NAME¶

Tk::Canvas - Create and manipulate Canvas widgets

SYNOPSIS¶

$canvas = $parent->Canvas(?options?);

STANDARD OPTIONS¶

-background -highlightthickness -insertwidth -state -borderwidth -insertbackground -relief -tile -cursor -insertborderwidth -selectbackground -takefocus -highlightbackground -insertofftime -selectborderwidth -xscrollcommand -highlightcolor -insertontime -selectforeground -yscrollcommand

WIDGET-SPECIFIC OPTIONS¶

Name: closeEnough

Class: CloseEnough

Switch: -closeenough

Specifies a floating-point value indicating how close the mouse cursor must be to an item before it is considered to be ``inside'' the item. Defaults to 1.0.

Name: confine

Class: Confine

Switch: -confine

Specifies a boolean value that indicates whether or not it should be allowable to set the canvas's view outside the region defined by the scrollRegion argument. Defaults to true, which means that the view will be constrained within the scroll region.

Name: height

Class: Height

Switch: -height

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

Name: scrollRegion

Class: ScrollRegion

Switch: -scrollregion

Specifies a list with four coordinates describing the left, top, right, and bottom coordinates of a rectangular region. This region is used for scrolling purposes and is considered to be the boundary of the information in the canvas. Each of the coordinates may be specified in any of the forms given in the "COORDINATES" section below.

Name: state

Class: State

Switch: -state

Modifies the default state of the canvas where state may be set to one of: normal, disabled, or hidden. Individual canvas objects all have their own state option, which overrides the default state. Many options can take separate specifications such that the appearance of the item can be different in different situations. The options that start with "active" control the appearence when the mouse pointer is over it, while the option starting with "disabled" controls the appearence when the state is disabled.

Name: width

Class: width

Switch: -width

Specifies a desired window width that the canvas widget should request from its geometry manager. The value may be specified in any of the forms described in the "COORDINATES" section below.

Name: xScrollIncrement

Class: ScrollIncrement

Switch: -xscrollincrement

Specifies an increment for horizontal scrolling, in any of the usual forms permitted for screen distances. If the value of this option is greater than zero, the horizontal view in the window will be constrained so that the canvas x coordinate at the left edge of the window is always an even multiple of xScrollIncrement; furthermore, the units for scrolling (e.g., the change in view when the left and right arrows of a scrollbar are selected) will also be xScrollIncrement. If the value of this option is less than or equal to zero, then horizontal scrolling is unconstrained.

Name: yScrollIncrement

Class: ScrollIncrement

Switch: -yscrollincrement

Specifies an increment for vertical scrolling, in any of the usual forms permitted for screen distances. If the value of this option is greater than zero, the vertical view in the window will be constrained so that the canvas y coordinate at the top edge of the window is always an even multiple of yScrollIncrement; furthermore, the units for scrolling (e.g., the change in view when the top and bottom arrows of a scrollbar are selected) will also be yScrollIncrement. If the value of this option is less than or equal to zero, then vertical scrolling is unconstrained.

DESCRIPTION¶

The Canvas method creates a new window (given by the $canvas argument) and makes it into a canvas widget. Additional options, described above, may be specified on the command line or in the option database to configure aspects of the canvas such as its colors and 3-D relief. The canvas command returns its $canvas argument. At the time this command is invoked, there must not exist a window named $canvas, but $canvas's parent must exist.

Canvas widgets implement structured graphics. A canvas displays any number of items, which may be things like rectangles, circles, lines, and text. Items may be manipulated (e.g. moved or re-colored) and callbacks may be associated with items in much the same way that the bind method allows callbacks to be bound to widgets. For example, a particular callback may be associated with the <Button-1> event so that the callback is invoked whenever button 1 is pressed with the mouse cursor over an item. This means that items in a canvas can have behaviors defined by the Callbacks bound to them.

DISPLAY LIST¶

The items in a canvas are ordered for purposes of display, with the first item in the display list being displayed first, followed by the next item in the list, and so on. Items later in the display list obscure those that are earlier in the display list and are sometimes referred to as being ``on top'' of earlier items. When a new item is created it is placed at the end of the display list, on top of everything else. Widget methods may be used to re-arrange the order of the display list.

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

ITEM IDS AND TAGS¶

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

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

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

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

When specifying items in canvas methods, if the specifier is an integer then it is assumed to refer to the single item with that id. If the specifier is not an integer, then it is assumed to refer to all of the items in the canvas that have a tag matching the specifier. The symbol tagOrId is used below to indicate that an argument specifies either an id that selects a single item or a tag that selects zero or more items.

tagOrId may contain a logical expressions of tags by using operators: '&&', '||', '^' '!', and parenthezised subexpressions. For example:

$c->find('withtag', '(a&&!b)|(!a&&b)');

or equivalently:

$c->find('withtag', 'a^b');

will find only those items with either "a" or "b" tags, but not both.

Some methods only operate on a single item at a time; if tagOrId is specified in a way that names multiple items, then the normal behavior is for the methods is to use the first (lowest) of these items in the display list that is suitable for the method. Exceptions are noted in the method descriptions below.

COORDINATES¶

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

TRANSFORMATIONS¶

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

Individual items may be moved or scaled using methods described below, but they may not be rotated.

INDICES¶

Text items support the notion of an index for identifying particular positions within the item.

