canvas(3tk) Tk Built-In Commands canvas(3tk)
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NAME
canvas - Create and manipulate 'canvas' hypergraphics drawing surface
widgets
SYNOPSIS
canvas pathName ?options?
STANDARD OPTIONS
-background -borderwidth -cursor
-highlightbackground -highlightcolor -highlightthickness
-insertbackground -insertborderwidth -insertofftime
-insertontime -insertwidth -relief
-selectbackground -selectborderwidth -selectforeground
-takefocus -xscrollcommand -yscrollcommand
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 considered 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 re-
gion.
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 COORDINATES section below.
Command-Line Name:-scrollregion
Database Name: scrollRegion
Database Class: ScrollRegion
Specifies a list with four coordinates describing the left, top,
right, and bottom coordinates of a rectangular region. This re-
gion is used for scrolling purposes and is considered to be the
boundary of the information in the canvas. Each of the coordi-
nates may be specified in any of the forms given in the COORDI-
NATES section 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 ob-
jects all have their own state option which may override the de-
fault 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 ap-
pearance when the mouse pointer is over it, while the option
starting with disabled controls the appearance when the state is
disabled. Canvas items which are disabled will not react to can-
vas 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 COORDINATES 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 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 xScrollIncre-
ment; 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 xScrollIncrement. If the value of this option is
less than or equal to zero, then horizontal scrolling is uncon-
strained.
Command-Line Name:-yscrollincrement
Database Name: yScrollIncrement
Database Class: ScrollIncrement
Specifies an increment for vertical scrolling, in any of the
usual forms permitted for screen distances. If the value of this
option is greater than zero, the vertical view in the window
will be constrained so that the canvas y coordinate at the top
edge of the window is always an even multiple of yScrollIncre-
ment; 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 yScrollIncrement. If the value of this option is
less than or equal to zero, then vertical scrolling is uncon-
strained.
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INTRODUCTION
The canvas 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 canvas command returns its pathName argument. At the time this com-
mand 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 bind
command allows commands to be bound to widgets. For example, a particu-
lar command may be associated with the <Button-1> 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 de-
fined 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 ob-
scure those that are earlier in the display list and are sometimes re-
ferred to as being “on top” of earlier items. When a new item is cre-
ated 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 dis-
play 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 ad-
dition, the stacking order of window items is not affected by any of
the canvas widget commands; you must use the Tk raise command and lower
command instead.
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” is not. 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 cur-
rent item, which is the topmost item whose drawn area covers the posi-
tion of the mouse cursor (different item types interpret this in vary-
ing ways; see the individual item type documentation for details). 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
symbol tagOrId is used below to indicate that an argument specifies ei-
ther 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 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.
COORDINATES
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 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 ad-
just the origin of the canvas coordinate system relative to the origin
of the window using the xview and yview widget commands; this is typi-
cally used for scrolling. Canvases do not support scaling or rotation
of the canvas coordinate system relative to the window coordinate sys-
tem.
Individual items may be moved or scaled using widget commands 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 in-
dex; 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 possi-
ble 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 do not support 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 poly-
gons, numbers less than 0 or greater than the length of the
coordinate list will be adjusted by adding or subtracting the
length until the result is between zero and the length, in-
clusive.
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 cur-
sor 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 is not in this item then this form is illegal.
sel.last Refers to the last selected character in the item. If the
selection is not 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.
DASH PATTERNS
Many items support the notion of a 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 transpar-
ent.
The second possible syntax is a character list containing only 5 possi-
ble characters “.,-_ ”. The space can be used to enlarge the space be-
tween other line elements, and cannot 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 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.
WIDGET COMMAND
The canvas 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 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 is not 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 (topmost) of these items in
the display list is used.
all Selects all the items in the canvas.
below 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.
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 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 ex-
ists, 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 rec-
tangular region given by x1, y1, x2, and y2. X1 must be
no greater than 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 than 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 re-
turn 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 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 command will be invoked. This
widget command is similar to the bind command except that it op-
erates 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 associated 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, Button-
Press, 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-re-
lated 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 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 terminates that script, and a break command ter-
minates that script and skips any remaining scripts for the
event, just as for the bind command.
