Provided by: perl-tk_804.031-1build1_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