Indices are used for methods such as inserting text, deleting a range of characters, and setting the insertion cursor position. An index may be specified in any of a number of ways, and different types of items may support different forms for specifying indices.

In a similar fashion, line and polygon items support index for identifying, inserting and deleting subsets of their coordinates. Indices are used for commands such as inserting or deleting a range of characters or coordinates, and setting the insertion cursor position. An index may be specified in any of a number of ways, and different types of items may support different forms for specifying indices.

Text items support the following forms for an index; if you define new types of text-like items, it would be advisable to support as many of these forms as practical. Note that it is possible to refer to the character just after the last one in the text item; this is necessary for such tasks as inserting new text at the end of the item. Lines and Polygons don't support the insertion cursor and the selection. Their indices are supposed to be even always, because coordinates always appear in pairs.

number

A decimal number giving the position of the desired character within the text item. 0 refers to the first character, 1 to the next character, and so on. If indexes are odd for lines and polygons, they will be automatically decremented by one. A number less than 0 is treated as if it were zero, and a number greater than the length of the text item is treated as if it were equal to the length of the text item. For polygons, numbers less than 0 or greater then the length of the coordinate list will be adjusted by adding or substracting the length until the result is between zero and the length, inclusive.

end

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

insert

Refers to the character just before which the insertion cursor is drawn in this item. Not valid for lines and polygons.

sel.first

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

sel.last

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

[x,y]

Refers to the character or coordinate at the point given by x and y, where x and y are specified in the coordinate system of the canvas. If x and y lie outside the coordinates covered by the text item, then they refer to the first or last character in the line that is closest to the given point. The Tcl string form "@x,y" is also allowed.

DASH PATTERNS¶

Many items support the notion of an dash pattern for outlines.

The first possible syntax is a list of integers. Each element represents the number of pixels of a line segment. Only the odd segments are drawn using the "outline" color. The other segments are drawn transparent.

The second possible syntax is a character list containing only 5 possible characters [.,-_ ], with the first 4 characters producing a segment of length 1 to 4, respectively, followed by a transparent segment of length 2. The space can be used repeatedly to enlarge the space between other line elements by 1, and can not occur as the first position in the string. The main difference of this syntax with the previous one is that it it shape-conserving. This means that all values in the dash list will be multiplied by the line width before display. This assures that "." will always be displayed as a dot and "-" always as a dash regardless of the line width.

Some examples, for a line width of 2:

 -dash .     = -dash [2,4]
 -dash -     = -dash [6,4]
 -dash -.    = -dash [6,4,2,4]
 -dash -..   = -dash [6,4,2,4,2,4]
 -dash '.  ' = -dash [2,8]
 -dash ','   = -dash [4,4]

On systems where only a limited set of dash patterns is available, the dash pattern will be displayed as the closest available dash pattern. For example, on Windows only the first 4 of the above examples are available. The last 2 examples will be displayed identically as the first one.

WIDGET METHODS¶

The Canvas method creates a widget object. This object supports the configure and cget methods described in Tk::options which can be used to enquire and modify the options described above. The widget also inherits all the methods provided by the generic Tk::Widget class.

The following additional methods are available for canvas widgets:

$canvas->addtag(tag, searchSpec, ?arg, arg, ...?)

For each item that meets the constraints specified by searchSpec and the args, add tag to the list of tags associated with the item if it isn't already present on that list. It is possible that no items will satisfy the constraints given by searchSpec and args, in which case the method has no effect. This command returns an empty string as result. SearchSpec and arg's may take any of the following forms:

$canvas->bbox(tagOrId, ?tagOrId, tagOrId, ...?)

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

$canvas->bind(tagOrId?, sequence? ?,callback?)

This method associates callback with all the items given by tagOrId such that whenever the event sequence given by sequence occurs for one of the items the callback will be invoked. This method is similar to the bind method except that it operates on items in a canvas rather than entire widgets. See Tk::bind for complete details on the syntax of sequence and the substitutions performed on callback before invoking it. If all arguments are specified then a new binding is created, replacing any existing binding for the same sequence and tagOrId (if the first character of command is ``+'' then command augments an existing binding rather than replacing it). In this case the return value is an empty string. If callback is omitted then the method returns the callback associated with tagOrId and sequence (an error occurs if there is no such binding). If both callback and sequence are omitted then the method returns a list of all the sequences for which bindings have been defined for tagOrId.

$canvas->canvasx(screenx?, gridspacing?)

Given a window x-coordinate in the canvas screenx, this method returns the canvas x-coordinate that is displayed at that location. If gridspacing is specified, then the canvas coordinate is rounded to the nearest multiple of gridspacing units.

$canvas->canvasy(screeny, ?gridspacing?)

Given a window y-coordinate in the canvas screeny this method returns the canvas y-coordinate that is displayed at that location. If gridspacing is specified, then the canvas coordinate is rounded to the nearest multiple of gridspacing units.

$canvas->coords(tagOrId ?x0,y0 ...?)

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

$canvas->create(type, x, y, ?x, y, ...?, ?option, value, ...?)

Create a new item in $canvas of type type. The exact format of the arguments after type depends on type, but usually they consist of the coordinates for one or more points, followed by specifications for zero or more item options. See the subsections on individual item types below for more on the syntax of this method. This method returns the id for the new item.

$canvas->dchars(tagOrId, first, ?last?)

