1canvas(n) Tk Built-In Commands canvas(n)
2______________________________________________________________________________
6
8 canvas - Create and manipulate canvas widgets
9
11 canvas pathName ?options?
12
14 -background -borderwidth -cursor
15 -highlightbackground -highlightcolor -highlightthickness
16 -insertbackground -insertborderwidth -insertofftime
17 -insertontime -insertwidth -relief
18 -selectbackground -selectborderwidth -selectforeground
19 -takefocus -xscrollcommand -yscrollcommand
20 See the options manual entry for details on the standard options.
22
24 [-closeenough closeEnough] Specifies a floating-point value indicating
25 how close the mouse cursor must be to an item before it is considered
26 to be “inside” the item. Defaults to 1.0. [-confine confine] Specifies
27 a boolean value that indicates whether or not it should be allowable to
28 set the canvas's view outside the region defined by the scrollRegion
29 argument. Defaults to true, which means that the view will be con‐
30 strained within the scroll region. [-height height] Specifies a
31 desired window height that the canvas widget should request from its
32 geometry manager. The value may be specified in any of the forms
33 described in the COORDINATES section below. [-scrollregion scrollRe‐
34 gion] Specifies a list with four coordinates describing the left, top,
35 right, and bottom coordinates of a rectangular region. This region is
36 used for scrolling purposes and is considered to be the boundary of the
37 information in the canvas. Each of the coordinates may be specified in
38 any of the forms given in the COORDINATES section below.
39 [-state state] Modifies the default state of the canvas where state may
40 be set to one of: normal, disabled, or hidden. Individual canvas
41 objects all have their own state option which may override the default
42 state. Many options can take separate specifications such that the
43 appearance of the item can be different in different situations. The
44 options that start with active control the appearance when the mouse
45 pointer is over it, while the option starting with disabled controls
46 the appearance when the state is disabled. Canvas items which are dis‐
47 abled will not react to canvas bindings. [-width width] Specifies a
48 desired window width that the canvas widget should request from its
49 geometry manager. The value may be specified in any of the forms
50 described in the COORDINATES section below. [-xscrollincre‐
51 ment xScrollIncrement] Specifies an increment for horizontal scrolling,
52 in any of the usual forms permitted for screen distances. If the value
53 of this option is greater than zero, the horizontal view in the window
54 will be constrained so that the canvas x coordinate at the left edge of
55 the window is always an even multiple of xScrollIncrement; further‐
56 more, the units for scrolling (e.g., the change in view when the left
57 and right arrows of a scrollbar are selected) will also be
58 xScrollIncrement. If the value of this option is less than or equal to
59 zero, then horizontal scrolling is unconstrained. [-yscrollincre‐
60 ment yScrollIncrement] Specifies an increment for vertical scrolling,
61 in any of the usual forms permitted for screen distances. If the value
62 of this option is greater than zero, the vertical view in the window
63 will be constrained so that the canvas y coordinate at the top edge of
64 the window is always an even multiple of yScrollIncrement; further‐
65 more, the units for scrolling (e.g., the change in view when the top
66 and bottom arrows of a scrollbar are selected) will also be
67 yScrollIncrement. If the value of this option is less than or equal to
68 zero, then vertical scrolling is unconstrained.
69_________________________________________________________________
70
72 The canvas command creates a new window (given by the pathName argu‐
73 ment) and makes it into a canvas widget. Additional options, described
74 above, may be specified on the command line or in the option database
75 to configure aspects of the canvas such as its colors and 3-D relief.
76 The canvas command returns its pathName argument. At the time this
77 command is invoked, there must not exist a window named pathName, but
78 pathName's parent must exist.
79 Canvas widgets implement structured graphics. A canvas displays any
81 number of items, which may be things like rectangles, circles, lines,
82 and text. Items may be manipulated (e.g. moved or re-colored) and com‐
83 mands may be associated with items in much the same way that the bind
84 command allows commands to be bound to widgets. For example, a partic‐
85 ular command may be associated with the <Button-1> event so that the
86 command is invoked whenever button 1 is pressed with the mouse cursor
87 over an item. This means that items in a canvas can have behaviors
88 defined by the Tcl scripts bound to them.
89
91 The items in a canvas are ordered for purposes of display, with the
92 first item in the display list being displayed first, followed by the
93 next item in the list, and so on. Items later in the display list
94 obscure those that are earlier in the display list and are sometimes
95 referred to as being “on top” of earlier items. When a new item is
96 created it is placed at the end of the display list, on top of every‐
97 thing else. Widget commands may be used to re-arrange the order of the
98 display list.
99 Window items are an exception to the above rules. The underlying win‐
101 dow systems require them always to be drawn on top of other items. In
102 addition, the stacking order of window items is not affected by any of
103 the canvas widget commands; you must use the raise and lower Tk com‐
104 mands instead.
105
107 Items in a canvas widget may be named in either of two ways: by id or
108 by tag. Each item has a unique identifying number, which is assigned
109 to that item when it is created. The id of an item never changes and
110 id numbers are never re-used within the lifetime of a canvas widget.
111 Each item may also have any number of tags associated with it. A tag
113 is just a string of characters, and it may take any form except that of
114 an integer. For example, “x123” is OK but “123” is not. The same tag
115 may be associated with many different items. This is commonly done to
116 group items in various interesting ways; for example, all selected
117 items might be given the tag “selected”.
118 The tag all is implicitly associated with every item in the canvas; it
120 may be used to invoke operations on all the items in the canvas.
121 The tag current is managed automatically by Tk; it applies to the cur‐
123 rent item, which is the topmost item whose drawn area covers the posi‐
124 tion of the mouse cursor (different item types interpret this in vary‐
125 ing ways; see the individual item type documentation for details). If
126 the mouse is not in the canvas widget or is not over an item, then no
127 item has the current tag.
128 When specifying items in canvas widget commands, if the specifier is an
130 integer then it is assumed to refer to the single item with that id.
131 If the specifier is not an integer, then it is assumed to refer to all
132 of the items in the canvas that have a tag matching the specifier. The
133 symbol tagOrId is used below to indicate that an argument specifies
134 either an id that selects a single item or a tag that selects zero or
135 more items.
136 tagOrId may contain a logical expressions of tags by using operators:
138 “&&”, “||”, “^”, “!”, and parenthesized subexpressions. For example:
139 .c find withtag {(a&&!b)||(!a&&b)}
140 or equivalently:
141 .c find withtag {a^b}
142 will find only those items with either “a” or “b” tags, but not both.
143 Some widget commands only operate on a single item at a time; if
145 tagOrId is specified in a way that names multiple items, then the nor‐
146 mal behavior is for the command to use the first (lowest) of these
147 items in the display list that is suitable for the command. Exceptions
148 are noted in the widget command descriptions below.
149
151 All coordinates related to canvases are stored as floating-point num‐
152 bers. Coordinates and distances are specified in screen units, which
153 are floating-point numbers optionally followed by one of several let‐
154 ters. If no letter is supplied then the distance is in pixels. If the
155 letter is m then the distance is in millimeters on the screen; if it
156 is c then the distance is in centimeters; i means inches, and p means
157 printers points (1/72 inch). Larger y-coordinates refer to points
158 lower on the screen; larger x-coordinates refer to points farther to
159 the right. Coordinates can be specified either as an even number of
160 parameters, or as a single list parameter containing an even number of
161 x and y coordinate values.
162 TRANSFORMATIONS
164 Normally the origin of the canvas coordinate system is at the upper-
165 left corner of the window containing the canvas. It is possible to
166 adjust the origin of the canvas coordinate system relative to the ori‐
167 gin of the window using the xview and yview widget commands; this is
168 typically used for scrolling. Canvases do not support scaling or rota‐
169 tion of the canvas coordinate system relative to the window coordinate
170 system.
171 Individual items may be moved or scaled using widget commands described
173 below, but they may not be rotated.
174 Note that the default origin of the canvas's visible area is coincident
176 with the origin for the whole window as that makes bindings using the
177 mouse position easier to work with; you only need to use the canvasx
178 and canvasy widget commands if you adjust the origin of the visible
179 area. However, this also means that any focus ring (as controlled by
180 the -highlightthickness option) and window border (as controlled by the
181 -borderwidth option) must be taken into account before you get to the
182 visible area of the canvas.
