Canvas(3pm) User Contributed Perl Documentation Canvas(3pm)
NAME
Tk::Canvas - Create and manipulate Canvas widgets
SYNOPSIS
$canvas = $parent->Canvas(?options?);
STANDARD OPTIONS
-background -highlightthickness -insertwidth -state
-borderwidth -insertbackground -relief -tile
-cursor -insertborderwidth -selectbackground -takefocus
-highlightbackground -insertofftime -selectborderwidth -xscrollcommand
-highlightcolor -insertontime -selectforeground -yscrollcommand
WIDGET-SPECIFIC OPTIONS
Name: closeEnough
Class: CloseEnough
Switch: -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.
Name: confine
Class: Confine
Switch: -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.
Name: height
Class: Height
Switch: -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.
Name: scrollRegion
Class: ScrollRegion
Switch: -scrollregion
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.
Name: state
Class: State
Switch: -state
Modifies the default state of the canvas where state may be set to
one of: normal, disabled, or hidden. Individual canvas objects all
have their own state option, which overrides the default state. Many
options can take separate specifications such that the appearance of
the item can be different in different situations. The options that
start with "active" control the appearance when the mouse pointer is
over it, while the option starting with "disabled" controls the
appearance when the state is disabled.
Name: width
Class: width
Switch: -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.
Name: xScrollIncrement
Class: ScrollIncrement
Switch: -xscrollincrement
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.
Name: yScrollIncrement
Class: ScrollIncrement
Switch: -yscrollincrement
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.
DESCRIPTION
The Canvas method creates a new window (given by the $canvas argument)
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 $canvas argument. At the time this command
is invoked, there must not exist a window named $canvas, but $canvas'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
callbacks may be associated with items in much the same way that the
bind method allows callbacks to be bound to widgets. For example, a
particular callback may be associated with the <Button-1> event so that
the callback 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 Callbacks 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 methods 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 methods; you must use the raise and lower Tk widget methods
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
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 methods, if the specifier is an integer
then it is assumed to refer to the single item with that id. If the
specifier is not an integer, then it is assumed to refer to all of the
items in the canvas that have a tag matching the specifier. The symbol
tagOrId is used below to indicate that an argument specifies either an
id that selects a single item or a tag that selects zero or more items.
tagOrId may contain a logical expressions of tags by using operators:
'&&', '||', '^' '!', and parenthezised subexpressions. For example:
$c->find('withtag', '(a&&!b)|(!a&&b)');
or equivalently:
$c->find('withtag', 'a^b');
will find only those items with either "a" or "b" tags, but not both.
Some methods 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 methods is to use the first (lowest) of these items in the
display list that is suitable for the method. Exceptions are noted in
the method 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 methods; 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 methods 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 methods 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.
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 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. 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 polygons, numbers less than 0 or greater then the
length of the coordinate list will be adjusted by adding or
substracting the length until the result is between zero and the
length, inclusive.
end Refers to the character or coordinate just after the last one in the
item (same as the number of characters or coordinates in the item).
insert
Refers to the character just before which the insertion cursor is
drawn in this item. Not valid for lines and polygons.
sel.first
Refers to the first selected character in the item. If the
selection isn't in this item then this form is illegal.
sel.last
Refers to the last selected character in the item. If the selection
isn't in this item then this form is illegal.
[x,y]
Refers to the character or coordinate at the point given by x and y,
where x and y are specified in the coordinate system of the canvas.
If x and y lie outside the coordinates covered by the text item,
then they refer to the first or last character in the line that is
closest to the given point. The Tcl string form "@x,y" is also
allowed.
DASH PATTERNS
Many items support the notion of an dash pattern for outlines.
The first possible syntax is a list of integers. Each element represents
the number of pixels of a line segment. Only the odd segments are drawn
using the "outline" color. The other segments are drawn transparent.
The second possible syntax is a character list containing only 5
possible characters [.,-_ ], with the first 4 characters producing a
segment of length 1 to 4, respectively, followed by a transparent
segment of length 2. The space can be used repeatedly to enlarge the
space between other line elements by 1, and can not occur as the first
position in the string. The main difference of this syntax with the
previous one is that it it shape-conserving. This means that all values
in the dash list will be multiplied by the line width before display.