For each item given by tagOrId, delete the characters, or coordinates, in the range given by first and last, inclusive. If some of the items given by tagOrId don't support Text items interpret first and last as indices to a character, line and polygon items interpret them indices to a coordinate (an x,y pair). within the item(s) as described in "INDICES" above. If last is omitted, it defaults to first. This method returns an empty string.

$canvas->delete(?tagOrId, tagOrId, ...?)

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

$canvas->dtag(tagOrId, ?tagToDelete?)

For each of the items given by tagOrId, delete the tag given by tagToDelete from the list of those associated with the item. If an item doesn't have the tag tagToDelete then the item is unaffected by the method. If tagToDelete is omitted then it defaults to tagOrId. This method returns an empty string.

$canvas->find(searchCommand, ?arg, arg, ...?)

This method returns a list consisting of all the items that meet the constraints specified by searchCommand and arg's. SearchCommand and args have any of the forms accepted by the addtag method. The items are returned in stacking order, with the lowest item first.

focus

$canvas->focus(?tagOrId?)

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

$canvas->gettags(tagOrId)

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

$canvas->icursor(tagOrId, index)

Set the position of the insertion cursor for the item(s) given by tagOrId to just before the character whose position is given by index. If some or all of the items given by tagOrId don't support an insertion cursor then this method has no effect on them. See "INDICES" above for a description of the legal forms for index. Note: the insertion cursor is only displayed in an item if that item currently has the keyboard focus (see the widget method focus, below), but the cursor position may be set even when the item doesn't have the focus. This method returns an empty string.

$canvas->index(tagOrId, index)

This method returns a decimal string giving the numerical index within tagOrId corresponding to index. Index gives a textual description of the desired position as described in "INDICES" above. Text items interpret index as an index to a character, line and polygon items interpret it as an index to a coordinate (an x,y pair). The return value is guaranteed to lie between 0 and the number of characters, or coordinates, within the item, inclusive. If tagOrId refers to multiple items, then the index is processed in the first of these items that supports indexing operations (in display list order).

$canvas->insert(tagOrId, beforeThis, string)

For each of the items given by tagOrId, if the item supports text or coordinate, insertion then string is inserted into the item's text just before the character, or coordinate, whose index is beforeThis. Text items interpret beforethis as an index to a character, line and polygon items interpret it as an index to a coordinate (an x,y pair). For lines and polygons the string must be a valid coordinate sequence. See "INDICES" above for information about the forms allowed for beforeThis. This method returns an empty string.

$canvas->itemcget(tagOrId, option)

Returns the current value of the configuration option for the item given by tagOrId whose name is option. This method is similar to the cget method except that it applies to a particular item rather than the widget as a whole. Option may have any of the values accepted by the create method when the item was created. If tagOrId is a tag that refers to more than one item, the first (lowest) such item is used.

$canvas->itemconfigure(tagOrId, ?option?, ?value?, ?option, value, ...?)

This method is similar to the configure method except that it modifies item-specific options for the items given by tagOrId instead of modifying options for the overall canvas widget. If no option is specified, returns a list describing all of the available options for the first item given by tagOrId (see Tk::options for information on the format of this list). If option is specified with no value, then the method returns a list describing the one named option (this list will be identical to the corresponding sublist of the value returned if no option is specified). If one or more option-value pairs are specified, then the method modifies the given widget option(s) to have the given value(s) in each of the items given by tagOrId; in this case the method returns an empty string. The options and values are the same as those permissible in the create method when the item(s) were created; see the sections describing individual item types below for details on the legal options.

$canvas->lower(tagOrId, ?belowThis?)

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

$canvas->move(tagOrId, xAmount, yAmount)

Move each of the items given by tagOrId in the canvas coordinate space by adding xAmount to the x-coordinate of each point associated with the item and yAmount to the y-coordinate of each point associated with the item. This method returns an empty string.

$canvas->postscript(?option, value, option, value, ...?)

Generate a Postscript representation for part or all of the canvas. If the -file option is specified then the Postscript is written to a file and an empty string is returned; otherwise the Postscript is returned as the result of the method. If the interpreter that owns the canvas is marked as safe, the operation will fail because safe interpreters are not allowed to write files. If the -channel option is specified, the argument denotes the name of a channel already opened for writing. The Postscript is written to that channel, and the channel is left open for further writing at the end of the operation. The Postscript is created in Encapsulated Postscript form using version 3.0 of the Document Structuring Conventions. Note: by default Postscript is only generated for information that appears in the canvas's window on the screen. If the canvas is freshly created it may still have its initial size of 1x1 pixel so nothing will appear in the Postscript. To get around this problem either invoke the update method to wait for the canvas window to reach its final size, or else use the -width and -height options to specify the area of the canvas to print. The option-value argument pairs provide additional information to control the generation of Postscript. The following options are supported:

$canvas->raise(tagOrId, ?aboveThis?)

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

$canvas->scale(tagOrId, xOrigin, yOrigin, xScale, yScale)

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

$canvas->scan(option, args)

This method is used to implement scanning on canvases. It has two forms, depending on option:

$canvas->select(option, ?tagOrId, arg?)

Manipulates the selection in one of several ways, depending on option. The method may take any of the forms described below. In all of the descriptions below, tagOrId must refer to an item that supports indexing and selection; if it refers to multiple items then the first of these that supports indexing and the selection is used. Index gives a textual description of a position within tagOrId, as described in "INDICES" above.