183
185 Text items support the notion of an index for identifying particular
186 positions within the item. In a similar fashion, line and polygon
187 items support index for identifying, inserting and deleting subsets of
188 their coordinates. Indices are used for commands such as inserting or
189 deleting a range of characters or coordinates, and setting the inser‐
190 tion cursor position. An index may be specified in any of a number of
191 ways, and different types of items may support different forms for
192 specifying indices. Text items support the following forms for an
193 index; if you define new types of text-like items, it would be advis‐
194 able to support as many of these forms as practical. Note that it is
195 possible to refer to the character just after the last one in the text
196 item; this is necessary for such tasks as inserting new text at the
197 end of the item. Lines and Polygons do not support the insertion cur‐
198 sor and the selection. Their indices are supposed to be even always,
199 because coordinates always appear in pairs.
200 number A decimal number giving the position of the desired character
202 within the text item. 0 refers to the first character, 1 to
203 the next character, and so on. If indexes are odd for lines
204 and polygons, they will be automatically decremented by one.
205 A number less than 0 is treated as if it were zero, and a
206 number greater than the length of the text item is treated as
207 if it were equal to the length of the text item. For poly‐
208 gons, numbers less than 0 or greater then the length of the
209 coordinate list will be adjusted by adding or subtracting the
210 length until the result is between zero and the length,
211 inclusive.
212 end Refers to the character or coordinate just after the last one
214 in the item (same as the number of characters or coordinates
215 in the item).
216 insert Refers to the character just before which the insertion cur‐
218 sor is drawn in this item. Not valid for lines and polygons.
219 sel.first Refers to the first selected character in the item. If the
221 selection is not in this item then this form is illegal.
222 sel.last Refers to the last selected character in the item. If the
224 selection is not in this item then this form is illegal.
225 @x,y Refers to the character or coordinate at the point given by x
227 and y, where x and y are specified in the coordinate system
228 of the canvas. If x and y lie outside the coordinates cov‐
229 ered by the text item, then they refer to the first or last
230 character in the line that is closest to the given point.
231
233 Many items support the notion of a dash pattern for outlines.
234 The first possible syntax is a list of integers. Each element repre‐
236 sents the number of pixels of a line segment. Only the odd segments are
237 drawn using the “outline” color. The other segments are drawn transpar‐
238 ent.
239 The second possible syntax is a character list containing only 5 possi‐
241 ble characters “.,-_ ”. The space can be used to enlarge the space
242 between other line elements, and cannot occur as the first position in
243 the string. Some examples:
244 -dash . → -dash {2 4}
245 -dash - → -dash {6 4}
246 -dash -. → -dash {6 4 2 4}
247 -dash -.. → -dash {6 4 2 4 2 4}
248 -dash {. } → -dash {2 8}
249 -dash , → -dash {4 4}
250 The main difference of this syntax with the previous is that it is
252 shape-conserving. This means that all values in the dash list will be
253 multiplied by the line width before display. This assures that “.”
254 will always be displayed as a dot and “-” always as a dash regardless
255 of the line width.
256 On systems which support only a limited set of dash patterns, the dash
258 pattern will be displayed as the closest dash pattern that is avail‐
259 able. For example, on Windows only the first 4 of the above examples
260 are available. The last 2 examples will be displayed identically to
261 the first one.
262
264 The canvas command creates a new Tcl command whose name is pathName.
265 This command may be used to invoke various operations on the widget.
266 It has the following general form:
267 pathName option ?arg arg ...?
268 Option and the args determine the exact behavior of the command. The
269 following widget commands are possible for canvas widgets:
270 pathName addtag tag searchSpec ?arg arg ...?
272 For each item that meets the constraints specified by searchSpec
273 and the args, add tag to the list of tags associated with the
274 item if it is not already present on that list. It is possible
275 that no items will satisfy the constraints given by searchSpec
276 and args, in which case the command has no effect. This command
277 returns an empty string as result. SearchSpec and arg's may
278 take any of the following forms:
279 above tagOrId
281 Selects the item just after (above) the one given by
282 tagOrId in the display list. If tagOrId denotes more
283 than one item, then the last (topmost) of these items in
284 the display list is used.
285 all Selects all the items in the canvas.
287 below tagOrId
289 Selects the item just before (below) the one given by
290 tagOrId in the display list. If tagOrId denotes more
291 than one item, then the first (lowest) of these items in
292 the display list is used.
293 closest x y ?halo? ?start?
295 Selects the item closest to the point given by x and y.
296 If more than one item is at the same closest distance
297 (e.g. two items overlap the point), then the top-most of
298 these items (the last one in the display list) is used.
299 If halo is specified, then it must be a non-negative
300 value. Any item closer than halo to the point is consid‐
301 ered to overlap it. The start argument may be used to
302 step circularly through all the closest items. If start
303 is specified, it names an item using a tag or id (if by
304 tag, it selects the first item in the display list with
305 the given tag). Instead of selecting the topmost closest
306 item, this form will select the topmost closest item that
307 is below start in the display list; if no such item
308 exists, then the selection behaves as if the start argu‐
309 ment had not been specified.
310 enclosed x1 y1 x2 y2
312 Selects all the items completely enclosed within the rec‐
313 tangular region given by x1, y1, x2, and y2. X1 must be
314 no greater then x2 and y1 must be no greater than y2.
315 overlapping x1 y1 x2 y2
317 Selects all the items that overlap or are enclosed within
318 the rectangular region given by x1, y1, x2, and y2. X1
319 must be no greater then x2 and y1 must be no greater than
320 y2.
321 withtag tagOrId
323 Selects all the items given by tagOrId.
324 pathName bbox tagOrId ?tagOrId tagOrId ...?
326 Returns a list with four elements giving an approximate bounding
327 box for all the items named by the tagOrId arguments. The list
328 has the form “x1 y1 x2 y2” such that the drawn areas of all the
329 named elements are within the region bounded by x1 on the left,
330 x2 on the right, y1 on the top, and y2 on the bottom. The
331 return value may overestimate the actual bounding box by a few
332 pixels. If no items match any of the tagOrId arguments or if
333 the matching items have empty bounding boxes (i.e. they have
334 nothing to display) then an empty string is returned.
335 pathName bind tagOrId ?sequence? ?command?
337 This command associates command with all the items given by
338 tagOrId such that whenever the event sequence given by sequence
339 occurs for one of the items the command will be invoked. This
340 widget command is similar to the bind command except that it
341 operates on items in a canvas rather than entire widgets. See
342 the bind manual entry for complete details on the syntax of
343 sequence and the substitutions performed on command before
344 invoking it. If all arguments are specified then a new binding
345 is created, replacing any existing binding for the same sequence
346 and tagOrId (if the first character of command is “+” then com‐
347 mand augments an existing binding rather than replacing it). In
348 this case the return value is an empty string. If command is
349 omitted then the command returns the command associated with
350 tagOrId and sequence (an error occurs if there is no such bind‐
351 ing). If both command and sequence are omitted then the command
352 returns a list of all the sequences for which bindings have been
353 defined for tagOrId.
354 The only events for which bindings may be specified are those
356 related to the mouse and keyboard (such as Enter, Leave, Button‐
357 Press, Motion, and KeyPress) or virtual events. The handling of
358 events in canvases uses the current item defined in ITEM IDS AND
359 TAGS above. Enter and Leave events trigger for an item when it
360 becomes the current item or ceases to be the current item; note
361 that these events are different than Enter and Leave events for
362 windows. Mouse-related events are directed to the current item,
363 if any. Keyboard-related events are directed to the focus item,
364 if any (see the focus widget command below for more on this).
365 If a virtual event is used in a binding, that binding can trig‐
366 ger only if the virtual event is defined by an underlying mouse-
367 related or keyboard-related event.
368 It is possible for multiple bindings to match a particular
370 event. This could occur, for example, if one binding is associ‐
371 ated with the item's id and another is associated with one of
372 the item's tags. When this occurs, all of the matching bindings
373 are invoked. A binding associated with the all tag is invoked
374 first, followed by one binding for each of the item's tags (in
375 order), followed by a binding associated with the item's id. If
376 there are multiple matching bindings for a single tag, then only
377 the most specific binding is invoked. A continue command in a
378 binding script terminates that script, and a break command ter‐
379 minates that script and skips any remaining scripts for the
380 event, just as for the bind command.
