canvas(3Tk) canvas(3Tk)
canvas - Create and manipulate canvas widgets
canvas pathName ?options?
background highlightThickness insertWidthtakeFocus |
borderWidth insertBackground reliefxScrollCommand |
cursor insertBorderWidth selectBackgroundyScrollCommand |
highlightColor insertOffTime selectBorderWidth |
highlightBackground insertOnTime selectForeground
See the ``options'' manual entry for details on the standard options.
WIDGET-SPECIFIC OPTIONS
Name: closeEnough
Class: CloseEnough
Command-Line 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
Command-Line 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
Command-Line 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
Command-Line 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.
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canvas(3Tk) canvas(3Tk)
Name: width
Class: width
Command-Line 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 |
Command-Line 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 |
Command-Line 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.
The canvas command creates a new window (given by the pathName 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 pathName argument. At the time this command
is invoked, there must not exist a window named pathName, but pathName's
parent must exist.
Canvas widgets implement structured graphics. A canvas displays any
number of items, which may be things like rectangles, circles, lines, and
text. Items may be manipulated (e.g. moved or re-colored) and commands
may be associated with items in much the same way that the bind command
allows commands to be bound to widgets. For example, a particular
command may be associated with the <Button-1> event so that the command
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canvas(3Tk) canvas(3Tk)
is invoked whenever button 1 is pressed with the mouse cursor over an
item. This means that items in a canvas can have behaviors defined by
the Tcl scripts bound to them.
DISPLAY LIST
The items in a canvas are ordered for purposes of display, with the first
item in the display list being displayed first, followed by the next item
in the list, and so on. Items later in the display list obscure those
that are earlier in the display list and are sometimes referred to as
being ``on top'' of earlier items. When a new item is created it is
placed at the end of the display list, on top of everything else. Widget
commands may be used to re-arrange the order of the display list.
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 widget commands, if the specifier is an
integer then it is assumed to refer to the single item with that id. If
the specifier is not an integer, then it is assumed to refer to all of
the items in the canvas that have a tag matching the specifier. The
symbol tagOrId is used below to indicate that an argument specifies
either an id that selects a single item or a tag that selects zero or
more items. Some widget commands only operate on a single item at a
time; if tagOrId is specified in a way that names multiple items, then
the normal behavior is for the command to use the first (lowest) of these
items in the display list that is suitable for the command. Exceptions
are noted in the widget command descriptions below.
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canvas(3Tk) canvas(3Tk)
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.
Normally the origin of the canvas coordinate system is at the upper-left
corner of the window containing the canvas. It is possible to adjust the
origin of the canvas coordinate system relative to the origin of the
window using the xview and yview widget commands; this is typically used
for scrolling. Canvases do not support scaling or rotation of the canvas
coordinate system relative to the window coordinate system.
Indidividual items may be moved or scaled using widget commands described
below, but they may not be rotated.
Text items support the notion of an index for identifying particular
positions within the item. Indices are used for commands such as
inserting text, deleting a range of characters, and setting the insertion
cursor position. An index may be specified in any of a number of ways,
and different types of items may support different forms for specifying
indices. Text items support the following forms for an index; if you
define new types of text-like items, it would be advisable to support as
many of these forms as practical. Note that it is possible to refer to
the character just after the last one in the text item; this is
necessary for such tasks as inserting new text at the end of the item.
number A decimal number giving the position of the desired character
within the text item. 0 refers to the first character, 1 to
the next character, and so on. A number less than 0 is treated
as if it were zero, and a number greater than the length of the
text item is treated as if it were equal to the length of the
text item.
end Refers to the character just after the last one in the item
(same as the number of characters in the item).
insert Refers to the character just before which the insertion cursor
is drawn in this item.
sel.first Refers to the first selected character in the item. If the
selection isn't in this item then this form is illegal.
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canvas(3Tk) canvas(3Tk)
sel.last Refers to the last selected character in the item. If the
selection isn't in this item then this form is illegal.