This assures that "." will always be displayed as a dot and "-" always
as a dash regardless of the line width.
Some examples, for a line width of 2:
-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]
On systems where only a limited set of dash patterns is available, the
dash pattern will be displayed as the closest available dash pattern.
For example, on Windows only the first 4 of the above examples are
available. The last 2 examples will be displayed identically as the
first one.
WIDGET METHODS
The Canvas method creates a widget object. This object supports the
configure and cget methods described in Tk::options which can be used to
enquire and modify the options described above. The widget also
inherits all the methods provided by the generic Tk::Widget class.
The following additional methods are available for canvas widgets:
$canvas->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 method 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.
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.
$canvas->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.
$canvas->bind(tagOrId?, sequence? ?,callback?)
This method associates callback with all the items given by tagOrId
such that whenever the event sequence given by sequence occurs for
one of the items the callback will be invoked. This method is
similar to the bind method except that it operates on items in a
canvas rather than entire widgets. See Tk::bind for complete
details on the syntax of sequence and the substitutions performed on
callback 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 callback is
omitted then the method returns the callback associated with tagOrId
and sequence (an error occurs if there is no such binding). If both
callback and sequence are omitted then the method returns a list of
all the sequences for which bindings have been defined for tagOrId.
The only events for which bindings may be specified are
those related to the mouse and keyboard (such as Enter,
Leave, ButtonPress, Motion, and KeyPress) or virtual events.
The handling of events in canvases uses the current item
defined in "ITEM IDS AND TAGS" above. Enter and Leave
events trigger for an item when it becomes the current item
or ceases to be the current item; note that these events are
different than Enter and Leave events for windows. Mouse-
related events are directed to the current item, if any.
Keyboard-related events are directed to the focus item, if
any (see the focus method 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 in a callback
terminates that subroutine, and a break method terminates
that subroutine and skips any remaining callbacks for the
event, just as for the bind method.
If bindings have been created for a canvas window using the
CanvasBind method, then they are invoked in addition to
bindings created for the canvas's items using the bind
method. The bindings for items will be invoked before any
of the bindings for the window as a whole.
$canvas->canvasx(screenx?, gridspacing?)
Given a window x-coordinate in the canvas screenx, this method
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.
$canvas->canvasy(screeny, ?gridspacing?)
Given a window y-coordinate in the canvas screeny this method
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.
$canvas->coords(tagOrId ?x0,y0 ...?)
Query or modify the coordinates that define an item. If no
coordinates are specified, this method 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.
$canvas->create(type, x, y, ?x, y, ...?, ?option, value, ...?)
Create a new item in $canvas 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 method. This method
returns the id for the new item.
$canvas->dchars(tagOrId, first, ?last?)
For each item given by tagOrId, delete the characters, or
coordinates, in the range given by first and last, inclusive. If
some of the items given by tagOrId don't support 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). within
the item(s) as described in "INDICES" above. If last is omitted, it
defaults to first. This method returns an empty string.
$canvas->delete(?tagOrId, tagOrId, ...?)
Delete each of the items given by each tagOrId, and return an empty
string.
$canvas->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 unaffected by
the method. If tagToDelete is omitted then it defaults to tagOrId.
This method returns an empty string.
$canvas->find(searchCommand, ?arg, arg, ...?)
This method 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 method. The items
are returned in stacking order, with the lowest item first.
focus
$canvas->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 method
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 method)
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 method
with the CanvasFocus method to set the focus window to the
canvas (if it wasn't there already).
$canvas->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.
$canvas->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 method has no effect on them. See
"INDICES" above for a description of the legal forms for index.
Note: the insertion cursor is only displayed in an item if that
item currently has the keyboard focus (see the widget method focus,
below), but the cursor position may be set even when the item
doesn't have the focus. This method returns an empty string.
$canvas->index(tagOrId, index)
This method 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).
$canvas->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 method returns an empty string.
