canvas(n)                    Tk Built-In Commands                    canvas(n)



NAME
       canvas - Create and manipulate canvas widgets

SYNOPSIS
       (canvas widget-name ?options?)
       :background    :highlightthickness :insertwidth   :takefocus
       :borderwidth   :insertbackground   :relief   :xscrollcommand
       :cursor   :insertborderwidth  :selectbackground   :yscrollcommand
       :highlightbackground     :insertofftime :selectborderwidth
       :highlightcolor     :insertontime  :selectforeground

WIDGET-SPECIFIC OPTIONS
       [:closeenough 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.  [:confine 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.  [:height 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.
       [:scrollregion 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.  [:width 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.
       [:xscrollincrement 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.  [:yscrollincrement 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.


INTRODUCTION
       The canvas procedure creates a new window (given by the widget-name
       argument) and makes it into a canvas widget.  Additional options,
       described above, may be specified on the procedure line or in the
       option database to configure aspects of the canvas such as its colors
       and 3-D relief.  The canvas procedure returns its widget-name argument.
       At the time this procedure is invoked, there must not exist a window
       named widget-name, but widget-name'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
       procedures may be associated with items in much the same way that the
       bind procedure allows procedures to be bound to widgets.  For example,
       a particular procedure may be associated with the <Button-1> event so
       that the procedure 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 STk 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 procedures may be used to re-arrange the order
       of the display list.

       Window items are an exception to the above rules.  The underlying
       window systems require them always to be drawn on top of other items.
       In addition, the stacking order of window items is not affected by any
       of the canvas widget commands; you must use the raise and lower Tk
       commands instead.


ITEM IDS AND TAGS
       Items in a canvas widget may be named in either of two ways: by id or
       by tag.  Each item has a unique identifying number which is assigned to
       that item when it is created.  The id of an item never changes and id
       numbers are never re-used within the lifetime of a canvas widget.

       Each item may also have any number of tags associated with it.  A tag
       is just a string of characters, and it may take any form except that of
       an integer.  For example, ``x123'' is OK but ``123'' isn't.  The same
       tag may be associated with many different items.  This is commonly done
       to group items in various interesting ways;  for example, all selected
       items might be given the tag ``selected''.

       The tag all is implicitly associated with every item in the canvas;  it
       may be used to invoke operations on all the items in the canvas.

       The tag current is managed automatically by Tk; it applies to the
       current item, which is the topmost item whose drawn area covers the
       position of the mouse cursor.  If the mouse is not in the canvas widget
       or is not over an item, then no item has the current tag.

       When specifying items in canvas widget procedures, 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 procedures 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 procedure to use the first (lowest) of
       these items in the display list that is suitable for the procedure.
       Exceptions are noted in the widget procedure descriptions below.


COORDINATES
       All coordinates related to canvases are stored as floating-point
       numbers.  Coordinates and distances are specified in screen units,
       which are floating-point numbers optionally followed by one of several
       letters.  If no letter is supplied then the distance is in pixels.  If
       the letter is m then the distance is in millimeters on the screen;  if
       it is c then the distance is in centimeters; i means inches, and p
       means printers points (1/72 inch).  Larger y-coordinates refer to
       points lower on the screen;  larger x-coordinates refer to points
       farther to the right.


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

       Individual items may be moved or scaled using widget procedures
       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 procedures 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.

       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.


WIDGET PROCEDURE
       The canvas procedure creates a new STk procedure whose name is
       widget-name.  This procedure may be used to invoke various operations
       on the widget.  It has the following general form: (widget-name option
       ?arg arg ...?)  Option and the args determine the exact behavior of the
       procedure.  The following widget procedures are possible for canvas
       widgets:

       (widget-name '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 procedure has no effect.  This
              procedure returns an empty list as result.  SearchSpec and arg's
              may take any of the following forms:

              above tagOrId
                     Selects the item just after (above) the one given by
                     tagOrId in the display list.  If tagOrId denotes more
                     than one item, then the last (topmost) of these items in
                     the display list is used.

              all    Selects all the items in the canvas.

              below tagOrId
                     Selects the item just before (below) the one given by
                     tagOrId in the display list.  If tagOrId denotes more
                     than one item, then the first (lowest) of these items in
                     the display list is used.

