CANVAS(9)                                               CANVAS(9)

     NAME
          canvas - Create and manipulate canvas widgets

     SYNOPSIS
          canvas pathName ?options?

     STANDARD OPTIONS
          -background        -selectbackground  -takefocus
          -borderwidth       -selectborderwidth -xscrollcommand
          -relief            -selectforeground  -yscrollcommand

     WIDGET-SPECIFIC OPTIONS
          -closeenough dist
               Specifies a floating-point value indicating how close
               the mouse cursor must be to an item before it is con-
               sidered to be ``inside'' the item.  Defaults to 1.0.

          -confine boolean
               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.

          -height dist
               Specifies a desired window height that the canvas wid-
               get should request from its geometry manager.  The
               value may be specified in any of the forms described in
               the COORDINATES section below.

          -scrollregion list
               Specifies a list with four dist coordinates describing
               the left, top, right, and bottom coordinates of a rect-
               angular region.  This region is used for scrolling pur-
               poses 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 COORDI-
               NATES section below.

          -width dist
               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.

          -xscrollincrement dist
               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 hor-
               izontal view in the window will be constrained so that

     CANVAS(9)                                               CANVAS(9)

               the canvas x coordinate at the left edge of the window
               is always an even multiple of xscrollicrement;  fur-
               thermore, the units for scrolling (e.g., the change in
               view when the left and right arrows of a scrollbar are
               selected) will also be xscrollicrement.  If the value
               of this option is less than or equal to zero, then hor-
               izontal scrolling is unconstrained.

          -yscrollincrement dist
               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 ver-
               tical 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 yscrollicrement;  fur-
               thermore, the units for scrolling (e.g., the change in
               view when the top and bottom arrows of a scrollbar are
               selected) will also be yscrollicrement.  If the value
               of this option is less than or equal to zero, then ver-
               tical scrolling is unconstrained.

          -buffer what
               Specifies how much of the canvas region will be backed
               by an offscreen bitmap buffer.  What can be one of all
               (the entire scroll region will be buffered), visible
               (only the visible area), none (no buffering) or auto
               (equivalent to either none or visible depending on
               whether the canvas is packed inside another canvas or
               not).

     INTRODUCTION
          The canvas command creates a new window (given by the path-
          Name argument) and makes it into a canvas widget.  Addi-
          tional options, described above, may be specified on the
          command line to configure aspects of the canvas such as its
          colours 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.

          Canvas widgets implement structured graphics.  A canvas dis-
          plays any number of items, which may be things like rectan-
          gles, circles, lines, and text.  Items may be manipulated
          (e.g. moved or re-coloured) and commands may be associated
          with items in much the same way that the bind command allows
          commands to be bound to widgets.  For example, a particular
          command may be associated with the <Button-1> event so that
          the command is invoked whenever button 1 is pressed with the
          mouse cursor over an item.  This means that items in a can-
          vas can have behaviours defined by the Tk scripts bound to
          them.

     CANVAS(9)                                               CANVAS(9)

     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 ear-
          lier in the display list and are sometimes referred to as
          being ``on top'' of earlier items.  When a new item is cre-
          ated 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.

     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 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 inte-
          ger, 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 oper-
          ate on a single item at a time;  if tagOrId is specified in
          a way that names multiple items, then the normal behaviour
          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.

     CANVAS(9)                                               CANVAS(9)

     COORDINATES
          All coordinates related to canvases are stored as fixed-
          point numbers.  Coordinates and distances are specified as
          documented in the dist section of types(9).

     TRANSFORMATIONS
          Normally the origin of the canvas coordinate system is at
          the upper-left corner of the window containing the canvas.
          It is possible to adjust the origin of the canvas coordinate
          system relative to the origin of the window using the xview
          and yview widget commands;  this is typically used for
          scrolling.  Canvases do not support scaling or rotation of
          the canvas coordinate system relative to the window coordi-
          nate system.

          Individual items may be moved or scaled using widget com-
          mands described below, but they may not be rotated.

