empty string.
pathName dtag 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 tagTo-
Delete then the item is unaffected by the command. If
tagToDelete is omitted then it defaults to tagOrId.
This command returns an empty string.
pathName find 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 addtag command. The items are
returned in stacking order, with the lowest item first.
pathName focus ?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 currently has the focus, or an
empty string if no item has the focus.
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Tk Built-In Commands canvas(1T)
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
focus 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 focus widget command with the
focus command to set the focus window to the canvas (if
it wasn't there already).
pathName gettags 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 display list. If tagOrId
doesn't refer to any items, or if the item contains no
tags, then an empty string is returned.
pathName icursor 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 widget command focus, below), but the
cursor position may be set even when the item doesn't
have the focus. This command returns an empty string.
pathName index tagOrId index
This command returns a decimal string giving the numer-
ical index within tagOrId corresponding to index.
Index gives a textual description of the desired posi-
tion as described in INDICES above. Text items inter-
pret 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 mul-
tiple items, then the index is processed in the first
of these items that supports indexing operations (in
display list order).
pathName insert 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 charac-
ter, or coordinate, whose index is beforeThis. Text
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Tk Built-In Commands canvas(1T)
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 itemcget 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 cget 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 create 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 itemconfigure tagOrId ?option? ?value? ?option value
This command is similar to the configure widget command
except that it modifies item-specific options for the
items given by tagOrId instead of modifying options for
the overall canvas widget. If no option is specified,
returns a list describing all of the available options
for the first item given by tagOrId (see
TkConfigureInfo 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 sub-
list 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 create widget command when the
item(s) were created; see the sections describing indi-
vidual item types below for details on the legal
options.
pathName lower tagOrId ?belowThis?
Move all of the items given by tagOrId to a new posi-
tion 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 raise and
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Tk Built-In Commands canvas(1T)
lower commands, not the raise and lower widget commands
for canvases. This command returns an empty string.
pathName move 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 associated with the item and yAmount to
the y-coordinate of each point associated with the
item. This command returns an empty string.
pathName postscript ?option value option value ...?
Generate a Postscript representation for part or all of
the canvas. If the -file 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 operation will fail
because safe interpreters are not allowed to write
files. If the -channel option is specified, the argu-
ment 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 Postscript is created in Encap-
sulated Postscript form using version 3.0 of the Docu-
ment 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 -width and
-height options to specify the area of the canvas to
print. The option-value argument pairs provide addi-
tional information to control the generation of
Postscript. The following options are supported:
-colormap varName
VarName must be the name of an array variable that
specifies a color mapping to use in the
Postscript. Each element of varName must consist
of Postscript code to set a particular color value
(e.g. ``1.0 1.0 0.0 setrgbcolor''). When output-
ting color information in the Postscript, Tk
checks to see if there is an element of varName
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.
Tk Last change: 8.3 14
Tk Built-In Commands canvas(1T)
-colormode mode
Specifies how to output color information. Mode
must be either color (for full color output), gray
(convert all colors to their gray-scale
equivalents) or mono (convert all colors to black
or white).
-file 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.
-fontmap varName
VarName must be the name of an array variable that
specifies a font mapping to use in the Postscript.
Each element of varName 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 varName 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,
-*-Courier-Bold-R-Normal--*-120-* will work but
*Courier-Bold-R-Normal*120* will not; Tk needs
the dashes to parse the font name).
-height size
Specifies the height of the area of the canvas to
print. Defaults to the height of the canvas win-
dow.
-pageanchor 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 -pagex and -pagey
options). For example, -pageanchor n 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
center.
-pageheight size
Specifies that the Postscript should be scaled in
both x and y so that the printed area is size high
on the Postscript page. Size consists of a
Tk Last change: 8.3 15
Tk Built-In Commands canvas(1T)
floating-point number followed by c for centime-
ters, i for inches, m for millimeters, or p or
nothing for printer's points (1/72 inch).
Defaults to the height of the printed area on the
screen. If both -pageheight and -pagewidth are
specified then the scale factor from -pagewidth is
used (non-uniform scaling is not implemented).
-pagewidth size
Specifies that the Postscript should be scaled in
both x and y so that the printed area is size wide
on the Postscript page. Size has the same form as
for -pageheight. Defaults to the width of the
printed area on the screen. If both -pageheight
and -pagewidth are specified then the scale factor
from -pagewidth is used (non-uniform scaling is
not implemented).
