canvas(n) Tk (4.0) canvas(n)
_________________________________________________________________
NAME
canvas - Create and manipulate canvas widgets
SYNOPSIS
canvas pathName ?options?
STANDARD OPTIONS
-background-highlightthickness-insertwidth-takefocus
-borderwidth-insertbackground-relief-xscrollcommand
-cursor-insertborderwidth-selectbackground-yscrollcommand
-highlightbackground-insertofftime-selectborderwidth
-highlightcolor -insertontime -selectforeground
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 region.
Command-Line Name:-height
Database Name: height
Database Class: Height
Specifies a desired window height that the canvas
widget should request from its geometry manager. The
value may be specified in any of the forms described in
the 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
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canvas(n) Tk (4.0) canvas(n)
rectangular region. This region is used for scrolling
purposes and is considered to be the boundary of the
information in the canvas. Each of the coordinates may
be specified in any of the forms given in the
COORDINATES section below.
Command-Line Name:-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 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 unconstrained.
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 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 argument) and makes it into a canvas widget.
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canvas(n) Tk (4.0) canvas(n)
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 commands may be
associated with items in much the same way that the bind
command allows commands to be bound to widgets. For
example, a particular command may be associated with the
<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 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 everything else. Widget commands may be used to re-
arrange the order of the display list.
Window items are an exception to the above rules. The
underlying window systems require them always to be drawn on
top of other items. In addition, the stacking order of
window items is not affected by any of the canvas widget
commands; you must use the raise and lower Tk commands
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
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canvas(n) Tk (4.0) canvas(n)
selected items might be given the tag ``selected''.
The tag all is implicitly associated with every item in the
canvas; it may be used to invoke operations on all the
items in the canvas.
The tag current is managed automatically by Tk; it applies
to the current item, which is the topmost item whose drawn
area covers the position of the mouse cursor. If the mouse
is not in the canvas widget or is not over an item, then no
item has the current tag.
When specifying items in canvas widget commands, if the
specifier is an integer then it is assumed to refer to the
single item with that id. If the specifier is not an
integer, then it is assumed to refer to all of the items in
the canvas that have a tag matching the specifier. The
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. Some widget commands only
operate on a single item at a time; if tagOrId is specified
in a way that names multiple items, then the normal behavior
is for the command to use the first (lowest) of these items
in the display list that is suitable for the command.
Exceptions are noted in the widget command descriptions
below.
COORDINATES
All coordinates related to canvases are stored as floating-
point numbers. Coordinates and distances are specified in
screen units, which are floating-point numbers optionally
followed by one of several letters. If no letter is
supplied then the distance is in pixels. If the letter is 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.
TRANSFORMATIONS
Normally the origin of the canvas coordinate system is at
the upper-left corner of the window containing the canvas.
It is possible to adjust the origin of the canvas coordinate
system relative to the origin of the window using the xview
and yview widget commands; this is typically used for
scrolling. Canvases do not support scaling or rotation of
the canvas coordinate system relative to the window
coordinate system.
Individual items may be moved or scaled using widget
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canvas(n) Tk (4.0) canvas(n)
commands described below, but they may not be rotated.
INDICES
Text items support the notion of an index for identifying
particular positions within the item. Indices are used for
commands such as inserting text, deleting a range of
characters, and setting the insertion cursor position. An
index may be specified in any of a number of ways, and
different types of items may support different forms for
specifying indices. Text items support the following forms
for an index; if you define new types of text-like items,
it would be advisable to support as many of these forms as
practical. Note that it is possible to refer to the
character just after the last one in the text item; this is
necessary for such tasks as inserting new text at the end of
the item.
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. 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.
end Refers to the character just after the last one in
the item (same as the number of characters in the
item).
insert Refers to the character just before which the
insertion cursor is drawn in this item.
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 at the point given by x
and y, where x and y are specified in the
coordinate system of the canvas. If x and y lie
outside the coordinates covered by the text item,
then they refer to the first or last character in
the line that is closest to the given point.