$canvas->itemcget(tagOrId, option)
Returns the current value of the configuration option for the item
given by tagOrId whose name is option. This method is similar to
the cget method 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 method when the item was created. If tagOrId
is a tag that refers to more than one item, the first (lowest) such
item is used.
$canvas->itemconfigure(tagOrId, ?option?, ?value?, ?option, value, ...?)
This method is similar to the configure method 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::options for
information on the format of this list). If option is specified
with no value, then the method 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 method modifies the
given widget option(s) to have the given value(s) in each of the
items given by tagOrId; in this case the method returns an empty
string. The options and values are the same as those permissible in
the create method when the item(s) were created; see the sections
describing individual item types below for details on the legal
options.
$canvas->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 method 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
methods of the widget, not the raise and lower methods for canvases.
This method returns an empty string.
$canvas->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 method returns an empty string.
$canvas->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 method. 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 method 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 => hashRef
HashRef must be a reference to a hash variable or an
anonymous hash that specifies a color mapping to use in the
Postscript. Each value of the hash 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 a key in the
hash with the same name as the color. If so, Tk uses the
value of the element as the Postscript method to set the
color. If this option hasn't been specified, or if there
isn't a key in hashRef 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 method instead
of being written to a file.
-fontmap => hashRef
HashRef must be a reference to a hash variable or an
anonymous hash that specifies a font mapping to use in the
Postscript. Each value of the hash must consist of an array
reference 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 hashRef
contains a value with the same name as the font. If there
is such an element, then the font information contained in
that element is used in the Postscript. Otherwise Tk
attempts to guess what Postscript font to use. Tk's guesses
generally only work for well-known fonts such as Times and
Helvetica and Courier, and only if the X font name does not
omit any dashes up through the point size. For example,
-*-Courier-Bold-R-Normal--*-120-* will work but
*Courier-Bold-R-Normal*120* will not; Tk needs the dashes
to parse the font name).
-height => size
Specifies the height of the area of the canvas to print.
Defaults to the height of the canvas 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 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.
$canvas->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 method 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
widget commands, not the raise and lower methods for canvases. This
method returns an empty string.
$canvas->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 method returns an empty string.
$canvas->scan(option, args)
This method is used to implement scanning on canvases. It has two
forms, depending on option:
$canvas->scanMark(x, y)
Records x and y and the canvas's current view; used in
conjunction with later scanDragto method. Typically this
method 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.
$canvas->scanDragto(x, y, ?gain?.)
This method computes the difference between its x and y
arguments (which are typically mouse coordinates) and the x
and y arguments to the last scanMark method for the widget.
It then adjusts the view by 10 times the difference in
coordinates. This method is typically associated It then
adjusts the view by gain times the difference 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 canvas at high speed
through its window. The return value is an empty string.
$canvas->select(option, ?tagOrId, arg?)
Manipulates the selection in one of several ways, depending on
option. The method 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.
$canvas->selectAdjust(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 selectTo method calls. If the
selection isn't currently in tagOrId then this method
behaves the same as the selectTo widget method. Returns an
empty string.
$canvas->selectClear
Clear the selection if it is in this widget. If the
selection isn't in this widget then the method has no
effect. Returns an empty string.
$canvas->selectFrom(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 method doesn't change the selection; it just
sets the fixed end of the selection for future selectTo
method calls. Returns an empty string.
$canvas->selectItem
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.
$canvas->selectTo(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 selectAdjust
or selectFrom method calls 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.
$canvas->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.
$canvas->xview(?args?)
This method 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:
$canvas->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
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.
$canvas->xviewMoveto(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.
$canvas->xviewScroll(number, what)
This method 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.
$canvas->yview(?args?)
This method 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:
$canvas->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.
$canvas->yviewMoveto(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.
$canvas->yviewScroll(number, what)
This method adjusts the view in the window up or down
according to number and what. Number must be an integer.
What must be either units or pages. If what is units, the
view adjusts up or down in units of the yScrollIncrement
option, if it is greater than zero, or in units of one-tenth
the window's height otherwise. If what is pages then the
view adjusts in units of nine-tenths the window's height.