-pagex position
Position gives the x-coordinate of the positioning
point on the Postscript page, using any of the
forms allowed for -pageheight. Used in conjunc-
tion with the -pagey and -pageanchor options to
determine where the printed area appears on the
Postscript page. Defaults to the center of the
page.
-pagey position
Position gives the y-coordinate of the positioning
point on the Postscript page, using any of the
forms allowed for -pageheight. Used in conjunc-
tion with the -pagex and -pageanchor options to
determine where the printed area appears on the
Postscript page. Defaults to the center of the
page.
-rotate 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 (``landscape'' orientation).
Defaults to non-rotated.
-width size
Specifies the width of the area of the canvas to
print. Defaults to the width of the canvas win-
dow.
-x position
Specifies the x-coordinate of the left edge of the
Tk Last change: 8.3 16
Tk Built-In Commands canvas(1T)
area of the canvas that is to be printed, in can-
vas coordinates, not window coordinates. Defaults
to the coordinate of the left edge of the window.
-y position
Specifies the y-coordinate of the top edge of the
area of the canvas that is to be printed, in can-
vas coordinates, not window coordinates. Defaults
to the coordinate of the top edge of the window.
pathName raise tagOrId ?aboveThis?
Move all of the items given by tagOrId to a new posi-
tion 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 (top-
most) 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 raise and lower
commands, not the raise and lower widget commands for
canvases. This command returns an empty string.
pathName scale 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. Simi-
larly, each y-coordinate is adjusted to change the dis-
tance from yOrigin by a factor of yScale. This command
returns an empty string.
pathName scan option args
This command is used to implement scanning on canvases.
It has two forms, depending on option:
pathName scan mark x y
Records x and y and the canvas's current view;
used in conjunction with later scan dragto com-
mands. 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 scan dragto x y ?gain?.
This command computes the difference between its x
Tk Last change: 8.3 17
Tk Built-In Commands canvas(1T)
and y arguments (which are typically mouse coordi-
nates) and the x and y arguments to the last scan
mark command for the widget. It then adjusts the
view by gain times the difference in coordinates,
where gain defaults to 10. This command is typi-
cally 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 select 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 position within tagOrId, as described in INDICES
above.
pathName select adjust 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. includ-
ing but not going beyond index). The other end of
the selection is made the anchor point for future
select to commands. If the selection isn't
currently in tagOrId then this command behaves the
same as the select to widget command. Returns an
empty string.
pathName select clear
Clear the selection if it is in this widget. If
the selection isn't in this widget then the com-
mand has no effect. Returns an empty string.
pathName select from 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 select to commands.
Returns an empty string.
pathName select item
Returns the id of the selected item, if the selec-
tion is in an item in this canvas. If the selec-
tion is not in this canvas then an empty string is
returned.
pathName select to tagOrId index
Tk Last change: 8.3 18
Tk Built-In Commands canvas(1T)
Set the selection to consist of those characters
of tagOrId between the selection anchor point and
index. The new selection will include the charac-
ter 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 select
adjust or select from command for this widget. If
the selection anchor point for the widget isn't
currently in tagOrId, then it is set to the same
character given by index. Returns an empty
string.
pathName type tagOrId
Returns the type of the item given by tagOrId, such as
rectangle or text. 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 xview ?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 xview
Returns a list containing two elements. Each ele-
ment 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 -scrollregion
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 -xscrollcom-
mand option.
pathName xview moveto 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 xview scroll 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 units or pages
or an abbreviation of one of these. If what is
units, the view adjusts left or right in units of
the xScrollIncrement option, if it is greater than
zero, or in units of one-tenth the window's width
Tk Last change: 8.3 19
Tk Built-In Commands canvas(1T)
otherwise. If what is pages 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 yview ?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 yview
Returns a list containing two elements. Each ele-
ment 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 -scrollre-
gion option) is visible in the window. These are
the same values passed to scrollbars via the
-yscrollcommand option.
pathName yview moveto fraction
Adjusts the view in the window so that fraction of
the canvas's area is off-screen to the top. Frac-
tion is a fraction between 0 and 1.
pathName yview scroll 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 units or pages.
If what is units, the view adjusts up or down in
units of the yScrollIncrement option, if it is
greater than zero, or in units of one-tenth the
window's height otherwise. If what is pages 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.