WIDGET COMMAND
The canvas command creates a new Tcl command whose name is
pathName. This command may be used to invoke various
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canvas(n) Tk (4.0) canvas(n)
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
considered to overlap it. The start argument may
be used to step circularly through all the closest
items. If start is specified, it names an item
using a tag or id (if by tag, it selects the first
item in the display list with the given tag).
Instead of selecting the topmost closest item,
this form will select the topmost closest item
that is below start in the display list; if no
such item exists, then the selection behaves as if
the start argument had not been specified.
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canvas(n) Tk (4.0) canvas(n)
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 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, |
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canvas(n) Tk (4.0) canvas(n)
Leave, ButtonPress, Motion, and KeyPress) or virtual |
events. The handling of events in canvases uses the |
current item defined in ITEM IDS AND TAGS above. Enter |
and Leave events trigger for an item when it becomes |
the current item or ceases to be the current item; note |
that these events are different than Enter and Leave |
events for windows. Mouse-related events are directed |
to the current item, if any. Keyboard-related events |
are directed to the focus item, if any (see the focus |
widget command below for more on this). If a virtual |
event is used in a binding, that binding can trigger |
only if the virtual event is defined by an underlying |
mouse-related or keyboard-related event.
It is possible for multiple bindings to match a
particular event. This could occur, for example, if
one binding is associated with the item's id and
another is associated with one of the item's tags.
When this occurs, all of the matching bindings are
invoked. A binding associated with the 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 terminates 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 bindings for items will be invoked
before any of the bindings for the window as a whole.
pathName canvasx screenx ?gridspacing?
Given a window x-coordinate in the canvas screenx, this
command returns the canvas x-coordinate that is
displayed at that location. If gridspacing is
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 location. 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
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canvas(n) Tk (4.0) canvas(n)
accepted by the canvas command.
pathName configure ?option? ?value? ?option value ...?
Query or modify the configuration options of the
widget. If no option is specified, returns a list
describing all of the available options for pathName
(see 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 ...?
Query or modify the coordinates that define an item.
If no coordinates are specified, this command returns a
list whose elements are the coordinates of the item
named by tagOrId. If coordinates are specified, then
they replace the current coordinates for the named
item. If tagOrId refers to multiple items, then the
first one in the display list is used.
pathName create type x y ?x y ...? ?option value ...?
Create a new item in pathName of type type. The exact
format of the arguments after type depends on type, but
usually they consist of the coordinates for one or more
points, followed by specifications for zero or more
item options. See the subsections on individual item
types below for more on the syntax of this command.
This command returns the id for the new item.
pathName dchars tagOrId first ?last?
For each item given by tagOrId, delete the characters
in the range given by first and last, inclusive. If
some of the items given by tagOrId don't support text
operations, then they are ignored. First and last are
indices of characters within the item(s) as 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
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canvas(n) Tk (4.0) canvas(n)
with the item. If an item doesn't have the tag
tagToDelete then the item is unaffected by the command.
If tagToDelete is omitted then it defaults to tagOrId.
This command returns an empty string.
pathName find searchCommand ?arg arg ...?
This command returns a list consisting of all the items
that meet the constraints specified by searchCommand
and arg's. SearchCommand and args have any of the
forms accepted by the addtag command. The items are
returned in stacking order, with the lowest item first.
pathName focus ?tagOrId?
Set the keyboard focus for the canvas widget to the
item given by tagOrId. If tagOrId refers to several
items, then the focus is set to the first such item in
the display list that supports the insertion cursor.
If tagOrId doesn't refer to any items, or if none of
them support the insertion cursor, then the focus isn't
changed. If tagOrId is an empty string, then the focus
item is reset so that no item has the focus. If
tagOrId is not specified then the command returns the
id for the item that currently has the focus, or an
empty string if no item has the focus.
