1canvas(n) Tk Built-In Commands canvas(n)
2______________________________________________________________________________
6
8 canvas - Create and manipulate 'canvas' hypergraphics drawing surface
9 widgets
10
12 canvas pathName ?options?
13
15 -background -borderwidth -cursor
16 -highlightbackground -highlightcolor -highlightthickness
17 -insertbackground -insertborderwidth -insertofftime
18 -insertontime -insertwidth -relief
19 -selectbackground -selectborderwidth -selectforeground
20 -takefocus -xscrollcommand -yscrollcommand
21 See the options manual entry for details on the standard options.
23
25 Command-Line Name:-closeenough
26 Database Name: closeEnough
27 Database Class: CloseEnough
28 Specifies a floating-point value indicating how close the mouse
30 cursor must be to an item before it is considered to be “inside”
31 the item. Defaults to 1.0.
32 Command-Line Name:-confine
34 Database Name: confine
35 Database Class: Confine
36 Specifies a boolean value that indicates whether or not it
38 should be allowable to set the canvas's view outside the region
39 defined by the scrollRegion argument. Defaults to true, which
40 means that the view will be constrained within the scroll re‐
41 gion.
42 Command-Line Name:-height
44 Database Name: height
45 Database Class: Height
46 Specifies a desired window height that the canvas widget should
48 request from its geometry manager. The value may be specified in
49 any of the forms described in the COORDINATES section below.
50 Command-Line Name:-scrollregion
52 Database Name: scrollRegion
53 Database Class: ScrollRegion
54 Specifies a list with four coordinates describing the left, top,
56 right, and bottom coordinates of a rectangular region. This re‐
57 gion is used for scrolling purposes and is considered to be the
58 boundary of the information in the canvas. Each of the coordi‐
59 nates may be specified in any of the forms given in the COORDI‐
60 NATES section below.
61 Command-Line Name:-state
63 Database Name: state
64 Database Class: State
65 Modifies the default state of the canvas where state may be set
67 to one of: normal, disabled, or hidden. Individual canvas ob‐
68 jects all have their own state option which may override the de‐
69 fault state. Many options can take separate specifications such
70 that the appearance of the item can be different in different
71 situations. The options that start with active control the ap‐
72 pearance when the mouse pointer is over it, while the option
73 starting with disabled controls the appearance when the state is
74 disabled. Canvas items which are disabled will not react to can‐
75 vas bindings.
76 Command-Line Name:-width
78 Database Name: width
79 Database Class: width
80 Specifies a desired window width that the canvas widget should
82 request from its geometry manager. The value may be specified in
83 any of the forms described in the COORDINATES section below.
84 Command-Line Name:-xscrollincrement
86 Database Name: xScrollIncrement
87 Database Class: ScrollIncrement
88 Specifies an increment for horizontal scrolling, in any of the
90 usual forms permitted for screen distances. If the value of this
91 option is greater than zero, the horizontal view in the window
92 will be constrained so that the canvas x coordinate at the left
93 edge of the window is always an even multiple of xScrollIncre‐
94 ment; furthermore, the units for scrolling (e.g., the change in
95 view when the left and right arrows of a scrollbar are selected)
96 will also be xScrollIncrement. If the value of this option is
97 less than or equal to zero, then horizontal scrolling is uncon‐
98 strained.
99 Command-Line Name:-yscrollincrement
101 Database Name: yScrollIncrement
102 Database Class: ScrollIncrement
103 Specifies an increment for vertical scrolling, in any of the
105 usual forms permitted for screen distances. If the value of this
106 option is greater than zero, the vertical view in the window
107 will be constrained so that the canvas y coordinate at the top
108 edge of the window is always an even multiple of yScrollIncre‐
109 ment; furthermore, the units for scrolling (e.g., the change in
110 view when the top and bottom arrows of a scrollbar are selected)
111 will also be yScrollIncrement. If the value of this option is
112 less than or equal to zero, then vertical scrolling is uncon‐
113 strained.
114______________________________________________________________________________
115
117 The canvas command creates a new window (given by the pathName argu‐
118 ment) and makes it into a canvas widget. Additional options, described
119 above, may be specified on the command line or in the option database
120 to configure aspects of the canvas such as its colors and 3-D relief.
121 The canvas command returns its pathName argument. At the time this com‐
122 mand is invoked, there must not exist a window named pathName, but
123 pathName's parent must exist.
124 Canvas widgets implement structured graphics. A canvas displays any
126 number of items, which may be things like rectangles, circles, lines,
127 and text. Items may be manipulated (e.g. moved or re-colored) and com‐
128 mands may be associated with items in much the same way that the bind
129 command allows commands to be bound to widgets. For example, a particu‐
130 lar command may be associated with the <Button-1> event so that the
131 command is invoked whenever button 1 is pressed with the mouse cursor
132 over an item. This means that items in a canvas can have behaviors de‐
133 fined by the Tcl scripts bound to them.
134
136 The items in a canvas are ordered for purposes of display, with the
137 first item in the display list being displayed first, followed by the
138 next item in the list, and so on. Items later in the display list ob‐
139 scure those that are earlier in the display list and are sometimes re‐
140 ferred to as being “on top” of earlier items. When a new item is cre‐
141 ated it is placed at the end of the display list, on top of everything
142 else. Widget commands may be used to re-arrange the order of the dis‐
143 play list.
144 Window items are an exception to the above rules. The underlying window
146 systems require them always to be drawn on top of other items. In ad‐
147 dition, the stacking order of window items is not affected by any of
148 the canvas widget commands; you must use the Tk raise command and lower
149 command instead.
150
152 Items in a canvas widget may be named in either of two ways: by id or
153 by tag. Each item has a unique identifying number, which is assigned
154 to that item when it is created. The id of an item never changes and id
155 numbers are never re-used within the lifetime of a canvas widget.
156 Each item may also have any number of tags associated with it. A tag is
158 just a string of characters, and it may take any form except that of an
159 integer. For example, “x123” is OK but “123” is not. The same tag may
160 be associated with many different items. This is commonly done to
161 group items in various interesting ways; for example, all selected
162 items might be given the tag “selected”.
163 The tag all is implicitly associated with every item in the canvas; it
165 may be used to invoke operations on all the items in the canvas.
166 The tag current is managed automatically by Tk; it applies to the cur‐
168 rent item, which is the topmost item whose drawn area covers the posi‐
169 tion of the mouse cursor (different item types interpret this in vary‐
170 ing ways; see the individual item type documentation for details). If
171 the mouse is not in the canvas widget or is not over an item, then no
172 item has the current tag.
173 When specifying items in canvas widget commands, if the specifier is an
175 integer then it is assumed to refer to the single item with that id.
176 If the specifier is not an integer, then it is assumed to refer to all
177 of the items in the canvas that have a tag matching the specifier. The
178 symbol tagOrId is used below to indicate that an argument specifies ei‐
179 ther an id that selects a single item or a tag that selects zero or
180 more items.
181 tagOrId may contain a logical expressions of tags by using operators:
183 “&&”, “||”, “^”, “!”, and parenthesized subexpressions. For example:
184 .c find withtag {(a&&!b)||(!a&&b)}
185 or equivalently:
186 .c find withtag {a^b}
187 will find only those items with either “a” or “b” tags, but not both.
188 Some widget commands only operate on a single item at a time; if
190 tagOrId is specified in a way that names multiple items, then the nor‐
191 mal behavior is for the command to use the first (lowest) of these
192 items in the display list that is suitable for the command. Exceptions
193 are noted in the widget command descriptions below.
194
196 All coordinates related to canvases are stored as floating-point num‐
197 bers. Coordinates and distances are specified in screen units, which
198 are floating-point numbers optionally followed by one of several let‐
199 ters. If no letter is supplied then the distance is in pixels. If the
200 letter is m then the distance is in millimeters on the screen; if it is
201 c then the distance is in centimeters; i means inches, and p means
202 printers points (1/72 inch). Larger y-coordinates refer to points
203 lower on the screen; larger x-coordinates refer to points farther to
204 the right. Coordinates can be specified either as an even number of
205 parameters, or as a single list parameter containing an even number of
206 x and y coordinate values.
207 TRANSFORMATIONS
209 Normally the origin of the canvas coordinate system is at the upper-
210 left corner of the window containing the canvas. It is possible to ad‐
211 just the origin of the canvas coordinate system relative to the origin
212 of the window using the xview and yview widget commands; this is typi‐
213 cally used for scrolling. Canvases do not support scaling or rotation
214 of the canvas coordinate system relative to the window coordinate sys‐
215 tem.
