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 -insertborderwidth -selectborderwidth
15 -borderwidth -insertofftime -selectforeground
16 -cursor -insertontime -takefocus
17 -highlightbackground -insertwidth -xscrollcommand
18 -highlightcolor -relief -yscrollcommand
19 -highlightthickness -state
20 -insertbackground -selectbackground
21 See the options manual entry for details on the standard options.
23
25 [-closeenough closeEnough] Specifies a floating-point value indicating
26 how close the mouse cursor must be to an item before it is considered
27 to be ``inside'' the item. Defaults to 1.0. [-confine confine] Speci‐
28 fies a boolean value that indicates whether or not it should be allow‐
29 able to set the canvas's view outside the region defined by the scroll‐
30 Region argument. Defaults to true, which means that the view will be
31 constrained within the scroll region. [-height height] Specifies a
32 desired window height that the canvas widget should request from its
33 geometry manager. The value may be specified in any of the forms
34 described in the COORDINATES section below. [-scrollregion scrollRe‐
35 gion] Specifies a list with four coordinates describing the left, top,
36 right, and bottom coordinates of a rectangular region. This region is
37 used for scrolling purposes and is considered to be the boundary of the
38 information in the canvas. Each of the coordinates may be specified in
39 any of the forms given in the COORDINATES section below.
40 [-state state] Modifies the default state of the canvas where state may
41 be set to one of: normal, disabled, or hidden. Individual canvas
42 objects all have their own state option which may override the default
43 state. Many options can take separate specifications such that the
44 appearance of the item can be different in different situations. The
45 options that start with active control the appearence when the mouse
46 pointer is over it, while the option starting with disabled controls
47 the appearence when the state is disabled. Canvas items which are dis‐
48 abled will not react to canvas bindings. [-width width] Specifies a
49 desired window width that the canvas widget should request from its
50 geometry manager. The value may be specified in any of the forms
51 described in the COORDINATES section below. [-xscrollincre‐
52 ment xScrollIncrement] Specifies an increment for horizontal scrolling,
53 in any of the usual forms permitted for screen distances. If the value
54 of this option is greater than zero, the horizontal view in the window
55 will be constrained so that the canvas x coordinate at the left edge of
56 the window is always an even multiple of xScrollIncrement; further‐
57 more, the units for scrolling (e.g., the change in view when the left
58 and right arrows of a scrollbar are selected) will also be
59 xScrollIncrement. If the value of this option is less than or equal to
60 zero, then horizontal scrolling is unconstrained. [-yscrollincre‐
61 ment yScrollIncrement] Specifies an increment for vertical scrolling,
62 in any of the usual forms permitted for screen distances. If the value
63 of this option is greater than zero, the vertical view in the window
64 will be constrained so that the canvas y coordinate at the top edge of
65 the window is always an even multiple of yScrollIncrement; further‐
66 more, the units for scrolling (e.g., the change in view when the top
67 and bottom arrows of a scrollbar are selected) will also be
68 yScrollIncrement. If the value of this option is less than or equal to
69 zero, then vertical scrolling is unconstrained.
70_________________________________________________________________
71
74 The canvas command creates a new window (given by the pathName argu‐
75 ment) and makes it into a canvas widget. Additional options, described
76 above, may be specified on the command line or in the option database
77 to configure aspects of the canvas such as its colors and 3-D relief.
78 The canvas command returns its pathName argument. At the time this
79 command is invoked, there must not exist a window named pathName, but
80 pathName's parent must exist.
81 Canvas widgets implement structured graphics. A canvas displays any
83 number of items, which may be things like rectangles, circles, lines,
84 and text. Items may be manipulated (e.g. moved or re-colored) and com‐
85 mands may be associated with items in much the same way that the bind
86 command allows commands to be bound to widgets. For example, a partic‐
87 ular command may be associated with the <Button-1> event so that the
88 command is invoked whenever button 1 is pressed with the mouse cursor
89 over an item. This means that items in a canvas can have behaviors
90 defined by the Tcl scripts bound to them.
91
93 The items in a canvas are ordered for purposes of display, with the
94 first item in the display list being displayed first, followed by the
95 next item in the list, and so on. Items later in the display list
96 obscure those that are earlier in the display list and are sometimes
97 referred to as being ``on top'' of earlier items. When a new item is
98 created it is placed at the end of the display list, on top of every‐
99 thing else. Widget commands may be used to re-arrange the order of the
100 display list.
101 Window items are an exception to the above rules. The underlying win‐
103 dow systems require them always to be drawn on top of other items. In
104 addition, the stacking order of window items is not affected by any of
105 the canvas widget commands; you must use the raise and lower Tk com‐
106 mands instead.
107
109 Items in a canvas widget may be named in either of two ways: by id or
110 by tag. Each item has a unique identifying number, which is assigned
111 to that item when it is created. The id of an item never changes and
112 id numbers are never re-used within the lifetime of a canvas widget.