@x,y Refers to the character at the point given by x and y, where x
and y are specified in the coordinate system of the canvas. If
x and y lie outside the coordinates covered by the text item,
then they refer to the first or last character in the line that
is closest to the given point.
The canvas command creates a new Tcl command whose name is pathName.
This command may be used to invoke various operations on the widget. It
has the following general form:
pathName option ?arg arg ...?
Option and the args determine the exact behavior of the command. The
following widget commands are possible for canvas widgets:
pathName addtag tag searchSpec ?arg arg ...?
For each item that meets the constraints specified by searchSpec and
the args, add tag to the list of tags associated with the item if it
isn't already present on that list. It is possible that no items
will satisfy the constraints given by searchSpec and args, in which
case the command has no effect. This command returns an empty
string as result. SearchSpec and arg's may take any of the
following forms:
above tagOrId
Selects the item just after (above) the one given by tagOrId in
the display list. If tagOrId denotes more than one item, then
the last (topmost) of these items in the display list is used.
all Selects all the items in the canvas.
below tagOrId
Selects the item just before (below) the one given by tagOrId
in the display list. If tagOrId denotes more than one item,
then the first (lowest) of these items in the display list is
used.
closest x y ?halo? ?start?
Selects the item closest to the point given by x and y. If
more than one item is at the same closest distance (e.g. two
items overlap the point), then the top-most of these items (the
last one in the display list) is used. If halo is specified,
then it must be a non-negative value. Any item closer than
halo to the point is 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
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canvas(3Tk) canvas(3Tk)
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.
pathName bbox tagOrId ?tagOrId tagOrId ...?
Returns a list with four elements giving an approximate bounding box
for all the items named by the tagOrId arguments. The list has the
form ``x1 y1 x2 y2'' such that the drawn areas of all the named
elements are within the region bounded by x1 on the left, x2 on the
right, y1 on the top, and y2 on the bottom. The return value may
overestimate the actual bounding box by a few pixels. If no items
match any of the tagOrId arguments then an empty string is returned.
pathName bind tagOrId ?sequence? ?command?
This command associates command with all the items given by tagOrId
such that whenever the event sequence given by sequence occurs for
one of the items the command will be invoked. This widget command
is similar to the bind command except that it operates on items in a
canvas rather than entire widgets. See the bind manual entry for
complete details on the syntax of sequence and the substitutions
performed on command before invoking it. If all arguments are
specified then a new binding is created, replacing any existing
binding for the same sequence and tagOrId (if the first character of
command is ``+'' then command augments an existing binding rather
than replacing it). In this case the return value is an empty
string. If command is omitted then the command returns the command
associated with tagOrId and sequence (an error occurs if there is no
such binding). If both command and sequence are omitted then the
command returns a list of all the sequences for which bindings have
been defined for tagOrId.
The only events for which bindings may be specified are those
related to the mouse and keyboard, such as Enter, Leave,
ButtonPress, Motion, and KeyPress. 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
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canvas(3Tk) canvas(3Tk)
events are different than Enter and Leave events for windows.
Mouse-related events are directed to the current item, if any.
Keyboard-related events are directed to the focus item, if any (see
the focus widget command below for more on this).
It is possible for multiple bindings to match a particular event. |
This could occur, for example, if one binding is associated with the|
item's id and another is associated with one of the item's tags. |
When this occurs, all of the matching bindings are invoked. A |
binding associated with the all tag is invoked first, followed by |
one binding for each of the item's tags (in order), followed by a |
binding associated with the item's id. If there are multiple |
matching bindings for a single tag, then only the most specific |
binding is invoked. A continue command in a binding script |
terminates that script, and a break command terminates that script |
and skips any remaining scripts for the event, just as for the bind |
command. |
If bindings have been created for a canvas window using the bind |
command, then they are invoked in addition to bindings created for |
the canvas's items using the bind widget command. The bindings for |
items will be invoked before any of the bindings for the window as a|
whole.
pathName canvasx screenx ?gridspacing?