If number is negative then higher information becomes
visible; if it is positive then lower information becomes
visible.
OVERVIEW OF ITEM TYPES
The sections below describe the various types of items supported by
canvas widgets. Each item type is characterized by two things: first,
the form of the create method 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 methods. Most items don't
support indexing or selection or the methods related to them, such as
index and insert. Where items do support these facilities, it is noted
explicitly in the descriptions below. At present, text, line and
polygon items provide this support. For lines and polygons the indexing
facility is used to manipulate the coordinates of the item.
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 methods of the following
form:
$canvas->createArc(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 methods to
change the item's configuration. The following options are supported
for arcs:
-dash => pattern
-activedash => pattern
-disableddash => pattern
This option specifies dash patterns for the normal state, the active
state, and the disabled state of an arc item. pattern may have any
of the forms accepted by Tk_GetDash. If the dash options are
omitted then the default is a solid outline.
-dashoffset => offset
The starting offset into the pattern provided by the -dash option.
-dashoffset is ignored if there is no -dash pattern.
-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
-activefill => color
-disabledfill => color
Specifies the color to be used to fill the arc region in its normal,
active, and disabled states, Color may have any of the forms
accepted by Tk_GetColor. If color is an empty string (the default),
then then the arc will not be filled.
-outline => color
-activeoutline => color
-disabledoutline => color
This option specifies the color that should be used to draw the
outline of the arc 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 undef then no outline
is drawn for the arc.
-outlinestipple => bitmap
-activeoutlinestipple => bitmap
-disabledoutlinestipple => bitmap
This option specifies stipple patterns that should be used to draw
the outline of the arc in its normal, active and disabled states.
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.
-state => state
Modifies the state of the arc item where state may be set to one of:
normal, disabled, hidden or "". If set to empty, the state of the
canvas itself is used. An arc item may also be in the "active" state
if the mouse is currently over it. Many options can take separate
specifications in normal, active and disabled states such that the
appearance of the item can be different in each state.
-stipple => bitmap
-activestipple => bitmap
-disabledstipple => bitmap
This option specifies stipple patterns that should be used to fill
the the arc 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 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.
-updatecommand => command
Specifies a callback that is to be executed every time the arc item
is updated on the screen.
-width => outlineWidth
-activewidth => outlineWidth
-disabledwidth => outlineWidth
Specifies the width of the outline to be drawn around the arc'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 undef 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 methods of the
following form:
$canvas->createBitmap(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 methods 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
-activebackground => color
-disabledbackground => color
Specifies the color to use for each of the bitmap's '0' valued
pixels in its normal, active and disabled states. Color may have
any of the forms accepted by Tk_GetColor. If this option isn't
specified, or if it is specified as undef, then nothing is displayed
where the bitmap pixels are 0; this produces a transparent effect.
-bitmap => bitmap
-activebitmap => bitmap
-disabledbitmap => bitmap
Specifies the bitmaps to display in the item in its normal, active
and disabled states. All bitmaps must have the same width and
height. Bitmap may have any of the forms accepted by Tk_GetBitmap.
-foreground => color
-activeforeground => color
-disabledforeground => color
Specifies the color to use for each of the bitmap's '1' valued
pixels in its normal, active and disabled states. Color may have
any of the forms accepted by Tk_GetColor and defaults to black.
-state => state
Modifies the state of the bitmap item where state may be set to one
of: normal, disabled, or hidden. An bitmap item may also be in the
"active" state if the mouse is currently over it. Many options can
take separate specifications in normal, active and disabled states
such that the appearance of the item can be different in each state.
-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.
-updatecommand => command
Specifies a callback that is to be executed every time the bitmap
item is updated on the screen.
GRID ITEMS
Items of type grid are intended for producing a visual reference for
interpreting other items. They can be drawn as either lines (with dash
style) or as rectangular "dots" at each grid point.
Items of type grid are unlike other items they always cover the whole of
the canvas, but are never enclosed by nor overlap any area and are not
near any point. That is they are intended to be always visible but not
"pickable", as such they do support the "active" state. They are like
other items in that: multiple grids are permitted, they can be raised
and lowered relative to other items, they can be moved and scaled. As
yet grids do not appear in PostScript output.