216 Individual items may be moved or scaled using widget commands described
218 below, but they may not be rotated.
219 Note that the default origin of the canvas's visible area is coincident
221 with the origin for the whole window as that makes bindings using the
222 mouse position easier to work with; you only need to use the canvasx
223 and canvasy widget commands if you adjust the origin of the visible
224 area. However, this also means that any focus ring (as controlled by
225 the -highlightthickness option) and window border (as controlled by the
226 -borderwidth option) must be taken into account before you get to the
227 visible area of the canvas.
228
230 Text items support the notion of an index for identifying particular
231 positions within the item. In a similar fashion, line and polygon
232 items support index for identifying, inserting and deleting subsets of
233 their coordinates. Indices are used for commands such as inserting or
234 deleting a range of characters or coordinates, and setting the inser‐
235 tion cursor position. An index may be specified in any of a number of
236 ways, and different types of items may support different forms for
237 specifying indices. Text items support the following forms for an in‐
238 dex; if you define new types of text-like items, it would be advisable
239 to support as many of these forms as practical. Note that it is possi‐
240 ble to refer to the character just after the last one in the text item;
241 this is necessary for such tasks as inserting new text at the end of
242 the item. Lines and Polygons do not support the insertion cursor and
243 the selection. Their indices are supposed to be even always, because
244 coordinates always appear in pairs.
245 number A decimal number giving the position of the desired character
247 within the text item. 0 refers to the first character, 1 to
248 the next character, and so on. If indexes are odd for lines
249 and polygons, they will be automatically decremented by one.
250 A number less than 0 is treated as if it were zero, and a
251 number greater than the length of the text item is treated as
252 if it were equal to the length of the text item. For poly‐
253 gons, numbers less than 0 or greater than the length of the
254 coordinate list will be adjusted by adding or subtracting the
255 length until the result is between zero and the length, in‐
256 clusive.
257 end Refers to the character or coordinate just after the last one
259 in the item (same as the number of characters or coordinates
260 in the item).
261 insert Refers to the character just before which the insertion cur‐
263 sor is drawn in this item. Not valid for lines and polygons.
264 sel.first Refers to the first selected character in the item. If the
266 selection is not in this item then this form is illegal.
267 sel.last Refers to the last selected character in the item. If the
269 selection is not in this item then this form is illegal.
270 @x,y Refers to the character or coordinate at the point given by x
272 and y, where x and y are specified in the coordinate system
273 of the canvas. If x and y lie outside the coordinates cov‐
274 ered by the text item, then they refer to the first or last
275 character in the line that is closest to the given point.
276
278 Many items support the notion of a dash pattern for outlines.
279 The first possible syntax is a list of integers. Each element repre‐
281 sents the number of pixels of a line segment. Only the odd segments are
282 drawn using the “outline” color. The other segments are drawn transpar‐
283 ent.
284 The second possible syntax is a character list containing only 5 possi‐
286 ble characters “.,-_ ”. The space can be used to enlarge the space be‐
287 tween other line elements, and cannot occur as the first position in
288 the string. Some examples:
289 -dash . → -dash {2 4}
290 -dash - → -dash {6 4}
291 -dash -. → -dash {6 4 2 4}
292 -dash -.. → -dash {6 4 2 4 2 4}
293 -dash {. } → -dash {2 8}
294 -dash , → -dash {4 4}
295 The main difference of this syntax with the previous is that it is
297 shape-conserving. This means that all values in the dash list will be
298 multiplied by the line width before display. This assures that “.”
299 will always be displayed as a dot and “-” always as a dash regardless
300 of the line width.
301 On systems which support only a limited set of dash patterns, the dash
303 pattern will be displayed as the closest dash pattern that is avail‐
304 able. For example, on Windows only the first 4 of the above examples
305 are available. The last 2 examples will be displayed identically to the
306 first one.
307
309 The canvas command creates a new Tcl command whose name is pathName.
310 This command may be used to invoke various operations on the widget. It
311 has the following general form:
312 pathName option ?arg arg ...?
313 Option and the args determine the exact behavior of the command. The
314 following widget commands are possible for canvas widgets:
315 pathName addtag tag searchSpec ?arg arg ...?
317 For each item that meets the constraints specified by searchSpec
318 and the args, add tag to the list of tags associated with the
319 item if it is not already present on that list. It is possible
320 that no items will satisfy the constraints given by searchSpec
321 and args, in which case the command has no effect. This command
322 returns an empty string as result. SearchSpec and arg's may
323 take any of the following forms:
324 above tagOrId
326 Selects the item just after (above) the one given by
327 tagOrId in the display list. If tagOrId denotes more
328 than one item, then the last (topmost) of these items in
329 the display list is used.
330 all Selects all the items in the canvas.
332 below tagOrId
334 Selects the item just before (below) the one given by
335 tagOrId in the display list. If tagOrId denotes more
336 than one item, then the first (lowest) of these items in
337 the display list is used.
338 closest x y ?halo? ?start?
340 Selects the item closest to the point given by x and y.
341 If more than one item is at the same closest distance
342 (e.g. two items overlap the point), then the top-most of
343 these items (the last one in the display list) is used.
344 If halo is specified, then it must be a non-negative
345 value. Any item closer than halo to the point is consid‐
346 ered to overlap it. The start argument may be used to
347 step circularly through all the closest items. If start
348 is specified, it names an item using a tag or id (if by
349 tag, it selects the first item in the display list with
350 the given tag). Instead of selecting the topmost closest
351 item, this form will select the topmost closest item that
352 is below start in the display list; if no such item ex‐
353 ists, then the selection behaves as if the start argument
354 had not been specified.
355 enclosed x1 y1 x2 y2
357 Selects all the items completely enclosed within the rec‐
358 tangular region given by x1, y1, x2, and y2. X1 must be
359 no greater than x2 and y1 must be no greater than y2.
360 overlapping x1 y1 x2 y2
362 Selects all the items that overlap or are enclosed within
363 the rectangular region given by x1, y1, x2, and y2. X1
364 must be no greater than x2 and y1 must be no greater than
365 y2.
366 withtag tagOrId
368 Selects all the items given by tagOrId.
369 pathName bbox tagOrId ?tagOrId tagOrId ...?
371 Returns a list with four elements giving an approximate bounding
372 box for all the items named by the tagOrId arguments. The list
373 has the form “x1 y1 x2 y2” such that the drawn areas of all the
374 named elements are within the region bounded by x1 on the left,
375 x2 on the right, y1 on the top, and y2 on the bottom. The re‐
376 turn value may overestimate the actual bounding box by a few
377 pixels. If no items match any of the tagOrId arguments or if
378 the matching items have empty bounding boxes (i.e. they have
379 nothing to display) then an empty string is returned.
380 pathName bind tagOrId ?sequence? ?command?
382 This command associates command with all the items given by
383 tagOrId such that whenever the event sequence given by sequence
384 occurs for one of the items the command will be invoked. This
385 widget command is similar to the bind command except that it op‐
386 erates on items in a canvas rather than entire widgets. See the
387 bind manual entry for complete details on the syntax of sequence
388 and the substitutions performed on command before invoking it.
389 If all arguments are specified then a new binding is created,
390 replacing any existing binding for the same sequence and tagOrId
391 (if the first character of command is “+” then command augments
392 an existing binding rather than replacing it). In this case the
393 return value is an empty string. If command is omitted then the
394 command returns the command associated with tagOrId and sequence
395 (an error occurs if there is no such binding). If both command
396 and sequence are omitted then the command returns a list of all
397 the sequences for which bindings have been defined for tagOrId.
398 The only events for which bindings may be specified are those
400 related to the mouse and keyboard (such as Enter, Leave, Button‐
401 Press, Motion, and KeyPress) or virtual events. The handling of
402 events in canvases uses the current item defined in ITEM IDS AND
403 TAGS above. Enter and Leave events trigger for an item when it
404 becomes the current item or ceases to be the current item; note
405 that these events are different than Enter and Leave events for
406 windows. Mouse-related events are directed to the current item,
407 if any. Keyboard-related events are directed to the focus item,
408 if any (see the focus widget command below for more on this). If
409 a virtual event is used in a binding, that binding can trigger
410 only if the virtual event is defined by an underlying mouse-re‐
411 lated or keyboard-related event.