              closest x y ?halo? ?start?
                     Selects the item closest to the point given by x and y.
                     If more than one item is at the same closest distance
                     (e.g. two items overlap the point), then the top-most of
                     these items (the last one in the display list) is used.
                     If halo is specified, then it must be a non-negative
                     value.  Any item closer than halo to the point is
                     considered to overlap it.  The start argument may be used
                     to step circularly through all the closest items.  If
                     start is specified, it names an item using a tag or id
                     (if by tag, it selects the first item in the display list
                     with the given tag).  Instead of selecting the topmost
                     closest item, this form will select the topmost closest
                     item that is below start in the display list;  if no such
                     item exists, then the selection behaves as if the start
                     argument had not been specified.

              enclosed x1 y1 x2 y2
                     Selects all the items completely enclosed within the
                     rectangular region given by x1, y1, x2, and y2.  X1 must
                     be no greater then x2 and y1 must be no greater than y2.

              overlapping x1 y1 x2 y2
                     Selects all the items that overlap or are enclosed within
                     the rectangular region given by x1, y1, x2, and y2.  X1
                     must be no greater then x2 and y1 must be no greater than
                     y2.

              withtag tagOrId
                     Selects all the items given by tagOrId.

       (widget-name '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 list is returned.

       (widget-name 'bind tagOrId ?sequence? ?procedure?)
              This procedure associates procedure with all the items given by
              tagOrId such that whenever the event sequence given by sequence
              occurs for one of the items the procedure will be invoked.  This
              widget procedure is similar to the bind procedure 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 procedure 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 procedure is ``+'' then
              procedure augments an existing binding rather than replacing
              it).  In this case the return value is an empty list.  If
              procedure is omitted then the procedure returns the procedure
              associated with tagOrId and sequence (an error occurs if there
              is no such binding).  If both procedure and sequence are omitted
              then the procedure returns a list of all the sequences for which
              bindings have been defined for tagOrId.

              Example: (pack (canvas '.c))
                          (define item (.c 'create 'rectangle 0 0 10 10))
                          (.c 'bind item "<Enter>" (lambda() (display "You
              enter0)))


              The only events for which bindings may be specified are those
              related to the mouse and keyboard (such as Enter, Leave,
              ButtonPress, Motion, and KeyPress) or virtual events.  The
              handling of events in canvases uses the current item defined in
              ITEM IDS AND TAGS above.  Enter and Leave events trigger for an
              item when it becomes the current item or ceases to be the
              current item; note that these events are different than Enter
              and Leave events for windows.  Mouse-related events are directed
              to the current item, if any.  Keyboard-related events are
              directed to the focus item, if any (see the focus widget command
              below for more on this).  If a virtual event is used in a
              binding, that binding can trigger only if the virtual event is
              defined by an underlying mouse-related or keyboard-related
              event.

              It is possible for multiple bindings to match a particular
              event.  This could occur, for example, if one binding is
              associated with the item's id and another is associated with one
              of the item's tags.  When this occurs, all of the matching
              bindings are invoked.  A binding associated with the all tag is
              invoked first, followed by one binding for each of the item's
              tags (in order), followed by a binding associated with the
              item's id.  If there are multiple matching bindings for a single
              tag, then only the most specific binding is invoked.  If a
              binding script returns the symbol break, remaining scripts for
              the event are skipped, just as for the bind procedure.


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

       (widget-name 'canvasx screenx)

       (widget-name 'canvasx screenx gridspacing)
              Given a window x-coordinate in the canvas 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.

       (widget-name 'canvasy screeny)

       (widget-name 'canvasy screeny gridspacing)
              Given a window y-coordinate in the canvas 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.

       (widget-name 'cget option)
              Returns the current value of the configuration option given by
              option.  Option may have any of the values accepted by the
              canvas procedure.

       (widget-name '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 widget-name (see Tk_ConfigureInfo for
              information on the format of this list).  If option is specified
              with no value, then the procedure 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 procedure modifies the given widget option(s) to have
              the given value(s);  in this case the procedure returns an empty
              list.  Option may have any of the values accepted by the canvas
              procedure.

       (widget-name 'coords tagOrId ?x0 y0 ...?)
              Query or modify the coordinates that define an item.  If no
              coordinates are specified, this procedure 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.

       (widget-name 'create type x y ?x y ...? ?option value ...?)
              Create a new item in widget-name 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 procedure.  This procedure returns the id for the
              new item.

       (widget-name 'dchars tagOrId first )

       (widget-name '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 procedure returns an empty list.

       (widget-name 'delete ?tagOrId tagOrId ...?)
              Delete each of the items given by each tagOrId, and return an
              empty list.