     INDICES
          Text items support the notion of an index for identifying
          particular positions within the item.  Indices are used for
          commands such as inserting text, deleting a range of charac-
          ters, 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.  Note that it is possible to refer to the character
          just after the last one in the text item;  this is necessary
          for such tasks as inserting new text at the end of the item.

          number    A decimal number giving the position of the
                    desired character within the text item.  0 refers
                    to the first character, 1 to the next character,
                    and so on.  A number less than 0 is treated as if
                    it were zero, and a number greater than the length
                    of the text item is treated as if it were equal to
                    the length of the text item.

          end       Refers to the character just after the last one in
                    the item (same as the number of characters in the
                    item).

          insert    Refers to the character just before which the
                    insertion cursor is drawn in this item.

          sel.first Refers to the first selected character in the
                    item.  If the selection isn't in this item then
                    this form is illegal.

          sel.last  Refers to the last selected character in the item.
                    If the selection isn't in this item then this form

     CANVAS(9)                                               CANVAS(9)

                    is illegal.

          @x,y      Refers to the character at the point given by x
                    and y, where x and y are specified in the coordi-
                    nate system of the canvas.  If x and y lie outside
                    the coordinates covered by the text item, then
                    they refer to the first or last character in the
                    line that is closest to the given point.

     WIDGET COMMAND
          The canvas command creates a new Tk command whose name is
          pathName.  This command may be used to invoke various opera-
          tions on the widget.  It has the following general form:
               pathName option ?arg arg ...?
          Option and the args determine the exact behaviour 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 (top-
                    most) 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 (low-
                    est) 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 clos-
                    est 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

     CANVAS(9)                                               CANVAS(9)

                    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.

          pathName bbox tagOrId ?tagOrId tagOrId ...?
               Returns a list with four elements giving an approximate
               bounding box for all the items named by the tagOrId
               arguments.  The list has the form ``x1 y1 x2 y2'' such
               that the drawn areas of all the named elements are
               within the region bounded by x1 on the left, x2 on the
               right, y1 on the top, and y2 on the bottom.  The return
               value may overestimate the actual bounding box by a few
               pixels.  If no items match any of the tagOrId arguments
               or if the matching items have empty bounding boxes
               (i.e. they have nothing to display) then an empty
               string is returned.

          pathName bind tagOrId ?sequence? ?command?
               This command associates command with all the items
               given by tagOrId such that whenever the event sequence
               given by sequence occurs for one of the items the com-
               mand 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 man-
               ual 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

     CANVAS(9)                                               CANVAS(9)

               case the return value is an empty string.  If command
               is omitted then the command returns the command associ-
               ated 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 trig-
               ger for an item when it becomes the current item or
               ceases to be the current item;  note that these events
               are different than Enter and Leave events for windows.
               Mouse-related events are directed to the current item,
               if any.  Keyboard-related events are directed to the
               focus item, if any (see the focus widget command below
               for more on this).

               It is possible for multiple bindings to match a partic-
               ular 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 termi-
               nates that script, and a break command terminates that
               script and skips any remaining scripts for the event,
               just as for the bind command.

               If bindings have been created for a canvas window using
               the bind command, then they are invoked in addition to
               bindings created for the canvas's items using the bind
               widget command.  The bindings for items will be invoked
               before any of the bindings for the window as a whole.

          pathName canvasx screenx ?gridspacing?
               Given a window x-coordinate in the canvas screenx, this
               command returns the canvas x-coordinate that is dis-
               played at that location.  If gridspacing is specified,
               then the canvas coordinate is rounded to the nearest
               multiple of gridspacing units.

          pathName canvasy screeny ?gridspacing?
               Given a window y-coordinate in the canvas screeny this
               command returns the canvas y-coordinate that is

     CANVAS(9)                                               CANVAS(9)

               displayed at that location.  If gridspacing is speci-
               fied, 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 wid-
               get.  If no option is specified, returns a list of all
               of the available options for pathName.  If one or more
               option-value pairs are specified, then the command mod-
               ifies the given widget option(s) to have the given
               value(s);  in this case the command returns an empty
               string.  Option may have any of the values accepted by
               the canvas command.