Once the focus has been set to an item, the item will
display the insertion cursor and all keyboard events
will be directed to that item. The focus item within a
canvas and the focus window on the screen (set with the
focus command) are totally independent: a given item
doesn't actually have the input focus unless (a) its
canvas is the focus window and (b) the item is the
focus item within the canvas. In most cases it is
advisable to follow the focus widget command with the
focus command to set the focus window to the canvas (if
it wasn't there already).
pathName gettags tagOrId
Return a list whose elements are the tags associated
with the item given by tagOrId. If tagOrId refers to
more than one item, then the tags are returned from the
first such item in the display list. If tagOrId
doesn't refer to any items, or if the item contains no
tags, then an empty string is returned.
pathName icursor tagOrId index
Set the position of the insertion cursor for the
item(s) given by tagOrId to just before the character
whose position is given by index. If some or all of
the items given by tagOrId don't support an insertion
cursor then this command has no effect on them. See
INDICES above for a description of the legal forms for
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canvas(n) Tk (4.0) canvas(n)
index. Note: the insertion cursor is only displayed
in an item if that item currently has the keyboard
focus (see the widget command focus, below), but the
cursor position may be set even when the item doesn't
have the focus. This command returns an empty string.
pathName index tagOrId index
This command returns a decimal string giving the
numerical index within tagOrId corresponding to index.
Index gives a textual description of the desired
position as described in INDICES above. The return
value is guaranteed to lie between 0 and the number of
characters within the item, inclusive. If 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 insertion then string is inserted into
the item's text just before the character whose index
is beforeThis. See INDICES above for information about
the forms allowed for beforeThis. This command returns
an empty string.
pathName itemcget tagOrId option
Returns the current value of the configuration option
for the item given by tagOrId whose name is option.
This command is similar to the cget widget command
except that it applies to a particular item rather than
the widget as a whole. Option may have any of the
values accepted by the create widget command when the
item was created. If tagOrId is a tag that refers to
more than one item, the first (lowest) such item is
used.
pathName itemconfigure tagOrId ?option? ?value? ?option value
This command is similar to the configure widget command
except that it modifies item-specific options for the
items given by tagOrId instead of modifying options for
the overall canvas widget. If no option is specified,
returns a list describing all of the available options
for the first item given by tagOrId (see
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
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canvas(n) Tk (4.0) canvas(n)
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 associated with the item and yAmount to
the y-coordinate of each point associated with the
item. This command returns an empty string.
pathName postscript ?option value option value ...?
Generate a Postscript representation for part or all of
the canvas. If the -file option is specified then the
Postscript is written to a file and an empty string is
returned; otherwise the Postscript is returned as the
result of the command. If the interpreter that owns |
the canvas is marked as safe, the operation will fail |
because safe interpreters are not allowed to write |
files. If the -channel option is specified, the |
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 Postscript is created in
Encapsulated Postscript form using version 3.0 of the
Document Structuring Conventions. Note: by default
Postscript is only generated for information that
appears in the canvas's window on the screen. If the
canvas is freshly created it may still have its initial
size of 1x1 pixel so nothing will appear in the
Postscript. To get around this problem either invoke
the "update" command to wait for the canvas window to
reach its final size, or else use the -width and
-height options to specify the area of the canvas to
print. The option-value argument pairs provide
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canvas(n) Tk (4.0) canvas(n)
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
specifies a color mapping to use in the
Postscript. Each element of varName must consist
of Postscript code to set a particular color value
(e.g. ``1.0 1.0 0.0 setrgbcolor''). When
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 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
specifies a font mapping to use in the Postscript.
Each element of varName must consist of a Tcl list
with two elements, which are the name and point
size of a Postscript font. When outputting
Postscript commands for a particular font, Tk
checks to see if varName contains an element with
the same name as the font. If there is such an
element, then the font information contained in
that element is used in the Postscript. Otherwise
Tk attempts to guess what Postscript font to use.
Tk's guesses generally only work for well-known
fonts such as Times and Helvetica and Courier, and
only if the X font name does not omit any dashes
up through the point size. For example,
-*-Courier-Bold-R-Normal--*-120-* will work but
*Courier-Bold-R-Normal*120* will not; Tk needs
the dashes to parse the font name).