$canvas->type(tagOrId)

Returns the type of the item given by tagOrId, such as rectangle or text. If tagOrId refers to more than one item, then the type of the first item in the display list is returned. If tagOrId doesn't refer to any items at all then an empty string is returned.

$canvas->xview(?args?)

This method is used to query and change the horizontal position of the information displayed in the canvas's window. It can take any of the following forms:

$canvas->yview(?args?)

This method is used to query and change the vertical position of the information displayed in the canvas's window. It can take any of the following forms:

OVERVIEW OF ITEM TYPES¶

The sections below describe the various types of items supported by canvas widgets. Each item type is characterized by two things: first, the form of the create method used to create instances of the type; and second, a set of configuration options for items of that type, which may be used in the create and itemconfigure methods. Most items don't support indexing or selection or the methods related to them, such as index and insert. Where items do support these facilities, it is noted explicitly in the descriptions below. At present, text, line and polygon items provide this support. For lines and polygons the indexing facility is used to manipulate the coordinates of the item.

ARC ITEMS¶

Items of type arc appear on the display as arc-shaped regions. An arc is a section of an oval delimited by two angles (specified by the -start and -extent options) and displayed in one of several ways (specified by the -style option). Arcs are created with methods of the following form:

 $canvas->createArc(x1, y1, x2, y2, ?option, value, option, value, ...?)

The arguments x1, y1, x2, and y2 give the coordinates of two diagonally opposite corners of a rectangular region enclosing the oval that defines the arc. After the coordinates there may be any number of option-value pairs, each of which sets one of the configuration options for the item. These same option-value pairs may be used in itemconfigure methods to change the item's configuration. The following options are supported for arcs:

-dash => pattern

-activedash => pattern

-disableddash => pattern

This option specifies dash patterns for the normal state, the active state, and the disabled state of an arc item. pattern may have any of the forms accepted by Tk_GetDash. If the dash options are omitted then the default is a solid outline.

-dashoffset => offset

The starting offset into the pattern provided by the -dash option. -dashoffset is ignored if there is no -dash pattern.

-extent => degrees

Specifies the size of the angular range occupied by the arc. The arc's range extends for degrees degrees counter-clockwise from the starting angle given by the -start option. Degrees may be negative. If it is greater than 360 or less than -360, then degrees modulo 360 is used as the extent.

-fill => color

-activefill => color

-disabledfill => color

Specifies the color to be used to fill the arc region in its normal, active, and disabled states, Color may have any of the forms accepted by Tk_GetColor. If color is an empty string (the default), then then the arc will not be filled.

-outline => color

-activeoutline => color

-disabledoutline => color

This option specifies the color that should be used to draw the outline of the arc in its normal, active and disabled states. Color may have any of the forms accepted by Tk_GetColor. This option defaults to black. If color is specified as undef then no outline is drawn for the arc.

-outlinestipple => bitmap

-activeoutlinestipple => bitmap

-disabledoutlinestipple => bitmap

This option specifies stipple patterns that should be used to draw the outline of the arc in its normal, active and disabled states. Indicates that the outline for the arc should be drawn with a stipple pattern; bitmap specifies the stipple pattern to use, in any of the forms accepted by Tk_GetBitmap. If the -outline option hasn't been specified then this option has no effect. If bitmap is an empty string (the default), then the outline is drawn in a solid fashion.

-start => degrees

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

-state => state

Modifies the state of the arc item where state may be set to one of: normal, disabled, hidden or "". If set to empty, the state of the canvas itself is used. An arc item may also be in the "active" state if the mouse is currently over it. Many options can take separate specifications in normal, active and disabled states such that the appearance of the item can be different in each state.

-stipple => bitmap

-activestipple => bitmap

-disabledstipple => bitmap

This option specifies stipple patterns that should be used to fill the the arc in its normal, active and disabled states. bitmap specifies the stipple pattern to use, in any of the forms accepted by Tk_GetBitmap. If the -fill option hasn't been specified then this option has no effect. If bitmap is an empty string (the default), then filling is done in a solid fashion.

-style => type

Specifies how to draw the arc. If type is pieslice (the default) then the arc's region is defined by a section of the oval's perimeter plus two line segments, one between the center of the oval and each end of the perimeter section. If type is chord then the arc's region is defined by a section of the oval's perimeter plus a single line segment connecting the two end points of the perimeter section. If type is arc then the arc's region consists of a section of the perimeter alone. In this last case the -fill option is ignored.

-tags => tagList

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

-updatecommand => command

Specifies a callback that is to be executed every time the arc item is updated on the screen.

-width => outlineWidth

-activewidth => outlineWidth

-disabledwidth => outlineWidth

Specifies the width of the outline to be drawn around the arc's region, in its normal, active and disabled states. outlineWidth may be in any of the forms described in the "COORDINATES" section above. If the -outline option has been specified as undef then this option has no effect. Wide outlines will be drawn centered on the edges of the arc's region. This option defaults to 1.0.

BITMAP ITEMS¶

Items of type bitmap appear on the display as images with two colors, foreground and background. Bitmaps are created with methods of the following form:

 $canvas->createBitmap(x, y, ?option, value, option, value, ...?)