OVERVIEW OF ITEM TYPES
The sections below describe the various types of items sup-
ported by canvas widgets. Each item type is characterized
by two things: first, the form of the create command used
to create instances of the type; and second, a set of con-
figuration options for items of that type, which may be used
in the create and itemconfigure widget commands. Most items
don't support indexing or selection or the commands related
to them, such as index and insert. Where items do support
these facilities, it is noted explicitly in the descriptions
below. At present, text, line and polygon items provide
this support. For lines and polygons the indexing facility
Tk Last change: 8.3 20
Tk Built-In Commands canvas(1T)
is used to manipulate the coordinates of the item.
COMON ITEM OPTIONS
Many items share a common set of options. These options are
explained here, and then referred to be each widget type for
brevity.
-dash pattern
-activedash pattern
-disableddash 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 TkGetDash. If
the dash options are omitted then the default is a
solid outline. See "DASH PATERNS" for more informa-
tion.
-dashoffset offset
The starting offset in pixels into the pattern provided
by the -dash option. -dashoffset is ignored if there
is no -dash pattern. The offset may have any of the
forms described in the CORDINATES section above.
-fill color
-activefill color
-disabledfill color
Specifies the color to be used to fill item's area. in
its normal, active, and disabled states, Color may have
any of the forms accepted by TkGetColor. If color is
an empty string (the default), 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.
-outline color
-activeoutline color
-disabledoutline 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 TkGetColor. This option defaults to
black. If color is specified as an empty string then
no outline is drawn for the item.
-offset offset
Specifies the offset of stipples. The offset value can
Tk Last change: 8.3 21
Tk Built-In Commands canvas(1T)
be of the form x,y or side, where side can be n, ne, e,
se, s, sw, w, nw, or center. In the first case the ori-
gin is the origin of the toplevel of the current win-
dow. For the canvas itself and canvas objects the ori-
gin is the canvas origin, but putting # in front of the
coordinate pair indicates using the toplevel origin
instead. For canvas objects, the -offset 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 stipple origin to one of the coordinate
points of the line/polygon.
-outlinestipple bitmap
-activeoutlinestipple bitmap
-disabledoutlinestipple 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 TkGetBitmap. If the -outline
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. Note
that stipples are not well supported on platforms that
do not use X11 as their drawing API.
-stipple bitmap
-activestipple bitmap
-disabledstipple bitmap
This option specifies stipple patterns that should be
used to fill the item in its normal, active and dis-
abled states. bitmap specifies the stipple pattern to
use, in any of the forms accepted by TkGetBitmap. If
the -fill option hasn't been specified 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. Note that
stipples are not well supported on platforms that do
not use X11 as their drawing API.
-state state
This allows an item to override the canvas widget's
global state option. It takes the same values: nor-
mal, disabled or hidden.
-tags tagList
Specifies a set of tags to apply to the item. TagList
Tk Last change: 8.3 22
Tk Built-In Commands canvas(1T)
consists of a list of tag names, which replace any
existing tags for the item. TagList may be an empty
list.
-width outlineWidth
-activewidth outlineWidth
-disabledwidth 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 CORDINATES section above. If the
-outline 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.
ARC ITEMS
Items of type arc appear on the display as arc-shaped
regions. An arc is a section of an oval delimited by two
angles (specified by the -start and -extent options) and
displayed in one of several ways (specified by the -style
option). Arcs are created with widget commands of the fol-
lowing form:
pathName create arc x1 y1 x2 y2 ?option value option value ...?
pathName create arc coordList ?option value option value ...?
The arguments x1, y1, x2, and y2 or coordList give the coor-
dinates of two diagonally opposite corners of a rectangular
region enclosing the oval that defines the arc. 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 itemcon-
figure 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
Tk Last change: 8.3 23
Tk Built-In Commands canvas(1T)
-state
-tags
-width
-activewidth
-disabledwidth
The following extra options are supported for arcs:
-extent 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
-start option. Degrees may be negative. If it is
greater than 360 or less than -360, then degrees modulo
360 is used as the extent.
-start degrees
Specifies the beginning of the angular range occupied
by the arc. Degrees is given in units of degrees meas-
ured counter-clockwise from the 3-o'clock position; it
may be either positive or negative.
-style type
Specifies how to draw the arc. If type is pieslice
(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 chord 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 arc then
the arc's region consists of a section of the perimeter
alone. In this last case the -fill option is ignored.