Grids have outline like configure options. Grids are created with
methods of the following form:
$canvas->createGrid(x1, y1, x2, y2, ?option, value, option, value, ...?)
The arguments x1, y1 give the origin of the grid. x2, and y2 give the
coordinates of the next grid point in their respective directions.
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 methods to change
the item's configuration.
The following options are supported for grids:
-lines => boolean
If -lines is set to a true value then lines are drawn for both X and
Y grids in the style determined by -dash. Otherwise retangular
"dots" are drawn at each grid point.
-dash => pattern
-disableddash => pattern
This option specifies dash patterns for the normal state, and the
disabled state of a grid item. pattern may have any of the forms
accepted by Tk_GetDash. If the dash options are omitted then the
default is a solid outline.
-dashoffset => offset
The starting offset into the pattern provided by the -dash option.
-dashoffset is ignored if there is no -dash pattern.
-color => color
-disabledcolor => color
This option specifies the color that should be used to draw the
outline of the grid in its normal and disabled states. Color may
have any of the forms accepted by Tk_GetColor. This option defaults
to black. If color is undef then no grid will be drawn.
-stipple => bitmap
-disabledstipple => bitmap
This option specifies stipple patterns that should be used to draw
the outline of the rectangle in its normal and disabled states.
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 outline is drawn in a solid fashion.
-state => state
Modifies the state of the rectangle item where state may be set to
one of: normal, disabled, or hidden. Many options can take separate
specifications in normal and disabled states such that the
appearance of the item can be different in each state.
-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.
-updatecommand => command
Specifies a callback that is to be executed every time the grid item
is updated on the screen.
-width => outlineWidth
-disabledwidth => outlineWidth
Specifies the width of the lines drawn by the grid or the size (in
both X and Y) of the dots, in its normal and disabled states. This
option defaults to 1.0.
IMAGE ITEMS
Items of type image are used to display images on a canvas. Images are
created with methods of the following form:
$canvas->createImage(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 methods 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
-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, see Tk::Image.
-state => state
Modifies the state of the image item where state may be set to one
of: normal, disabled, or hidden. An image item may also be in the
"active" state if the mouse is currently over it. Many options can
take separate specifications in normal, active and disabled states
such that the appearance of the item can be different in each state.
-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.
-updatecommand => command
Specifies a callback that is to be executed every time the image
item is updated on the screen.
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 methods: dchars, index, insert. Lines are created with
methods of the following form:
$canvas->createLine(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 methods to change the
item's configuration. The following options are supported for lines:
-arrow => where
Indicates whether or not arrowheads are to be drawn at one or both
ends of the line. Where must have one of the values none (for no
arrowheads), first (for an arrowhead at the first point of the
line), last (for an arrowhead at the last point of the line), or
both (for arrowheads at both ends). This option defaults to none.
-arrowshape => shape
This option indicates how to draw arrowheads. The shape argument
must be a list with three elements, each specifying a distance in
any of the forms described in the "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.
-dash => pattern
-activedash => pattern
-disableddash => pattern
This option specifies dash patterns for the normal state, the active
state, and the disabled state of a line item. pattern may have any
of the forms accepted by Tk_GetDash. If the dash options are
omitted then the default is a solid outline.
-dashoffset => offset
The starting offset into the pattern provided by the -dash option.
-dashoffset is ignored if there is no -dash pattern.
-fill => color
-activefill => color
-disabledfill => color
Specifies the color to be used to fill the line in its normal,
active, and disabled states. Color may have any of the forms
acceptable to Tk_GetColor. It may also be undef, 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 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.
-state => state
Modifies the state of the line item where state may be set to one
of: normal, disabled, or hidden. A line item may also be in the
"active" state if the mouse is currently over it. Many options can
take separate specifications in normal, active and disabled states
such that the appearance of the item can be different in each state.
-stipple => bitmap
-activestipple => bitmap
-disabledstipple => bitmap
This option specifies stipple patterns that should be used to fill
the the line in its normal, active and disabled states. 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.