381 If bindings have been created for a canvas window using the bind
383 command, then they are invoked in addition to bindings created
384 for the canvas's items using the bind widget command. The bind‐
385 ings for items will be invoked before any of the bindings for
386 the window as a whole.
387 pathName canvasx screenx ?gridspacing?
389 Given a window x-coordinate in the canvas screenx, this command
390 returns the canvas x-coordinate that is displayed at that loca‐
391 tion. If gridspacing is specified, then the canvas coordinate
392 is rounded to the nearest multiple of gridspacing units.
393 pathName canvasy screeny ?gridspacing?
395 Given a window y-coordinate in the canvas screeny this command
396 returns the canvas y-coordinate that is displayed at that loca‐
397 tion. If gridspacing is specified, then the canvas coordinate
398 is rounded to the nearest multiple of gridspacing units.
399 pathName cget option
401 Returns the current value of the configuration option given by
402 option. Option may have any of the values accepted by the can‐
403 vas command.
404 pathName configure ?option? ?value? ?option value ...?
406 Query or modify the configuration options of the widget. If no
407 option is specified, returns a list describing all of the avail‐
408 able options for pathName (see Tk_ConfigureInfo for information
409 on the format of this list). If option is specified with no
410 value, then the command returns a list describing the one named
411 option (this list will be identical to the corresponding sublist
412 of the value returned if no option is specified). If one or
413 more option-value pairs are specified, then the command modifies
414 the given widget option(s) to have the given value(s); in this
415 case the command returns an empty string. Option may have any
416 of the values accepted by the canvas command.
417 pathName coords tagOrId ?x0 y0 ...?
419 pathName coords tagOrId ?coordList?
421 Query or modify the coordinates that define an item. If no
422 coordinates are specified, this command returns a list whose
423 elements are the coordinates of the item named by tagOrId. If
424 coordinates are specified, then they replace the current coordi‐
425 nates for the named item. If tagOrId refers to multiple items,
426 then the first one in the display list is used.
427 pathName create type x y ?x y ...? ?option value ...?
429 pathName create type coordList ?option value ...?
431 Create a new item in pathName of type type. The exact format of
432 the arguments after type depends on type, but usually they con‐
433 sist of the coordinates for one or more points, followed by
434 specifications for zero or more item options. See the subsec‐
435 tions on individual item types below for more on the syntax of
436 this command. This command returns the id for the new item.
437 pathName dchars tagOrId first ?last?
439 For each item given by tagOrId, delete the characters, or coor‐
440 dinates, in the range given by first and last, inclusive. If
441 some of the items given by tagOrId do not support indexing oper‐
442 ations then they ignore dchars. Text items interpret first and
443 last as indices to a character, line and polygon items interpret
444 them indices to a coordinate (an x,y pair). Indices are
445 described in INDICES above. If last is omitted, it defaults to
446 first. This command returns an empty string.
447 pathName delete ?tagOrId tagOrId ...?
449 Delete each of the items given by each tagOrId, and return an
450 empty string.
451 pathName dtag tagOrId ?tagToDelete?
453 For each of the items given by tagOrId, delete the tag given by
454 tagToDelete from the list of those associated with the item. If
455 an item does not have the tag tagToDelete then the item is unaf‐
456 fected by the command. If tagToDelete is omitted then it
457 defaults to tagOrId. This command returns an empty string.
458 pathName find searchCommand ?arg arg ...?
460 This command returns a list consisting of all the items that
461 meet the constraints specified by searchCommand and arg's.
462 SearchCommand and args have any of the forms accepted by the
463 addtag command. The items are returned in stacking order, with
464 the lowest item first.
465 pathName focus ?tagOrId?
467 Set the keyboard focus for the canvas widget to the item given
468 by tagOrId. If tagOrId refers to several items, then the focus
469 is set to the first such item in the display list that supports
470 the insertion cursor. If tagOrId does not refer to any items,
471 or if none of them support the insertion cursor, then the focus
472 is not changed. If tagOrId is an empty string, then the focus
473 item is reset so that no item has the focus. If tagOrId is not
474 specified then the command returns the id for the item that cur‐
475 rently has the focus, or an empty string if no item has the
476 focus.
477 Once the focus has been set to an item, the item will display
479 the insertion cursor and all keyboard events will be directed to
480 that item. The focus item within a canvas and the focus window
481 on the screen (set with the focus command) are totally indepen‐
482 dent: a given item does not actually have the input focus unless
483 (a) its canvas is the focus window and (b) the item is the focus
484 item within the canvas. In most cases it is advisable to follow
485 the focus widget command with the focus command to set the focus
486 window to the canvas (if it was not there already).
487 pathName gettags tagOrId
489 Return a list whose elements are the tags associated with the
490 item given by tagOrId. If tagOrId refers to more than one item,
491 then the tags are returned from the first such item in the dis‐
492 play list. If tagOrId does not refer to any items, or if the
493 item contains no tags, then an empty string is returned.
494 pathName icursor tagOrId index
496 Set the position of the insertion cursor for the item(s) given
497 by tagOrId to just before the character whose position is given
498 by index. If some or all of the items given by tagOrId do not
499 support an insertion cursor then this command has no effect on
500 them. See INDICES above for a description of the legal forms
501 for index. Note: the insertion cursor is only displayed in an
502 item if that item currently has the keyboard focus (see the wid‐
503 get command focus, below), but the cursor position may be set
504 even when the item does not have the focus. This command
505 returns an empty string.
506 pathName index tagOrId index
508 This command returns a decimal string giving the numerical index
509 within tagOrId corresponding to index. Index gives a textual
510 description of the desired position as described in INDICES
511 above. Text items interpret index as an index to a character,
512 line and polygon items interpret it as an index to a coordinate
513 (an x,y pair). The return value is guaranteed to lie between 0
514 and the number of characters, or coordinates, within the item,
515 inclusive. If tagOrId refers to multiple items, then the index
516 is processed in the first of these items that supports indexing
517 operations (in display list order).
518 pathName insert tagOrId beforeThis string
520 For each of the items given by tagOrId, if the item supports
521 text or coordinate, insertion then string is inserted into the
522 item's text just before the character, or coordinate, whose
523 index is beforeThis. Text items interpret beforeThis as an
524 index to a character, line and polygon items interpret it as an
525 index to a coordinate (an x,y pair). For lines and polygons the
526 string must be a valid coordinate sequence. See INDICES above
527 for information about the forms allowed for beforeThis. This
528 command returns an empty string.
529 pathName itemcget tagOrId option
531 Returns the current value of the configuration option for the
532 item given by tagOrId whose name is option. This command is
533 similar to the cget widget command except that it applies to a
534 particular item rather than the widget as a whole. Option may
535 have any of the values accepted by the create widget command
536 when the item was created. If tagOrId is a tag that refers to
537 more than one item, the first (lowest) such item is used.
538 pathName itemconfigure tagOrId ?option? ?value? ?option value ...?
540 This command is similar to the configure widget command except
541 that it modifies item-specific options for the items given by
542 tagOrId instead of modifying options for the overall canvas wid‐
543 get. If no option is specified, returns a list describing all
544 of the available options for the first item given by tagOrId
545 (see Tk_ConfigureInfo for information on the format of this
546 list). If option is specified with no value, then the command
547 returns a list describing the one named option (this list will
548 be identical to the corresponding sublist of the value returned
549 if no option is specified). If one or more option-value pairs
550 are specified, then the command modifies the given widget
551 option(s) to have the given value(s) in each of the items given
552 by tagOrId; in this case the command returns an empty string.
553 The options and values are the same as those permissible in the
554 create widget command when the item(s) were created; see the
555 sections describing individual item types below for details on
556 the legal options.
557 pathName lower tagOrId ?belowThis?
559 Move all of the items given by tagOrId to a new position in the
560 display list just before the item given by belowThis. If
561 tagOrId refers to more than one item then all are moved but the
562 relative order of the moved items will not be changed.