-height size
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canvas(n) Tk (4.0) canvas(n)
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 Postscript page. Size consists of a
floating-point number followed by c for
centimeters, i for inches, m for millimeters, or p
or nothing for printer's points (1/72 inch).
Defaults to the height of the printed area on the
screen. If both -pageheight and -pagewidth are
specified then the scale factor from -pagewidth is
used (non-uniform scaling is not implemented).
-pagewidth size
Specifies that the Postscript should be scaled in
both x and y so that the printed area is size wide
on the Postscript page. Size has the same form as
for -pageheight. Defaults to the width of the
printed area on the screen. If both -pageheight
and -pagewidth are specified then the scale factor
from -pagewidth is used (non-uniform scaling is
not implemented).
-pagex position
Position gives the x-coordinate of the positioning
point on the Postscript page, using any of the
forms allowed for -pageheight. Used in
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
Page 14 (printed 2/26/99)
canvas(n) Tk (4.0) canvas(n)
center of the page.
-rotate boolean
Boolean specifies whether the printed area is to
be rotated 90 degrees. In non-rotated output the
x-axis of the printed area runs along the short
dimension of the page (``portrait'' orientation);
in rotated output the x-axis runs along the long
dimension of the page (``landscape'' orientation).
Defaults to non-rotated.
-width size
Specifies the width of the area of the canvas to
print. Defaults to the width of the canvas
window.
-x position
Specifies the x-coordinate of the left edge of the
area of the canvas that is to be printed, in
canvas coordinates, not window coordinates.
Defaults to the coordinate of the left edge of the
window.
-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 destination location for the moved items. Note:
this command has no effect on window items. Window
items always obscure other item types, and the stacking
order of window items is determined by the raise and
lower commands, not the raise and lower widget commands
for canvases. This command returns an empty string.
pathName scale tagOrId xOrigin yOrigin xScale yScale
Rescale all of the items given by tagOrId in canvas
coordinate space. XOrigin and yOrigin identify the
origin for the scaling operation and xScale and yScale
identify the scale factors for x- and y-coordinates,
respectively (a scale factor of 1.0 implies no change
to that coordinate). For each of the points defining
Page 15 (printed 2/26/99)
canvas(n) Tk (4.0) canvas(n)
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.
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 10 times the difference in
coordinates. This command is typically associated
with mouse motion events in the widget, to produce
the effect of dragging the canvas at high speed
through its window. The return value is an empty
string.
pathName select option ?tagOrId arg?
Manipulates the selection in one of several ways,
depending on option. The command may take any of the
forms described below. In all of the descriptions
below, tagOrId must refer to an item that supports
indexing and selection; if it refers to multiple items
then the first of these that supports indexing and the
selection is used. Index gives a textual description
of a position within tagOrId, as described in INDICES
above.
pathName select adjust tagOrId index
Locate the end of the selection in tagOrId nearest
to the character given by index, and adjust that
end of the selection to be at index (i.e.
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.
Page 16 (printed 2/26/99)
canvas(n) Tk (4.0) canvas(n)
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
widget. If the selection anchor point for the
widget isn't currently in tagOrId, then it is set
to the same character given by index. Returns an
empty string.
pathName type tagOrId
Returns the type of the item given by tagOrId, such as
rectangle or text. If tagOrId refers to more than one
item, then the type of the first item in the display
list is returned. If tagOrId doesn't refer to any
items at all then an empty string is returned.
pathName xview ?args?
This command is used to query and change the horizontal
position of the information displayed in the canvas's
window. It can take any of the following forms:
pathName xview
Returns a list containing two elements. Each
element is a real fraction between 0 and 1;
together they describe the horizontal span that is
visible in the window. For example, if the first
element is .2 and the second element is .6, 20% of
the canvas's area (as defined by the -scrollregion
Page 17 (printed 2/26/99)
canvas(n) Tk (4.0) canvas(n)
option) is off-screen to the left, the middle 40%
is visible in the window, and 40% of the canvas is
off-screen to the right. These are the same
values passed to scrollbars via the
-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 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
Page 18 (printed 2/26/99)
canvas(n) Tk (4.0) canvas(n)
units of the yScrollIncrement option, if it is
greater than zero, or in units of one-tenth the
window's height otherwise. If what is pages then
the view adjusts in units of nine-tenths the
window's height. If number is negative then
higher information becomes visible; if it is
positive then lower information becomes visible.
