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canvas(n) Tk Built-In Commands canvas(n)
NAME
canvas - Create and manipulate canvas widgets
SYNOPSIS
canvas pathName ?options? -background -insertborderwidth -select-
borderwidth -borderwidth -insertofftime -selectforeground -cur-
sor -insertontime -takefocus -highlightbackground -inser-
twidth -xscrollcommand -highlightcolor -relief -yscrollcommand
-highlightthickness -state -insertbackground -selectbackground
WIDGET-SPECIFIC OPTIONS
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. 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. 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. Specifies a list with four
coordinates describing the left, top, right, and bottom coordinates of
a rectangular region. This region is used for scrolling purposes and
is considered to be the boundary of the information in the canvas.
Each of the coordinates may be specified in any of the forms given in
the COORDINATES section below. Modifies the default state of the can-
vas 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 specifica-
tions such that the appearance of the item can be different in differ-
ent situations. The options that start with active control the
appearence when the mouse pointer is over it, while the option starting
with disabled controls the appearence when the state is disabled. Can-
vas items which are disabled will not react to canvas bindings. Speci-
fies 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. 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 hori-
zontal 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; 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. 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 win-
dow is always an even multiple of yScrollIncrement; 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 unconstrained.
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
command is invoked, there must not exist a window named pathName, but
pathName's parent must exist.
Canvas widgets implement structured graphics. A canvas displays any
number of items, which may be things like rectangles, circles, lines,
and text. Items may be manipulated (e.g. moved or re-colored) and com-
mands may be associated with items in much the same way that the bind
command allows commands to be bound to widgets. For example, a partic-
ular command may be associated with the event so that the
command is invoked whenever button 1 is pressed with the mouse cursor
over an item. This means that items in a canvas can have behaviors
defined by the Tcl scripts bound to them.
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 earlier in the display list and are sometimes
referred to as being ``on top'' of earlier items. When a new item is
created it is placed at the end of the display list, on top of every-
thing else. Widget commands may be used to re-arrange the order of the
display list.
Window items are an exception to the above rules. The underlying win-
dow systems require them always to be drawn on top of other items. In
addition, the stacking order of window items is not affected by any of
the canvas widget commands; you must use the raise and lower Tk com-
mands 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'' 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 cur-
rent item, which is the topmost item whose drawn area covers the posi-
tion of the mouse cursor. If the mouse is not in the canvas widget or
is not over an item, then no item has the 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
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 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
adjust the origin of the canvas coordinate system relative to the ori-
gin of the window using the xview and yview widget commands; this is
typically used for scrolling. Canvases do not support scaling or rota-
tion of the canvas coordinate system relative to the window coordinate
system.
Individual items may be moved or scaled using widget commands described
below, but they may not be rotated.
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 advis-
able to support as many of these forms as practical. Note that it is
possible to refer to the character just after the last one in the text
item; this is necessary for such tasks as inserting new text at the
end of the item. Lines and Polygons don't support the insertion cursor
and the selection. Their 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 then the length of the
coordinate list will be adjusted by adding or subtracting 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 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 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 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
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 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 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 (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
exists, then the selection behaves as if the start argu-
ment 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.
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
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 associated with
tagOrId and sequence (an error occurs if there is no such bind-
ing). If both command and sequence are omitted then the command
returns a list of all the sequences for which bindings have been
defined for tagOrId.
The only events for which bindings may be specified are those
related to the mouse and keyboard (such as 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 trig-
ger only if the virtual event is defined by an underlying mouse-
related or keyboard-related event.
It is possible for multiple bindings to match a particular
event. This could occur, for example, if one binding is associ-
ated with the item's id and another is associated with one of
the item's tags. When this occurs, all of the matching bindings
are invoked. A binding associated with the 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
coordinates are specified, this command returns a list whose
elements are the coordinates of the item named by tagOrId. If
coordinates are specified, then they replace the current coordi-
nates for the named item. If tagOrId refers to multiple items,
then the first one in the display list is used.
pathName 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 don't support indexing opera-
tions then they ignore dchars. Text items interpret first and
last as indices to a character, line and polygon items interpret
them indices to a coordinate (an x,y pair). Indices are
described in INDICES above. If last is omitted, it defaults to
first. This command returns an empty string.
pathName 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 tagToDelete then the item is unaf-
fected by the command. If tagToDelete is omitted then it
defaults to tagOrId. This command returns an empty string.
pathName 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 cur-
rently has the focus, or an empty string if no item has the
focus.