412 It is possible for multiple bindings to match a particular
414 event. This could occur, for example, if one binding is associ‐
415 ated with the item's id and another is associated with one of
416 the item's tags. When this occurs, all of the matching bindings
417 are invoked. A binding associated with the all tag is invoked
418 first, followed by one binding for each of the item's tags (in
419 order), followed by a binding associated with the item's id. If
420 there are multiple matching bindings for a single tag, then only
421 the most specific binding is invoked. A continue command in a
422 binding script terminates that script, and a break command ter‐
423 minates that script and skips any remaining scripts for the
424 event, just as for the bind command.
425 If bindings have been created for a canvas window using the bind
427 command, then they are invoked in addition to bindings created
428 for the canvas's items using the bind widget command. The bind‐
429 ings for items will be invoked before any of the bindings for
430 the window as a whole.
431 pathName canvasx screenx ?gridspacing?
433 Given a window x-coordinate in the canvas screenx, this command
434 returns the canvas x-coordinate that is displayed at that loca‐
435 tion. If gridspacing is specified, then the canvas coordinate
436 is rounded to the nearest multiple of gridspacing units.
437 pathName canvasy screeny ?gridspacing?
439 Given a window y-coordinate in the canvas screeny this command
440 returns the canvas y-coordinate that is displayed at that loca‐
441 tion. If gridspacing is specified, then the canvas coordinate
442 is rounded to the nearest multiple of gridspacing units.
443 pathName cget option
445 Returns the current value of the configuration option given by
446 option. Option may have any of the values accepted by the can‐
447 vas command.
448 pathName configure ?option? ?value? ?option value ...?
450 Query or modify the configuration options of the widget. If no
451 option is specified, returns a list describing all of the avail‐
452 able options for pathName (see Tk_ConfigureInfo for information
453 on the format of this list). If option is specified with no
454 value, then the command returns a list describing the one named
455 option (this list will be identical to the corresponding sublist
456 of the value returned if no option is specified). If one or more
457 option-value pairs are specified, then the command modifies the
458 given widget option(s) to have the given value(s); in this case
459 the command returns an empty string. Option may have any of the
460 values accepted by the canvas command.
461 pathName coords tagOrId ?x0 y0 ...?
463 pathName coords tagOrId ?coordList?
465 Query or modify the coordinates that define an item. If no co‐
466 ordinates are specified, this command returns a list whose ele‐
467 ments are the coordinates of the item named by tagOrId. If co‐
468 ordinates are specified, then they replace the current coordi‐
469 nates for the named item. If tagOrId refers to multiple items,
470 then the first one in the display list is used.
471 Note that for rectangles, ovals and arcs the returned list of
473 coordinates has a fixed order, namely the left, top, right and
474 bottom coordinates, which may not be the order originally given.
475 Also the coordinates are always returned in screen units with no
476 units (that is, in pixels). So if the original coordinates were
477 specified for instance in centimeters or inches, the returned
478 values will nevertheless be in pixels.
479 pathName create type x y ?x y ...? ?option value ...?
481 pathName create type coordList ?option value ...?
483 Create a new item in pathName of type type. The exact format of
484 the arguments after type depends on type, but usually they con‐
485 sist of the coordinates for one or more points, followed by
486 specifications for zero or more item options. See the subsec‐
487 tions on individual item types below for more on the syntax of
488 this command. This command returns the id for the new item.
489 pathName dchars tagOrId first ?last?
491 For each item given by tagOrId, delete the characters, or coor‐
492 dinates, in the range given by first and last, inclusive. If
493 some of the items given by tagOrId do not support indexing oper‐
494 ations then they ignore this operation. Text items interpret
495 first and last as indices to a character, line and polygon items
496 interpret them as indices to a coordinate (an x,y pair). In‐
497 dices are described in INDICES above. If last is omitted, it
498 defaults to first. This command returns an empty string.
499 pathName delete ?tagOrId tagOrId ...?
501 Delete each of the items given by each tagOrId, and return an
502 empty string.
503 pathName dtag tagOrId ?tagToDelete?
505 For each of the items given by tagOrId, delete the tag given by
506 tagToDelete from the list of those associated with the item. If
507 an item does not have the tag tagToDelete then the item is unaf‐
508 fected by the command. If tagToDelete is omitted then it de‐
509 faults to tagOrId. This command returns an empty string.
510 pathName find searchCommand ?arg arg ...?
512 This command returns a list consisting of all the items that
513 meet the constraints specified by searchCommand and arg's.
514 SearchCommand and args have any of the forms accepted by the ad‐
515 dtag command. The items are returned in stacking order, with
516 the lowest item first.
517 pathName focus ?tagOrId?
519 Set the keyboard focus for the canvas widget to the item given
520 by tagOrId. If tagOrId refers to several items, then the focus
521 is set to the first such item in the display list that supports
522 the insertion cursor. If tagOrId does not refer to any items,
523 or if none of them support the insertion cursor, then the focus
524 is not changed. If tagOrId is an empty string, then the focus
525 item is reset so that no item has the focus. If tagOrId is not
526 specified then the command returns the id for the item that cur‐
527 rently has the focus, or an empty string if no item has the fo‐
528 cus.
529 Once the focus has been set to an item, the item will display
531 the insertion cursor and all keyboard events will be directed to
532 that item. The focus item within a canvas and the focus window
533 on the screen (set with the focus command) are totally indepen‐
534 dent: a given item does not actually have the input focus unless
535 (a) its canvas is the focus window and (b) the item is the focus
536 item within the canvas. In most cases it is advisable to follow
537 the focus widget command with the focus command to set the focus
538 window to the canvas (if it was not there already).
539 pathName gettags tagOrId
541 Return a list whose elements are the tags associated with the
542 item given by tagOrId. If tagOrId refers to more than one item,
543 then the tags are returned from the first such item in the dis‐
544 play list. If tagOrId does not refer to any items, or if the
545 item contains no tags, then an empty string is returned.
546 pathName icursor tagOrId index
548 Set the position of the insertion cursor for the item(s) given
549 by tagOrId to just before the character whose position is given
550 by index. If some or all of the items given by tagOrId do not
551 support an insertion cursor then this command has no effect on
552 them. See INDICES above for a description of the legal forms
553 for index. Note: the insertion cursor is only displayed in an
554 item if that item currently has the keyboard focus (see the fo‐
555 cus widget command, above), but the cursor position may be set
556 even when the item does not have the focus. This command re‐
557 turns an empty string.
558 pathName imove tagOrId index x y
560 This command causes the index'th coordinate of each of the items │
561 indicated by tagOrId to be relocated to the location (x,y). │
562 Each item interprets index independently according to the rules │
563 described in INDICES above. Out of the standard set of items, │
564 only line and polygon items may have their coordinates relocated │
565 this way.
566 pathName index tagOrId index
568 This command returns a decimal string giving the numerical index
569 within tagOrId corresponding to index. Index gives a textual
570 description of the desired position as described in INDICES
571 above. Text items interpret index as an index to a character,
572 line and polygon items interpret it as an index to a coordinate
573 (an x,y pair). The return value is guaranteed to lie between 0
574 and the number of characters, or coordinates, within the item,
575 inclusive. If tagOrId refers to multiple items, then the index
576 is processed in the first of these items that supports indexing
577 operations (in display list order).
578 pathName insert tagOrId beforeThis string
580 For each of the items given by tagOrId, if the item supports
581 text or coordinate, insertion then string is inserted into the
582 item's text just before the character, or coordinate, whose in‐
583 dex is beforeThis. Text items interpret beforeThis as an index
584 to a character, line and polygon items interpret it as an index
585 to a coordinate (an x,y pair). For lines and polygons the
586 string must be a valid coordinate sequence. See INDICES above
587 for information about the forms allowed for beforeThis. This
588 command returns an empty string.
589 pathName itemcget tagOrId option
591 Returns the current value of the configuration option for the
592 item given by tagOrId whose name is option. This command is
593 similar to the cget widget command except that it applies to a
594 particular item rather than the widget as a whole. Option may
595 have any of the values accepted by the create widget command
596 when the item was created. If tagOrId is a tag that refers to
597 more than one item, the first (lowest) such item is used.
598 pathName itemconfigure tagOrId ?option? ?value? ?option value ...?
600 This command is similar to the configure widget command except
601 that it modifies item-specific options for the items given by
602 tagOrId instead of modifying options for the overall canvas wid‐
603 get. If no option is specified, returns a list describing all
604 of the available options for the first item given by tagOrId
605 (see Tk_ConfigureInfo for information on the format of this
606 list). If option is specified with no value, then the command
607 returns a list describing the one named option (this list will
608 be identical to the corresponding sublist of the value returned
609 if no option is specified). If one or more option-value pairs
610 are specified, then the command modifies the given widget op‐
611 tion(s) to have the given value(s) in each of the items given by
612 tagOrId; in this case the command returns an empty string. The
613 options and values are the same as those permissible in the cre‐
614 ate widget command when the item(s) were created; see the sec‐
615 tions describing individual item types below for details on the
616 legal options.