The arguments x and y specify the coordinates of a point used to position the bitmap on the display (see the -anchor option below for more information on how bitmaps are displayed). After the coordinates there may be any number of option-value pairs, each of which sets one of the configuration options for the item. These same option-value pairs may be used in itemconfigure methods to change the item's configuration. The following options are supported for bitmaps:

-anchor => anchorPos

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

-background => color

-activebackground => color

-disabledbackground => color

Specifies the color to use for each of the bitmap's '0' valued pixels in its normal, active and disabled states. Color may have any of the forms accepted by Tk_GetColor. If this option isn't specified, or if it is specified as undef, then nothing is displayed where the bitmap pixels are 0; this produces a transparent effect.

-bitmap => bitmap

-activebitmap => bitmap

-disabledbitmap => bitmap

Specifies the bitmaps to display in the item in its normal, active and disabled states. All bitmaps must have the same width and height. Bitmap may have any of the forms accepted by Tk_GetBitmap.

-foreground => color

-activeforeground => color

-disabledforeground => color

Specifies the color to use for each of the bitmap's '1' valued pixels in its normal, active and disabled states. Color may have any of the forms accepted by Tk_GetColor and defaults to black.

-state => state

Modifies the state of the bitmap item where state may be set to one of: normal, disabled, or hidden. An bitmap item may also be in the "active" state if the mouse is currently over it. Many options can take separate specifications in normal, active and disabled states such that the appearance of the item can be different in each state.

-tags => tagList

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

-updatecommand => command

Specifies a callback that is to be executed every time the bitmap item is updated on the screen.

GRID ITEMS¶

Items of type grid are intended for producing a visual reference for interpreting other items. They can be drawn as either lines (with dash style) or as rectangular "dots" at each grid point.

Items of type grid are unlike other items they always cover the whole of the canvas, but are never enclosed by nor overlap any area and are not near any point. That is they are intended to be always visible but not "pickable", as such they do support the "active" state. They are like other items in that: multiple grids are permitted, they can be raised and lowered relative to other items, they can be moved and scaled. As yet grids do not appear in PostScript output.

Grids have outline like configure options. Grids are created with methods of the following form:

 $canvas->createGrid(x1, y1, x2, y2, ?option, value, option, value, ...?)

The arguments x1, y1 give the origin of the grid. x2, and y2 give the coordinates of the next grid point in their respective directions. After the coordinates there may be any number of option-value pairs, each of which sets one of the configuration options for the item. These same option-value pairs may be used in itemconfigure methods to change the item's configuration.

The following options are supported for grids:

-lines => boolean

If -lines is set to a true value then lines are drawn for both X and Y grids in the style determined by -dash. Otherwise retangular "dots" are drawn at each grid point.

-dash => pattern

-disableddash => pattern

This option specifies dash patterns for the normal state, and the disabled state of a grid item. pattern may have any of the forms accepted by Tk_GetDash. If the dash options are omitted then the default is a solid outline.

-dashoffset => offset

The starting offset into the pattern provided by the -dash option. -dashoffset is ignored if there is no -dash pattern.

-color => color

-disabledcolor => color

This option specifies the color that should be used to draw the outline of the grid in its normal and disabled states. Color may have any of the forms accepted by Tk_GetColor. This option defaults to black. If color is undef then no grid will be drawn.

-stipple => bitmap

-disabledstipple => bitmap

This option specifies stipple patterns that should be used to draw the outline of the rectangle in its normal and disabled states. bitmap specifies the stipple pattern to use, in any of the forms accepted by Tk_GetBitmap. If bitmap is an empty string (the default), then the outline is drawn in a solid fashion.

-state => state

Modifies the state of the rectangle item where state may be set to one of: normal, disabled, or hidden. Many options can take separate specifications in normal and disabled states such that the appearance of the item can be different in each state.

-tags => tagList

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

-updatecommand => command

Specifies a callback that is to be executed every time the grid item is updated on the screen.

-width => outlineWidth

-disabledwidth => outlineWidth

Specifies the width of the lines drawn by the grid or the size (in both X and Y) of the dots, in its normal and disabled states. This option defaults to 1.0.

IMAGE ITEMS¶

Items of type image are used to display images on a canvas. Images are created with methods of the following form:

 $canvas->createImage(x, y, ?option, value, option, value, ...?)

The arguments x and y specify the coordinates of a point used to position the image on the display (see the -anchor option below for more information). After the coordinates there may be any number of option-value pairs, each of which sets one of the configuration options for the item. These same option-value pairs may be used in itemconfigure methods to change the item's configuration. The following options are supported for images:

-anchor => anchorPos

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

-image => name

-activeimage => name

-disabledimage => name

Specifies the name of the images to display in the item in is normal, active and disabled states. This image must have been created previously, see Tk::Image.

-state => state

Modifies the state of the image item where state may be set to one of: normal, disabled, or hidden. An image item may also be in the "active" state if the mouse is currently over it. Many options can take separate specifications in normal, active and disabled states such that the appearance of the item can be different in each state.

-tags => tagList

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

-updatecommand => command

Specifies a callback that is to be executed every time the image item is updated on the screen.

LINE ITEMS¶

Items of type line appear on the display as one or more connected line segments or curves. Line items support coordinate indexing operations using the canvas methods: dchars, index, insert. Lines are created with methods of the following form:

 $canvas->createLine(x1, y1..., xn, yn, ?option, value, option, value, ...?)