563 BelowThis is a tag or id; if it refers to more than one item
564 then the first (lowest) of these items in the display list is
565 used as the destination location for the moved items. Note:
566 this command has no effect on window items. Window items always
567 obscure other item types, and the stacking order of window items
568 is determined by the raise and lower commands, not the raise and
569 lower widget commands for canvases. This command returns an
570 empty string.
571 pathName move tagOrId xAmount yAmount
573 Move each of the items given by tagOrId in the canvas coordinate
574 space by adding xAmount to the x-coordinate of each point asso‐
575 ciated with the item and yAmount to the y-coordinate of each
576 point associated with the item. This command returns an empty
577 string.
578 pathName postscript ?option value option value ...?
580 Generate a Postscript representation for part or all of the can‐
581 vas. If the -file option is specified then the Postscript is
582 written to a file and an empty string is returned; otherwise
583 the Postscript is returned as the result of the command. If the
584 interpreter that owns the canvas is marked as safe, the opera‐
585 tion will fail because safe interpreters are not allowed to
586 write files. If the -channel option is specified, the argument
587 denotes the name of a channel already opened for writing. The
588 Postscript is written to that channel, and the channel is left
589 open for further writing at the end of the operation. The Post‐
590 script is created in Encapsulated Postscript form using version
591 3.0 of the Document Structuring Conventions. Note: by default
592 Postscript is only generated for information that appears in the
593 canvas's window on the screen. If the canvas is freshly created
594 it may still have its initial size of 1x1 pixel so nothing will
595 appear in the Postscript. To get around this problem either
596 invoke the update command to wait for the canvas window to reach
597 its final size, or else use the -width and -height options to
598 specify the area of the canvas to print. The option-value argu‐
599 ment pairs provide additional information to control the genera‐
600 tion of Postscript. The following options are supported:
601 -colormap varName
603 VarName must be the name of an array variable that speci‐
604 fies a color mapping to use in the Postscript. Each ele‐
605 ment of varName must consist of Postscript code to set a
606 particular color value (e.g. “1.0 1.0 0.0 setrgbcolor”).
607 When outputting color information in the Postscript, Tk
608 checks to see if there is an element of varName with the
609 same name as the color. If so, Tk uses the value of the
610 element as the Postscript command to set the color. If
611 this option has not been specified, or if there is no
612 entry in varName for a given color, then Tk uses the red,
613 green, and blue intensities from the X color.
614 -colormode mode
616 Specifies how to output color information. Mode must be
617 either color (for full color output), gray (convert all
618 colors to their gray-scale equivalents) or mono (convert
619 all colors to black or white).
620 -file fileName
622 Specifies the name of the file in which to write the
623 Postscript. If this option is not specified then the
624 Postscript is returned as the result of the command
625 instead of being written to a file.
626 -fontmap varName
628 VarName must be the name of an array variable that speci‐
629 fies a font mapping to use in the Postscript. Each ele‐
630 ment of varName must consist of a Tcl list with two ele‐
631 ments, which are the name and point size of a Postscript
632 font. When outputting Postscript commands for a particu‐
633 lar font, Tk checks to see if varName contains an element
634 with the same name as the font. If there is such an ele‐
635 ment, then the font information contained in that element
636 is used in the Postscript. Otherwise Tk attempts to
637 guess what Postscript font to use. Tk's guesses gener‐
638 ally only work for well-known fonts such as Times and
639 Helvetica and Courier, and only if the X font name does
640 not omit any dashes up through the point size. For exam‐
641 ple, -*-Courier-Bold-R-Normal--*-120-* will work but
642 *Courier-Bold-R-Normal*120* will not; Tk needs the
643 dashes to parse the font name).
644 -height size
646 Specifies the height of the area of the canvas to print.
647 Defaults to the height of the canvas window.
648 -pageanchor anchor
650 Specifies which point of the printed area of the canvas
651 should appear over the positioning point on the page
652 (which is given by the -pagex and -pagey options). For
653 example, -pageanchor n means that the top center of the
654 area of the canvas being printed (as it appears in the
655 canvas window) should be over the positioning point.
656 Defaults to center.
657 -pageheight size
659 Specifies that the Postscript should be scaled in both x
660 and y so that the printed area is size high on the Post‐
661 script page. Size consists of a floating-point number
662 followed by c for centimeters, i for inches, m for mil‐
663 limeters, or p or nothing for printer's points (1/72
664 inch). Defaults to the height of the printed area on the
665 screen. If both -pageheight and -pagewidth are specified
666 then the scale factor from -pagewidth is used (non-uni‐
667 form scaling is not implemented).
668 -pagewidth size
670 Specifies that the Postscript should be scaled in both x
671 and y so that the printed area is size wide on the Post‐
672 script page. Size has the same form as for -pageheight.
673 Defaults to the width of the printed area on the screen.
674 If both -pageheight and -pagewidth are specified then the
675 scale factor from -pagewidth is used (non-uniform scal‐
676 ing is not implemented).
677 -pagex position
679 Position gives the x-coordinate of the positioning point
680 on the Postscript page, using any of the forms allowed
681 for -pageheight. Used in conjunction with the -pagey and
682 -pageanchor options to determine where the printed area
683 appears on the Postscript page. Defaults to the center
684 of the page.
685 -pagey position
687 Position gives the y-coordinate of the positioning point
688 on the Postscript page, using any of the forms allowed
689 for -pageheight. Used in conjunction with the -pagex and
690 -pageanchor options to determine where the printed area
691 appears on the Postscript page. Defaults to the center
692 of the page.
693 -rotate boolean
695 Boolean specifies whether the printed area is to be
696 rotated 90 degrees. In non-rotated output the x-axis of
697 the printed area runs along the short dimension of the
698 page (“portrait”orientation); in rotated output the x-
699 axis runs along the long dimension of the page (“land‐
700 scape”orientation). Defaults to non-rotated.
701 -width size
703 Specifies the width of the area of the canvas to print.
704 Defaults to the width of the canvas window.
705 -x position
707 Specifies the x-coordinate of the left edge of the area
708 of the canvas that is to be printed, in canvas coordi‐
709 nates, not window coordinates. Defaults to the coordi‐
710 nate of the left edge of the window.
711 -y position
713 Specifies the y-coordinate of the top edge of the area of
714 the canvas that is to be printed, in canvas coordinates,
715 not window coordinates. Defaults to the coordinate of
716 the top edge of the window.
717 pathName raise tagOrId ?aboveThis?
719 Move all of the items given by tagOrId to a new position in the
720 display list just after the item given by aboveThis. If tagOrId
721 refers to more than one item then all are moved but the relative
722 order of the moved items will not be changed. AboveThis is a
723 tag or id; if it refers to more than one item then the last
724 (topmost) of these items in the display list is used as the des‐
725 tination location for the moved items. Note: this command has
726 no effect on window items. Window items always obscure other
727 item types, and the stacking order of window items is determined
728 by the raise and lower commands, not the raise and lower widget
729 commands for canvases. This command returns an empty string.
730 pathName scale tagOrId xOrigin yOrigin xScale yScale
732 Rescale all of the items given by tagOrId in canvas coordinate
733 space. XOrigin and yOrigin identify the origin for the scaling
734 operation and xScale and yScale identify the scale factors for
735 x- and y-coordinates, respectively (a scale factor of 1.0
736 implies no change to that coordinate). For each of the points
737 defining each item, the x-coordinate is adjusted to change the
738 distance from xOrigin by a factor of xScale. Similarly, each y-
739 coordinate is adjusted to change the distance from yOrigin by a
740 factor of yScale. This command returns an empty string.
741 pathName scan option args
743 This command is used to implement scanning on canvases. It has
744 two forms, depending on option:
745 pathName scan mark x y
747 Records x and y and the canvas's current view; used in
748 conjunction with later scan dragto commands. Typically
749 this command is associated with a mouse button press in
750 the widget and x and y are the coordinates of the mouse.
751 It returns an empty string.
752 pathName scan dragto x y ?gain?.
754 This command computes the difference between its x and y
755 arguments (which are typically mouse coordinates) and the
756 x and y arguments to the last scan mark command for the
757 widget. It then adjusts the view by gain times the dif‐
758 ference in coordinates, where gain defaults to 10. This
759 command is typically associated with mouse motion events
760 in the widget, to produce the effect of dragging the can‐
761 vas at high speed through its window. The return value
762 is an empty string.