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 bind-
ings 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 loca-
tion. If gridspacing is specified, 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 loca-
tion. If gridspacing is specified, 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 can-
vas 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 avail-
able options for pathName (see Tk_ConfigureInfo 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 canvas command.
pathName coords tagOrId ?x0 y0 ...?
pathName coords tagOrId ?coordList?
Query or modify the coordinates that define an item. If no co-
ordinates are specified, this command returns a list whose ele-
ments are the coordinates of the item named by tagOrId. If co-
ordinates 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.
Note that for rectangles, ovals and arcs the returned list of
coordinates has a fixed order, namely the left, top, right and
bottom coordinates, which may not be the order originally given.
Also the coordinates are always returned in screen units with no
units (that is, in pixels). So if the original coordinates were
specified for instance in centimeters or inches, the returned
values will nevertheless be in pixels.
pathName create type x y ?x y ...? ?option value ...?
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 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 dchars 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 do not support indexing oper-
ations then they ignore this operation. Text items interpret
first and last as indices to a character, line and polygon items
interpret them as indices to a coordinate (an x,y pair). In-
dices 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 does not have the tag tagToDelete then the item is unaf-
fected by the command. If tagToDelete is omitted then it de-
faults 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 ad-
dtag 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 does not refer to any items,
or if none of them support the insertion cursor, then the focus
is not 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 fo-
cus.
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 indepen-
dent: a given item does not 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 was not 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 dis-
play list. If tagOrId does not 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 do not
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 fo-
cus widget command, above), but the cursor position may be set
even when the item does not have the focus. This command re-
turns an empty string.
pathName imove tagOrId index x y
This command causes the index'th coordinate of each of the items │
indicated by tagOrId to be relocated to the location (x,y). │
Each item interprets index independently according to the rules │
described in INDICES above. Out of the standard set of items, │
only line and polygon items may have their coordinates relocated │
this way.
pathName index 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 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 character, or coordinate, whose in-
dex 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 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 wid-
get. If no option is specified, returns a list describing all
of the available options for the first item given by tagOrId
(see Tk_ConfigureInfo 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 op-
tion(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 cre-
ate widget command when the item(s) were created; see the sec-
tions describing individual item types below for details on the
legal options.
pathName lower 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. Be-
lowThis 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 com-
mand has no effect on window items. Window items always obscure
other item types, and the stacking order of window items is de-
termined by the raise command and lower command, not the raise
widget command and lower widget command for canvases. This com-
mand 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 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 moveto tagOrId xPos yPos
Move the items given by tagOrId in the canvas coordinate space │
so that the first coordinate pair (the upper-left corner of the │
bounding box) of the first item (the lowest in the display list) │
with tag tagOrId is located at position (xPos,yPos). xPos and │
yPos may be the empty string, in which case the corresponding │
coordinate will be unchanged. All items matching tagOrId remain │
in the same positions relative to each other. This command re- │
turns an empty string.
pathName postscript ?option value option value ...?
Generate a Postscript representation for part or all of the can-
vas. 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 in-
terpreter 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 argument de-
notes 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 in-
voke 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 argu-
ment pairs provide additional information to control the genera-
tion of Postscript. The following options are supported:
-channel channelName
Specifies the name of the channel to which to write the
Postscript. If this option and the -file option are not
specified then the Postscript is returned as the result
of the command.
-colormap 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. “1.0 1.0 0.0 setrgbcolor”).
When outputting 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 has not been specified, or if there is no en-
try in varName for a given color, then Tk uses the red,
green, and blue intensities from the X color.
-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 and the -channel option are
not specified then the Postscript is returned as the re-
sult of the command.
-fontmap 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, -*-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 window.