The arguments x1 through yn give the coordinates for a series of two or more points that describe a series of connected line segments. After the coordinates there may be any number of option-value pairs, each of which sets one of the configuration options for the item. These same option-value pairs may be used in itemconfigure methods to change the item's configuration. The following options are supported for lines:

-arrow => where

Indicates whether or not arrowheads are to be drawn at one or both ends of the line. Where must have one of the values none (for no arrowheads), first (for an arrowhead at the first point of the line), last (for an arrowhead at the last point of the line), or both (for arrowheads at both ends). This option defaults to none.

-arrowshape => shape

This option indicates how to draw arrowheads. The shape argument must be a list with three elements, each specifying a distance in any of the forms described in the "COORDINATES" section above. The first element of the list gives the distance along the line from the neck of the arrowhead to its tip. The second element gives the distance along the line from the trailing points of the arrowhead to the tip, and the third element gives the distance from the outside edge of the line to the trailing points. If this option isn't specified then Tk picks a ``reasonable'' shape.

-capstyle => style

Specifies the ways in which caps are to be drawn at the endpoints of the line. Style may have any of the forms accepted by Tk_GetCapStyle (butt, projecting, or round). If this option isn't specified then it defaults to butt. Where arrowheads are drawn the cap style is ignored.

-dash => pattern

-activedash => pattern

-disableddash => pattern

This option specifies dash patterns for the normal state, the active state, and the disabled state of a line item. pattern may have any of the forms accepted by Tk_GetDash. If the dash options are omitted then the default is a solid outline.

-dashoffset => offset

The starting offset into the pattern provided by the -dash option. -dashoffset is ignored if there is no -dash pattern.

-fill => color

-activefill => color

-disabledfill => color

Specifies the color to be used to fill the line in its normal, active, and disabled states. Color may have any of the forms acceptable to Tk_GetColor. It may also be undef, in which case the line will be transparent. This option defaults to black.

-joinstyle => style

Specifies the ways in which joints are to be drawn at the vertices of the line. Style may have any of the forms accepted by Tk_GetCapStyle (bevel, miter, or round). If this option isn't specified then it defaults to miter. If the line only contains two points then this option is irrelevant.

-smooth => boolean

Boolean must have one of the forms accepted by Tk_GetBoolean. It indicates whether or not the line should be drawn as a curve. If so, the line is rendered as a set of parabolic splines: one spline is drawn for the first and second line segments, one for the second and third, and so on. Straight-line segments can be generated within a curve by duplicating the end-points of the desired line segment.

-splinesteps => number

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

-state => state

Modifies the state of the line item where state may be set to one of: normal, disabled, or hidden. A line item may also be in the "active" state if the mouse is currently over it. Many options can take separate specifications in normal, active and disabled states such that the appearance of the item can be different in each state.

-stipple => bitmap

-activestipple => bitmap

-disabledstipple => bitmap

This option specifies stipple patterns that should be used to fill the the line in its normal, active and disabled states. bitmap specifies the stipple pattern to use, in any of the forms accepted by Tk_GetBitmap. If bitmap is an empty string (the default), then filling is done in a solid fashion.

-tags => tagList

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

-updatecommand => command

Specifies a callback that is to be executed every time the line item is updated on the screen.

-width => lineWidth

-activewidth => lineWidth

-disabledwidth => lineWidth

Specifies the width of the line in its normal, active and disabled states. lineWidth may be in any of the forms described in the "COORDINATES" section above.

Wide lines will be drawn centered on the path specified by the points. If this option isn't specified then it defaults to 1.0.

OVAL ITEMS¶

Items of type oval appear as circular or oval regions on the display. Each oval may have an outline, a fill, or both. Ovals are created with methods of the following form:

 $canvas->createOval(x1, y1, x2, y2, ?option, value, option, value, ...?)

The arguments x1, y1, x2, and y2 give the coordinates of two diagonally opposite corners of a rectangular region enclosing the oval. The oval will include the top and left edges of the rectangle not the lower or right edges. If the region is square then the resulting oval is circular; otherwise it is elongated in shape. After the coordinates there may be any number of option-value pairs, each of which sets one of the configuration options for the item. These same option-value pairs may be used in itemconfigure methods to change the item's configuration. The following options are supported for ovals:

-dash => pattern

-activedash => pattern

-disableddash => pattern

This option specifies dash patterns for the normal state, the active state, and the disabled state of an oval item. pattern may have any of the forms accepted by Tk_GetDash. If the dash options are omitted then the default is a solid outline.

-dashoffset => offset

The starting offset into the pattern provided by the -dash option. -dashoffset is ignored if there is no -dash pattern.

-fill => color

-activefill => color

-disabledfill => color

Specifies the color to be used to fill the oval in its normal, active, and disabled states. Color may have any of the forms accepted by Tk_GetColor. If color is undef (the default), then then the oval will not be filled.

-outline => color

-activeoutline => color

-disabledoutline => color

This option specifies the color that should be used to draw the outline of the oval in its normal, active and disabled states. Color may have any of the forms accepted by Tk_GetColor. This option defaults to black. If color is undef then no outline will be drawn for the oval.

-outlinestipple => bitmap

-activeoutlinestipple => bitmap

-disabledoutlinestipple => bitmap

This option specifies stipple patterns that should be used to draw the outline of the oval in its normal, active and disabled states. bitmap specifies the stipple pattern to use, in any of the forms accepted by Tk_GetBitmap. If the -outline option hasn't been specified then this option has no effect. If bitmap is an empty string (the default), then the outline is drawn in a solid fashion.