763 pathName select option ?tagOrId arg?
765 Manipulates the selection in one of several ways, depending on
766 option. The command may take any of the forms described below.
767 In all of the descriptions below, tagOrId must refer to an item
768 that supports indexing and selection; if it refers to multiple
769 items then the first of these that supports indexing and the
770 selection is used. Index gives a textual description of a posi‐
771 tion within tagOrId, as described in INDICES above.
772 pathName select adjust tagOrId index
774 Locate the end of the selection in tagOrId nearest to the
775 character given by index, and adjust that end of the
776 selection to be at index (i.e. including but not going
777 beyond index). The other end of the selection is made
778 the anchor point for future select to commands. If the
779 selection is not currently in tagOrId then this command
780 behaves the same as the select to widget command.
781 Returns an empty string.
782 pathName select clear
784 Clear the selection if it is in this widget. If the
785 selection is not in this widget then the command has no
786 effect. Returns an empty string.
787 pathName select from tagOrId index
789 Set the selection anchor point for the widget to be just
790 before the character given by index in the item given by
791 tagOrId. This command does not change the selection; it
792 just sets the fixed end of the selection for future
793 select to commands. Returns an empty string.
794 pathName select item
796 Returns the id of the selected item, if the selection is
797 in an item in this canvas. If the selection is not in
798 this canvas then an empty string is returned.
799 pathName select to tagOrId index
801 Set the selection to consist of those characters of
802 tagOrId between the selection anchor point and index.
803 The new selection will include the character given by
804 index; it will include the character given by the anchor
805 point only if index is greater than or equal to the
806 anchor point. The anchor point is determined by the most
807 recent select adjust or select from command for this wid‐
808 get. If the selection anchor point for the widget is not
809 currently in tagOrId, then it is set to the same charac‐
810 ter given by index. Returns an empty string.
811 pathName type tagOrId
813 Returns the type of the item given by tagOrId, such as rectangle
814 or text. If tagOrId refers to more than one item, then the type
815 of the first item in the display list is returned. If tagOrId
816 does not refer to any items at all then an empty string is
817 returned.
818 pathName xview ?args?
820 This command is used to query and change the horizontal position
821 of the information displayed in the canvas's window. It can
822 take any of the following forms:
823 pathName xview
825 Returns a list containing two elements. Each element is
826 a real fraction between 0 and 1; together they describe
827 the horizontal span that is visible in the window. For
828 example, if the first element is .2 and the second ele‐
829 ment is .6, 20% of the canvas's area (as defined by the
830 -scrollregion option) is off-screen to the left, the mid‐
831 dle 40% is visible in the window, and 40% of the canvas
832 is off-screen to the right. These are the same values
833 passed to scrollbars via the -xscrollcommand option.
834 pathName xview moveto fraction
836 Adjusts the view in the window so that fraction of the
837 total width of the canvas is off-screen to the left.
838 Fraction must be a fraction between 0 and 1.
839 pathName xview scroll number what
841 This command shifts the view in the window left or right
842 according to number and what. Number must be an integer.
843 What must be either units or pages or an abbreviation of
844 one of these. If what is units, the view adjusts left or
845 right in units of the xScrollIncrement option, if it is
846 greater than zero, or in units of one-tenth the window's
847 width otherwise. If what is pages then the view adjusts
848 in units of nine-tenths the window's width. If number is
849 negative then information farther to the left becomes
850 visible; if it is positive then information farther to
851 the right becomes visible.
852 pathName yview ?args?
854 This command is used to query and change the vertical position
855 of the information displayed in the canvas's window. It can
856 take any of the following forms:
857 pathName yview
859 Returns a list containing two elements. Each element is
860 a real fraction between 0 and 1; together they describe
861 the vertical span that is visible in the window. For
862 example, if the first element is .6 and the second ele‐
863 ment is 1.0, the lowest 40% of the canvas's area (as
864 defined by the -scrollregion option) is visible in the
865 window. These are the same values passed to scrollbars
866 via the -yscrollcommand option.
867 pathName yview moveto fraction
869 Adjusts the view in the window so that fraction of the
870 canvas's area is off-screen to the top. Fraction is a
871 fraction between 0 and 1.
872 pathName yview scroll number what
874 This command adjusts the view in the window up or down
875 according to number and what. Number must be an integer.
876 What must be either units or pages. If what is units,
877 the view adjusts up or down in units of the yScrollIncre‐
878 ment option, if it is greater than zero, or in units of
879 one-tenth the window's height otherwise. If what is
880 pages then the view adjusts in units of nine-tenths the
881 window's height. If number is negative then higher
882 information becomes visible; if it is positive then
883 lower information becomes visible.
884
886 The sections below describe the various types of items supported by
887 canvas widgets. Each item type is characterized by two things: first,
888 the form of the create command used to create instances of the type;
889 and second, a set of configuration options for items of that type,
890 which may be used in the create and itemconfigure widget commands.
891 Most items do not support indexing or selection or the commands related
892 to them, such as index and insert. Where items do support these facil‐
893 ities, it is noted explicitly in the descriptions below. At present,
894 text, line and polygon items provide this support. For lines and poly‐
895 gons the indexing facility is used to manipulate the coordinates of the
896 item.
897 COMMON ITEM OPTIONS
899 Many items share a common set of options. These options are explained
900 here, and then referred to be each widget type for brevity.
901 -dash pattern
903 -activedash pattern
905 -disableddash pattern
907 This option specifies dash patterns for the normal, active
908 state, and disabled state of an item. pattern may have any of
909 the forms accepted by Tk_GetDash. If the dash options are omit‐
910 ted then the default is a solid outline. See DASH PATTERNS for
911 more information.
912 -dashoffset offset
914 The starting offset in pixels into the pattern provided by the
915 -dash option. -dashoffset is ignored if there is no -dash pat‐
916 tern. The offset may have any of the forms described in the
917 COORDINATES section above.
918 -fill color
920 -activefill color
922 -disabledfill color
924 Specifies the color to be used to fill item's area. in its nor‐
925 mal, active, and disabled states, Color may have any of the
926 forms accepted by Tk_GetColor. If color is an empty string (the
927 default), then the item will not be filled. For the line item,
928 it specifies the color of the line drawn. For the text item, it
929 specifies the foreground color of the text.
930 -outline color
932 -activeoutline color
934 -disabledoutline color
936 This option specifies the color that should be used to draw the
937 outline of the item in its normal, active and disabled states.
938 Color may have any of the forms accepted by Tk_GetColor. This
939 option defaults to black. If color is specified as an empty
940 string then no outline is drawn for the item.
941 -offset offset
943 Specifies the offset of stipples. The offset value can be of
944 the form x,y or side, where side can be n, ne, e, se, s, sw, w,
945 nw, or center. In the first case the origin is the origin of the
946 toplevel of the current window. For the canvas itself and can‐
947 vas objects the origin is the canvas origin, but putting # in
948 front of the coordinate pair indicates using the toplevel origin
949 instead. For canvas objects, the -offset option is used for
950 stippling as well. For the line and polygon canvas items you
951 can also specify an index as argument, which connects the stip‐
952 ple origin to one of the coordinate points of the line/polygon.
953 -outlinestipple bitmap
955 -activeoutlinestipple bitmap
957 -disabledoutlinestipple bitmap
959 This option specifies stipple patterns that should be used to
960 draw the outline of the item in its normal, active and disabled
961 states. Indicates that the outline for the item should be drawn
962 with a stipple pattern; bitmap specifies the stipple pattern to
963 use, in any of the forms accepted by Tk_GetBitmap. If the -out‐
964 line option has not been specified then this option has no
965 effect. If bitmap is an empty string (the default), then the
966 outline is drawn in a solid fashion. Note that stipples are not
967 well supported on platforms that do not use X11 as their drawing
968 API.
969 -outlineoffset offset
971 Specifies the offset of the stipple pattern used for outlines.
972 The offset value can be of the form “x,y” or the description of
973 a side (one of n, ne, e, se, s, sw, w, nw, or center). This
974 option only has an effect when the outline is drawn as a stipple
975 pattern, and is only supported under X11.