Once the focus has been set to an item, the item will display
the insertion cursor and all keyboard events will be directed to
that item. The focus item within a canvas and the focus window
on the screen (set with the focus command) are totally indepen-
dent: a given item doesn't actually have the input focus unless
(a) its canvas is the focus window and (b) the item is the focus
item within the canvas. In most cases it is advisable to follow
the 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 dis-
play list. If tagOrId doesn't refer to any items, or if the
item contains no tags, then an empty string is returned.
pathName 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 wid-
get 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 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
index is beforeThis. Text items interpret beforeThis as an
index to a character, line and polygon items interpret it as an
index to a coordinate (an x,y pair). For lines and polygons the
string must be a valid coordinate sequence. See INDICES above
for information about the forms allowed for beforeThis. This
command returns an empty string.
pathName 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
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 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.
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 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 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 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
interpreter that owns the canvas is marked as safe, the opera-
tion will fail because safe interpreters are not allowed to
write files. If the -channel option is specified, the argument
denotes the name of a channel already opened for writing. The
Postscript is written to that channel, and the channel is left
open for further writing at the end of the operation. The Post-
script is created in Encapsulated Postscript form using version
3.0 of the Document Structuring Conventions. Note: by default
Postscript is only generated for information that appears in the
canvas's window on the screen. If the canvas is freshly created
it may still have its initial size of 1x1 pixel so nothing will
appear in the Postscript. To get around this problem either
invoke the "update" command to wait for the canvas window to
reach its final size, or else use the -width and -height options
to specify the area of the canvas to print. The option-value
argument pairs provide additional information to control the
generation of Postscript. The following options are supported:
-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 setrgb-
color''). When outputting color information in the Post-
script, Tk checks to see if there is an element of var-
Name with the same name as the color. If so, Tk uses the
value of the element as the Postscript command to set the
color. If this option hasn't been specified, or if there
isn't an entry in varName for a given color, then Tk uses
the red, green, and blue intensities from the X color.
-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 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.
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 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 scal-
ing 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
rotated 90 degrees. In non-rotated output the x-axis of
the printed area runs along the short dimension of the
page (``portrait'' orientation); in rotated output the x-
axis runs along the long dimension of the page (``land-
scape'' orientation). Defaults to non-rotated.
-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. 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. Similarly, each y-
coordinate is adjusted to change the distance 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 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
selection 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
selection to be at index (i.e. including but not going
beyond index). The other end of the selection is made
the anchor point for future 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 command 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 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
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 wid-
get. If the selection anchor point for the widget isn't
currently in tagOrId, then it is set to the same charac-
ter given by index. Returns an empty string.
pathName 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 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
example, if the first element is .6 and the second ele-
ment is 1.0, the lowest 40% of the canvas's area (as
defined by the -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
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 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 don't 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.
-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
COORDINATES 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. 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 Tk_GetColor. 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 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 stip-
ple 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 Tk_GetBitmap. If the -out-
line 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.
-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
accepted by Tk_GetBitmap. If the -fill option hasn't been spec-
ified then this option has no effect. If bitmap is an empty
string (the default), then filling is done in a solid fashion.
For the text item, it affects the actual text.
-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.
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
option value ...? pathName create arc coordList ?option value option
value ...? The arguments x1, y1, x2, and y2 or coordList give the
coordinates of two diagonally opposite corners of a rectangular region
enclosing the oval that defines the arc. After the coordinates there
may be any 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.
The following standard options are supported by arcs: -dash -activedash
-disableddash -dashoffset -fill -activefill -disabledfill -offset -out-
line -activeoutline -disabledoutline -outlinestipple -activeout-
linestipple -disabledoutlinestipple -stipple -activestipple -disabled-
stipple -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 posi-
tive 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:
-anchor anchorPos
AnchorPos tells how to position the bitmap relative to the posi-
tioning point for the item; it may have any of the forms
accepted by Tk_GetAnchor. 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 Tk_GetColor. If this option
isn't specified, or if it is specified as an empty string, then
nothing is displayed where the bitmap pixels are 0; this pro-
duces a transparent effect.
-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 Tk_GetBitmap.