          pathName coords tagOrId ?x0 y0 ...?
               Query or modify the coordinates that define an item.
               If no coordinates are specified, this command returns a
               list whose elements are the coordinates of the item
               named by tagOrId.  If coordinates are specified, then
               they replace the current coordinates for the named
               item.  If tagOrId refers to multiple items, then the
               first one in the display list is used.

          pathName create type x y ?x y ...? ?option value ...?
               Create a new item in pathName of type type.  The exact
               format of the arguments after type depends on type, but
               usually they consist of the coordinates for one or more
               points, followed by specifications for zero or more
               item options.  See the subsections on individual item
               types below for more on the syntax of this command.
               This command returns the id for the new item.

          pathName dchars tagOrId first ?last?
               For each item given by tagOrId, delete the characters
               in the range given by first and last, inclusive.  If
               some of the items given by tagOrId don't support text
               operations, then they are ignored.  First and last are
               indices of characters within the item(s) as described
               in INDICES above.  If last is omitted, it defaults to
               first.  This command returns an empty string.

          pathName delete ?tagOrId tagOrId ...?
               Delete each of the items given by each tagOrId, and
               return an empty string.

          pathName dtag tagOrId ?tagToDelete?
               For each of the items given by tagOrId, delete the tag

     CANVAS(9)                                               CANVAS(9)

               given by tagToDelete from the list of those associated
               with the item.  If an item doesn't have the tag tag-
               ToDelete 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.  If searchCommand
               is enclosed, overlapping, or all, the items are
               returned in display-list order, i.e. bottommost first.

          pathName focus ?tagOrId?
               Set the keyboard focus for the canvas widget to the
               item given by tagOrId.  If tagOrId refers to several
               items, then the focus is set to the first such item in
               the display list that supports the insertion cursor.
               If tagOrId doesn't refer to any items, or if none of
               them support the insertion cursor, then the focus isn't
               changed.  If tagOrId is an empty string, then the focus
               item is reset so that no item has the focus.  If
               tagOrId is not specified then the command returns the
               id for the item that currently has the focus, or an
               empty string if no item has the focus.

               Once the focus has been set to an item, the item will
               display the insertion cursor and all keyboard events
               will be directed to that item.  The focus item within a
               canvas and the focus window on the screen (set with the
               focus command) are totally independent: a given item
               doesn't actually have the input focus unless (a) its
               canvas is the focus window and (b) the item is the
               focus item within the canvas.  In most cases it is
               advisable to follow the focus widget command with the
               focus command to set the focus window to the canvas (if
               it wasn't there already).

          pathName gettags tagOrId
               Return a list whose elements are the tags associated
               with the item given by tagOrId.  If tagOrId refers to
               more than one item, then the tags are returned from the
               first such item in the display list.  If tagOrId
               doesn't refer to any items, then an error is returned.
               If the item contains no tags, then an empty string is
               returned.

          pathName grab what tagOrId
               Does for canvas widgets what grab(9) does for normal tk
               widgets: mouse events will only be delivered to
               tagOrId. If tagOrId refers to more than one item, then

     CANVAS(9)                                               CANVAS(9)

               the first such item in the display list is grabbed.
               What is as described in grab(9).

          Note that the canvas grab item, as set by this command, and
          the tk grab item, as set by grab(9) are totally independent;
          a canvas item doesn't actually grab the mouse unless a) the
          canvas itself has grabbed the mouse or b) the mouse events
          are being delivered to the canvas as a matter of course.