617 pathName lower tagOrId ?belowThis?
619 Move all of the items given by tagOrId to a new position in the
620 display list just before the item given by belowThis. If
621 tagOrId refers to more than one item then all are moved but the
622 relative order of the moved items will not be changed. Be‐
623 lowThis is a tag or id; if it refers to more than one item then
624 the first (lowest) of these items in the display list is used as
625 the destination location for the moved items. Note: this com‐
626 mand has no effect on window items. Window items always obscure
627 other item types, and the stacking order of window items is de‐
628 termined by the raise command and lower command, not the raise
629 widget command and lower widget command for canvases. This com‐
630 mand returns an empty string.
631 pathName move tagOrId xAmount yAmount
633 Move each of the items given by tagOrId in the canvas coordinate
634 space by adding xAmount to the x-coordinate of each point asso‐
635 ciated with the item and yAmount to the y-coordinate of each
636 point associated with the item. This command returns an empty
637 string.
638 pathName moveto tagOrId xPos yPos
640 Move the items given by tagOrId in the canvas coordinate space │
641 so that the first coordinate pair (the upper-left corner of the │
642 bounding box) of the first item (the lowest in the display list) │
643 with tag tagOrId is located at position (xPos,yPos). xPos and │
644 yPos may be the empty string, in which case the corresponding │
645 coordinate will be unchanged. All items matching tagOrId remain │
646 in the same positions relative to each other. This command re‐ │
647 turns an empty string.
648 pathName postscript ?option value option value ...?
650 Generate a Postscript representation for part or all of the can‐
651 vas. If the -file option is specified then the Postscript is
652 written to a file and an empty string is returned; otherwise the
653 Postscript is returned as the result of the command. If the in‐
654 terpreter that owns the canvas is marked as safe, the operation
655 will fail because safe interpreters are not allowed to write
656 files. If the -channel option is specified, the argument de‐
657 notes the name of a channel already opened for writing. The
658 Postscript is written to that channel, and the channel is left
659 open for further writing at the end of the operation. The Post‐
660 script is created in Encapsulated Postscript form using version
661 3.0 of the Document Structuring Conventions. Note: by default
662 Postscript is only generated for information that appears in the
663 canvas's window on the screen. If the canvas is freshly created
664 it may still have its initial size of 1x1 pixel so nothing will
665 appear in the Postscript. To get around this problem either in‐
666 voke the update command to wait for the canvas window to reach
667 its final size, or else use the -width and -height options to
668 specify the area of the canvas to print. The option-value argu‐
669 ment pairs provide additional information to control the genera‐
670 tion of Postscript. The following options are supported:
671 -channel channelName
673 Specifies the name of the channel to which to write the
674 Postscript. If this option and the -file option are not
675 specified then the Postscript is returned as the result
676 of the command.
677 -colormap varName
679 VarName must be the name of an array variable that speci‐
680 fies a color mapping to use in the Postscript. Each ele‐
681 ment of varName must consist of Postscript code to set a
682 particular color value (e.g. “1.0 1.0 0.0 setrgbcolor”).
683 When outputting color information in the Postscript, Tk
684 checks to see if there is an element of varName with the
685 same name as the color. If so, Tk uses the value of the
686 element as the Postscript command to set the color. If
687 this option has not been specified, or if there is no en‐
688 try in varName for a given color, then Tk uses the red,
689 green, and blue intensities from the X color.
690 -colormode mode
692 Specifies how to output color information. Mode must be
693 either color (for full color output), gray (convert all
694 colors to their gray-scale equivalents) or mono (convert
695 all colors to black or white).
696 -file fileName
698 Specifies the name of the file in which to write the
699 Postscript. If this option and the -channel option are
700 not specified then the Postscript is returned as the re‐
701 sult of the command.
702 -fontmap varName
704 VarName must be the name of an array variable that speci‐
705 fies a font mapping to use in the Postscript. Each ele‐
706 ment of varName must consist of a Tcl list with two ele‐
707 ments, which are the name and point size of a Postscript
708 font. When outputting Postscript commands for a particu‐
709 lar font, Tk checks to see if varName contains an element
710 with the same name as the font. If there is such an ele‐
711 ment, then the font information contained in that element
712 is used in the Postscript. Otherwise Tk attempts to
713 guess what Postscript font to use. Tk's guesses gener‐
714 ally only work for well-known fonts such as Times and
715 Helvetica and Courier, and only if the X font name does
716 not omit any dashes up through the point size. For exam‐
717 ple, -*-Courier-Bold-R-Normal--*-120-* will work but
718 *Courier-Bold-R-Normal*120* will not; Tk needs the dashes
719 to parse the font name).
720 -height size
722 Specifies the height of the area of the canvas to print.
723 Defaults to the height of the canvas window.
724 -pageanchor anchor
726 Specifies which point of the printed area of the canvas
727 should appear over the positioning point on the page
728 (which is given by the -pagex and -pagey options). For
729 example, -pageanchor n means that the top center of the
730 area of the canvas being printed (as it appears in the
731 canvas window) should be over the positioning point. De‐
732 faults to center.
733 -pageheight size
735 Specifies that the Postscript should be scaled in both x
736 and y so that the printed area is size high on the Post‐
737 script page. Size consists of a floating-point number
738 followed by c for centimeters, i for inches, m for mil‐
739 limeters, or p or nothing for printer's points (1/72
740 inch). Defaults to the height of the printed area on the
741 screen. If both -pageheight and -pagewidth are specified
742 then the scale factor from -pagewidth is used (non-uni‐
743 form scaling is not implemented).
744 -pagewidth size
746 Specifies that the Postscript should be scaled in both x
747 and y so that the printed area is size wide on the Post‐
748 script page. Size has the same form as for -pageheight.
749 Defaults to the width of the printed area on the screen.
750 If both -pageheight and -pagewidth are specified then the
751 scale factor from -pagewidth is used (non-uniform scaling
752 is not implemented).
753 -pagex position
755 Position gives the x-coordinate of the positioning point
756 on the Postscript page, using any of the forms allowed
757 for -pageheight. Used in conjunction with the -pagey and
758 -pageanchor options to determine where the printed area
759 appears on the Postscript page. Defaults to the center
760 of the page.
761 -pagey position
763 Position gives the y-coordinate of the positioning point
764 on the Postscript page, using any of the forms allowed
765 for -pageheight. Used in conjunction with the -pagex and
766 -pageanchor options to determine where the printed area
767 appears on the Postscript page. Defaults to the center
768 of the page.
769 -rotate boolean
771 Boolean specifies whether the printed area is to be ro‐
772 tated 90 degrees. In non-rotated output the x-axis of
773 the printed area runs along the short dimension of the
774 page (“portrait” orientation); in rotated output the x-
775 axis runs along the long dimension of the page (“land‐
776 scape” orientation). Defaults to non-rotated.
777 -width size
779 Specifies the width of the area of the canvas to print.
780 Defaults to the width of the canvas window.
781 -x position
783 Specifies the x-coordinate of the left edge of the area
784 of the canvas that is to be printed, in canvas coordi‐
785 nates, not window coordinates. Defaults to the coordi‐
786 nate of the left edge of the window.
787 -y position
789 Specifies the y-coordinate of the top edge of the area of
790 the canvas that is to be printed, in canvas coordinates,
791 not window coordinates. Defaults to the coordinate of
792 the top edge of the window.
793 pathName raise tagOrId ?aboveThis?
795 Move all of the items given by tagOrId to a new position in the
796 display list just after the item given by aboveThis. If tagOrId
797 refers to more than one item then all are moved but the relative
798 order of the moved items will not be changed. AboveThis is a
799 tag or id; if it refers to more than one item then the last
800 (topmost) of these items in the display list is used as the des‐
801 tination location for the moved items. This command returns an
802 empty string.
803 Note: this command has no effect on window items. Window items
805 always obscure other item types, and the stacking order of win‐
806 dow items is determined by the raise command and lower command,
807 not the raise widget command and lower widget command for can‐
808 vases.
809 pathName rchars tagOrId first last string
811 This command causes the text or coordinates between first and │
812 last for each of the items indicated by tagOrId to be replaced │
813 by string. Each item interprets first and last independently ac‐ │
814 cording to the rules described in INDICES above. Out of the │
815 standard set of items, text items support this operation by al‐ │
816 tering their text as directed, and line and polygon items sup‐ │
817 port this operation by altering their coordinate list (in which │
818 case string should be a list of coordinates to use as a replace‐ │
819 ment). The other items ignore this operation.