-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. De-
faults 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 Post-
script page. Size consists of a floating-point number
followed by c for centimeters, i for inches, m for mil-
limeters, 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-uni-
form 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 Post-
script 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 conjunction 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 conjunction 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 ro-
tated 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.
-width size
Specifies the width of the area of the canvas to print.
Defaults to the width of the canvas window.
-x 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.
-y 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 raise 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. This command returns an
empty string.
Note: this command has no effect on window items. Window items
always obscure other item types, and the stacking order of win-
dow items is determined by the raise command and lower command,
not the raise widget command and lower widget command for can-
vases.
pathName rchars tagOrId first last string
This command causes the text or coordinates between first and │
last for each of the items indicated by tagOrId to be replaced │
by string. Each item interprets first and last independently ac- │
cording to the rules described in INDICES above. Out of the │
standard set of items, text items support this operation by al- │
tering their text as directed, and line and polygon items sup- │
port this operation by altering their coordinate list (in which │
case string should be a list of coordinates to use as a replace- │
ment). The other items ignore this operation.
pathName scale tagOrId xOrigin yOrigin xScale yScale
Rescale the coordinates of all of the items given by tagOrId in
canvas coordinate space. XOrigin and yOrigin identify the ori-
gin 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. Sim-
ilarly, each y-coordinate is adjusted to change the distance
from yOrigin by a factor of yScale. This command returns an
empty string.
Note that some items have only a single pair of coordinates
(e.g., text, images and windows) and so scaling of them by this
command can only move them around.
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 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 scan dragto 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 scan mark 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 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 se-
lection is used. Index gives a textual description of a posi-
tion 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 se-
lection to be at index (i.e. including but not going be-
yond index). The other end of the selection is made the
anchor point for future select to commands. If the se-
lection is not currently in tagOrId then this command be-
haves 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 se-
lection is not in this widget then the command has no ef-
fect. 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 does not change the selection; it
just sets the fixed end of the selection for future se-
lect to commands. Returns an empty string.
pathName select item
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 select to 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 in-
dex; it will include the character given by the anchor
point only if index is greater than or equal to the an-
chor point. The anchor point is determined by the most
recent select adjust or select from command for this wid-
get. If the selection anchor point for the widget is not
currently in tagOrId, then it is set to the same charac-
ter 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
does not refer to any items at all then an empty string is re-
turned.
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 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
-scrollregion 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 -xscrollcommand 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 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 element is
a real fraction between 0 and 1; together they describe
the vertical span that is visible in the window. For ex-
ample, 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 -scrollregion 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. Fraction 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 yScrollIncre-
ment 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 in-
formation becomes visible; if it is positive then lower
information becomes visible.
OVERVIEW OF ITEM TYPES
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 create 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 create and itemconfigure widget commands.
Most items do not support indexing or selection or the commands related
to them, such as index and insert. 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.
COMMON 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.
-anchor anchorPos
AnchorPos tells how to position the item relative to the posi-
tioning point for the item; it may have any of the forms ac-
cepted by Tk_GetAnchor. For example, if anchorPos is center then
the item is centered on the point; if anchorPos is n then the
item will be drawn so that its top center point is at the posi-
tioning point. This option defaults to center.
-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 Tk_GetDash. If the dash options are omit-
ted then the default is a solid outline. See DASH PATTERNS for
more information.
-dashoffset offset
The starting offset in pixels into the pattern provided by the
-dash option. -dashoffset is ignored if there is no -dash pat-
tern. The offset may have any of the forms described in the CO-
ORDINATES section above.
-fill color
-activefill color
-disabledfill 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 Tk_GetColor. For the line item, it specifies
the color of the line drawn. For the text item, it specifies
the foreground color of the text. If color is an empty string
(the default for all canvas items except line and text), then
the item will not be filled.
-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 Tk_GetColor. 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 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 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 -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. Note
that stipple offsets are only supported on X11; they are
silently ignored on other platforms.