OVERVIEW OF ITEM TYPES
The sections below describe the various types of items
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 facilities, it is noted explicitly in
the descriptions below (at present, only text items provide
this support).
ARC ITEMS
Items of type arc appear on the display as arc-shaped
regions. An arc is a section of an oval delimited by two
angles (specified by the -start and -extent options) and
displayed in one of several ways (specified by the -style
option). Arcs are created with widget commands of the
following form:
pathName create arc x1 y1 x2 y2 ?option value option value ...?
The arguments x1, y1, x2, and y2 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
configuration. The following 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.
-fill color
Fill the region of the arc with color. Color may have
any of the forms accepted by Tk_GetColor. If color is
Page 19 (printed 2/26/99)
canvas(n) Tk (4.0) canvas(n)
an empty string (the default), then then the arc will
not be filled.
-outline color
Color specifies a color to use for drawing the arc's
outline; it 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 arc.
-outlinestipple bitmap
Indicates that the outline for the arc 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 -outline option hasn't been
specified then this option has no effect. If bitmap is
an empty string (the default), then the outline is
drawn in a solid fashion.
-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.
-stipple bitmap
Indicates that the arc should be filled in a stipple
pattern; bitmap specifies the stipple pattern to use,
in any of the forms accepted by Tk_GetBitmap. If the
-fill option hasn't been specified then this option has
no effect. If bitmap is an empty string (the default),
then filling is done in a solid fashion.
-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.
-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
Page 20 (printed 2/26/99)
canvas(n) Tk (4.0) canvas(n)
Specifies the width of the outline to be drawn around
the arc's region, 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. Wide outlines will be drawn centered on the
edges of the arc's region. This option defaults to
1.0.
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 ...?
The arguments x and y 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 options are
supported for bitmaps:
-anchor anchorPos
AnchorPos tells how to position the bitmap relative to
the positioning point for the item; it may have any of
the forms accepted by 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
Specifies a color to use for each of the bitmap pixels
whose value is 0. 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 produces a transparent effect.
-bitmap bitmap
Specifies the bitmap to display in the item. Bitmap
may have any of the forms accepted by Tk_GetBitmap.
-foreground color
Specifies a color to use for each of the bitmap pixels
whose value is 1. Color may have any of the forms
accepted by Tk_GetColor and defaults to black.
-tags tagList
Specifies a set of tags to apply to the item. TagList
Page 21 (printed 2/26/99)
canvas(n) Tk (4.0) canvas(n)
consists of a list of tag names, which replace any
existing tags for the item. TagList may be an empty
list.
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 ...?
The arguments x and y 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
commands to change the item's configuration. The following
options are supported for images:
-anchor anchorPos
AnchorPos tells how to position the image relative to
the positioning point for the item; it may have any of
the forms accepted by 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
Specifies the name of the image to display in the item.
This image must have been created previously with the
image create command.
-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; it may be an empty list.
LINE ITEMS
Items of type line appear on the display as one or more
connected line segments or curves. Lines are created with
widget commands of the following form:
pathName create line x1 y1... xn yn ?option value option value ...?
The arguments x1 through yn 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
options are supported for lines:
Page 22 (printed 2/26/99)
canvas(n) Tk (4.0) canvas(n)-arrow where
Indicates whether or not arrowheads are to be drawn at
one or both ends of the line. Where must have one of
the values none (for no arrowheads), first (for an
arrowhead at the first point of the line), last (for an
arrowhead at the last point of the line), or both (for
arrowheads at both ends). This option defaults to
none.
-arrowshape shape
This option indicates how to draw arrowheads. The
shape argument must be a list with three elements, each
specifying a distance in any of the forms described in
the 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 ``reasonable'' shape.
