Provided by: perl-tk_804.033-2build1_amd64 
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