820 pathName scale tagOrId xOrigin yOrigin xScale yScale
822 Rescale the coordinates of all of the items given by tagOrId in
823 canvas coordinate space. XOrigin and yOrigin identify the ori‐
824 gin for the scaling operation and xScale and yScale identify the
825 scale factors for x- and y-coordinates, respectively (a scale
826 factor of 1.0 implies no change to that coordinate). For each
827 of the points defining each item, the x-coordinate is adjusted
828 to change the distance from xOrigin by a factor of xScale. Sim‐
829 ilarly, each y-coordinate is adjusted to change the distance
830 from yOrigin by a factor of yScale. This command returns an
831 empty string.
832 Note that some items have only a single pair of coordinates
834 (e.g., text, images and windows) and so scaling of them by this
835 command can only move them around.
836 pathName scan option args
838 This command is used to implement scanning on canvases. It has
839 two forms, depending on option:
840 pathName scan mark x y
842 Records x and y and the canvas's current view; used in
843 conjunction with later scan dragto commands. Typically
844 this command is associated with a mouse button press in
845 the widget and x and y are the coordinates of the mouse.
846 It returns an empty string.
847 pathName scan dragto x y ?gain?
849 This command computes the difference between its x and y
850 arguments (which are typically mouse coordinates) and the
851 x and y arguments to the last scan mark command for the
852 widget. It then adjusts the view by gain times the dif‐
853 ference in coordinates, where gain defaults to 10. This
854 command is typically associated with mouse motion events
855 in the widget, to produce the effect of dragging the can‐
856 vas at high speed through its window. The return value is
857 an empty string.
858 pathName select option ?tagOrId arg?
860 Manipulates the selection in one of several ways, depending on
861 option. The command may take any of the forms described below.
862 In all of the descriptions below, tagOrId must refer to an item
863 that supports indexing and selection; if it refers to multiple
864 items then the first of these that supports indexing and the se‐
865 lection is used. Index gives a textual description of a posi‐
866 tion within tagOrId, as described in INDICES above.
867 pathName select adjust tagOrId index
869 Locate the end of the selection in tagOrId nearest to the
870 character given by index, and adjust that end of the se‐
871 lection to be at index (i.e. including but not going be‐
872 yond index). The other end of the selection is made the
873 anchor point for future select to commands. If the se‐
874 lection is not currently in tagOrId then this command be‐
875 haves the same as the select to widget command. Returns
876 an empty string.
877 pathName select clear
879 Clear the selection if it is in this widget. If the se‐
880 lection is not in this widget then the command has no ef‐
881 fect. Returns an empty string.
882 pathName select from tagOrId index
884 Set the selection anchor point for the widget to be just
885 before the character given by index in the item given by
886 tagOrId. This command does not change the selection; it
887 just sets the fixed end of the selection for future se‐
888 lect to commands. Returns an empty string.
889 pathName select item
891 Returns the id of the selected item, if the selection is
892 in an item in this canvas. If the selection is not in
893 this canvas then an empty string is returned.
894 pathName select to tagOrId index
896 Set the selection to consist of those characters of
897 tagOrId between the selection anchor point and index.
898 The new selection will include the character given by in‐
899 dex; it will include the character given by the anchor
900 point only if index is greater than or equal to the an‐
901 chor point. The anchor point is determined by the most
902 recent select adjust or select from command for this wid‐
903 get. If the selection anchor point for the widget is not
904 currently in tagOrId, then it is set to the same charac‐
905 ter given by index. Returns an empty string.
906 pathName type tagOrId
908 Returns the type of the item given by tagOrId, such as rectangle
909 or text. If tagOrId refers to more than one item, then the type
910 of the first item in the display list is returned. If tagOrId
911 does not refer to any items at all then an empty string is re‐
912 turned.
913 pathName xview ?args?
915 This command is used to query and change the horizontal position
916 of the information displayed in the canvas's window. It can
917 take any of the following forms:
918 pathName xview
920 Returns a list containing two elements. Each element is
921 a real fraction between 0 and 1; together they describe
922 the horizontal span that is visible in the window. For
923 example, if the first element is .2 and the second ele‐
924 ment is .6, 20% of the canvas's area (as defined by the
925 -scrollregion option) is off-screen to the left, the mid‐
926 dle 40% is visible in the window, and 40% of the canvas
927 is off-screen to the right. These are the same values
928 passed to scrollbars via the -xscrollcommand option.
929 pathName xview moveto fraction
931 Adjusts the view in the window so that fraction of the
932 total width of the canvas is off-screen to the left.
933 Fraction must be a fraction between 0 and 1.
934 pathName xview scroll number what
936 This command shifts the view in the window left or right
937 according to number and what. Number must be an integer.
938 What must be either units or pages or an abbreviation of
939 one of these. If what is units, the view adjusts left or
940 right in units of the xScrollIncrement option, if it is
941 greater than zero, or in units of one-tenth the window's
942 width otherwise. If what is pages then the view adjusts
943 in units of nine-tenths the window's width. If number is
944 negative then information farther to the left becomes
945 visible; if it is positive then information farther to
946 the right becomes visible.
947 pathName yview ?args?
949 This command is used to query and change the vertical position
950 of the information displayed in the canvas's window. It can
951 take any of the following forms:
952 pathName yview
954 Returns a list containing two elements. Each element is
955 a real fraction between 0 and 1; together they describe
956 the vertical span that is visible in the window. For ex‐
957 ample, if the first element is .6 and the second element
958 is 1.0, the lowest 40% of the canvas's area (as defined
959 by the -scrollregion option) is visible in the window.
960 These are the same values passed to scrollbars via the
961 -yscrollcommand option.
962 pathName yview moveto fraction
964 Adjusts the view in the window so that fraction of the
965 canvas's area is off-screen to the top. Fraction is a
966 fraction between 0 and 1.
967 pathName yview scroll number what
969 This command adjusts the view in the window up or down
970 according to number and what. Number must be an integer.
971 What must be either units or pages. If what is units,
972 the view adjusts up or down in units of the yScrollIncre‐
973 ment option, if it is greater than zero, or in units of
974 one-tenth the window's height otherwise. If what is
975 pages then the view adjusts in units of nine-tenths the
976 window's height. If number is negative then higher in‐
977 formation becomes visible; if it is positive then lower
978 information becomes visible.
979
981 The sections below describe the various types of items supported by
982 canvas widgets. Each item type is characterized by two things: first,
983 the form of the create command used to create instances of the type;
984 and second, a set of configuration options for items of that type,
985 which may be used in the create and itemconfigure widget commands.
986 Most items do not support indexing or selection or the commands related
987 to them, such as index and insert. Where items do support these facil‐
988 ities, it is noted explicitly in the descriptions below. At present,
989 text, line and polygon items provide this support. For lines and poly‐
990 gons the indexing facility is used to manipulate the coordinates of the
991 item.
992 COMMON ITEM OPTIONS
994 Many items share a common set of options. These options are explained
995 here, and then referred to be each widget type for brevity.
996 -anchor anchorPos
998 AnchorPos tells how to position the item relative to the posi‐
999 tioning point for the item; it may have any of the forms ac‐
1000 cepted by Tk_GetAnchor. For example, if anchorPos is center then
1001 the item is centered on the point; if anchorPos is n then the
1002 item will be drawn so that its top center point is at the posi‐
1003 tioning point. This option defaults to center.
1004 -dash pattern
1006 -activedash pattern
1008 -disableddash pattern
1010 This option specifies dash patterns for the normal, active
1011 state, and disabled state of an item. pattern may have any of
1012 the forms accepted by Tk_GetDash. If the dash options are omit‐
1013 ted then the default is a solid outline. See DASH PATTERNS for
1014 more information.
1015 -dashoffset offset
1017 The starting offset in pixels into the pattern provided by the
1018 -dash option. -dashoffset is ignored if there is no -dash pat‐
1019 tern. The offset may have any of the forms described in the CO‐
1020 ORDINATES section above.
1021 -fill color
1023 -activefill color
1025 -disabledfill color
1027 Specifies the color to be used to fill item's area. in its nor‐
1028 mal, active, and disabled states, Color may have any of the
1029 forms accepted by Tk_GetColor. For the line item, it specifies
1030 the color of the line drawn. For the text item, it specifies
1031 the foreground color of the text. If color is an empty string
1032 (the default for all canvas items except line and text), then
1033 the item will not be filled.