Given a screen x-coordinate screenx this command returns the canvas
x-coordinate that is displayed at that location. If gridspacing is
specified, then the canvas coordinate is rounded to the nearest
multiple of gridspacing units.
pathName canvasy screeny ?gridspacing?
Given a screen y-coordinate screeny this command returns the canvas
y-coordinate that is displayed at that location. If gridspacing is
specified, then the canvas coordinate is rounded to the nearest
multiple of gridspacing units.
pathName cget option
Returns the current value of the configuration option given by |
option. Option may have any of the values accepted by the canvas |
command.
pathName configure ?option? ?value? ?option value ...?
Query or modify the configuration options of the widget. If no
option is specified, returns a list describing all of the available
options for pathName (see Tk_ConfigureInfo for information on the
format of this list). If option is specified with no value, then
the command returns a list describing the one named option (this
list will be identical to the corresponding sublist of the value
returned if no option is specified). If one or more option-value
pairs are specified, then the command modifies the given widget
option(s) to have the given value(s); in this case the command
returns an empty string. Option may have any of the values accepted
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canvas(3Tk) canvas(3Tk)
by the canvas command.
pathName coords tagOrId ?x0 y0 ...?
Query or modify the coordinates that define an item. If no
coordinates are specified, this command returns a list whose
elements are the coordinates of the item named by tagOrId. If
coordinates are specified, then they replace the current coordinates
for the named item. If tagOrId refers to multiple items, then the
first one in the display list is used.
pathName create type x y ?x y ...? ?option value ...?
Create a new item in pathName of type type. The exact format of the
arguments after type depends on type, but usually they consist of
the coordinates for one or more points, followed by specifications
for zero or more item options. See the subsections on individual
item types below for more on the syntax of this command. This
command returns the id for the new item.
pathName dchars tagOrId first ?last?
For each item given by tagOrId, delete the characters in the range
given by first and last, inclusive. If some of the items given by
tagOrId don't support text operations, then they are ignored. First
and last are indices of characters within the item(s) as described
in INDICES above. If last is omitted, it defaults to first. This
command returns an empty string.
pathName delete ?tagOrId tagOrId ...?
Delete each of the items given by each tagOrId, and return an empty
string.
pathName dtag tagOrId ?tagToDelete?
For each of the items given by tagOrId, delete the tag given by
tagToDelete from the list of those associated with the item. If an
item doesn't have the tag tagToDelete then the item is unaffected by
the command. If tagToDelete is omitted then it defaults to tagOrId.
This command returns an empty string.
pathName find searchCommand ?arg arg ...?
This command returns a list consisting of all the items that meet
the constraints specified by searchCommand and arg's. SearchCommand
and args have any of the forms accepted by the addtag command.
pathName focus ?tagOrId?
Set the keyboard focus for the canvas widget to the item given by
tagOrId. If tagOrId refers to several items, then the focus is set
to the first such item in the display list that supports the
insertion cursor. If tagOrId doesn't refer to any items, or if none
of them support the insertion cursor, then the focus isn't changed.
If tagOrId is an empty string, then the focus item is reset so that
no item has the focus. If tagOrId is not specified then the command
returns the id for the item that currently has the focus, or an
empty string if no item has the focus.
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canvas(3Tk) canvas(3Tk)
Once the focus has been set to an item, the item will display the
insertion cursor and all keyboard events will be directed to that
item. The focus item within a canvas and the focus window on the
screen (set with the focus command) are totally independent: a
given item doesn't actually have the input focus unless (a) its
canvas is the focus window and (b) the item is the focus item within
the canvas. In most cases it is advisable to follow the focus
widget command with the focus command to set the focus window to the
canvas (if it wasn't there already).
pathName gettags tagOrId
Return a list whose elements are the tags associated with the item
given by tagOrId. If tagOrId refers to more than one item, then the
tags are returned from the first such item in the display list. If
tagOrId doesn't refer to any items, or if the item contains no tags,
then an empty string is returned.