          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 numer-
               ical index within tagOrId corresponding to index.
               Index gives a textual description of the desired posi-
               tion as described in INDICES above.  The return value
               is guaranteed to lie between 0 and the number of char-
               acters 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 val-
               ues accepted by the create widget command when the item
               was created.  If tagOrId is a tag that refers to more
               than one item, the first (lowest) such item is used.

          pathName itemconfigure tagOrId ?option? ?value? ?option value

     CANVAS(9)                                               CANVAS(9)

               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 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 val-
               ues 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 posi-
               tion 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 (low-
               est) 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 raise tagOrId ?aboveThis?
               Move all of the items given by tagOrId to a new posi-
               tion 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 (top-
               most) 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 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.  Simi-
               larly, each y-coordinate is adjusted to change the

     CANVAS(9)                                               CANVAS(9)

               distance from yOrigin by a factor of yScale.  This com-
               mand returns an empty string.

          pathName screenx canvasx
               Given an x-coordinate canvasx in the canvas, this com-
               mand returns the equivalent screen x-coordinate.

          pathName screeny canvasy
               Given an x-coordinate canvasy in the canvas, this com-
               mand returns the equivalent screen y-coordinate.

          pathName see x1 y1 ?x2 y2?
               Adjusts the view in the window such that, if possible
               the point [x1, y1] (and, if given, the point [x2, y2])
               are made visible.

          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. includ-
                    ing 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 cur-
                    rently in 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 com-
                    mand 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

     CANVAS(9)                                               CANVAS(9)

                    Returns the id of the selected item, if the selec-
                    tion is in an item in this canvas.  If the selec-
                    tion 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 charac-
                    ter 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 ele-
                    ment 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 val-
                    ues passed to scrollbars via the -xscrollcommand
                    option.

               pathName xview moveto fraction
                    Adjusts the view in the window so that fraction of
                    the total width of the canvas is off-screen to the
                    left.  Fraction must be a fraction between 0 and
                    1.

               pathName xview scroll number what
                    This command shifts the view in the window left or

     CANVAS(9)                                               CANVAS(9)

                    right according to number and what.  Number must
                    be an integer.  What must be either units or
                    pages.  If what is units, the view adjusts left or
                    right in units of the xscrollicrement 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 infor-
                    mation 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 ele-
                    ment 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 -scrollre-
                    gion 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.  Frac-
                    tion 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 yscrollicrement 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 pos-
                    itive then lower information becomes visible.

     OVERVIEW OF ITEM TYPES
          The sections below describe the various types of items sup-
          ported by canvas widgets.  Each item type is characterized
          by two things: first, the form of the create command used to
          create instances of the type;  and second, a set of

     CANVAS(9)                                               CANVAS(9)

          configuration options for items of that type, which may be
          used in the create and itemconfigure widget commands.  Most
          items don't support indexing or selection or the commands
          related to them, such as index and insert.  Where items do
          support these facilities, it is noted explicitly in the
          descriptions below (at present, only text items provide this
          support).

     ARC ITEMS
          Items of type arc appear on the display as arc-shaped
          regions.  An arc is a section of an oval delimited by two
          angles (specified by the -start and -extent options) and
          displayed in one of several ways (specified by the -style
          option).  Arcs are created with widget commands of the fol-
          lowing 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 enclos-
          ing 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 colour
               Fill the region of the arc with colour.  If colour is
               an empty string (the default), then the arc will not be
               filled.

          -outline colour
               Colour specifies a colour to use for drawing the arc's
               outline.  This option defaults to black.  If colour is
               specified as an empty string then no outline is drawn
               for the arc.

          -start degrees
               Specifies the beginning of the angular range occupied
               by the arc.  Degrees is given in units of degrees mea-
               sured counter-clockwise from the 3-o'clock position;
               it may be either positive or negative.

          -stipple bitmap

     CANVAS(9)                                               CANVAS(9)

               Indicates that the arc should be filled in a stipple
               pattern; bitmap specifies the stipple pattern to use.
               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.
               The results are undefined if bitmap is not a 1-bit
               image.

          -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.  This type is not
               implemented at the moment. It behaves as arc.  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.