113 Each item may also have any number of tags associated with it. A tag
115 is just a string of characters, and it may take any form except that of
116 an integer. For example, ``x123'' is OK but ``123'' isn't. The same
117 tag may be associated with many different items. This is commonly done
118 to group items in various interesting ways; for example, all selected
119 items might be given the tag ``selected''.
120 The tag all is implicitly associated with every item in the canvas; it
122 may be used to invoke operations on all the items in the canvas.
123 The tag current is managed automatically by Tk; it applies to the cur‐
125 rent item, which is the topmost item whose drawn area covers the posi‐
126 tion of the mouse cursor. If the mouse is not in the canvas widget or
127 is not over an item, then no 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
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 don't support the insertion cursor
198 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 isn't in this item then this form is illegal.
222 sel.last Refers to the last selected character in the item. If the
224 selection isn't 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 can not 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 "." will
254 always be displayed as a dot and "-" always as a dash regardless of the
255 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 isn't 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
329 the named elements are within the region bounded by x1 on the
330 left, 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
347 command augments an existing binding rather than replacing it).
348 In 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 don't support indexing opera‐
442 tions 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 doesn't 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 doesn't refer to any items, or
471 if none of them support the insertion cursor, then the focus
472 isn't 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 doesn't 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 wasn't 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 doesn't 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 don't
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 doesn't have the focus. This command returns
505 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
597 reach its final size, or else use the -width and -height options
598 to specify the area of the canvas to print. The option-value
599 argument pairs provide additional information to control the
600 generation 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 setrgb‐
607 color''). When outputting color information in the Post‐
608 script, Tk checks to see if there is an element of var‐
609 Name with the same name as the color. If so, Tk uses the
610 value of the element as the Postscript command to set the
611 color. If this option hasn't been specified, or if there
612 isn't an entry in varName for a given color, then Tk uses
613 the red, 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 isn't 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 isn't 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 isn't 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 doesn't 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 isn't
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 doesn't 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 don't 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
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"
911 for 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 hasn't 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 -stipple bitmap
971 -activestipple bitmap
973 -disabledstipple bitmap
975 This option specifies stipple patterns that should be used to
976 fill the item in its normal, active and disabled states. bitmap
977 specifies the stipple pattern to use, in any of the forms
978 accepted by Tk_GetBitmap. If the -fill option hasn't been spec‐
979 ified then this option has no effect. If bitmap is an empty
980 string (the default), then filling is done in a solid fashion.
981 For the text item, it affects the actual text. Note that stip‐
982 ples are not well supported on platforms that do not use X11 as
983 their drawing API.
984 -state state
986 This allows an item to override the canvas widget's global state
987 option. It takes the same values: normal, disabled or hidden.
988 -tags tagList
990 Specifies a set of tags to apply to the item. TagList consists
991 of a list of tag names, which replace any existing tags for the
992 item. TagList may be an empty list.
993 -width outlineWidth
995 -activewidth outlineWidth
997 -disabledwidth outlineWidth
999 Specifies the width of the outline to be drawn around the item's
1000 region, in its normal, active and disabled states. outlineWidth
1001 may be in any of the forms described in the COORDINATES section
1002 above. If the -outline option has been specified as an empty
1003 string then this option has no effect. This option defaults to
1004 1.0. For arcs, wide outlines will be drawn centered on the
1005 edges of the arc's region.
1006
1008 Items of type arc appear on the display as arc-shaped regions. An arc
1009 is a section of an oval delimited by two angles (specified by the
1010 -start and -extent options) and displayed in one of several ways (spec‐
1011 ified by the -style option). Arcs are created with widget commands of
1012 the following form:
1013 pathName create arc x1 y1 x2 y2 ?option value option value ...?
1014 pathName create arc coordList ?option value option value ...?
1015 The arguments x1, y1, x2, and y2 or coordList give the coordinates of
1016 two diagonally opposite corners of a rectangular region enclosing the
1017 oval that defines the arc. After the coordinates there may be any num‐
1018 ber of option-value pairs, each of which sets one of the configuration
1019 options for the item. These same option-value pairs may be used in
1020 itemconfigure widget commands to change the item's configuration.
1021 The following standard options are supported by arcs:
1022 -dash
1023 -activedash
1024 -disableddash
1025 -dashoffset
1026 -fill
1027 -activefill
1028 -disabledfill
1029 -offset
1030 -outline
1031 -activeoutline
1032 -disabledoutline
1033 -outlinestipple
1034 -activeoutlinestipple
1035 -disabledoutlinestipple
1036 -stipple
1037 -activestipple
1038 -disabledstipple
1039 -state
1040 -tags
1041 -width
1042 -activewidth
1043 -disabledwidth
1044 The following extra options are supported for arcs:
1045 -extent degrees
1047 Specifies the size of the angular range occupied by the arc.
1048 The arc's range extends for degrees degrees counter-clockwise
1049 from the starting angle given by the -start option. Degrees may
1050 be negative. If it is greater than 360 or less than -360, then
1051 degrees modulo 360 is used as the extent.