pathName icursor tagOrId index
Set the position of the insertion cursor for the item(s) given by
tagOrId to just before the character whose position is given by
index. If some or all of the items given by tagOrId don't support
an insertion cursor then this command has no effect on them. See
INDICES above for a description of the legal forms for index. Note:
the insertion cursor is only displayed in an item if that item
currently has the keyboard focus (see the widget command focus,
below), but the cursor position may be set even when the item
doesn't have the focus. This command returns an empty string.
pathName index tagOrId index
This command returns a decimal string giving the numerical index
within tagOrId corresponding to index. Index gives a textual
description of the desired position as described in INDICES above.
The return value is guaranteed to lie between 0 and the number of
characters within the item, inclusive. If tagOrId refers to
multiple items, then the index is processed in the first of these
items that supports indexing operations (in display list order).
pathName insert tagOrId beforeThis string
For each of the items given by tagOrId, if the item supports text
insertion then string is inserted into the item's text just before
the character whose index is beforeThis. See INDICES above for
information about the forms allowed for beforeThis. This command
returns an empty string.
pathName itemcget tagOrId option
Returns the current value of the configuration option for the item |
given by tagOrId whose name is option. This command is similar to |
the cget widget command except that it applies to a particular item |
rather than the widget as a whole. Option may have any of the |
values accepted by the create widget command when the item was |
created. If tagOrId is a tag that refers to more than one item, the|
first (lowest) such item is used.
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canvas(3Tk) canvas(3Tk)
pathName itemconfigure tagOrId ?option? ?value? ?option value ...?
This command is similar to the configure widget command except that
it modifies item-specific options for the items given by tagOrId
instead of modifying options for the overall canvas widget. If no
option is specified, returns a list describing all of the available
options for the first item given by tagOrId (see Tk_ConfigureInfo
for information on the format of this list). If option is specified
with no value, then the command returns a list describing the one
named option (this list will be identical to the corresponding
sublist of the value returned if no option is specified). If one or
more option-value pairs are specified, then the command modifies the
given widget option(s) to have the given value(s) in each of the
items given by tagOrId; in this case the command returns an empty
string. The options and values are the same as those permissible in
the create widget command when the item(s) were created; see the
sections describing individual item types below for details on the
legal options.
pathName lower tagOrId ?belowThis?
Move all of the items given by tagOrId to a new position in the
display list just before the item given by belowThis. If tagOrId
refers to more than one item then all are moved but the relative
order of the moved items will not be changed. BelowThis is a tag or
id; if it refers to more than one item then the first (lowest) of
these items in the display list is used as the destination location
for the moved items. This command returns an empty string.
pathName move tagOrId xAmount yAmount
Move each of the items given by tagOrId in the canvas coordinate
space by adding xAmount to the x-coordinate of each point associated
with the item and yAmount to the y-coordinate of each point
associated with the item. This command returns an empty string.
pathName postscript ?option value option value ...?
Generate a Postscript representation for part or all of the canvas.
If the -file option is specified then the Postscript is written to a
file and an empty string is returned; otherwise the Postscript is
returned as the result of the command. The Postscript is created in
Encapsulated Postscript form using version 3.0 of the Document
Structuring Conventions. The option-value argument pairs provide
additional information to control the generation of Postscript. The
following options are supported:
-colormap varName
VarName must be the name of an array variable that specifies a
color mapping to use in the Postscript. Each element of
varName must consist of Postscript code to set a particular
color value (e.g. ``1.0 1.0 0.0 setrgbcolor''). When
outputting color information in the Postscript, Tk checks to
see if there is an element of varName with the same name as the
color. If so, Tk uses the value of the element as the
Postscript command to set the color. If this option hasn't
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canvas(3Tk) canvas(3Tk)
been specified, or if there isn't an entry in varName for a
given color, then Tk uses the red, green, and blue intensities
from the X color.
-colormode mode
Specifies how to output color information. Mode must be either
color (for full color output), gray (convert all colors to
their gray-scale equivalents) or mono (convert all colors to
black or white).