-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 Tk_GetBitmap. If the -out-
line option has not been specified then this option has no ef-
fect. If bitmap is an empty string (the default), then the out-
line is drawn in a solid fashion. Note that stipples are not
well supported on platforms that do not use X11 as their drawing
API.
-outlineoffset offset
Specifies the offset of the stipple pattern used for outlines,
in the same way that the -outline option controls fill stipples.
(See the -outline option for a description of the syntax of off-
set.)
-stipple bitmap
-activestipple bitmap
-disabledstipple bitmap
This option specifies stipple patterns that should be used to
fill the item in its normal, active and disabled states. bitmap
specifies the stipple pattern to use, in any of the forms ac-
cepted by Tk_GetBitmap. If the -fill option has not been speci-
fied 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 stip-
ples 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: normal, disabled or hidden.
-tags 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.
-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 COORDINATES 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.
STANDARD ITEM TYPES
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 (spec-
ified by the -style option). Arcs are created with widget commands of
the following form:
pathName create arc x1 y1 x2 y2 ?option value ...?
pathName create arc coordList ?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
itemconfigure widget commands to change the item's configuration. An
arc item becomes the current item when the mouse pointer is over any
part that is painted or (when fully transparent) that would be painted
if both the -fill and -outline options were non-empty.
The following standard options are supported by arcs:
-dash -activedash
-disableddash -dashoffset
-fill -activefill
-disabledfill -offset
-outline -activeoutline
-disabledoutline -outlineoffset
-outlinestipple -activeoutlinestipple
-disabledoutlinestipple -stipple
-activestipple -disabledstipple
-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 measured 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 ...?
pathName create bitmap coordList ?option value ...?
The arguments x and y or coordList (which must have two elements) spec-
ify the coordinates of a point used to position the bitmap on the dis-
play, as controlled by the -anchor option. 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 configu-
ration. A bitmap item becomes the current item when the mouse pointer
is over any part of its bounding box.
The following standard options are supported by bitmaps:
-anchor -state
-tags
The following extra options are supported for bitmaps:
-background color
-activebackground color
-disabledbackground color
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 Tk_GetColor. If this option
is not 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.
-bitmap bitmap
-activebitmap bitmap
-disabledbitmap bitmap
Specifies the bitmaps to display in the item in its normal, ac-
tive and disabled states. Bitmap may have any of the forms ac-
cepted by Tk_GetBitmap.
-foreground color
-activeforeground color
-disabledforeground color
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 Tk_GetColor.
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 ...?
pathName create image coordList ?option value ...?
The arguments x and y or coordList specify the coordinates of a point
used to position the image on the display, as controlled by the -anchor
option. 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. An image item becomes the
current item when the mouse pointer is over any part of its bounding
box.
The following standard options are supported by images:
-anchor -state
-tags
The following extra options are supported for images:
-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 connected line
segments or curves. Line items support coordinate indexing operations
using the dchars, index and insert widget commands. Lines are created
with widget commands of the following form:
pathName create line x1 y1... xn yn ?option value ...?
pathName create line coordList ?option value ...?
The arguments x1 through yn or coordList give the coordinates for a se-
ries of two or more points that describe a series of connected line
segments. After the coordinates there may be any number of op-
tion-value pairs, each of which sets one of the configuration options
for the item. These same option-value pairs may be used in itemconfig-
ure widget commands to change the item's configuration. A line item is
the current item whenever the mouse pointer is over any segment of the
line, whether drawn or not and whether or not the line is smoothed.
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:
-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 de-
faults to none. When requested to draw an arrowhead, Tk inter-
nally adjusts the corresponding line end point so that the ren-
dered line ends at the neck of the arrowhead rather than at its
tip so that the line doesn't extend past the edge of the arrow-
head. This may trigger a Leave event if the mouse is hovering
this line end. Conversely, when removing an arrowhead Tk adjusts
the corresponding line point the other way round, which may
trigger an Enter event.
-arrowshape 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 is not specified then Tk picks a “rea-
sonable” shape.