       (widget-name 'dtag tagOrId )

       (widget-name '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 procedure.  If tagToDelete is omitted then it
              defaults to tagOrId.  This procedure returns an empty list.

       (widget-name 'find searchProcedure ?arg arg ...?)
              This procedure returns a list consisting of all the items that
              meet the constraints specified by searchProcedure and arg's.
              SearchProcedure and args have any of the forms accepted by the
              addtag procedure.  The items are returned in stacking order,
              with the lowest item first.

       (widget-name 'focus )

       (widget-name '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 procedure returns the id for the item that
              currently has the focus, or an empty list 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 procedure) 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 procedure with the focus option to
              set the focus window to the canvas (if it wasn't there already).

       (widget-name '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 list is returned.

       (widget-name '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 procedure 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 procedure focus, below), but the cursor position may be
              set even when the item doesn't have the focus.  This procedure
              returns an empty list.

       (widget-name 'index tagOrId index)
              This procedure 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).

       (widget-name '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 procedure returns an empty list.

       (widget-name 'itemcget tagOrId option)
              Returns the current value of the configuration option for the
              item given by tagOrId whose name is option.  This procedure is
              similar to the cget widget procedure 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 procedure
              when the item was created.  If tagOrId is a tag that refers to
              more than one item, the first (lowest) such item is used.

       (widget-name 'itemconfigure tagOrId ?option? ?value? ?option value
       ...?)
              This procedure is similar to the configure widget procedure
              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
              procedure 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 procedure modifies
              the given widget option(s) to have the given value(s) in each of
              the items given by tagOrId;  in this case the procedure returns
              an empty list.  The options and values are the same as those
              permissible in the create widget procedure when the item(s) were
              created; see the sections describing individual item types below
              for details on the legal options.

       (widget-name 'lower tagOrId )

       (widget-name 'lower tagOrId belowThis)
              Move all of the items given by tagOrId to a new position in the
              display list just before the item given by belowThis.  If
              tagOrId refers to more than one item then all are moved but the
              relative order of the moved items will not be changed.
              BelowThis is a tag or id;  if it refers to more than one item
              then the first (lowest) of these items in the display list is
              used as the destination location for the moved items.  Note:
              this procedure has no effect on window items.  Window items
              always obscure other item types, and the stacking order of
              window items is determined by the raise and lower commands, not
              the raise and lower widget commands for canvases.  This
              procedure returns an empty list.

       (widget-name '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 procedure returns an empty
              list.

       (widget-name '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 list is returned;  otherwise the
              Postscript is returned as the result of the procedure.  The
              Postscript is created in Encapsulated Postscript form using
              version 3.0 of the Document Structuring Conventions.  Note: by
              default Postscript is only generated for information that
              appears in the canvas's window on the screen.  If the canvas is
              freshly created it may still have its initial size of 1x1 pixel
              so nothing will appear in the Postscript.  To get around this
              problem either invoke the "update" procedure to wait for the
              canvas window to reach its final size, or else use the :width
              and :height options to specify the area of the canvas to print.
              The option-value argument pairs provide additional information
              to control the generation of Postscript.  The following options
              are supported:

              :colormap varName
                     NOT IMPLEMENTED IN STk

              :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 procedure
                     instead of being written to a file.

              :fontmap varName
                     NOT IMPLEMENTED IN STk

              :height size
                     Specifies the height of the area of the canvas to print.
                     Defaults to the height of the canvas window.

              :pageanchor anchor
                     Specifies which point of the printed area of the canvas
                     should appear over the positioning point on the page
                     (which is given by the :pagex and :pagey options).  For
                     example, :pageanchor n means that the top center of the
                     area of the canvas being printed (as it appears in the
                     canvas window) should be over the positioning point.
                     Defaults to center.

              :pageheight size
                     Specifies that the Postscript should be scaled in both x
                     and y so that the printed area is size high on the
                     Postscript page.  Size consists of a floating-point
                     number followed by c for centimeters, i for inches, m for
                     millimeters, or p or nothing for printer's points (1/72
                     inch).  Defaults to the height of the printed area on the
                     screen.  If both :pageheight and :pagewidth are specified
                     then the scale factor from :pagewidth  is used (non-
                     uniform scaling is not implemented).

              :pagewidth size
                     Specifies that the Postscript should be scaled in both x
                     and y so that the printed area is size wide on the
                     Postscript page.  Size has the same form as for
                     :pageheight.  Defaults to the width of the printed area
                     on the screen.  If both :pageheight and :pagewidth are
                     specified then the scale factor from  :pagewidth is used
                     (non-uniform scaling is not implemented).