-file fileName
Specifies the name of the file in which to write the
Postscript. If this option isn't specified then the Postscript
is returned as the result of the command instead of being
written to a file.
-fontmap varName
VarName must be the name of an array variable that specifies a
font mapping to use in the Postscript. Each element of varName
must consist of a Tcl list with two elements, which are the
name and point size of a Postscript font. When outputting
Postscript commands for a particular font, Tk checks to see if
varName contains an element with the same name as the font. If
there is such an element, then the font information contained
in that element is used in the Postscript. Otherwise Tk
attempts to guess what Postscript font to use. Tk's guesses
generally only work for well-known fonts such as Times and
Helvetica and Courier, and only if the X font name does not
omit any dashes up through the point size. For example,
-*-Courier-Bold-R-Normal--*-120-* will work but
*Courier-Bold-R-Normal*120* will not; Tk needs the dashes to
parse the font name).
-height size
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 should be 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 printed area 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 the later
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canvas(3Tk) canvas(3Tk)
option 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 the
later option 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.
pathName raise tagOrId ?aboveThis?
Move all of the items given by tagOrId to a new position in the
display list just after the item given by aboveThis. If tagOrId
refers to more than one item then all are moved but the relative
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canvas(3Tk) canvas(3Tk)
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. This command returns an empty string.
pathName scale tagOrId xOrigin yOrigin xScale yScale
Rescale all of the items given by tagOrId in canvas coordinate
space. XOrigin and yOrigin identify the origin for the scaling
operation and xScale and yScale identify the scale factors for xand
y-coordinates, respectively (a scale factor of 1.0 implies no
change to that coordinate). For each of the points defining each
item, the x-coordinate is adjusted to change the distance from
xOrigin by a factor of xScale. Similarly, each y-coordinate is
adjusted to change the distance from yOrigin by a factor of yScale.
This command returns an empty string.
pathName scan option args
This command is used to implement scanning on canvases. It has two
forms, depending on option:
pathName scan mark x y
Records x and y and the canvas's current view; used in
conjunction with later scan dragto commands. Typically this
command is associated with a mouse button press in the widget
and x and y are the coordinates of the mouse. It returns an
empty string.
pathName scan dragto x y.
This command computes the difference between its x and y
arguments (which are typically mouse coordinates) and the x and
y arguments to the last scan mark command for the widget. It
then adjusts the view by 10 times the difference in
coordinates. This command is typically associated with mouse
motion events in the widget, to produce the effect of dragging
the canvas at high speed through its window. The return value
is an empty string.
pathName select option ?tagOrId arg?
Manipulates the selection in one of several ways, depending on
option. The command may take any of the forms described below. In
all of the descriptions below, tagOrId must refer to an item that
supports indexing and selection; if it refers to multiple items
then the first of these that supports indexing and the selection is
used. Index gives a textual description of a position within
tagOrId, as described in INDICES above.
pathName select adjust tagOrId index
Locate the end of the selection in tagOrId nearest to the
character given by index, and adjust that end of the selection
to be at index (i.e. including but not going beyond index).
The other end of the selection is made the anchor point for
future select to commands. If the selection isn't currently in
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canvas(3Tk) canvas(3Tk)
tagOrId then this command behaves the same as the select to
widget command. Returns an empty string.
pathName select clear
Clear the selection if it is in this widget. If the selection
isn't in this widget then the command has no effect. Returns
an empty string.
pathName select from tagOrId index
Set the selection anchor point for the widget to be just before
the character given by index in the item given by tagOrId.
This command doesn't change the selection; it just sets the
fixed end of the selection for future select to commands.