BITMAP ITEMS
Items of type bitmap appear on the display as images with
two colors, foreground and background. Bitmaps are created
with widget commands of the following form:
pathName create bitmap x y ?option value option value ...?
pathName create bitmap 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 -anchor 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 itemconfigure 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:
Tk Last change: 8.3 24
Tk Built-In Commands canvas(1T)
-anchor anchorPos
AnchorPos tells how to position the bitmap relative to
the positioning point for the item; it may have any of
the forms accepted by TkGetAnchor. For example, if
anchorPos is center then the bitmap is centered on the
point; if anchorPos is n then the bitmap will be drawn
so that its top center point is at the positioning
point. This option defaults to center.
-background color
-activebackground bitmap
-disabledbackground 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
TkGetColor. 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 produces
a transparent effect.
-bitmap bitmap
-activebitmap bitmap
-disabledbitmap 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 TkGetBitmap.
-foreground color
-activeforeground bitmap
-disabledforeground 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
TkGetColor and defaults to black.
IMAGE ITEMS
Items of type image are used to display images on a canvas.
Images are created with widget commands of the following
form:
pathName create image x y ?option value option value ...?
pathName create image 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 -anchor 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
Tk Last change: 8.3 25
Tk Built-In Commands canvas(1T)
item. These same option-value pairs may be used in itemcon-
figure 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:
-anchor anchorPos
AnchorPos tells how to position the image relative to
the positioning point for the item; it may have any of
the forms accepted by TkGetAnchor. For example, if
anchorPos is center then the image is centered on the
point; if anchorPos is n then the image will be drawn
so that its top center point is at the positioning
point. This option defaults to center.
-image name
-activeimage name
-disabledimage 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 image create
command.
LINE ITEMS
Items of type line appear on the display as one or more con-
nected line segments or curves. Line items support coordi-
nate indexing operations using the canvas widget commands:
dchars, index, insert. Lines are created with widget com-
mands of the following form:
pathName create line x1 y1... xn yn ?option value option value ...?
pathName create line coordList ?option value option value ...?
The arguments x1 through yn or coordList give the coordi-
nates 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 itemconfigure 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
Tk Last change: 8.3 26
Tk Built-In Commands canvas(1T)
-state
-tags
-width
-activewidth
-disabledwidth
The following extra options are supported for lines:
-arrow 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 none (for no arrowheads), first (for an
arrowhead at the first point of the line), last (for an
arrowhead at the last point of the line), or both (for
arrowheads at both ends). This option defaults to
none.
-arrowshape shape
This option indicates how to draw arrowheads. The
shape argument must be a list with three elements, each
specifying a distance in any of the forms described in
the CORDINATES 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 ele-
ment gives the distance from the outside edge of the
line to the trailing points. If this option isn't
specified then Tk picks a ``reasonable'' shape.
-capstyle style
Specifies the ways in which caps are to be drawn at the
endpoints of the line. Style may have any of the forms
accepted by TkGetCapStyle (butt, projecting, or
round). If this option isn't specified then it
defaults to butt. Where arrowheads are drawn the cap
style is ignored.
-joinstyle style
Specifies the ways in which joints are to be drawn at
the vertices of the line. Style may have any of the
forms accepted by TkGetCapStyle (bevel, miter, or
round). If this option isn't specified then it
defaults to miter. If the line only contains two
points then this option is irrelevant.
-smooth smoothMethod
smoothMethod must have one of the forms accepted by
TclGetBoolean or a line smoothing method. Only bezier
is supported in the core, but more can be added at run-
time. If a boolean false value or empty string is
given, no smoothing is applied. A boolean truth value
assume bezier smoothing. It indicates whether or not
Tk Last change: 8.3 27
Tk Built-In Commands canvas(1T)
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.
-splinesteps number
Specifies the degree of smoothness desired for curves:
each spline will be approximated with number line seg-
ments. This option is ignored unless the -smooth
option is true.
OVAL ITEMS
Items of type oval 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 create oval x1 y1 x2 y2 ?option value option value ...?
pathName create oval coordList ?option value option value ...?
The arguments x1, y1, x2, and y2 or coordList give the coor-
dinates 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 resulting 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 itemcon-
figure 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
Tk Last change: 8.3 28
Tk Built-In Commands canvas(1T)
-activewidth
-disabledwidth
POLYGON ITEMS
Items of type polygon appear as polygonal or curved filled
regions on the display. Polygon items support coordinate
indexing operations using the canvas widget commands:
dchars, index, insert. Polygons are created with widget
commands of the following form:
pathName create polygon x1 y1 ... xn yn ?option value option value ...?
pathName create polygon coordList ?option value option value ...?