1034 -outline color
1036 -activeoutline color
1038 -disabledoutline color
1040 This option specifies the color that should be used to draw the
1041 outline of the item in its normal, active and disabled states.
1042 Color may have any of the forms accepted by Tk_GetColor. If
1043 color is specified as an empty string then no outline is drawn
1044 for the item.
1045 -offset offset
1047 Specifies the offset of stipples. The offset value can be of the
1048 form x,y or side, where side can be n, ne, e, se, s, sw, w, nw,
1049 or center. In the first case the origin is the origin of the
1050 toplevel of the current window. For the canvas itself and can‐
1051 vas objects the origin is the canvas origin, but putting # in
1052 front of the coordinate pair indicates using the toplevel origin
1053 instead. For canvas objects, the -offset option is used for
1054 stippling as well. For the line and polygon canvas items you can
1055 also specify an index as argument, which connects the stipple
1056 origin to one of the coordinate points of the line/polygon. Note
1057 that stipple offsets are only supported on X11; they are
1058 silently ignored on other platforms.
1059 -outlinestipple bitmap
1061 -activeoutlinestipple bitmap
1063 -disabledoutlinestipple bitmap
1065 This option specifies stipple patterns that should be used to
1066 draw the outline of the item in its normal, active and disabled
1067 states. Indicates that the outline for the item should be drawn
1068 with a stipple pattern; bitmap specifies the stipple pattern to
1069 use, in any of the forms accepted by Tk_GetBitmap. If the -out‐
1070 line option has not been specified then this option has no ef‐
1071 fect. If bitmap is an empty string (the default), then the out‐
1072 line is drawn in a solid fashion. Note that stipples are not
1073 well supported on platforms that do not use X11 as their drawing
1074 API.
1075 -outlineoffset offset
1077 Specifies the offset of the stipple pattern used for outlines,
1078 in the same way that the -outline option controls fill stipples.
1079 (See the -outline option for a description of the syntax of off‐
1080 set.)
1081 -stipple bitmap
1083 -activestipple bitmap
1085 -disabledstipple bitmap
1087 This option specifies stipple patterns that should be used to
1088 fill the item in its normal, active and disabled states. bitmap
1089 specifies the stipple pattern to use, in any of the forms ac‐
1090 cepted by Tk_GetBitmap. If the -fill option has not been speci‐
1091 fied then this option has no effect. If bitmap is an empty
1092 string (the default), then filling is done in a solid fashion.
1093 For the text item, it affects the actual text. Note that stip‐
1094 ples are not well supported on platforms that do not use X11 as
1095 their drawing API.
1096 -state state
1098 This allows an item to override the canvas widget's global state
1099 option. It takes the same values: normal, disabled or hidden.
1100 -tags tagList
1102 Specifies a set of tags to apply to the item. TagList consists
1103 of a list of tag names, which replace any existing tags for the
1104 item. TagList may be an empty list.
1105 -width outlineWidth
1107 -activewidth outlineWidth
1109 -disabledwidth outlineWidth
1111 Specifies the width of the outline to be drawn around the item's
1112 region, in its normal, active and disabled states. outlineWidth
1113 may be in any of the forms described in the COORDINATES section
1114 above. If the -outline option has been specified as an empty
1115 string then this option has no effect. This option defaults to
1116 1.0. For arcs, wide outlines will be drawn centered on the
1117 edges of the arc's region.
1118
1120 ARC ITEMS
1121 Items of type arc appear on the display as arc-shaped regions. An arc
1122 is a section of an oval delimited by two angles (specified by the
1123 -start and -extent options) and displayed in one of several ways (spec‐
1124 ified by the -style option). Arcs are created with widget commands of
1125 the following form:
1126 pathName create arc x1 y1 x2 y2 ?option value ...?
1127 pathName create arc coordList ?option value ...?
1128 The arguments x1, y1, x2, and y2 or coordList give the coordinates of
1129 two diagonally opposite corners of a rectangular region enclosing the
1130 oval that defines the arc. After the coordinates there may be any num‐
1131 ber of option-value pairs, each of which sets one of the configuration
1132 options for the item. These same option-value pairs may be used in
1133 itemconfigure widget commands to change the item's configuration. An
1134 arc item becomes the current item when the mouse pointer is over any
1135 part that is painted or (when fully transparent) that would be painted
1136 if both the -fill and -outline options were non-empty.
1137 The following standard options are supported by arcs:
1139 -dash -activedash
1141 -disableddash -dashoffset
1142 -fill -activefill
1143 -disabledfill -offset
1144 -outline -activeoutline
1145 -disabledoutline -outlineoffset
1146 -outlinestipple -activeoutlinestipple
1147 -disabledoutlinestipple -stipple
1148 -activestipple -disabledstipple
1149 -state -tags
1150 -width -activewidth
1151 -disabledwidth
1152 The following extra options are supported for arcs:
1154 -extent degrees
1156 Specifies the size of the angular range occupied by the arc.
1157 The arc's range extends for degrees degrees counter-clockwise
1158 from the starting angle given by the -start option. Degrees may
1159 be negative. If it is greater than 360 or less than -360, then
1160 degrees modulo 360 is used as the extent.
1161 -start degrees
1163 Specifies the beginning of the angular range occupied by the
1164 arc. Degrees is given in units of degrees measured counter-
1165 clockwise from the 3-o'clock position; it may be either positive
1166 or negative.
1167 -style type
1169 Specifies how to draw the arc. If type is pieslice (the default)
1170 then the arc's region is defined by a section of the oval's
1171 perimeter plus two line segments, one between the center of the
1172 oval and each end of the perimeter section. If type is chord
1173 then the arc's region is defined by a section of the oval's
1174 perimeter plus a single line segment connecting the two end
1175 points of the perimeter section. If type is arc then the arc's
1176 region consists of a section of the perimeter alone. In this
1177 last case the -fill option is ignored.
1178 BITMAP ITEMS
1180 Items of type bitmap appear on the display as images with two colors,
1181 foreground and background. Bitmaps are created with widget commands of
1182 the following form:
1183 pathName create bitmap x y ?option value ...?
1184 pathName create bitmap coordList ?option value ...?
1185 The arguments x and y or coordList (which must have two elements) spec‐
1186 ify the coordinates of a point used to position the bitmap on the dis‐
1187 play, as controlled by the -anchor option. After the coordinates there
1188 may be any number of option-value pairs, each of which sets one of the
1189 configuration options for the item. These same option-value pairs may
1190 be used in itemconfigure widget commands to change the item's configu‐
1191 ration. A bitmap item becomes the current item when the mouse pointer
1192 is over any part of its bounding box.
1193 The following standard options are supported by bitmaps:
1195 -anchor -state
1197 -tags
1198 The following extra options are supported for bitmaps:
1200 -background color
1202 -activebackground color
1204 -disabledbackground color
1206 Specifies the color to use for each of the bitmap's “0” valued
1207 pixels in its normal, active and disabled states. Color may
1208 have any of the forms accepted by Tk_GetColor. If this option
1209 is not specified, or if it is specified as an empty string, then
1210 nothing is displayed where the bitmap pixels are 0; this pro‐
1211 duces a transparent effect.
1212 -bitmap bitmap
1214 -activebitmap bitmap
1216 -disabledbitmap bitmap
1218 Specifies the bitmaps to display in the item in its normal, ac‐
1219 tive and disabled states. Bitmap may have any of the forms ac‐
1220 cepted by Tk_GetBitmap.
1221 -foreground color
1223 -activeforeground color
1225 -disabledforeground color
1227 Specifies the color to use for each of the bitmap's “1” valued
1228 pixels in its normal, active and disabled states. Color may
1229 have any of the forms accepted by Tk_GetColor.
1230 IMAGE ITEMS
1232 Items of type image are used to display images on a canvas. Images are
1233 created with widget commands of the following form:
1234 pathName create image x y ?option value ...?
1235 pathName create image coordList ?option value ...?
1236 The arguments x and y or coordList specify the coordinates of a point
1237 used to position the image on the display, as controlled by the -anchor
1238 option. After the coordinates there may be any number of option-value
1239 pairs, each of which sets one of the configuration options for the
1240 item. These same option-value pairs may be used in itemconfigure widget
1241 commands to change the item's configuration. An image item becomes the
1242 current item when the mouse pointer is over any part of its bounding
1243 box.
1244 The following standard options are supported by images:
1246 -anchor -state
1248 -tags
1249 The following extra options are supported for images:
1251 -image name
1253 -activeimage name
1255 -disabledimage name
1257 Specifies the name of the images to display in the item in is
1258 normal, active and disabled states. This image must have been
1259 created previously with the image create command.