     BITMAP ITEMS
          Items of type bitmap appear on the display as images with
          two colours, 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 dis-
          played).  After the coordinates there may be any number of
          option-value pairs, each of which sets one of the configura-
          tion 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:

     CANVAS(9)                                               CANVAS(9)

          -anchor anchorPos
               AnchorPos tells how to position the bitmap relative to
               the positioning point for the item.  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.

          -bitmap bitmap
               Specifies the bitmap to display in the item.

          -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.

     IMAGE ITEMS
          Items of type image are used to display images on a canvas.
          Images are created with widget commands of the following
          form:
               pathName create image x y ?option value option value ...?
          The arguments x and y specify the coordinates of a point
          used to position the image on the display (see the -anchor
          option below for more information).  After the coordinates
          there may be any number of option-value pairs, each of which
          sets one of the configuration options for the item.  These
          same option-value pairs may be used in itemconfigure widget
          commands to change the item's configuration.  The following
          options are supported for images:

          -anchor anchorPos
               AnchorPos tells how to position the image relative to
               the positioning point for the item.  For example, if
               anchorPos is center then the image is centered on the
               point;  if anchorPos is n then the image will be drawn
               so that its top center point is at the positioning
               point.  This option defaults to center.

          -image name
               Specifies the name of the image to display in the item.
               This image must have been created previously with the
               image create command.

          -tags tagList
               Specifies a set of tags to apply to the item.  TagList
               consists of a list of tag names, which replace any
               existing tags for the item;  it may be an empty list.

     LINE ITEMS

     CANVAS(9)                                               CANVAS(9)

          Items of type line appear on the display as one or more con-
          nected line segments or curves.  Lines are created with wid-
          get 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 con-
          nected 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 ele-
               ment 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 one of butt, project-
               ing, or round.  If this option isn't specified then it
               defaults to butt.  Where arrowheads are drawn the cap
               style is ignored. Note that the first two options cur-
               rently have the same effect.

          -fill colour
               Colour specifies a colour to use for drawing the line.
               It may also be an empty string, in which case the line
               will be transparent.  This option defaults to black.

          -smooth boolean
               Boolean 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

     CANVAS(9)                                               CANVAS(9)

               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.

          -stipple bitmap
               Indicates that the line should be filled in a stipple
               pattern; bitmap specifies the stipple pattern to use.
               If bitmap is an empty string (the default), then fill-
               ing is done in a solid fashion.  The results are unde-
               fined if bitmap is not a 1-bit image.

          -tags tagList
               Specifies a set of tags to apply to the item.  TagList
               consists of a list of tag names, which replace any
               existing tags for the item.  TagList may be an empty
               list.

          -width lineWidth
               LineWidth specifies the width of the line, in any of
               the forms described in the COORDINATES section above.
               Wide lines will be drawn centered on the path specified
               by the points.  If this option isn't specified then it
               defaults to 1.0.

     OVAL ITEMS
          Items of type oval appear as circular or oval regions on the
          display.  Each oval may have an outline, a fill, or both.
          Ovals are created with widget commands of the following
          form:
               pathName create oval x1 y1 x2 y2 ?option value option value ...?
          The arguments x1, y1, x2, and y2 give the coordinates of two
          diagonally opposite corners of a rectangular region enclos-
          ing 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; other-
          wise it is elongated in shape.  After the coordinates there
          may be any number of option-value pairs, each of which sets
          one of the configuration options for the item.  These same
          option-value pairs may be used in itemconfigure widget com-
          mands to change the item's configuration.  The following
          options are supported for ovals:

          -fill colour
               Fill the area of the oval with colour.  If colour is an
               empty string (the default), then then the oval will not
               be filled.

          -outline colour
               Colour specifies a colour to use for drawing the oval's
               outline.  This option defaults to black.  If colour is

     CANVAS(9)                                               CANVAS(9)

               an empty string then no outline will be drawn for the
               oval.

          -stipple bitmap
               Indicates that the oval should be filled in a stipple
               pattern; bitmap specifies the stipple pattern to use.
               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.
               The results are undefined if bitmap is not a 1-bit
               image.