The arguments x1 through yn or coordList specify the coordi-
nates 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 itemconfigure widget com-
mands 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:
-joinstyle style
Specifies the ways in which joints are to be drawn at
the vertices of the outline. Style may have any of the
forms accepted by TkGetCapStyle (bevel, miter, or
round). If this option isn't specified then it
defaults to miter.
Tk Last change: 8.3 29
Tk Built-In Commands canvas(1T)
-smooth boolean
Boolean must have one of the forms accepted by
TclGetBoolean. 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 para-
bolic 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.
-splinesteps number
Specifies the degree of smoothness desired for curves:
each spline will be approximated with number line seg-
ments. This option is ignored unless the -smooth
option is true.
Polygon items are different from other items such as rectan-
gles, ovals and arcs in that interior points are considered
to be ``inside'' a polygon (e.g. for purposes of the find
closest and find overlapping 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 con-
sidered to be inside the polygon, use a line item instead.
RECTANGLE ITEMS
Items of type rectangle 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 create rectangle x1 y1 x2 y2 ?option value option value ...?
pathName create rectangle coordList ?option value option value ...?
The arguments x1, y1, x2, and y2 or coordList give the coor-
dinates 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 itemconfigure 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
Tk Last change: 8.3 30
Tk Built-In Commands canvas(1T)
-activeoutline
-disabledoutline
-outlinestipple
-activeoutlinestipple
-disabledoutlinestipple
-stipple
-activestipple
-disabledstipple
-state
-tags
-width
-activewidth
-disabledwidth
TEXT ITEMS
A text item displays a string of characters on the screen in
one or more lines. Text items support indexing and selec-
tion, along with the following text-related canvas widget
commands: dchars, focus, icursor, index, insert, select.
Text items are created with widget commands of the following
form:
pathName create text x y ?option value option value ...?
pathName create text 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 confi-
guration options for the item. These same option-value
pairs may be used in itemconfigure 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:
-anchor anchorPos
AnchorPos tells how to position the text relative to
the positioning point for the text; it may have any of
the forms accepted by TkGetAnchor. For example, if
anchorPos is center then the text is centered on the
point; if anchorPos is n then the text will be drawn
such that the top center point of the rectangular
region occupied by the text will be at the positioning
point. This option defaults to center.
Tk Last change: 8.3 31
Tk Built-In Commands canvas(1T)
-font fontName
Specifies the font to use for the text item. FontName
may be any string acceptable to TkGetFont. If this
option isn't specified, it defaults to a system-
dependent font.
-justify how
Specifies how to justify the text within its bounding
region. How must be one of the values left, right, or
center. This option will only matter if the text is
displayed as multiple lines. If the option is omitted,
it defaults to left.
-text 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
insert and delete widget commands. This option
defaults to an empty string.
-width lineLength
Specifies a maximum line length for the text, in any of
the forms described in the CORDINATES 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 lineLength;
the space character is treated as if it were a newline
character.
WINDOW ITEMS
Items of type window 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 create window x y ?option value option value ...?
pathName create window 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 -anchor 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 itemconfigure 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:
-anchor anchorPos
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Tk Built-In Commands canvas(1T)
AnchorPos tells how to position the window relative to
the positioning point for the item; it may have any of
the forms accepted by TkGetAnchor. For example, if
anchorPos is center then the window is centered on the
point; if anchorPos is n then the window will be drawn
so that its top center point is at the positioning
point. This option defaults to center.
-height pixels
Specifies the height to assign to the item's window.
Pixels may have any of the forms described in the COR-
DINATES section above. If this option isn't specified,
or if it is specified as an empty string, then the win-
dow is given whatever height it requests internally.
-width pixels
Specifies the width to assign to the item's window.
Pixels may have any of the forms described in the COR-
DINATES section above. If this option isn't specified,
or if it is specified as an empty string, then the win-
dow is given whatever width it requests internally.
-window pathName
Specifies the window to associate with this item. The
window specified by pathName must either be a child of
the canvas widget 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, regard-
less of their order in the display list.
APLICATION-DEFINED ITEM TYPES
It is possible for individual applications to define new
item types for canvas widgets using C code. See the docu-
mentation for TkCreateItemType.
BINDINGS
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.
CREDITS
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 canvases.
Tk Last change: 8.3 33
Tk Built-In Commands canvas(1T)
SEE ALSO
bind(1T), font(1T), image(1T), scrollbar(1T)
KEYWORDS
canvas, widget
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWTk
Interface Stability Uncommitted
NOTES
Source for Tk is available on http:/opensolaris.org.
Tk Last change: 8.3 34
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