976 -stipple bitmap
978 -activestipple bitmap
980 -disabledstipple bitmap
982 This option specifies stipple patterns that should be used to
983 fill the item in its normal, active and disabled states. bitmap
984 specifies the stipple pattern to use, in any of the forms
985 accepted by Tk_GetBitmap. If the -fill option has not been
986 specified then this option has no effect. If bitmap is an empty
987 string (the default), then filling is done in a solid fashion.
988 For the text item, it affects the actual text. Note that stip‐
989 ples are not well supported on platforms that do not use X11 as
990 their drawing API.
991 -state state
993 This allows an item to override the canvas widget's global state
994 option. It takes the same values: normal, disabled or hidden.
995 -tags tagList
997 Specifies a set of tags to apply to the item. TagList consists
998 of a list of tag names, which replace any existing tags for the
999 item. TagList may be an empty list.
1000 -width outlineWidth
1002 -activewidth outlineWidth
1004 -disabledwidth outlineWidth
1006 Specifies the width of the outline to be drawn around the item's
1007 region, in its normal, active and disabled states. outlineWidth
1008 may be in any of the forms described in the COORDINATES section
1009 above. If the -outline option has been specified as an empty
1010 string then this option has no effect. This option defaults to
1011 1.0. For arcs, wide outlines will be drawn centered on the
1012 edges of the arc's region.
1013
1015 Items of type arc appear on the display as arc-shaped regions. An arc
1016 is a section of an oval delimited by two angles (specified by the
1017 -start and -extent options) and displayed in one of several ways (spec‐
1018 ified by the -style option). Arcs are created with widget commands of
1019 the following form:
1020 pathName create arc x1 y1 x2 y2 ?option value option value ...?
1021 pathName create arc coordList ?option value option value ...?
1022 The arguments x1, y1, x2, and y2 or coordList give the coordinates of
1023 two diagonally opposite corners of a rectangular region enclosing the
1024 oval that defines the arc. After the coordinates there may be any num‐
1025 ber of option-value pairs, each of which sets one of the configuration
1026 options for the item. These same option-value pairs may be used in
1027 itemconfigure widget commands to change the item's configuration. An
1028 arc item becomes the current item when the mouse pointer is over any
1029 part that is painted or (when fully transparent) that would be painted
1030 if both the -fill and -outline options were non-empty.
1031 The following standard options are supported by arcs:
1033 -dash
1034 -activedash
1035 -disableddash
1036 -dashoffset
1037 -fill
1038 -activefill
1039 -disabledfill
1040 -offset
1041 -outline
1042 -activeoutline
1043 -disabledoutline
1044 -outlineoffset
1045 -outlinestipple
1046 -activeoutlinestipple
1047 -disabledoutlinestipple
1048 -stipple
1049 -activestipple
1050 -disabledstipple
1051 -state
1052 -tags
1053 -width
1054 -activewidth
1055 -disabledwidth
1056 The following extra options are supported for arcs:
1057 -extent degrees
1059 Specifies the size of the angular range occupied by the arc.
1060 The arc's range extends for degrees degrees counter-clockwise
1061 from the starting angle given by the -start option. Degrees may
1062 be negative. If it is greater than 360 or less than -360, then
1063 degrees modulo 360 is used as the extent.
1064 -start degrees
1066 Specifies the beginning of the angular range occupied by the
1067 arc. Degrees is given in units of degrees measured counter-
1068 clockwise from the 3-o'clock position; it may be either posi‐
1069 tive or negative.
1070 -style type
1072 Specifies how to draw the arc. If type is pieslice (the
1073 default) then the arc's region is defined by a section of the
1074 oval's perimeter plus two line segments, one between the center
1075 of the oval and each end of the perimeter section. If type is
1076 chord then the arc's region is defined by a section of the
1077 oval's perimeter plus a single line segment connecting the two
1078 end points of the perimeter section. If type is arc then the
1079 arc's region consists of a section of the perimeter alone. In
1080 this last case the -fill option is ignored.
1081
1083 Items of type bitmap appear on the display as images with two colors,
1084 foreground and background. Bitmaps are created with widget commands of
1085 the following form:
1086 pathName create bitmap x y ?option value option value ...?
1087 pathName create bitmap coordList ?option value option value ...?
1088 The arguments x and y or coordList (which must have two elements) spec‐
1089 ify the coordinates of a point used to position the bitmap on the dis‐
1090 play (see the -anchor option below for more information on how bitmaps
1091 are displayed). After the coordinates there may be any number of
1092 option-value pairs, each of which sets one of the configuration options
1093 for the item. These same option-value pairs may be used in itemconfig‐
1094 ure widget commands to change the item's configuration. A bitmap item
1095 becomes the current item when the mouse pointer is over any part of its
1096 bounding box.
1097 The following standard options are supported by bitmaps:
1099 -state
1100 -tags
1101 The following extra options are supported for bitmaps:
1102 -anchor anchorPos
1104 AnchorPos tells how to position the bitmap relative to the posi‐
1105 tioning point for the item; it may have any of the forms
1106 accepted by Tk_GetAnchor. For example, if anchorPos is center
1107 then the bitmap is centered on the point; if anchorPos is n
1108 then the bitmap will be drawn so that its top center point is at
1109 the positioning point. This option defaults to center.
1110 -background color
1112 -activebackground color
1114 -disabledbackground color
1116 Specifies the color to use for each of the bitmap's “0” valued
1117 pixels in its normal, active and disabled states. Color may
1118 have any of the forms accepted by Tk_GetColor. If this option
1119 is not specified, or if it is specified as an empty string, then
1120 nothing is displayed where the bitmap pixels are 0; this pro‐
1121 duces a transparent effect.
1122 -bitmap bitmap
1124 -activebitmap bitmap
1126 -disabledbitmap bitmap
1128 Specifies the bitmaps to display in the item in its normal,
1129 active and disabled states. Bitmap may have any of the forms
1130 accepted by Tk_GetBitmap.
1131 -foreground color
1133 -activeforeground color
1135 -disabledforeground color
1137 Specifies the color to use for each of the bitmap's “1” valued
1138 pixels in its normal, active and disabled states. Color may
1139 have any of the forms accepted by Tk_GetColor and defaults to
1140 black.
1141
1143 Items of type image are used to display images on a canvas. Images are
1144 created with widget commands of the following form:
1145 pathName create image x y ?option value option value ...?
1146 pathName create image coordList ?option value option value ...?
1147 The arguments x and y or coordList specify the coordinates of a point
1148 used to position the image on the display (see the -anchor option below
1149 for more information). After the coordinates there may be any number
1150 of option-value pairs, each of which sets one of the configuration
1151 options for the item. These same option-value pairs may be used in
1152 itemconfigure widget commands to change the item's configuration. An
1153 image item becomes the current item when the mouse pointer is over any
1154 part of its bounding box.
1155 The following standard options are supported by images:
1157 -state
1158 -tags
1159 The following extra options are supported for images:
1160 -anchor anchorPos
1162 AnchorPos tells how to position the image relative to the posi‐
1163 tioning point for the item; it may have any of the forms
1164 accepted by Tk_GetAnchor. For example, if anchorPos is center
1165 then the image is centered on the point; if anchorPos is n then
1166 the image will be drawn so that its top center point is at the
1167 positioning point. This option defaults to center.
1168 -image name
1170 -activeimage name
1172 -disabledimage name
1174 Specifies the name of the images to display in the item in is
1175 normal, active and disabled states. This image must have been
1176 created previously with the image create command.
1177
1179 Items of type line appear on the display as one or more connected line
1180 segments or curves. Line items support coordinate indexing operations
1181 using the canvas widget commands: dchars, index, insert. Lines are
1182 created with widget commands of the following form:
1183 pathName create line x1 y1... xn yn ?option value option value ...?
1184 pathName create line coordList ?option value option value ...?
1185 The arguments x1 through yn or coordList give the coordinates for a
1186 series of two or more points that describe a series of connected line
1187 segments. After the coordinates there may be any number of
1188 option-value pairs, each of which sets one of the configuration options
1189 for the item. These same option-value pairs may be used in itemconfig‐
1190 ure widget commands to change the item's configuration. A line item is
1191 the current item whenever the mouse pointer is over any segment of the
1192 line, whether drawn or not and whether or not the line is smoothed.