              :pagex position
                     Position gives the x-coordinate of the positioning point
                     on the Postscript page, using any of the forms allowed
                     for :pageheight.  Used in conjunction with the :pagey and
                     :pageanchor options to determine where the printed area
                     appears on the Postscript page.  Defaults to the center
                     of the page.

              :pagey position
                     Position gives the y-coordinate of the positioning point
                     on the Postscript page, using any of the forms allowed
                     for :pageheight.  Used in conjunction with the :pagex and
                     :pageanchor options to determine where the printed area
                     appears on the Postscript page.  Defaults to the center
                     of the page.

              :rotate boolean
                     Boolean specifies whether the printed area is to be
                     rotated 90 degrees.  In non-rotated output the x-axis of
                     the printed area runs along the short dimension of the
                     page (``portrait'' orientation); in rotated output the x-
                     axis runs along the long dimension of the page
                     (``landscape'' orientation).  Defaults to non-rotated.

              :width size
                     Specifies the width of the area of the canvas to print.
                     Defaults to the width of the canvas window.

              :x position
                     Specifies the x-coordinate of the left edge of the area
                     of the canvas that is to be printed, in canvas
                     coordinates, not window coordinates.  Defaults to the
                     coordinate of the left edge of the window.

              :y position
                     Specifies the y-coordinate of the top edge of the area of
                     the canvas that is to be printed, in canvas coordinates,
                     not window coordinates.  Defaults to the coordinate of
                     the top edge of the window.

       (widget-name 'raise tagOrId )

       (widget-name 'raise tagOrId aboveThis)
              Move all of the items given by tagOrId to a new position in the
              display list just after the item given by aboveThis.  If tagOrId
              refers to more than one item then all are moved but the relative
              order of the moved items will not be changed.  AboveThis is a
              tag or id;  if it refers to more than one item then the last
              (topmost) of these items in the display list is used as the
              destination location for the moved items.  Note: this procedure
              has no effect on window items.  Window items always obscure
              other item types, and the stacking order of window items is
              determined by the raise and lower commands, not the raise and
              lower widget commands for canvases.  This procedure returns an
              empty list.

       (widget-name 'scale tagOrId xOrigin yOrigin xScale yScale)
              Rescale all of the items given by tagOrId in canvas coordinate
              space.  XOrigin and yOrigin identify the origin for the scaling
              operation and xScale and yScale identify the scale factors for
              x- and y-coordinates, respectively (a scale factor of 1.0
              implies no change to that coordinate).  For each of the points
              defining each item, the x-coordinate is adjusted to change the
              distance from xOrigin by a factor of xScale.  Similarly, each y-
              coordinate is adjusted to change the distance from yOrigin by a
              factor of yScale.  This procedure returns an empty list.

       (widget-name 'scan option args)
              This procedure is used to implement scanning on canvases.  It
              has two forms, depending on option:

              (widget-name 'scan 'mark x y)
                     Records x and y and the canvas's current view;  used in
                     conjunction with later scan dragto procedures.  Typically
                     this procedure is associated with a mouse button press in
                     the widget and x and y are the coordinates of the mouse.
                     It returns an empty list.

              (widget-name 'scan 'dragto x y)
                     This procedure 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 procedure for
                     the widget.  It then adjusts the view by 10 times the
                     difference in coordinates.  This procedure 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 list.

       (widget-name 'select option ?tagOrId arg?)
              Manipulates the selection in one of several ways, depending on
              option.  The procedure 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.

              (widget-name '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 procedures.  If the
                     selection isn't currently in tagOrId then this procedure
                     behaves the same as the select to widget procedure.
                     Returns an empty list.

              (widget-name 'select 'clear)
                     Clear the selection if it is in this widget.  If the
                     selection isn't in this widget then the procedure has no
                     effect.  Returns an empty list.

              (widget-name '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 procedure doesn't change the selection;
                     it just sets the fixed end of the selection for future
                     select to procedures.  Returns an empty list.

              (widget-name '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 list is returned.

              (widget-name '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 procedure 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 list.

       (widget-name '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 list is
              returned.

       (widget-name 'xview  ?args?)
              This procedure 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:

              (widget-name '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.

              (widget-name '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.

              (widget-name 'xview 'scroll number what)
                     This procedure 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.

       (widget-name 'yview ?args?)
              This procedure 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:

              (widget-name '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.

              (widget-name '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.