1260 LINE ITEMS
1262 Items of type line appear on the display as one or more connected line
1263 segments or curves. Line items support coordinate indexing operations
1264 using the dchars, index and insert widget commands. Lines are created
1265 with widget commands of the following form:
1266 pathName create line x1 y1... xn yn ?option value ...?
1267 pathName create line coordList ?option value ...?
1268 The arguments x1 through yn or coordList give the coordinates for a se‐
1269 ries of two or more points that describe a series of connected line
1270 segments. After the coordinates there may be any number of op‐
1271 tion-value pairs, each of which sets one of the configuration options
1272 for the item. These same option-value pairs may be used in itemconfig‐
1273 ure widget commands to change the item's configuration. A line item is
1274 the current item whenever the mouse pointer is over any segment of the
1275 line, whether drawn or not and whether or not the line is smoothed.
1276 The following standard options are supported by lines:
1278 -dash -activedash
1280 -disableddash -dashoffset
1281 -fill -activefill
1282 -disabledfill -stipple
1283 -activestipple -disabledstipple
1284 -state -tags
1285 -width -activewidth
1286 -disabledwidth
1287 The following extra options are supported for lines:
1289 -arrow where
1291 Indicates whether or not arrowheads are to be drawn at one or
1292 both ends of the line. Where must have one of the values none
1293 (for no arrowheads), first (for an arrowhead at the first point
1294 of the line), last (for an arrowhead at the last point of the
1295 line), or both (for arrowheads at both ends). This option de‐
1296 faults to none. When requested to draw an arrowhead, Tk inter‐
1297 nally adjusts the corresponding line end point so that the ren‐
1298 dered line ends at the neck of the arrowhead rather than at its
1299 tip so that the line doesn't extend past the edge of the arrow‐
1300 head. This may trigger a Leave event if the mouse is hovering
1301 this line end. Conversely, when removing an arrowhead Tk adjusts
1302 the corresponding line point the other way round, which may
1303 trigger an Enter event.
1304 -arrowshape shape
1306 This option indicates how to draw arrowheads. The shape argu‐
1307 ment must be a list with three elements, each specifying a dis‐
1308 tance in any of the forms described in the COORDINATES section
1309 above. The first element of the list gives the distance along
1310 the line from the neck of the arrowhead to its tip. The second
1311 element gives the distance along the line from the trailing
1312 points of the arrowhead to the tip, and the third element gives
1313 the distance from the outside edge of the line to the trailing
1314 points. If this option is not specified then Tk picks a “rea‐
1315 sonable” shape.
1316 -capstyle style
1318 Specifies the ways in which caps are to be drawn at the end‐
1319 points of the line. Style may have any of the forms accepted by
1320 Tk_GetCapStyle (butt, projecting, or round). If this option is
1321 not specified then it defaults to butt. Where arrowheads are
1322 drawn the cap style is ignored.
1323 -joinstyle style
1325 Specifies the ways in which joints are to be drawn at the ver‐
1326 tices of the line. Style may have any of the forms accepted by
1327 Tk_GetJoinStyle (bevel, miter, or round). If this option is not
1328 specified then it defaults to round. If the line only contains
1329 two points then this option is irrelevant.
1330 -smooth smoothMethod
1332 smoothMethod must have one of the forms accepted by Tcl_Get‐
1333 Boolean or a line smoothing method. Only true and raw are sup‐
1334 ported in the core (with bezier being an alias for true), but
1335 more can be added at runtime. If a boolean false value or empty
1336 string is given, no smoothing is applied. A boolean truth value
1337 assumes true smoothing. If the smoothing method is true, this
1338 indicates that the line should be drawn as a curve, rendered as
1339 a set of quadratic splines: one spline is drawn for the first
1340 and second line segments, one for the second and third, and so
1341 on. Straight-line segments can be generated within a curve by
1342 duplicating the end-points of the desired line segment. If the
1343 smoothing method is raw, this indicates that the line should
1344 also be drawn as a curve but where the list of coordinates is
1345 such that the first coordinate pair (and every third coordinate
1346 pair thereafter) is a knot point on a cubic Bezier curve, and
1347 the other coordinates are control points on the cubic Bezier
1348 curve. Straight line segments can be generated within a curve by
1349 making control points equal to their neighbouring knot points.
1350 If the last point is a control point and not a knot point, the
1351 point is repeated (one or two times) so that it also becomes a
1352 knot point.
1353 -splinesteps number
1355 Specifies the degree of smoothness desired for curves: each
1356 spline will be approximated with number line segments. This op‐
1357 tion is ignored unless the -smooth option is true or raw.
1358 OVAL ITEMS
1360 Items of type oval appear as circular or oval regions on the display.
1361 Each oval may have an outline, a fill, or both. Ovals are created with
1362 widget commands of the following form:
1363 pathName create oval x1 y1 x2 y2 ?option value ...?
1364 pathName create oval coordList ?option value ...?
1365 The arguments x1, y1, x2, and y2 or coordList give the coordinates of
1366 two diagonally opposite corners of a rectangular region enclosing the
1367 oval. The oval will include the top and left edges of the rectangle
1368 not the lower or right edges. If the region is square then the result‐
1369 ing oval is circular; otherwise it is elongated in shape. After the
1370 coordinates there may be any number of option-value pairs, each of
1371 which sets one of the configuration options for the item. These same
1372 option-value pairs may be used in itemconfigure widget commands to
1373 change the item's configuration. An oval item becomes the current item
1374 when the mouse pointer is over any part that is painted or (when fully
1375 transparent) that would be painted if both the -fill and -outline op‐
1376 tions were non-empty.
1377 The following standard options are supported by ovals:
1379 -dash -activedash
1381 -disableddash -dashoffset
1382 -fill -activefill
1383 -disabledfill -offset
1384 -outline -activeoutline
1385 -disabledoutline -outlineoffset
1386 -outlinestipple -activeoutlinestipple
1387 -disabledoutlinestipple -stipple
1388 -activestipple -disabledstipple
1389 -state -tags
1390 -width -activewidth
1391 -disabledwidth
1392 There are no oval-specific options.
1394 POLYGON ITEMS
1396 Items of type polygon appear as polygonal or curved filled regions on
1397 the display. Polygon items support coordinate indexing operations us‐
1398 ing the dchars, index and insert widget commands. Polygons are created
1399 with widget commands of the following form:
1400 pathName create polygon x1 y1 ... xn yn ?option value ...?
1401 pathName create polygon coordList ?option value ...?
1402 The arguments x1 through yn or coordList specify the coordinates for
1403 three or more points that define a polygon. The first point should not
1404 be repeated as the last to close the shape; Tk will automatically close
1405 the periphery between the first and last points. After the coordinates
1406 there may be any number of option-value pairs, each of which sets one
1407 of the configuration options for the item. These same option-value
1408 pairs may be used in itemconfigure widget commands to change the item's
1409 configuration. A polygon item is the current item whenever the mouse
1410 pointer is over any part of the polygon, whether drawn or not and
1411 whether or not the outline is smoothed.
1412 The following standard options are supported by polygons:
1414 -dash -activedash
1416 -disableddash -dashoffset
1417 -fill -activefill
1418 -disabledfill -offset
1419 -outline -activeoutline
1420 -disabledoutline -outlineoffset
1421 -outlinestipple -activeoutlinestipple
1422 -disabledoutlinestipple -stipple
1423 -activestipple -disabledstipple
1424 -state -tags
1425 -width -activewidth
1426 -disabledwidth
1427 The following extra options are supported for polygons:
1429 -joinstyle style
1431 Specifies the ways in which joints are to be drawn at the ver‐
1432 tices of the outline. Style may have any of the forms accepted
1433 by Tk_GetJoinStyle (bevel, miter, or round). If this option is
1434 not specified then it defaults to round.
1435 -smooth boolean
1437 Boolean must have one of the forms accepted by Tcl_GetBoolean or
1438 a line smoothing method. Only true and raw are supported in the
1439 core (with bezier being an alias for true), but more can be
1440 added at runtime. If a boolean false value or empty string is
1441 given, no smoothing is applied. A boolean truth value assumes
1442 true smoothing. If the smoothing method is true, this indicates
1443 that the polygon should be drawn as a curve, rendered as a set
1444 of quadratic splines: one spline is drawn for the first and sec‐
1445 ond line segments, one for the second and third, and so on.