-capstyle style
Specifies the ways in which caps are to be drawn at the
endpoints of the line. Style may have any of the forms
accepted by 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.
-fill color
Color specifies a color to use for drawing the line; it
may have any of the forms acceptable to Tk_GetColor.
It may also be an empty string, in which case the line
will be transparent. This option defaults to black.
-joinstyle style
Specifies the ways in which joints are to be drawn at
the vertices of the line. Style may have any of the
forms accepted by 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 boolean
Boolean must have one of the forms accepted by
Tk_GetBoolean. 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
Page 23 (printed 2/26/99)
canvas(n) Tk (4.0) canvas(n)
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.
-stipple bitmap
Indicates that the line should be filled in a stipple
pattern; bitmap specifies the stipple pattern to use,
in any of the forms accepted by Tk_GetBitmap. If
bitmap is an empty string (the default), then filling
is done in a solid fashion.
-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 lineWidth
LineWidth specifies the width of the line, in any of
the forms described in the COORDINATES section above.
Wide lines will be drawn centered on the path specified
by the points. If this option isn't specified then it
defaults to 1.0.
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 ...?
The arguments x1, y1, x2, and y2 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 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 itemconfigure widget
commands to change the item's configuration. The following
options are supported for ovals:
-fill color
Fill the area of the oval with color. Color may have
any of the forms accepted by Tk_GetColor. If color is
an empty string (the default), then then the oval will
not be filled.
Page 24 (printed 2/26/99)
canvas(n) Tk (4.0) canvas(n)-outline color
Color specifies a color to use for drawing the oval's
outline; it may have any of the forms accepted by
Tk_GetColor. This option defaults to black. If color
is an empty string then no outline will be drawn for
the oval.
-stipple bitmap
Indicates that the oval should be filled in a stipple
pattern; bitmap specifies the stipple pattern to use,
in any of the forms accepted by Tk_GetBitmap. If the
-fill option hasn't been specified then this option has
no effect. If bitmap is an empty string (the default),
then filling is done in a solid fashion.
-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
outlineWidth specifies the width of the outline to be
drawn around the oval, in any of the forms described in
the COORDINATES section above. If the -outline option
hasn't been specified then this option has no effect.
Wide outlines are drawn centered on the oval path
defined by x1, y1, x2, and y2. This option defaults to
1.0.
POLYGON ITEMS
Items of type polygon appear as polygonal or curved filled
regions on the display. Polygons are created with widget
commands of the following form:
pathName create polygon x1 y1 ... xn yn ?option value option value ...?
The arguments x1 through yn specify the coordinates for
three or more points that define a closed polygon. The
first and last points may be the same; whether they are or
not, Tk will draw the polygon as a closed polygon. 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 options are supported for
polygons:
-fill color
Color specifies a color to use for filling the area of
the polygon; it may have any of the forms acceptable to
Tk_GetColor. If color is an empty string then the
polygon will be transparent. This option defaults to
Page 25 (printed 2/26/99)
canvas(n) Tk (4.0) canvas(n)
black.
-outline color
Color specifies a color to use for drawing the
polygon's outline; it may have any of the forms
accepted by Tk_GetColor. If color is an empty string
then no outline will be drawn for the polygon. This
option defaults to empty (no outline).
-smooth boolean
Boolean must have one of the forms accepted by
Tk_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.
-stipple bitmap
Indicates that the polygon should be filled in a
stipple pattern; bitmap specifies the stipple pattern
to use, in any of the forms accepted by Tk_GetBitmap.
If bitmap is an empty string (the default), then
filling is done in a solid fashion.
-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
OutlineWidth specifies the width of the outline to be
drawn around the polygon, in any of the forms described
in the COORDINATES section above. If the -outline
option hasn't been specified then this option has no
effect. This option defaults to 1.0.
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
Page 26 (printed 2/26/99)
canvas(n) Tk (4.0) canvas(n)
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 ...?