              (widget-name 'yview 'scroll number what)
                     This procedure adjusts the view in the window up or down
                     according to number and what.  Number must be an integer.
                     What must be either units or pages.  If what is units,
                     the view adjusts up or down in units of the
                     yScrollIncrement option, if it is greater than zero, or
                     in units of one-tenth the window's height otherwise.  If
                     what is pages then the view adjusts in units of nine-
                     tenths the window's height.  If number is negative then
                     higher information becomes visible;  if it is positive
                     then lower information becomes visible.


OVERVIEW OF ITEM TYPES
       The sections below describe the various types of items supported by
       canvas widgets.  Each item type is characterized by two things: first,
       the form of the create procedure used to create instances of the type;
       and second, a set of configuration options for items of that type,
       which may be used in the create and itemconfigure widget procedures.
       Most items don't support indexing or selection or the procedures
       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
       procedures of the following form: (widget-name '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 procedures 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.

       :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.


BITMAP ITEMS
       Items of type bitmap appear on the display as images with two colors,
       foreground and background.  Bitmaps are created with widget procedures
       of the following form: (widget-name '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 procedures to
       change the item's configuration.  The following options are supported
       for bitmaps:

       :anchor anchorPos
              AnchorPos tells how to position the bitmap relative to the
              positioning point for the item;  it may have any of the forms
              accepted by Tk_GetAnchor.  For example, if anchorPos is center
              then the bitmap is centered on the point;  if anchorPos is n
              then the bitmap will be drawn so that its top center point is at
              the positioning point.  This option defaults to center.

       :background color
              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.


IMAGE ITEMS
       Items of type image are used to display images on a canvas.  Images are
       created with widget procedures of the following form: (widget-name
       '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 procedures to
       change the item's configuration.  The following options are supported
       for images:

       :anchor anchorPos
              AnchorPos tells how to position the image relative to the
              positioning point for the item;  it may have any of the forms
              accepted by Tk_GetAnchor.  For example, if anchorPos is center
              then the image is centered on the point;  if anchorPos is n then
              the image will be drawn so that its top center point is at the
              positioning point.  This option defaults to center.

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

       :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
       Items of type line appear on the display as one or more connected line
       segments or curves.  Lines are created with widget procedures of the
       following form: (widget-name '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 procedures 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 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 parabolic splines: one
              spline is drawn for the first and second line segments, one for
              the second and third, and so on.  Straight-line segments can be
              generated within a curve by duplicating the end-points of the
              desired line segment.

       :splinesteps number
              Specifies the degree of smoothness desired for curves:  each
              spline will be approximated with number line segments.  This
              option is ignored unless the :smooth option is true.

       :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.


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 procedures of the following form: (widget-name '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 circular; otherwise it is
       elongated in shape.  After the coordinates there may be any number of
       option-value pairs, each of which sets one of the configuration options
       for the item.  These same option-value pairs may be used in
       itemconfigure widget procedures to change the item's configuration.
       The following options are supported for ovals:

       :fill color
              Fill the area of the oval with color.  Color may have any of the
              forms accepted by Tk_GetColor.  If color is an empty string (the
              default), then then the oval will not be filled.

       :outline color
              Color specifies a color to use for drawing the oval's outline;
              it may have any of the forms accepted by Tk_GetColor.  This
              option defaults to black.  If color is 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, in any of the forms
              accepted by Tk_GetBitmap.  If the :fill option hasn't been
              specified then this option has no effect.  If bitmap is an empty
              string (the default), then filling is done in a solid fashion.

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

       :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 procedures of the
       following form: (widget-name '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 procedures to change the item's
       configuration.  The following options are supported for polygons:

       :fill color
              Color specifies a color to use for filling the area of the
              polygon; it may have any of the forms acceptable to Tk_GetColor.
              If color is an empty string then the polygon will be
              transparent.  This option defaults to black.

       :outline color
              Color specifies a color to use for drawing the polygon's
              outline;  it may have any of the forms accepted by Tk_GetColor.
              If color is an empty string then no outline will be drawn for
              the polygon.  This option defaults to empty (no outline).

       :smooth boolean
              Boolean must have one of the forms accepted by Tk_GetBoolean It
              indicates whether or not the polygon should be drawn with a
              curved perimeter.  If so, the outline of the polygon becomes a
              set of parabolic splines, one spline for the first and second
              line segments, one for the second and third, and so on.
              Straight-line segments can be generated in a smoothed polygon by
              duplicating the end-points of the desired line segment.