-capstyle 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
Tk_GetCapStyle (butt, projecting, or round). If this option is
not 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 ver-
tices of the line. Style may have any of the forms accepted by
Tk_GetJoinStyle (bevel, miter, or round). If this option is not
specified then it defaults to round. If the line only contains
two points then this option is irrelevant.
-smooth smoothMethod
smoothMethod must have one of the forms accepted by Tcl_Get-
Boolean or a line smoothing method. Only true and raw are sup-
ported in the core (with bezier being an alias for true), 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
assumes true smoothing. If the smoothing method is true, this
indicates that the line should be drawn as a curve, rendered as
a set of quadratic 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. If the
smoothing method is raw, this indicates that the line should
also be drawn as a curve but where the list of coordinates is
such that the first coordinate pair (and every third coordinate
pair thereafter) is a knot point on a cubic Bezier curve, and
the other coordinates are control points on the cubic Bezier
curve. Straight line segments can be generated within a curve by
making control points equal to their neighbouring knot points.
If the last point is a control point and not a knot point, the
point is repeated (one or two times) so that it also becomes a
knot point.
-splinesteps number
Specifies the degree of smoothness desired for curves: each
spline will be approximated with number line segments. This op-
tion is ignored unless the -smooth option is true or raw.
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 ...?
pathName create oval coordList ?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 itemconfigure widget commands to
change the item's configuration. An oval item becomes the current item
when the mouse pointer is over any part that is painted or (when fully
transparent) that would be painted if both the -fill and -outline op-
tions were non-empty.
The following standard options are supported by ovals:
-dash -activedash
-disableddash -dashoffset
-fill -activefill
-disabledfill -offset
-outline -activeoutline
-disabledoutline -outlineoffset
-outlinestipple -activeoutlinestipple
-disabledoutlinestipple -stipple
-activestipple -disabledstipple
-state -tags
-width -activewidth
-disabledwidth
There are no oval-specific options.
POLYGON ITEMS
Items of type polygon appear as polygonal or curved filled regions on
the display. Polygon items support coordinate indexing operations us-
ing the dchars, index and insert widget commands. Polygons are created
with widget commands of the following form:
pathName create polygon x1 y1 ... xn yn ?option value ...?
pathName create polygon coordList ?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 itemconfigure widget commands to change the item's
configuration. A polygon item is the current item whenever the mouse
pointer is over any part of the polygon, whether drawn or not and
whether or not the outline is smoothed.
The following standard options are supported by polygons:
-dash -activedash
-disableddash -dashoffset
-fill -activefill
-disabledfill -offset
-outline -activeoutline
-disabledoutline -outlineoffset
-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 ver-
tices of the outline. Style may have any of the forms accepted
by Tk_GetJoinStyle (bevel, miter, or round). If this option is
not specified then it defaults to round.
-smooth boolean
Boolean must have one of the forms accepted by Tcl_GetBoolean or
a line smoothing method. Only true and raw are supported in the
core (with bezier being an alias for true), 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 assumes
true smoothing. If the smoothing method is true, this indicates
that the polygon should be drawn as a curve, rendered as a set
of quadratic splines: one spline is drawn for the first and sec-
ond line segments, one for the second and third, and so on.
Straight-line segments can be generated within a curve by dupli-
cating the end-points of the desired line segment. If the
smoothing method is raw, this indicates that the polygon should
also be drawn as a curve but where the list of coordinates is
such that the first coordinate pair (and every third coordinate
pair thereafter) is a knot point on a cubic Bezier curve, and
the other coordinates are control points on the cubic Bezier
curve. Straight line segments can be venerated within a curve by
making control points equal to their neighbouring knot points.
If the last point is not the second point of a pair of control
points, the point is repeated (one or two times) so that it also
becomes the second point of a pair of control points (the asso-
ciated knot point will be the first control point).
-splinesteps number
Specifies the degree of smoothness desired for curves: each
spline will be approximated with number line segments. This op-
tion is ignored unless the -smooth option is true or raw.