1193 The following standard options are supported by lines:
1195 -dash
1196 -activedash
1197 -disableddash
1198 -dashoffset
1199 -fill
1200 -activefill
1201 -disabledfill
1202 -stipple
1203 -activestipple
1204 -disabledstipple
1205 -state
1206 -tags
1207 -width
1208 -activewidth
1209 -disabledwidth
1210 The following extra options are supported for lines:
1211 -arrow where
1213 Indicates whether or not arrowheads are to be drawn at one or
1214 both ends of the line. Where must have one of the values none
1215 (for no arrowheads), first (for an arrowhead at the first point
1216 of the line), last (for an arrowhead at the last point of the
1217 line), or both (for arrowheads at both ends). This option
1218 defaults to none.
1219 -arrowshape shape
1221 This option indicates how to draw arrowheads. The shape argu‐
1222 ment must be a list with three elements, each specifying a dis‐
1223 tance in any of the forms described in the COORDINATES section
1224 above. The first element of the list gives the distance along
1225 the line from the neck of the arrowhead to its tip. The second
1226 element gives the distance along the line from the trailing
1227 points of the arrowhead to the tip, and the third element gives
1228 the distance from the outside edge of the line to the trailing
1229 points. If this option is not specified then Tk picks a “rea‐
1230 sonable” shape.
1231 -capstyle style
1233 Specifies the ways in which caps are to be drawn at the end‐
1234 points of the line. Style may have any of the forms accepted by
1235 Tk_GetCapStyle (butt, projecting, or round). If this option is
1236 not specified then it defaults to butt. Where arrowheads are
1237 drawn the cap style is ignored.
1238 -joinstyle style
1240 Specifies the ways in which joints are to be drawn at the ver‐
1241 tices of the line. Style may have any of the forms accepted by
1242 Tk_GetCapStyle (bevel, miter, or round). If this option is not
1243 specified then it defaults to round. If the line only contains
1244 two points then this option is irrelevant.
1245 -smooth smoothMethod
1247 smoothMethod must have one of the forms accepted by Tcl_Get‐
1248 Boolean or a line smoothing method. Only true and raw are sup‐ │
1249 ported in the core (with bezier being an alias for true), but │
1250 more can be added at runtime. If a boolean false value or empty │
1251 string is given, no smoothing is applied. A boolean truth value │
1252 assumes true smoothing. If the smoothing method is true, this │
1253 indicates that the line should be drawn as a curve, rendered as │
1254 a set of quadratic splines: one spline is drawn for the first │
1255 and second line segments, one for the second and third, and so │
1256 on. Straight-line segments can be generated within a curve by │
1257 duplicating the end-points of the desired line segment. If the │
1258 smoothing method is raw, this indicates that the line should │
1259 also be drawn as a curve but where the list of coordinates is │
1260 such that the first coordinate pair (and every third coordinate │
1261 pair thereafter) is a knot point on a cubic Bezier curve, and │
1262 the other coordinates are control points on the cubic Bezier │
1263 curve. Straight line segments can be generated within a curve │
1264 by making control points equal to their neighbouring knot │
1265 points. If the last point is a control point and not a knot │
1266 point, the point is repeated (one or two times) so that it also │
1267 becomes a knot point.
1268 -splinesteps number
1270 Specifies the degree of smoothness desired for curves: each
1271 spline will be approximated with number line segments. This
1272 option is ignored unless the -smooth option is true or raw.
1273
1275 Items of type oval appear as circular or oval regions on the display.
1276 Each oval may have an outline, a fill, or both. Ovals are created with
1277 widget commands of the following form:
1278 pathName create oval x1 y1 x2 y2 ?option value option value ...?
1279 pathName create oval coordList ?option value option value ...?
1280 The arguments x1, y1, x2, and y2 or coordList give the coordinates of
1281 two diagonally opposite corners of a rectangular region enclosing the
1282 oval. The oval will include the top and left edges of the rectangle
1283 not the lower or right edges. If the region is square then the result‐
1284 ing oval is circular; otherwise it is elongated in shape. After the
1285 coordinates there may be any number of option-value pairs, each of
1286 which sets one of the configuration options for the item. These same
1287 option-value pairs may be used in itemconfigure widget commands to
1288 change the item's configuration. An oval item becomes the current item
1289 when the mouse pointer is over any part that is painted or (when fully
1290 transparent) that would be painted if both the -fill and -outline
1291 options were non-empty.
1292 The following standard options are supported by ovals:
1294 -dash
1295 -activedash
1296 -disableddash
1297 -dashoffset
1298 -fill
1299 -activefill
1300 -disabledfill
1301 -offset
1302 -outline
1303 -activeoutline
1304 -disabledoutline
1305 -outlineoffset
1306 -outlinestipple
1307 -activeoutlinestipple
1308 -disabledoutlinestipple
1309 -stipple
1310 -activestipple
1311 -disabledstipple
1312 -state
1313 -tags
1314 -width
1315 -activewidth
1316 -disabledwidth
1317
1319 Items of type polygon appear as polygonal or curved filled regions on
1320 the display. Polygon items support coordinate indexing operations
1321 using the canvas widget commands: dchars, index, insert. Polygons are
1322 created with widget commands of the following form:
1323 pathName create polygon x1 y1 ... xn yn ?option value option value ...?
1324 pathName create polygon coordList ?option value option value ...?
1325 The arguments x1 through yn or coordList specify the coordinates for
1326 three or more points that define a polygon. The first point should not
1327 be repeated as the last to close the shape; Tk will automatically close
1328 the periphery between the first and last points. After the coordinates
1329 there may be any number of option-value pairs, each of which sets one
1330 of the configuration options for the item. These same option-value
1331 pairs may be used in itemconfigure widget commands to change the item's
1332 configuration. A polygon item is the current item whenever the mouse
1333 pointer is over any part of the polygon, whether drawn or not and
1334 whether or not the outline is smoothed.
1335 The following standard options are supported by polygons:
1337 -dash
1338 -activedash
1339 -disableddash
1340 -dashoffset
1341 -fill
1342 -activefill
1343 -disabledfill
1344 -offset
1345 -outline
1346 -activeoutline
1347 -disabledoutline
1348 -outlinestipple
1349 -activeoutlinestipple
1350 -disabledoutlinestipple
1351 -stipple
1352 -activestipple
1353 -disabledstipple
1354 -state
1355 -tags
1356 -width
1357 -activewidth
1358 -disabledwidth
1359 The following extra options are supported for polygons:
1360 -joinstyle style
1362 Specifies the ways in which joints are to be drawn at the ver‐
1363 tices of the outline. Style may have any of the forms accepted
1364 by Tk_GetCapStyle (bevel, miter, or round). If this option is
1365 not specified then it defaults to round.
1366 -smooth boolean
1368 Boolean must have one of the forms accepted by Tcl_GetBoolean or │
1369 a line smoothing method. Only true and raw are supported in the │
1370 core (with bezier being an alias for true), but more can be │
1371 added at runtime. If a boolean false value or empty string is │
1372 given, no smoothing is applied. A boolean truth value assumes │
1373 true smoothing. If the smoothing method is true, this indicates │
1374 that the polygon should be drawn as a curve, rendered as a set │
1375 of quadratic splines: one spline is drawn for the first and sec‐ │
1376 ond line segments, one for the second and third, and so on. │
1377 Straight-line segments can be generated within a curve by dupli‐ │
1378 cating the end-points of the desired line segment. If the │
1379 smoothing method is raw, this indicates that the polygon should │
1380 also be drawn as a curve but where the list of coordinates is │
1381 such that the first coordinate pair (and every third coordinate │
1382 pair thereafter) is a knot point on a cubic Bezier curve, and │
1383 the other coordinates are control points on the cubic Bezier │
1384 curve. Straight line segments can be venerated within a curve │
1385 by making control points equal to their neighbouring knot │
1386 points. If the last point is not the second point of a pair of │
1387 control points, the point is repeated (one or two times) so that │
1388 it also becomes the second point of a pair of control points │
1389 (the associated knot point will be the first control point).