Returns an empty string.
pathName select item
Returns the id of the selected item, if the selection is in an
item in this canvas. If the selection is not in this canvas
then an empty string is returned.
pathName select to tagOrId index
Set the selection to consist of those characters of tagOrId
between the selection anchor point and index. The new
selection will include the character given by index; it will
include the character given by the anchor point only if index
is greater than or equal to the anchor point. The anchor point
is determined by the most recent select adjust or select from
command for this widget. If the selection anchor point for the
widget isn't currently in tagOrId, then it is set to the same
character given by index. Returns an empty string.
pathName type tagOrId
Returns the type of the item given by tagOrId, such as rectangle or
text. If tagOrId refers to more than one item, then the type of the
first item in the display list is returned. If tagOrId doesn't
refer to any items at all then an empty string is returned.
pathName xview ?args?
This command is used to query and change the horizontal position of |
the information displayed in the canvas's window. It can take any |
of the following forms:
pathName xview
Returns a list containing two elements. Each element is a real|
fraction between 0 and 1; together they describe the |
horizontal span that is visible in the window. For example, if|
the first element is .2 and the second element is .6, 20% of |
the canvas's area (as defined by the -scrollregion 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.
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canvas(3Tk) canvas(3Tk)
pathName xview moveto fraction
Adjusts the view in the window so that fraction of the total |
width of the canvas is off-screen to the left. Fraction must |
be a fraction between 0 and 1.
pathName xview scroll number what
This command shifts the view in the window left or right |
according to number and what. Number must be an integer. What|
must be either units or pages or an abbreviation of one of |
these. If what is units, the view adjusts left or right in |
units of the xScrollIncrement option, if it is greater than |
zero, or in units of one-tenth the window's width otherwise. |
If what is pages then the view adjusts in units of nine-tenths |
the window's width. If number is negative then information |
farther to the left becomes visible; if it is positive then |
information farther to the right becomes visible.
pathName yview ?args?
This command is used to query and change the vertical position of |
the information displayed in the canvas's window. It can take any |
of the following forms:
pathName yview
Returns a list containing two elements. Each element is a real|
fraction between 0 and 1; together they describe the vertical |
span that is visible in the window. For example, if the first |
element is .6 and the second element is 1.0, the lowest 40% of |
the canvas's area (as defined by the -scrollregion option) is |
visible in the window. These are the same values passed to |
scrollbars via the -yscrollcommand option.
pathName yview moveto fraction
Adjusts the view in the window so that fraction of the canvas's|
area is off-screen to the top. Fraction is a fraction between |
0 and 1.
pathName yview scroll number what
This command adjusts the view in the window up or down |
according to number and what. Number must be an integer. What|
must be either units or pages. If what is units, the view |
adjusts up or down in 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 [Toc] [Back] The sections below describe the various types of items supported by
canvas widgets. Each item type is characterized by two things: first,
the form of the create command used to create instances of the type; and
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canvas(3Tk) canvas(3Tk)
second, a set of configuration options for items of that type, which may
be used in the create and itemconfigure widget commands. Most items
don't support indexing or selection or the commands related to them, such
as index and insert. Where items do support these facilities, it is
noted explicitly in the descriptions below (at present, only text items
provide this support).
Items of type arc appear on the display as arc-shaped regions. An arc is
a section of an oval delimited by two angles (specified by the -start and
-extent options) and displayed in one of several ways (specified by the
-style option). Arcs are created with widget commands of the following
form:
pathName create arc x1 y1 x2 y2 ?option value option value ...?
The arguments x1, y1, x2, and y2 give the coordinates of two diagonally
opposite corners of a rectangular region enclosing the oval that defines
the arc. After the coordinates there may be any number of option-value
pairs, each of which sets one of the configuration options for the item.
These same option-value pairs may be used in itemconfigure widget
commands to change the item's configuration. The following options are
supported for arcs:
-extent degrees
Specifies the size of the angular range occupied by the arc. The
arc's range extends for degrees degrees counter-clockwise from the
starting angle given by the -start option. Degrees may be negative.|
If it is greater than 360 or less than -360, then degrees modulo 360|
is used as the extent.
-fill color
Fill the region of the arc with color. Color may have any of the
forms accepted by Tk_GetColor. If color is an empty string (the
default), then then the arc will not be filled.