Polygon items are different from other items such as rectangles, ovals
and arcs in that interior points are considered to be “inside” a poly-
gon (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 in-
terior 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.
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 ...?
pathName create rectangle coordList ?option value ...?
The arguments x1, y1, x2, and y2 or coordList (which must have four el-
ements) 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 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
itemconfigure widget commands to change the item's configuration. A
rectangle item becomes the current item when the mouse pointer is over
any part that is painted or (when fully transparent) that would be
painted if both the -fill and -outline options were non-empty.
The following standard options are supported by rectangles:
-dash -activedash
-disableddash -dashoffset
-fill -activefill
-disabledfill -offset
-outline -activeoutline
-disabledoutline -outlineoffset
-outlinestipple -activeoutlinestipple
-disabledoutlinestipple -stipple
-activestipple -disabledstipple
-state -tags
-width -activewidth
-disabledwidth
There are no rectangle-specific options.
TEXT ITEMS
A text item displays a string of characters on the screen in one or
more lines. Text items support indexing, editing and selection through
the dchars widget command, the focus widget command, the icursor widget
command, the index widget command, the insert widget command, and the
select widget command. Text items are created with widget commands of
the following form:
pathName create text x y ?option value ...?
pathName create text coordList ?option value ...?
The arguments x and y or coordList (which must have two elements) spec-
ify 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 itemconfigure widget commands to
change the item's configuration. A text item becomes the current item
when the mouse pointer is over any part of its bounding box.
The following standard options are supported by text items:
-anchor -fill
-activefill -disabledfill
-stipple -activestipple
-disabledstipple -state
-tags
The following extra options are supported for text items:
-angle rotationDegrees
RotationDegrees tells how many degrees to rotate the text anti- │
clockwise about the positioning point for the text; it may have │
any floating-point value from 0.0 to 360.0. For example, if ro- │
tationDegrees is 90, then the text will be drawn vertically from │
bottom to top. This option defaults to 0.0.
-font fontName
Specifies the font to use for the text item. FontName may be
any string acceptable to Tk_GetFont. If this option is not
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 op-
tion 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.
-underline
Specifies the integer index of a character within the text to be
underlined. 0 corresponds to the first character of the text
displayed, 1 to the next character, and so on. -1 means that no
underline should be drawn (if the whole text item is to be un-
derlined, the appropriate font should be used instead).
-width lineLength
Specifies a maximum line length for the text, in any of the
forms described in the COORDINATES section above. If this op-
tion 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 be-
fore a space character to make the line shorter than lineLength;
the space character is treated as if it were a newline charac-
ter.
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 ...?
pathName create window coordList ?option value ...?
The arguments x and y or coordList (which must have two elements) spec-
ify the coordinates of a point used to position the window on the dis-
play, as controlled by the -anchor option. 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 configu-
ration. Theoretically, a window item becomes the current item when the
mouse pointer is over any part of its bounding box, but in practice
this typically does not happen because the mouse pointer ceases to be
over the canvas at that point.
The following standard options are supported by window items:
-anchor -state
-tags
The following extra options are supported for window items:
-height 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 is not specified, or if it is specified
as zero, then the window 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 COORDINATES section
above. If this option is not specified, or if it is specified
as zero, then the window is given whatever width it requests in-
ternally.
-window 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. Also note
that window items, unlike other canvas items, are not clipped for dis-
play by their containing canvas's border, and are instead clipped by
the parent widget of the window specified by the -window option; when
the parent widget is the canvas, this means that the window item can
overlap the canvas's border.
APPLICATION-DEFINED ITEM TYPES
It is possible for individual applications to define new item types for
canvas widgets using C code. See the documentation for Tk_CreateItem-
Type.
BINDINGS
In the current implementation, new canvases are not given any default
behavior: you will 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 plac-
ing and animating graphical objects inspired the functions of canvases.
SEE ALSO
bind(3tk), font(3tk), image(3tk), scrollbar(3tk)
KEYWORDS
canvas, widget
Tk 8.3 canvas(3tk)
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