The arguments x1, y1, x2, and y2 give the coordinates of two
diagonally opposite corners of the rectangle (the rectangle
will include its upper and left edges but not its lower or
right edges). After the coordinates there may be any number
of option-value pairs, each of which sets one of the
configuration options for the item. These same option-value
pairs may be used in itemconfigure widget commands to change
the item's configuration. The following options are
supported for rectangles:
-fill color
Fill the area of the rectangle with color, which may be
specified in any of the forms accepted by Tk_GetColor.
If color is an empty string (the default), then the
rectangle will not be filled.
-outline color
Draw an outline around the edge of the rectangle in
color. Color may have any of the forms accepted by
Tk_GetColor. This option defaults to black. If color
is an empty string then no outline will be drawn for
the rectangle.
-stipple bitmap
Indicates that the rectangle should be filled in a
stipple pattern; bitmap specifies the stipple pattern
to use, in any of the forms accepted by Tk_GetBitmap.
If the -fill option hasn't been specified then this
option has no effect. If bitmap is an empty string
(the default), then filling is done in a solid fashion.
-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
OutlineWidth specifies the width of the outline to be
drawn around the rectangle, in any of the forms
Page 27 (printed 2/26/99)
canvas(n) Tk (4.0) canvas(n)
described in the COORDINATES section above. If the
-outline option hasn't been specified then this option
has no effect. Wide outlines are drawn centered on the
rectangular path defined by x1, y1, x2, and y2. This
option defaults to 1.0.
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 ...?
The arguments x and y 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 options are supported for text
items:
-anchor anchorPos
AnchorPos tells how to position the text relative to
the positioning point for the text; it may have any of
the forms accepted by 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 positioning
point. This option defaults to center.
-fill color
Color specifies a color to use for filling the text
characters; it may have any of the forms accepted by
Tk_GetColor. If color is an empty string then the text
will be transparent. If this option isn't specified
then it defaults to black.
-font fontName
Specifies the font to use for the text item. FontName
may be any string acceptable to Tk_GetFontStruct. If
this option isn't specified, it defaults to a system-
dependent font.
-justify how
Specifies how to justify the text within its bounding
region. How must be one of the values left, right, or
center. This option will only matter if the text is
Page 28 (printed 2/26/99)
canvas(n) Tk (4.0) canvas(n)
displayed as multiple lines. If the option is omitted,
it defaults to left.
-stipple bitmap
Indicates that the text should be drawn in a stippled
pattern rather than solid; bitmap specifies the stipple
pattern to use, in any of the forms accepted by
Tk_GetBitmap. If bitmap is an empty string (the
default) then the text is drawn in a solid fashion.
-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.
-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 lineLength;
the space character is treated as if it were a newline
character.
WINDOW ITEMS
Items of type window cause a particular window to be
displayed at a given position on the canvas. Window items
are created with widget commands of the following form:
pathName create window x y ?option value option value ...?
The arguments x and y specify the coordinates of a point
used to position the window on the display (see the -anchor
option below for more information on how bitmaps are
displayed). After the coordinates there may be any number
of option-value pairs, each of which sets one of the
configuration options for the item. These same option-value
pairs may be used in itemconfigure widget commands to change
the item's configuration. The following options are
supported for window items:
-anchor anchorPos
AnchorPos tells how to position the window relative to
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canvas(n) Tk (4.0) canvas(n)
the positioning 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.
-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 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 widget or a child of some ancestor of the
canvas widget. PathName may not refer to a top-level
window.
Note: due to restrictions in the ways that windows are
managed, it is not possible to draw other graphical items
(such as lines and images) on top of window items. A window
item always obscures any graphics that overlap it,
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_CreateItemType.
BINDINGS
In the current implementation, new canvases are not given
any default behavior: you'll have to execute explicit Tcl
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canvas(n) Tk (4.0) canvas(n)
commands to give the canvas its behavior.
CREDITS
Tk's canvas widget is a blatant ripoff of ideas from Joel
Bartlett's ezd program. Ezd provides structured graphics in
a Scheme environment and preceded canvases by a year or two.
Its simple mechanisms for placing and animating graphical
objects inspired the functions of canvases.
KEYWORDS
canvas, widget
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