-outline color
Color specifies a color to use for drawing the arc's outline; it
may have any of the forms accepted by Tk_GetColor. This option
defaults to black. If color is specified as an empty string then no
outline is drawn for the arc.
-outlinestipple bitmap
Indicates that the outline for the arc should be drawn with a |
stipple pattern; bitmap specifies the stipple pattern to use, in any|
of the forms accepted by Tk_GetBitmap. If the -outline option |
hasn't been specified then this option has no effect. If bitmap is |
an empty string (the default), then the outline is drawn in a solid |
fashion.
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canvas(3Tk) canvas(3Tk)
-start degrees
Specifies the beginning of the angular range occupied by the arc.
Degrees is given in units of degrees measured counter-clockwise from
the 3-o'clock position; it may be either positive or negative.
-stipple bitmap
Indicates that the arc should be filled in a stipple pattern; bitmap
specifies the stipple pattern to use, in any of the forms accepted
by Tk_GetBitmap. If the -fill option hasn't been specified then
this option has no effect. If bitmap is an empty string (the
default), then filling is done in a solid fashion.
-style type
Specifies how to draw the arc. If type is pieslice (the default)
then the arc's region is defined by a section of the oval's
perimeter plus two line segments, one between the center of the oval
and each end of the perimeter section. If type is chord then the
arc's region is defined by a section of the oval's perimeter plus a
single line segment connecting the two end points of the perimeter
section. If type is arc then the arc's region consists of a section
of the perimeter alone. In this last case the -fill option is |
ignored.
-tags tagList
Specifies a set of tags to apply to the item. TagList consists of a
list of tag names, which replace any existing tags for the item.
TagList may be an empty list.
-width outlineWidth
Specifies the width of the outline to be drawn around the arc's
region, in any of the forms described in the COORDINATES section
above. If the -outline option has been specified as an empty string
then this option has no effect. Wide outlines will be drawn
centered on the edges of the arc's region. This option defaults to
1.0.
Items of type bitmap appear on the display as images with two colors,
foreground and background. Bitmaps are created with widget commands of
the following form:
pathName create bitmap x y ?option value option value ...?
The arguments x and y specify the coordinates of a point used to position
the bitmap on the display (see the -anchor option below for more
information on how bitmaps are displayed). After the coordinates there
may be any number of option-value pairs, each of which sets one of the
configuration options for the item. These same option-value pairs may be
used in itemconfigure widget commands to change the item's configuration.
The following options are supported for bitmaps:
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canvas(3Tk) canvas(3Tk)
-anchor anchorPos
AnchorPos tells how to position the bitmap relative to the
positioning point for the item; it may have any of the forms
accepted by Tk_GetAnchor. For example, if anchorPos is center then
the bitmap is centered on the point; if anchorPos is n then the
bitmap will be drawn so that its top center point is at the
positioning point. This option defaults to center.
-background color
Specifies a color to use for each of the bitmap pixels whose value
is 0. Color may have any of the forms accepted by Tk_GetColor. If
this option isn't specified, or if it is specified as an empty |
string, then nothing is displayed where the bitmap pixels are 0; |
this produces a transparent effect.
-bitmap bitmap
Specifies the bitmap to display in the item. Bitmap may have any of
the forms accepted by Tk_GetBitmap.
-foreground color
Specifies a color to use for each of the bitmap pixels whose value
is 1. Color may have any of the forms accepted by Tk_GetColor and
defaults to black.
-tags tagList
Specifies a set of tags to apply to the item. TagList consists of a
list of tag names, which replace any existing tags for the item.
TagList may be an empty list.
Items of type image are used to display images on a canvas. Images are |
created with widget commands of the following form: |
pathName create image x y ?option value option value ...? |
The arguments x and y specify the coordinates of a point used to position|
the image on the display (see the -anchor option below for more |
information). After the coordinates there may be any number of |
option-value pairs, each of which sets one of the configuration options |
for the item. These same option-value pairs may be used in itemconfigure|
widget commands to change the item's configuration. The following |
options are supported for images:
-anchor anchorPos
AnchorPos tells how to position the image relative to the |
positioning point for the item; it may have any of the forms |
accepted by Tk_GetAnchor. For example, if anchorPos is center then |
the image is centered on the point; if anchorPos is n then the |
image will be drawn so that its top center point is at the |
positioning point. This option defaults to center.