-state => state

Modifies the state of the oval item where state may be set to one of: normal, disabled, or hidden. An oval item may also be in the "active" state if the mouse is currently over it. Many options can take separate specifications in normal, active and disabled states such that the appearance of the item can be different in each state.

-stipple => bitmap

-activestipple => bitmap

-disabledstipple => bitmap

This option specifies stipple patterns that should be used to fill the the oval in its normal, active and disabled states. bitmap specifies the stipple pattern to use, in any of the forms accepted by Tk_GetBitmap. If the -fill option hasn't been specified then this option has no effect. If bitmap is an empty string (the default), then filling is done in a solid fashion.

-tags => tagList

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

-updatecommand => command

Specifies a callback that is to be executed every time the oval item is updated on the screen.

-width => outlineWidth

-activewidth => outlineWidth

-disabledwidth => outlineWidth

Specifies the width of the outline to be drawn around the oval, in its normal, active and disabled states. outlineWidth specifies the width of the outline to be drawn around the oval, in any of the forms described in the "COORDINATES" section above.

If the -outline option hasn't been specified then this option has no effect. Wide outlines are drawn centered on the oval path defined by x1, y1, x2, and y2. This option defaults to 1.0.

POLYGON ITEMS¶

Items of type polygon appear as polygonal or curved filled regions on the display. Polygon items support coordinate indexing operations using the canvas methods: dchars, index, insert. Polygons are created with methods of the following form:

 $canvas->createPolygon(x1, y1, ..., xn, yn, ?option, value, option, value, ...?)

The arguments x1 through yn specify the coordinates for three or more points that define a closed polygon. The first and last points may be the same; whether they are or not, Tk will draw the polygon as a closed polygon. After the coordinates there may be any number of option-value pairs, each of which sets one of the configuration options for the item. These same option-value pairs may be used in itemconfigure methods to change the item's configuration. The following options are supported for polygons:

-dash => pattern

-activedash => pattern

-disableddash => pattern

This option specifies dash patterns for the normal state, the active state, and the disabled state of an polygon item. pattern may have any of the forms accepted by Tk_GetDash. If the dash options are omitted then the default is a solid outline.

-dashoffset => offset

The starting offset into the pattern provided by the -dash option. -dashoffset is ignored if there is no -dash pattern.

-fill => color

-activefill => color

-disabledfill => color

Specifies the color to be used to fill the polygon in its normal, active, and disabled states. Color may have any of the forms acceptable to Tk_GetColor. If color is undef then the polygon will be transparent. This option defaults to black.

-joinstyle => style

Specifies the ways in which joints are to be drawn at the vertices of the outline. Style may have any of the forms accepted by Tk_GetCapStyle (bevel, miter, or round). If this option isn't specified then it defaults to miter.

-outline => color

-activeoutline => color

-disabledoutline => color

This option specifies the color that should be used to draw the outline of the polygon in its normal, active and disabled states. Color may have any of the forms accepted by Tk_GetColor. If color is undef then no outline will be drawn for the polygon. This option defaults to undef (no outline).

-outlinestipple => bitmap

-activeoutlinestipple => bitmap

-disabledoutlinestipple => bitmap

This option specifies stipple patterns that should be used to draw the outline of the polygon in its normal, active and disabled states. bitmap specifies the stipple pattern to use, in any of the forms accepted by Tk_GetBitmap. If the -outline option hasn't been specified then this option has no effect. If bitmap is an empty string (the default), then the outline is drawn in a solid fashion.

-smooth => boolean

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

-splinesteps => number

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

-state => state

Modifies the state of the polygon item where state may be set to one of: normal, disabled, or hidden. A polygon item may also be in the "active" state if the mouse is currently over it. Many options can take separate specifications in normal, active and disabled states such that the appearance of the item can be different in each state.

-stipple => bitmap

-activestipple => bitmap

-disabledstipple => bitmap

This option specifies stipple patterns that should be used to fill the the polygon in its normal, active and disabled states. bitmap specifies the stipple pattern to use, in any of the forms accepted by Tk_GetBitmap. If bitmap is an empty string (the default), then filling is done in a solid fashion.

-tags => tagList

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

-updatecommand => command

Specifies a callback that is to be executed every time the polygon item is updated on the screen.

-width => outlineWidth

-activewidth => outlineWidth

-disabledwidth => outlineWidth

Specifies the width of the outline to be drawn around

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

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

RECTANGLE ITEMS¶

Items of type rectangle appear as rectangular regions on the display. Each rectangle may have an outline, a fill, or both. Rectangles are created with methods of the following form:

 $canvas->createRectangle(x1, y1, x2, y2, ?option, value, option, value, ...?)

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

-dash => pattern

-activedash => pattern

-disableddash => pattern

This option specifies dash patterns for the normal state, the active state, and the disabled state of a rectangle item. pattern may have any of the forms accepted by Tk_GetDash. If the dash options are omitted then the default is a solid outline.

-dashoffset => offset

The starting offset into the pattern provided by the -dash option. -dashoffset is ignored if there is no -dash pattern.

-fill => color

-activefill => color

-disabledfill => color

Specifies the color to be used to fill the rectangle in its normal, active, and disabled states. Color may be specified in any of the forms accepted by Tk_GetColor. If color is undef (the default), then the rectangle will not be filled.