          -tags tagList
               Specifies a set of tags to apply to the item.  TagList
               consists of a list of tag names, which replace any
               existing tags for the item.  TagList may be an empty
               list.

          -width outlineWidth
               outlineWidth specifies the width of the outline to be
               drawn around the oval, in any of the forms described in
               the COORDINATES section above.  If the -outline option
               hasn't been specified then this option has no effect.
               Wide outlines are drawn centered on the oval path
               defined by x1, y1, x2, and y2.  This option defaults to
               1.0.

     POLYGON ITEMS
          Items of type polygon appear as polygonal or curved filled
          regions on the display.  Polygons are created with widget
          commands of the following form:
               pathName create polygon x1 y1 ... xn yn ?option value option value ...?
          The arguments x1 through yn specify the coordinates for
          three or more points that define a closed polygon.  The
          first and last points may be the same;  whether they are or
          not, Tk will draw the polygon as a closed polygon.  After
          the coordinates there may be any number of option-value
          pairs, each of which sets one of the configuration options
          for the item.  These same option-value pairs may be used in
          itemconfigure widget commands to change the item's configu-
          ration.  The following options are supported for polygons:

          -fill colour
               Colour specifies a colour to use for filling the area
               of the polygon.  If colour is an empty string then the
               polygon will be transparent.  This option defaults to
               the empty string (transparent).

          -outline colour
               Colour specifies a colour to use for drawing the
               polygon's outline.  If colour is an empty string then

     CANVAS(9)                                               CANVAS(9)

               no outline will be drawn for the polygon.  This option
               defaults to black.

          -smooth boolean
               Boolean indicates whether or not the polygon should be
               drawn with a curved perimeter.  If so, the outline of
               the polygon becomes a set of Bezier 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.

          -stipple bitmap
               Indicates that the polygon should be filled in a stip-
               ple pattern; bitmap specifies the stipple pattern to
               use.  If bitmap is an empty string (the default), then
               filling is done in a solid fashion.  The results are
               undefined if bitmap is not a 1-bit image.

          -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.

          -winding type
               Specifies the winding rule to use when filling the
               polygon.  Type can be either nonzero (the default) or
               odd See fillpoly in draw-image(2) for an explanation.

          -width outlineWidth
               OutlineWidth specifies the width of the outline to be
               drawn around the polygon, in any of the forms described
               in the COORDINATES section above.  If the -outline
               option hasn't been specified then this option has no
               effect.  This option defaults to 1.0.

          Polygon items are different from other items such as rectan-
          gles, ovals and arcs in that interior points are considered
          to be ``inside'' a polygon (e.g. for purposes of the find
          closest and find overlapping widget commands) even if it is
          not filled.  For most other item types, an interior point is
          considered to be inside the item only if the item is filled
          or if it has neither a fill nor an outline.  If you would
          like an unfilled polygon whose interior points are not con-
          sidered to be inside the polygon, use a line item instead.

     RECTANGLE ITEMS
          Items of type rectangle appear as rectangular regions on the
          display.  Each rectangle may have an outline, a fill, or
          both.  Rectangles are created with widget commands of the

     CANVAS(9)                                               CANVAS(9)

          following form:
               pathName create rectangle x1 y1 x2 y2 ?option value option value ...?
          The arguments x1, y1, x2, and y2 give the coordinates of two
          diagonally opposite corners of the rectangle (the rectangle
          will include its upper and left edges but not its lower or
          right edges).  After the coordinates there may be any number
          of option-value pairs, each of which sets one of the config-
          uration options for the item.  These same option-value pairs
          may be used in itemconfigure widget commands to change the
          item's configuration.  The following options are supported
          for rectangles:

          -fill colour
               Fill the area of the rectangle with colour.  If colour
               is an empty string (the default), then the rectangle
               will not be filled.

          -outline colour
               Draw an outline around the edge of the rectangle in
               colour.  This option defaults to black.  If colour is
               an empty string then no outline will be drawn for the
               rectangle.