1446 Straight-line segments can be generated within a curve by dupli‐
1447 cating the end-points of the desired line segment. If the
1448 smoothing method is raw, this indicates that the polygon should
1449 also be drawn as a curve but where the list of coordinates is
1450 such that the first coordinate pair (and every third coordinate
1451 pair thereafter) is a knot point on a cubic Bezier curve, and
1452 the other coordinates are control points on the cubic Bezier
1453 curve. Straight line segments can be venerated within a curve by
1454 making control points equal to their neighbouring knot points.
1455 If the last point is not the second point of a pair of control
1456 points, the point is repeated (one or two times) so that it also
1457 becomes the second point of a pair of control points (the asso‐
1458 ciated knot point will be the first control point).
1459 -splinesteps number
1461 Specifies the degree of smoothness desired for curves: each
1462 spline will be approximated with number line segments. This op‐
1463 tion is ignored unless the -smooth option is true or raw.
1464 Polygon items are different from other items such as rectangles, ovals
1466 and arcs in that interior points are considered to be “inside” a poly‐
1467 gon (e.g. for purposes of the find closest and find overlapping widget
1468 commands) even if it is not filled. For most other item types, an in‐
1469 terior point is considered to be inside the item only if the item is
1470 filled or if it has neither a fill nor an outline. If you would like an
1471 unfilled polygon whose interior points are not considered to be inside
1472 the polygon, use a line item instead.
1473 RECTANGLE ITEMS
1475 Items of type rectangle appear as rectangular regions on the display.
1476 Each rectangle may have an outline, a fill, or both. Rectangles are
1477 created with widget commands of the following form:
1478 pathName create rectangle x1 y1 x2 y2 ?option value ...?
1479 pathName create rectangle coordList ?option value ...?
1480 The arguments x1, y1, x2, and y2 or coordList (which must have four el‐
1481 ements) give the coordinates of two diagonally opposite corners of the
1482 rectangle (the rectangle will include its upper and left edges but not
1483 its lower or right edges). After the coordinates there may be any num‐
1484 ber of option-value pairs, each of which sets one of the configuration
1485 options for the item. These same option-value pairs may be used in
1486 itemconfigure widget commands to change the item's configuration. A
1487 rectangle item becomes the current item when the mouse pointer is over
1488 any part that is painted or (when fully transparent) that would be
1489 painted if both the -fill and -outline options were non-empty.
1490 The following standard options are supported by rectangles:
1492 -dash -activedash
1494 -disableddash -dashoffset
1495 -fill -activefill
1496 -disabledfill -offset
1497 -outline -activeoutline
1498 -disabledoutline -outlineoffset
1499 -outlinestipple -activeoutlinestipple
1500 -disabledoutlinestipple -stipple
1501 -activestipple -disabledstipple
1502 -state -tags
1503 -width -activewidth
1504 -disabledwidth
1505 There are no rectangle-specific options.
1507 TEXT ITEMS
1509 A text item displays a string of characters on the screen in one or
1510 more lines. Text items support indexing, editing and selection through
1511 the dchars widget command, the focus widget command, the icursor widget
1512 command, the index widget command, the insert widget command, and the
1513 select widget command. Text items are created with widget commands of
1514 the following form:
1515 pathName create text x y ?option value ...?
1516 pathName create text coordList ?option value ...?
1517 The arguments x and y or coordList (which must have two elements) spec‐
1518 ify the coordinates of a point used to position the text on the display
1519 (see the options below for more information on how text is displayed).
1520 After the coordinates there may be any number of option-value pairs,
1521 each of which sets one of the configuration options for the item. These
1522 same option-value pairs may be used in itemconfigure widget commands to
1523 change the item's configuration. A text item becomes the current item
1524 when the mouse pointer is over any part of its bounding box.
1525 The following standard options are supported by text items:
1527 -anchor -fill
1529 -activefill -disabledfill
1530 -stipple -activestipple
1531 -disabledstipple -state
1532 -tags
1533 The following extra options are supported for text items:
1535 -angle rotationDegrees
1537 RotationDegrees tells how many degrees to rotate the text anti‐ │
1538 clockwise about the positioning point for the text; it may have │
1539 any floating-point value from 0.0 to 360.0. For example, if ro‐ │
1540 tationDegrees is 90, then the text will be drawn vertically from │
1541 bottom to top. This option defaults to 0.0.
1542 -font fontName
1544 Specifies the font to use for the text item. FontName may be
1545 any string acceptable to Tk_GetFont. If this option is not
1546 specified, it defaults to a system-dependent font.
1547 -justify how
1549 Specifies how to justify the text within its bounding region.
1550 How must be one of the values left, right, or center. This op‐
1551 tion will only matter if the text is displayed as multiple
1552 lines. If the option is omitted, it defaults to left.
1553 -text string
1555 String specifies the characters to be displayed in the text
1556 item. Newline characters cause line breaks. The characters in
1557 the item may also be changed with the insert and delete widget
1558 commands. This option defaults to an empty string.
1559 -underline
1561 Specifies the integer index of a character within the text to be
1562 underlined. 0 corresponds to the first character of the text
1563 displayed, 1 to the next character, and so on. -1 means that no
1564 underline should be drawn (if the whole text item is to be un‐
1565 derlined, the appropriate font should be used instead).
1566 -width lineLength
1568 Specifies a maximum line length for the text, in any of the
1569 forms described in the COORDINATES section above. If this op‐
1570 tion is zero (the default) the text is broken into lines only at
1571 newline characters. However, if this option is non-zero then
1572 any line that would be longer than lineLength is broken just be‐
1573 fore a space character to make the line shorter than lineLength;
1574 the space character is treated as if it were a newline charac‐
1575 ter.
1576 WINDOW ITEMS
1578 Items of type window cause a particular window to be displayed at a
1579 given position on the canvas. Window items are created with widget
1580 commands of the following form:
1581 pathName create window x y ?option value ...?
1582 pathName create window coordList ?option value ...?
1583 The arguments x and y or coordList (which must have two elements) spec‐
1584 ify the coordinates of a point used to position the window on the dis‐
1585 play, as controlled by the -anchor option. After the coordinates there
1586 may be any number of option-value pairs, each of which sets one of the
1587 configuration options for the item. These same option-value pairs may
1588 be used in itemconfigure widget commands to change the item's configu‐
1589 ration. Theoretically, a window item becomes the current item when the
1590 mouse pointer is over any part of its bounding box, but in practice
1591 this typically does not happen because the mouse pointer ceases to be
1592 over the canvas at that point.
1593 The following standard options are supported by window items:
1595 -anchor -state
1597 -tags
1598 The following extra options are supported for window items:
1600 -height pixels
1602 Specifies the height to assign to the item's window. Pixels may
1603 have any of the forms described in the COORDINATES section
1604 above. If this option is not specified, or if it is specified
1605 as zero, then the window is given whatever height it requests
1606 internally.
1607 -width pixels
1609 Specifies the width to assign to the item's window. Pixels may
1610 have any of the forms described in the COORDINATES section
1611 above. If this option is not specified, or if it is specified
1612 as zero, then the window is given whatever width it requests in‐
1613 ternally.
1614 -window pathName
1616 Specifies the window to associate with this item. The window
1617 specified by pathName must either be a child of the canvas wid‐
1618 get or a child of some ancestor of the canvas widget. PathName
1619 may not refer to a top-level window.
1620 Note: due to restrictions in the ways that windows are managed, it is
1622 not possible to draw other graphical items (such as lines and images)
1623 on top of window items. A window item always obscures any graphics that
1624 overlap it, regardless of their order in the display list. Also note
1625 that window items, unlike other canvas items, are not clipped for dis‐
1626 play by their containing canvas's border, and are instead clipped by
1627 the parent widget of the window specified by the -window option; when
1628 the parent widget is the canvas, this means that the window item can
1629 overlap the canvas's border.
1630
1632 It is possible for individual applications to define new item types for
1633 canvas widgets using C code. See the documentation for Tk_CreateItem‐
1634 Type.
1635
1637 In the current implementation, new canvases are not given any default
1638 behavior: you will have to execute explicit Tcl commands to give the
1639 canvas its behavior.
1640
1642 Tk's canvas widget is a blatant ripoff of ideas from Joel Bartlett's
1643 ezd program. Ezd provides structured graphics in a Scheme environment
1644 and preceded canvases by a year or two. Its simple mechanisms for plac‐
1645 ing and animating graphical objects inspired the functions of canvases.
1646
1648 bind(n), font(n), image(n), scrollbar(n)
1649
1651 canvas, widget
1652Tk 8.3 canvas(n)