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canvas(3Tk) canvas(3Tk)
-image name
Specifies the name of the image to display in the item. This image |
must have been created previously with the image create command.
-tags tagList
Specifies a set of tags to apply to the item. TagList consists of a|
list of tag names, which replace any existing tags for the item; it|
may be an empty list.
Items of type line appear on the display as one or more connected line
segments or curves. Lines are created with widget commands of the
following form:
pathName create line x1 y1... xn yn ?option value option value ...?
The arguments x1 through yn give the coordinates for a series of two or
more points that describe a series of connected line segments. After the
coordinates there may be any number of option-value pairs, each of which
sets one of the configuration options for the item. These same
option-value pairs may be used in itemconfigure widget commands to change
the item's configuration. The following options are supported for lines:
-arrow where
Indicates whether or not arrowheads are to be drawn at one or both
ends of the line. Where must have one of the values none (for no
arrowheads), first (for an arrowhead at the first point of the
line), last (for an arrowhead at the last point of the line), or
both (for arrowheads at both ends). This option defaults to none.
-arrowshape shape
This option indicates how to draw arrowheads. The shape argument
must be a list with three elements, each specifying a distance in
any of the forms described in the COORDINATES section above. The
first element of the list gives the distance along the line from the
neck of the arrowhead to its tip. The second element gives the
distance along the line from the trailing points of the arrowhead to
the tip, and the third element gives the distance from the outside
edge of the line to the trailing points. If this option isn't
specified then Tk picks a ``reasonable'' shape.
-capstyle style
Specifies the ways in which caps are to be drawn at the endpoints of
the line. Style may have any of the forms accepted by
Tk_GetCapStyle (butt, projecting, or round). If this option isn't
specified then it defaults to butt. Where arrowheads are drawn the
cap style is ignored.
-fill color
Color specifies a color to use for drawing the line; it may have any
of the forms acceptable to Tk_GetColor. It may also be an empty
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canvas(3Tk) canvas(3Tk)
string, in which case the line will be transparent. This option
defaults to black.
-joinstyle style
Specifies the ways in which joints are to be drawn at the vertices
of the line. Style may have any of the forms accepted by
Tk_GetCapStyle (bevel, miter, or round). If this option isn't
specified then it defaults to miter. If the line only contains two
points then this option is irrelevant.
-smooth boolean
Boolean must have one of the forms accepted by Tk_GetBoolean. It
indicates whether or not the line should be drawn as a curve. If
so, the line is rendered as a set of Bezier 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.
-stipple bitmap
Indicates that the line should be filled in a stipple pattern;
bitmap specifies the stipple pattern to use, in any of the forms
accepted by Tk_GetBitmap. If bitmap is an empty string (the
default), then filling is done in a solid fashion.
-tags tagList
Specifies a set of tags to apply to the item. TagList consists of a
list of tag names, which replace any existing tags for the item.
TagList may be an empty list.
-width lineWidth
LineWidth specifies the width of the line, in any of the forms
described in the COORDINATES section above. Wide lines will be
drawn centered on the path specified by the points. If this option
isn't specified then it defaults to 1.0.
Items of type oval appear as circular or oval regions on the display.
Each oval may have an outline, a fill, or both. Ovals are created with
widget commands of the following form:
pathName create oval x1 y1 x2 y2 ?option value option value ...?
The arguments x1, y1, x2, and y2 give the coordinates of two diagonally
opposite corners of a rectangular region enclosing the oval. The oval
will include the top and left edges of the rectangle not the lower or
right edges. If the region is square then the resulting oval is
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canvas(3Tk) canvas(3Tk)
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 pai
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