-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 Tk_GetColor 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 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 images: -state -tags
The following extra options are supported for images:
-anchor anchorPos
AnchorPos tells how to position the image relative to the posi-
tioning point for the item; it may have any of the forms
accepted by Tk_GetAnchor. 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 connected line
segments or curves. Line items support coordinate indexing operations
using the canvas widget commands: dchars, index, insert. Lines are
created with widget commands 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 coordinates for a series of two or
more points that describe a series of connected line segments. After
the coordinates there may be any number of option-value pairs, each of
which sets one of the configuration options for the item. These same
option-value pairs may be used in 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 -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 argu-
ment must be a list with three elements, each specifying a dis-
tance in any of the forms described in the COORDINATES section
above. The first element of the list gives the distance along
the line from the neck of the arrowhead to its tip. The second
element gives the distance along the line from the trailing
points of the arrowhead to the tip, and the third element gives
the distance from the outside edge of the line to the trailing
points. If this option isn't specified then Tk picks a ``rea-
sonable'' shape.
-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
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 ver-
tices of the line. Style may have any of the forms accepted by
Tk_GetCapStyle (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 Tcl_Get-
Boolean or a line smoothing method. Only bezier is supported in
the core, but more can be added at runtime. If a boolean false
value or empty string is given, no smoothing is applied. A
boolean truth value assume bezier smoothing. It indicates
whether or not the line should be drawn as a curve. If so, the
line is rendered as a set of parabolic splines: one spline is
drawn for the first and second line segments, one for the second
and third, and so on. Straight-line segments can be generated
within a curve by duplicating the end-points of the desired line
segment.
-splinesteps number
Specifies the degree of smoothness desired for curves: each
spline will be approximated with number line segments. 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 coordinates of two diagonally opposite corners of a rectangu-
lar 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 itemconfig-
ure widget commands to change the item's configuration.
The following standard options are supported by ovals: -dash
-activedash -disableddash -dashoffset -fill -activefill -disabledfill
-offset -outline -activeoutline -disabledoutline -outlinestipple
-activeoutlinestipple -disabledoutlinestipple -stipple -activestipple
-disabledstipple -state -tags -width -activewidth -disabledwidth
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 cre-
ate polygon coordList ?option value option value ...? The arguments x1
through yn or coordList specify the coordinates for three or more
points that define a polygon. The first point should not be repeated
as the last to close the shape; Tk will automatically close the periph-
ery 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 con-
figuration options for the item. These same option-value pairs may be
used in itemconfigure widget commands to change the item's configura-
tion.
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 ver-
tices of the outline. Style may have any of the forms accepted
by Tk_GetCapStyle (bevel, miter, or round). If this option
isn't specified then it defaults to miter.
-smooth boolean
Boolean must have one of the forms accepted by Tcl_GetBoolean.
It indicates whether or not the polygon should be drawn with a
curved perimeter. If so, the outline of the polygon becomes a
set of parabolic splines, one spline for the first and second
line segments, one for the second and third, and so on.
Straight-line segments can be generated in a smoothed polygon by
duplicating the end-points of the desired line segment.
-splinesteps number
Specifies the degree of smoothness desired for curves: each
spline will be approximated with number line segments. This
option is ignored unless the -smooth option is true.
Polygon items are different from other items such as rectangles, ovals
and arcs in that interior points are considered to be ``inside'' a
polygon (e.g. for purposes of the 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 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 option value ...? pathName create
rectangle coordList ?option value option value ...? The arguments x1,
y1, x2, and y2 or coordList give the coordinates of two diagonally
opposite corners of the rectangle (the rectangle will include its upper
and left edges but not its lower or right edges). After the coordi-
nates 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 rectangles: -dash
-activedash -disableddash -dashoffset -fill -activefill -disabledfill
-offset -outline -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 selection, 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 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 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 posi-
tioning point for the text; it may have any of the forms
accepted by Tk_GetAnchor. 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 position-
ing point. This option defaults to center.
-font fontName
Specifies the font to use for the text item. FontName may be
any string acceptable to Tk_GetFont. If this option isn't spec-
ified, 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 COORDINATES section above. If this
option is zero (the default) the text is broken into lines only
at newline characters. However, if this option is non-zero then
any line that would be longer than lineLength is broken just
before a space character to make the line shorter than line-
Length; the space character is treated as if it were a newline
character.
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 coor-
dinates of a point used to position the window on the display (see the
-anchor option below for more information on how bitmaps are dis-
played). 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 wid-
get 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
AnchorPos tells how to position the window relative to the posi-
tioning point for the item; it may have any of the forms
accepted by Tk_GetAnchor. 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 COORDINATES section
above. If this option isn't specified, or if it is specified as
an empty string, then the window is given whatever height it
requests internally.
-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 isn't specified, or if it is specified as
an empty string, then the window 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 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.
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'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 can-
vases.
SEE ALSO
bind(n), font(n), image(n), scrollbar(n)
KEYWORDS
canvas, widget
Tk 8.3 canvas(n)
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