-updatecommand => command
Specifies a callback that is to be executed every time the line item
is updated on the screen.
-width => lineWidth
-activewidth => lineWidth
-disabledwidth => lineWidth
Specifies the width of the line in its normal, active and disabled
states. lineWidth may be 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
methods of the following form:
$canvas->createOval(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 methods to change the item's configuration.
The following options are supported for ovals:
-dash => pattern
-activedash => pattern
-disableddash => pattern
This option specifies dash patterns for the normal state, the active
state, and the disabled state of an oval item. pattern may have any
of the forms accepted by Tk_GetDash. If the dash options are
omitted then the default is a solid outline.
-dashoffset => offset
The starting offset into the pattern provided by the -dash option.
-dashoffset is ignored if there is no -dash pattern.
-fill => color
-activefill => color
-disabledfill => color
Specifies the color to be used to fill the oval in its normal,
active, and disabled states. Color may have any of the forms
accepted by Tk_GetColor. If color is undef (the default), then then
the oval will not be filled.
-outline => color
-activeoutline => color
-disabledoutline => color
This option specifies the color that should be used to draw the
outline of the oval 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 undef then no outline will be
drawn for the oval.
-outlinestipple => bitmap
-activeoutlinestipple => bitmap
-disabledoutlinestipple => bitmap
This option specifies stipple patterns that should be used to draw
the outline of the oval 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 -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.
-state => state
Modifies the state of the oval item where state may be set to one
of: normal, disabled, or hidden. An oval item may also be in the
"active" state if the mouse is currently over it. Many options can
take separate specifications in normal, active and disabled states
such that the appearance of the item can be different in each state.
-stipple => bitmap
-activestipple => bitmap
-disabledstipple => bitmap
This option specifies stipple patterns that should be used to fill
the the oval 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 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.
-updatecommand => command
Specifies a callback that is to be executed every time the oval item
is updated on the screen.
-width => outlineWidth
-activewidth => outlineWidth
-disabledwidth => outlineWidth
Specifies the width of the outline to be drawn around the oval, in
its normal, active and disabled states. 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. Polygon items support coordinate indexing operations using
the canvas methods: dchars, index, insert. Polygons are created with
methods of the following form:
$canvas->createPolygon(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 methods to
change the item's configuration. The following options are supported
for polygons:
-dash => pattern
-activedash => pattern
-disableddash => pattern
This option specifies dash patterns for the normal state, the active
state, and the disabled state of an polygon item. pattern may have
any of the forms accepted by Tk_GetDash. If the dash options are
omitted then the default is a solid outline.
-dashoffset => offset
The starting offset into the pattern provided by the -dash option.
-dashoffset is ignored if there is no -dash pattern.
-fill => color
-activefill => color
-disabledfill => color
Specifies the color to be used to fill the polygon in its normal,
active, and disabled states. Color may have any of the forms
acceptable to Tk_GetColor. If color is undef then the polygon 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 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.
-outline => color
-activeoutline => color
-disabledoutline => color
This option specifies the color that should be used to draw the
outline of the polygon in its normal, active and disabled states.
Color may have any of the forms accepted by Tk_GetColor. If color
is undef then no outline will be drawn for the polygon. This option
defaults to undef (no outline).
-outlinestipple => bitmap
-activeoutlinestipple => bitmap
-disabledoutlinestipple => bitmap
This option specifies stipple patterns that should be used to draw
the outline of the polygon 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 -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.
-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.
-state => state
Modifies the state of the polygon item where state may be set to one
of: normal, disabled, or hidden. A polygon item may also be in the
"active" state if the mouse is currently over it. Many options can
take separate specifications in normal, active and disabled states
such that the appearance of the item can be different in each state.
-stipple => bitmap
-activestipple => bitmap
-disabledstipple => bitmap
This option specifies stipple patterns that should be used to fill
the the polygon in its normal, active and disabled states. 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.
-updatecommand => command
Specifies a callback that is to be executed every time the polygon
item is updated on the screen.