-outline => color

-activeoutline => color

-disabledoutline => color

This option specifies the color that should be used to draw the outline of the rectangle in its normal, active and disabled states. Color may have any of the forms accepted by Tk_GetColor. This option defaults to black. If color is undef then no outline will be drawn for the rectangle.

-outlinestipple => bitmap

-activeoutlinestipple => bitmap

-disabledoutlinestipple => bitmap

This option specifies stipple patterns that should be used to draw the outline of the rectangle in its normal, active and disabled states. bitmap specifies the stipple pattern to use, in any of the forms accepted by Tk_GetBitmap. If the -outline option hasn't been specified then this option has no effect. If bitmap is an empty string (the default), then the outline is drawn in a solid fashion.

-state => state

Modifies the state of the rectangle item where state may be set to one of: normal, disabled, or hidden. A rectangle item may also be in the "active" state if the mouse is currently over it. Many options can take separate specifications in normal, active and disabled states such that the appearance of the item can be different in each state.

-stipple => bitmap

-activestipple => bitmap

-disabledstipple => bitmap

This option specifies stipple patterns that should be used to fill the the rectangle in its normal, active and disabled states. bitmap specifies the stipple pattern to use, in any of the forms accepted by Tk_GetBitmap. If the -fill option hasn't been specified then this option has no effect. If bitmap is an empty string (the default), then filling is done in a solid fashion.

-tags => tagList

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

-updatecommand => command

Specifies a callback that is to be executed every time the rectangle item is updated on the screen.

-width => outlineWidth

-activewidth => outlineWidth

-disabledwidth => outlineWidth

Specifies the width of the outline to be drawn around the rectangle, in its normal, active and disabled states. OutlineWidth specifies the width of the outline to be drawn around the rectangle, in any of the forms described in the "COORDINATES" section above.

If the -outline option hasn't been specified then this option has no effect. Wide outlines are drawn centered on the rectangular path defined by x1, y1, x2, and y2. This option defaults to 1.0.

TEXT ITEMS¶

A text item displays a string of characters on the screen in one or more lines. Text items support indexing and selection, along with the following text-related canvas methods: dchars, focus, icursor, index, insert, select. Text items are created with methods of the following form:

 $canvas->createText(x, y, ?option, value, option, value, ...?)

The arguments x and y specify the coordinates of a point used to position the text on the display (see the options below for more information on how text is displayed). After the coordinates there may be any number of option-value pairs, each of which sets one of the configuration options for the item. These same option-value pairs may be used in itemconfigure methods to change the item's configuration. The following options are supported for text items:

-anchor => anchorPos

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

-fill => color

-activefill => color

-disabledfill => color

Specifies the color to be used to fill the text in its normal, active, and disabled states. Color may have any of the forms accepted by Tk_GetColor. If color is undef then the text will be transparent. If this option isn't specified then it defaults to black.

-font => fontName

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

-justify => how

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

-state => state

Modifies the state of the text item where state may be set to one of: normal, disabled, or hidden. A text item may also be in the "active" state if the mouse is currently over it. Many options can take separate specifications in normal, active and disabled states such that the appearance of the item can be different in each state.

-stipple => bitmap

-activestipple => bitmap

-disabledstipple => bitmap

This option specifies stipple patterns that should be used to fill the the text in its normal, active and disabled states. bitmap specifies the stipple pattern to use, in any of the forms accepted by Tk_GetBitmap. If bitmap is an empty string (the default) then the text is drawn in a solid fashion.

-tags => tagList

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

-text => string

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

-updatecommand => command

Specifies a callback that is to be executed every time the text item is updated on the screen.

-width => lineLength

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

WINDOW ITEMS¶

Items of type window cause a particular window to be displayed at a given position on the canvas. Window items are created with methods of the following form:

    $canvas->createWindow(x, y?, -option=>value, -option=>value, ...?)

The arguments x and y specify the coordinates of a point used to position the window on the display (see the -anchor option below for more information on how bitmaps are displayed). After the coordinates there may be any number of option-value pairs, each of which sets one of the configuration options for the item. These same option-value pairs may be used in itemconfigure method to change the item's configuration. The following options are supported for window items:

-anchor => anchorPos

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

-height => pixels

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

-state => state

Modifies the state of the window item where state may be set to one of: normal, disabled, or hidden.

-tags => tagList

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

-updatecommand => command

Specifies a callback that is to be executed every time the window item is updated on the screen.

-width => pixels

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

-window => $widget

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

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

APPLICATION-DEFINED ITEM TYPES¶

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

BINDINGS¶

Canvas has default bindings to allow scrolling if necessary: <Up>, <Down>, <Left> and <Right> (and their <Control-*> counter parts). Further <Proir>, <Next>, <Home> and <End>. These bindings allow you to navigate the same way as in other widgets that can scroll.

Perl/Tk Methods¶

The following methods are added as perl code:

$canvas->get_corners

Returns the bounding box in Canvas coordinates of the visible portion of the Canvas. (Written by Slaven Rezic.)

CREDITS¶

Tk's canvas widget is a blatant ripoff of ideas from Joel Bartlett's ezd program. Ezd provides structured graphics in a Scheme environment and preceded canvases by a year or two. Its simple mechanisms for placing and animating graphical objects inspired the functions of canvases.

KEYWORDS¶

canvas, widget