       :splinesteps number
              Specifies the degree of smoothness desired for curves:  each
              spline will be approximated with number line segments.  This
              option is ignored unless the :smooth option is true.

       :stipple bitmap
              Indicates that the polygon 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 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 rectangles, ovals
       and arcs in that interior points are considered to be ``inside'' a
       polygon (e.g. for purposes of the find closest and find overlapping
       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 considered to be
       inside the polygon, use a line item instead.


RECTANGLE ITEMS
       Items of type rectangle appear as rectangular regions on the display.
       Each rectangle may have an outline, a fill, or both.  Rectangles are
       created with widget procedures of the following form: (widget-name
       '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 configuration options for the item.  These same
       option-value pairs may be used in itemconfigure widget procedures to
       change the item's configuration.  The following options are supported
       for rectangles:

       :fill color
              Fill the area of the rectangle with color, which may be
              specified in any of the forms accepted by Tk_GetColor.  If color
              is an empty string (the default), then the rectangle will not be
              filled.

       :outline color
              Draw an outline around the edge of the rectangle in color.
              Color may have any of the forms accepted by Tk_GetColor.  This
              option defaults to black.  If color 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, in any of
              the forms accepted by Tk_GetBitmap.  If the :fill option hasn't
              been specified then this option has no effect.  If bitmap is an
              empty string (the default), then filling is done in a solid
              fashion.

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

       :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 selection, along with the
       following text-related canvas widget procedures:  dchars, focus,
       icursor, index, insert, select.  Text items are created with widget
       procedures of the following form: (widget-name '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
       procedures to change the item's configuration.  The following options
       are supported for text items:

       :anchor anchorPos
              AnchorPos tells how to position the text relative to the
              positioning point for the text;  it may have any of the forms
              accepted by Tk_GetAnchor.  For example, if anchorPos is center
              then the text is centered on the point;  if anchorPos is n then
              the text will be drawn such that the top center point of the
              rectangular region occupied by the text will be at the
              positioning point.  This option defaults to center.

       :fill color
              Color specifies a color to use for filling the text characters;
              it may have any of the forms accepted by Tk_GetColor.  If this
              option isn't specified then it defaults to black.

       :font fontName
              Specifies the font to use for the text item.  FontName may be
              any string acceptable to Tk_GetFontStruct.  If this option isn't
              specified, it defaults to a system-dependent font.

       :justify how
              Specifies how to justify the text within its bounding region.
              How must be one of the values left, right, or center.  This
              option will only matter if the text is displayed as multiple
              lines.  If the option is omitted, it defaults to left.

       :stipple bitmap
              Indicates that the text should be drawn in a stippled pattern
              rather than solid; bitmap specifies the stipple pattern to use,
              in any of the forms accepted by Tk_GetBitmap.  If bitmap is an
              empty string (the default) then the text is drawn in a solid
              fashion.

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

       :text string
              String specifies the characters to be displayed in the text
              item.  Newline characters cause line breaks.  The characters in
              the item may also be changed with the insert and delete widget
              procedures.  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 displayed at a
       given position on the canvas.  Window items are created with widget
       procedures of the following form: (widget-name '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
       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 procedures to change the item's configuration.
       The following options are supported for window items:

       :anchor anchorPos
              AnchorPos tells how to position the window relative to the
              positioning point for the item;  it may have any of the forms
              accepted by Tk_GetAnchor.  For example, if anchorPos is center
              then the window is centered on the point;  if anchorPos is n
              then the window will be drawn so that its top center point is at
              the positioning point.  This option defaults to center.

       :height pixels
              Specifies the height to assign to the item's window.  Pixels may
              have any of the forms described in the COORDINATES section
              above.  If this option isn't specified, or if it is specified as
              an empty string, then the window is given whatever height it
              requests internally.

       :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 pixels
              Specifies the width to assign to the item's window.  Pixels may
              have any of the forms described in the COORDINATES section
              above.  If this option isn't specified, or if it is specified as
              an empty string, then the window is given whatever width it
              requests internally.

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

       Note:  due to restrictions in the ways that windows are managed, it is
       not possible to draw other graphical items (such as lines and images)
       on top of window items.  A window item always obscures any graphics
       that overlap it, regardless of their order in the display list.



APPLICATION-DEFINED ITEM TYPES
       It is possible for individual applications to define new item types for
       canvas widgets using C code.  See the documentation for
       Tk_CreateItemType.



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


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.




STk                                   4.0                            canvas(n)