-width => outlineWidth
-activewidth => outlineWidth
-disabledwidth => outlineWidth
Specifies the width of the outline to be drawn around
the polygon, in its normal, active and disabled states.
outlineWidth may be in any of the forms described in the COORDINATES
section above. 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 methods) 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 methods of the following form:
$canvas->createRectangle(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 methods to change the item's configuration.
The following options are supported for rectangles:
-dash => pattern
-activedash => pattern
-disableddash => pattern
This option specifies dash patterns for the normal state, the active
state, and the disabled state of a rectangle item. pattern may have
any of the forms accepted by Tk_GetDash. If the dash options are
omitted then the default is a solid outline.
-dashoffset => offset
The starting offset into the pattern provided by the -dash option.
-dashoffset is ignored if there is no -dash pattern.
-fill => color
-activefill => color
-disabledfill => color
Specifies the color to be used to fill the rectangle in its normal,
active, and disabled states. Color may be specified in any of the
forms accepted by Tk_GetColor. If color is undef (the default),
then the rectangle will not be filled.
-outline => color
-activeoutline => color
-disabledoutline => color
This option specifies the color that should be used to draw the
outline of the rectangle 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 undef then no outline will be
drawn for the rectangle.
-outlinestipple => bitmap
-activeoutlinestipple => bitmap
-disabledoutlinestipple => bitmap
This option specifies stipple patterns that should be used to draw
the outline of the rectangle 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 -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.
-state => state
Modifies the state of the rectangle item where state may be set to
one of: normal, disabled, or hidden. A rectangle item may also be
in the "active" state if the mouse is currently over it. Many
options can take separate specifications in normal, active and
disabled states such that the appearance of the item can be
different in each state.
-stipple => bitmap
-activestipple => bitmap
-disabledstipple => bitmap
This option specifies stipple patterns that should be used to fill
the the rectangle 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 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.
-updatecommand => command
Specifies a callback that is to be executed every time the rectangle
item is updated on the screen.
-width => outlineWidth
-activewidth => outlineWidth
-disabledwidth => outlineWidth
Specifies the width of the outline to be drawn around the rectangle,
in its normal, active and disabled states. OutlineWidth specifies
the width of the outline to be drawn around the rectangle, 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 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 methods: dchars, focus, icursor, index,
insert, select. Text items are created with methods of the following
form:
$canvas->createText(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 methods 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
-activefill => color
-disabledfill => color
Specifies the color to be used to fill the text in its normal,
active, and disabled states. Color may have any of the forms
accepted by Tk_GetColor. If color is undef 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 displayed as multiple lines. If the
option is omitted, it defaults to left.
-state => state
Modifies the state of the text item where state may be set to one
of: normal, disabled, or hidden. A text item may also be in the
"active" state if the mouse is currently over it. Many options can
take separate specifications in normal, active and disabled states
such that the appearance of the item can be different in each state.
-stipple => bitmap
-activestipple => bitmap
-disabledstipple => bitmap
This option specifies stipple patterns that should be used to fill
the the text in its normal, active and disabled states. 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 methods. This option
defaults to an empty string.
-updatecommand => command
Specifies a callback that is to be executed every time the text item
is updated on the screen.
-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 methods of
the following form:
$canvas->createWindow(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 method 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 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.
-state => state
Modifies the state of the window item where state may be set to one
of: 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.
-updatecommand => command
Specifies a callback that is to be executed every time the window
item is updated on the screen.
-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 => $widget
Specifies the window to associate with this item. The window
specified by $widget 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
Canvas has default bindings to allow scrolling if necessary: <Up>,
<Down>, <Left> and <Right> (and their <Control-*> counter parts).
Further <Proir>, <Next>, <Home> and <End>. These bindings allow you to
navigate the same way as in other widgets that can scroll.
Perl/Tk Methods
The following methods are added as perl code:
$canvas->get_corners
Returns the bounding box in Canvas coordinates of the visible
portion of the Canvas. (Written by Slaven Rezic.)
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
perl v5.40.1 2025-04-13 Canvas(3pm)
Generated by dwww version 1.16 on Sat Oct 3 06:47:52 CEST 2026.