          -stipple bitmap
               Indicates that the rectangle should be filled in a
               stipple pattern; bitmap specifies the stipple pattern
               to use.  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.  The results are undefined if bitmap is not a
               1-bit image.

          -tags tagList
               Specifies a set of tags to apply to the item.  TagList
               consists of a list of tag names, which replace any
               existing tags for the item.  TagList may be an empty
               list.

          -width outlineWidth
               OutlineWidth specifies the width of the outline to be
               drawn around the rectangle, in any of the forms
               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 selec-
          tion, along with the following text-related canvas widget

     CANVAS(9)                                               CANVAS(9)

          commands:  dchars, focus, icursor, index, insert, select.
          Text items are created with widget commands of the following
          form:
               pathName create text x y ?option value option value ...?
          The arguments x and y specify the coordinates of a point
          used to position the text on the display (see the options
          below for more information on how text is displayed).  After
          the coordinates there may be any number of option-value
          pairs, each of which sets one of the configuration options
          for the item.  These same option-value pairs may be used in
          itemconfigure widget commands to change the item's configu-
          ration.  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. 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 colour
               Colour specifies a colour to use for filling the text
               characters.  If this option isn't specified then it
               defaults to black.

          -font font
               Specifies the font to use for the text item.  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.

          -stipple bitmap
               Indicates that the text should be drawn in a stippled
               pattern rather than solid; bitmap specifies the stipple
               pattern to use.  If bitmap is an empty string (the
               default) then the text is drawn in a solid fashion.
               The results are undefined if bitmap is not a 1-bit
               image.

          -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.

     CANVAS(9)                                               CANVAS(9)

          -text string
               String specifies the characters to be displayed in the
               text item.  Newline characters cause line breaks.  The
               characters in the item may also be changed with the
               insert and delete widget commands.  This option
               defaults to an empty string.

          -width lineLength
               Specifies a maximum line length for the text, in any of
               the forms described in the COORDINATES section above.
               If this option is zero (the default) the text is broken
               into lines only at newline characters.  However, if
               this option is non-zero then any line that would be
               longer than lineLength is broken just before a space
               character to make the line shorter than lineLength;
               the space character is treated as if it were a newline
               character.

     WINDOW ITEMS
          Items of type window cause a particular window to be dis-
          played at a given position on the canvas.  Window items are
          created with widget commands of the following form:
               pathName create window x y ?option value option value ...?
          The arguments x and y specify the coordinates of a point
          used to position the window on the display (see the -anchor
          option below for more information on how bitmaps are dis-
          played).  After the coordinates there may be any number of
          option-value pairs, each of which sets one of the configura-
          tion options for the item.  These same option-value pairs
          may be used in itemconfigure widget commands to change the
          item's configuration.  The following options are supported
          for window items:

          -anchor anchorPos
               AnchorPos tells how to position the window relative to
               the positioning point for the item.  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 dist
               Specifies the height to assign to the item's window.
               Dist may have any of the forms described in the COORDI-
               NATES section above.  If this option isn't specified,
               or if it is specified as an empty string, then the win-
               dow is given whatever height it requests internally.

          -tags tagList
               Specifies a set of tags to apply to the item.  TagList
               consists of a list of tag names, which replace any

     CANVAS(9)                                               CANVAS(9)

               existing tags for the item.  TagList may be an empty
               list.

          -width dist
               Specifies the width to assign to the item's window.
               Dist may have any of the forms described in the COORDI-
               NATES section above.  If this option isn't specified,
               or if it is specified as an empty string, then the win-
               dow is given whatever width it requests internally.

          -window pathName
               Specifies the window to associate with this item.  The
               window specified by pathName must either be a child of
               the canvas widget or a child of some ancestor of the
               canvas widget.  PathName may not refer to a top-level
               window.

     BINDINGS
          In the current implementation, new canvases are not given
          any default behaviour:  you'll have to execute explicit Tk
          commands to give the canvas its behaviour.

     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.

     SEE ALSO
          options(9), types(9)