1390 -splinesteps number
1392 Specifies the degree of smoothness desired for curves: each
1393 spline will be approximated with number line segments. This
1394 option is ignored unless the -smooth option is true or raw.
1395 Polygon items are different from other items such as rectangles, ovals
1397 and arcs in that interior points are considered to be “inside” a poly‐
1398 gon (e.g. for purposes of the find closest and find overlapping widget
1399 commands) even if it is not filled. For most other item types, an
1400 interior point is considered to be inside the item only if the item is
1401 filled or if it has neither a fill nor an outline. If you would like
1402 an unfilled polygon whose interior points are not considered to be
1403 inside the polygon, use a line item instead.
1404
1406 Items of type rectangle appear as rectangular regions on the display.
1407 Each rectangle may have an outline, a fill, or both. Rectangles are
1408 created with widget commands of the following form:
1409 pathName create rectangle x1 y1 x2 y2 ?option value option value ...?
1410 pathName create rectangle coordList ?option value option value ...?
1411 The arguments x1, y1, x2, and y2 or coordList (which must have four
1412 elements) give the coordinates of two diagonally opposite corners of
1413 the rectangle (the rectangle will include its upper and left edges but
1414 not its lower or right edges). After the coordinates there may be any
1415 number of option-value pairs, each of which sets one of the configura‐
1416 tion options for the item. These same option-value pairs may be used
1417 in itemconfigure widget commands to change the item's configuration. A
1418 rectangle item becomes the current item when the mouse pointer is over
1419 any part that is painted or (when fully transparent) that would be
1420 painted if both the -fill and -outline options were non-empty.
1421 The following standard options are supported by rectangles:
1423 -dash
1424 -activedash
1425 -disableddash
1426 -dashoffset
1427 -fill
1428 -activefill
1429 -disabledfill
1430 -offset
1431 -outline
1432 -activeoutline
1433 -disabledoutline
1434 -outlineoffset
1435 -outlinestipple
1436 -activeoutlinestipple
1437 -disabledoutlinestipple
1438 -stipple
1439 -activestipple
1440 -disabledstipple
1441 -state
1442 -tags
1443 -width
1444 -activewidth
1445 -disabledwidth
1446
1448 A text item displays a string of characters on the screen in one or
1449 more lines. Text items support indexing and selection, along with the
1450 following text-related canvas widget commands: dchars, focus, icursor,
1451 index, insert, select. Text items are created with widget commands of
1452 the following form:
1453 pathName create text x y ?option value option value ...?
1454 pathName create text coordList ?option value option value ...?
1455 The arguments x and y or coordList (which must have two elements) spec‐
1456 ify the coordinates of a point used to position the text on the display
1457 (see the options below for more information on how text is displayed).
1458 After the coordinates there may be any number of option-value pairs,
1459 each of which sets one of the configuration options for the item.
1460 These same option-value pairs may be used in itemconfigure widget com‐
1461 mands to change the item's configuration. A text item becomes the cur‐
1462 rent item when the mouse pointer is over any part of its bounding box.
1463 The following standard options are supported by text items:
1465 -fill
1466 -activefill
1467 -disabledfill
1468 -stipple
1469 -activestipple
1470 -disabledstipple
1471 -state
1472 -tags
1473 The following extra options are supported for text items:
1474 -anchor anchorPos
1476 AnchorPos tells how to position the text relative to the posi‐
1477 tioning point for the text; it may have any of the forms
1478 accepted by Tk_GetAnchor. For example, if anchorPos is center
1479 then the text is centered on the point; if anchorPos is n then
1480 the text will be drawn such that the top center point of the
1481 rectangular region occupied by the text will be at the position‐
1482 ing point. This option defaults to center.
1483 -font fontName
1485 Specifies the font to use for the text item. FontName may be
1486 any string acceptable to Tk_GetFont. If this option is not
1487 specified, it defaults to a system-dependent font.
1488 -justify how
1490 Specifies how to justify the text within its bounding region.
1491 How must be one of the values left, right, or center. This
1492 option will only matter if the text is displayed as multiple
1493 lines. If the option is omitted, it defaults to left.
1494 -text string
1496 String specifies the characters to be displayed in the text
1497 item. Newline characters cause line breaks. The characters in
1498 the item may also be changed with the insert and delete widget
1499 commands. This option defaults to an empty string. │
1500 -underline │
1502 Specifies the integer index of a character within the text to be │
1503 underlined. 0 corresponds to the first character of the text │
1504 displayed, 1 to the next character, and so on. -1 means that no │
1505 underline should be drawn (if the whole text item is to be │
1506 underlined, the appropriate font should be used instead).
1507 -width lineLength
1509 Specifies a maximum line length for the text, in any of the
1510 forms described in the COORDINATES section above. If this
1511 option is zero (the default) the text is broken into lines only
1512 at newline characters. However, if this option is non-zero then
1513 any line that would be longer than lineLength is broken just
1514 before a space character to make the line shorter than line‐
1515 Length; the space character is treated as if it were a newline
1516 character.
1517
1519 Items of type window cause a particular window to be displayed at a
1520 given position on the canvas. Window items are created with widget
1521 commands of the following form:
1522 pathName create window x y ?option value option value ...?
1523 pathName create window coordList ?option value option value ...?
1524 The arguments x and y or coordList (which must have two elements) spec‐
1525 ify the coordinates of a point used to position the window on the dis‐
1526 play (see the -anchor option below for more information on how bitmaps
1527 are displayed). After the coordinates there may be any number of
1528 option-value pairs, each of which sets one of the configuration options
1529 for the item. These same option-value pairs may be used in itemconfig‐
1530 ure widget commands to change the item's configuration. Theoretically,
1531 a window item becomes the current item when the mouse pointer is over
1532 any part of its bounding box, but in practice this typically does not
1533 happen because the mouse pointer ceases to be over the canvas at that
1534 point.
1535 The following standard options are supported by window items:
1537 -state
1538 -tags
1539 The following extra options are supported for window items:
1540 -anchor anchorPos
1542 AnchorPos tells how to position the window relative to the posi‐
1543 tioning point for the item; it may have any of the forms
1544 accepted by Tk_GetAnchor. For example, if anchorPos is center
1545 then the window is centered on the point; if anchorPos is n
1546 then the window will be drawn so that its top center point is at
1547 the positioning point. This option defaults to center.
1548 -height pixels
1550 Specifies the height to assign to the item's window. Pixels may
1551 have any of the forms described in the COORDINATES section
1552 above. If this option is not specified, or if it is specified
1553 as zero, then the window is given whatever height it requests
1554 internally.
1555 -width pixels
1557 Specifies the width to assign to the item's window. Pixels may
1558 have any of the forms described in the COORDINATES section
1559 above. If this option is not specified, or if it is specified
1560 as zero, then the window is given whatever width it requests
1561 internally.
1562 -window pathName
1564 Specifies the window to associate with this item. The window
1565 specified by pathName must either be a child of the canvas wid‐
1566 get or a child of some ancestor of the canvas widget. PathName
1567 may not refer to a top-level window.
1568 Note: due to restrictions in the ways that windows are managed, it is
1570 not possible to draw other graphical items (such as lines and images)
1571 on top of window items. A window item always obscures any graphics
1572 that overlap it, regardless of their order in the display list. Also
1573 note that window items, unlike other canvas items, are not clipped for
1574 display by their containing canvas's border, and are instead clipped by
1575 the parent widget of the window specified by the -window option; when
1576 the parent widget is the canvas, this means that the window item can
1577 overlap the canvas's border.
1578
1580 It is possible for individual applications to define new item types for
1581 canvas widgets using C code. See the documentation for Tk_CreateItem‐
1582 Type.
1583
1585 In the current implementation, new canvases are not given any default
1586 behavior: you will have to execute explicit Tcl commands to give the
1587 canvas its behavior.
1588
1590 Tk's canvas widget is a blatant ripoff of ideas from Joel Bartlett's
1591 ezd program. Ezd provides structured graphics in a Scheme environment
1592 and preceded canvases by a year or two. Its simple mechanisms for
1593 placing and animating graphical objects inspired the functions of can‐
1594 vases.
1595
1597 bind(n), font(n), image(n), scrollbar(n)
1598
1600 canvas, widget
1601Tk 8.3 canvas(n)