1052 -start degrees
1054 Specifies the beginning of the angular range occupied by the
1055 arc. Degrees is given in units of degrees measured counter-
1056 clockwise from the 3-o'clock position; it may be either posi‐
1057 tive or negative.
1058 -style type
1060 Specifies how to draw the arc. If type is pieslice (the
1061 default) then the arc's region is defined by a section of the
1062 oval's perimeter plus two line segments, one between the center
1063 of the oval and each end of the perimeter section. If type is
1064 chord then the arc's region is defined by a section of the
1065 oval's perimeter plus a single line segment connecting the two
1066 end points of the perimeter section. If type is arc then the
1067 arc's region consists of a section of the perimeter alone. In
1068 this last case the -fill option is ignored.
1069
1071 Items of type bitmap appear on the display as images with two colors,
1072 foreground and background. Bitmaps are created with widget commands of
1073 the following form:
1074 pathName create bitmap x y ?option value option value ...?
1075 pathName create bitmap coordList ?option value option value ...?
1076 The arguments x and y or coordList specify the coordinates of a point
1077 used to position the bitmap on the display (see the -anchor option
1078 below for more information on how bitmaps are displayed). After the
1079 coordinates there may be any number of option-value pairs, each of
1080 which sets one of the configuration options for the item. These same
1081 option-value pairs may be used in itemconfigure widget commands to
1082 change the item's configuration.
1083 The following standard options are supported by bitmaps:
1084 -state
1085 -tags
1086 The following extra options are supported for bitmaps:
1087 -anchor anchorPos
1089 AnchorPos tells how to position the bitmap relative to the posi‐
1090 tioning point for the item; it may have any of the forms
1091 accepted by Tk_GetAnchor. For example, if anchorPos is center
1092 then the bitmap is centered on the point; if anchorPos is n
1093 then the bitmap will be drawn so that its top center point is at
1094 the positioning point. This option defaults to center.
1095 -background color
1097 -activebackground bitmap
1099 -disabledbackground bitmap
1101 Specifies the color to use for each of the bitmap's '0' valued
1102 pixels in its normal, active and disabled states. Color may
1103 have any of the forms accepted by Tk_GetColor. If this option
1104 isn't specified, or if it is specified as an empty string, then
1105 nothing is displayed where the bitmap pixels are 0; this pro‐
1106 duces a transparent effect.
1107 -bitmap bitmap
1109 -activebitmap bitmap
1111 -disabledbitmap bitmap
1113 Specifies the bitmaps to display in the item in its normal,
1114 active and disabled states. Bitmap may have any of the forms
1115 accepted by Tk_GetBitmap.
1116 -foreground color
1118 -activeforeground bitmap
1120 -disabledforeground bitmap
1122 Specifies the color to use for each of the bitmap's '1' valued
1123 pixels in its normal, active and disabled states. Color may
1124 have any of the forms accepted by Tk_GetColor and defaults to
1125 black.
1126
1128 Items of type image are used to display images on a canvas. Images are
1129 created with widget commands of the following form:
1130 pathName create image x y ?option value option value ...?
1131 pathName create image coordList ?option value option value ...?
1132 The arguments x and y or coordList specify the coordinates of a point
1133 used to position the image on the display (see the -anchor option below
1134 for more information). After the coordinates there may be any number
1135 of option-value pairs, each of which sets one of the configuration
1136 options for the item. These same option-value pairs may be used in
1137 itemconfigure widget commands to change the item's configuration.
1138 The following standard options are supported by images:
1139 -state
1140 -tags
1141 The following extra options are supported for images:
1142 -anchor anchorPos
1144 AnchorPos tells how to position the image relative to the posi‐
1145 tioning point for the item; it may have any of the forms
1146 accepted by Tk_GetAnchor. For example, if anchorPos is center
1147 then the image is centered on the point; if anchorPos is n then
1148 the image will be drawn so that its top center point is at the
1149 positioning point. This option defaults to center.
1150 -image name
1152 -activeimage name
1154 -disabledimage name
1156 Specifies the name of the images to display in the item in is
1157 normal, active and disabled states. This image must have been
1158 created previously with the image create command.
1159
1161 Items of type line appear on the display as one or more connected line
1162 segments or curves. Line items support coordinate indexing operations
1163 using the canvas widget commands: dchars, index, insert. Lines are
1164 created with widget commands of the following form:
1165 pathName create line x1 y1... xn yn ?option value option value ...?
1166 pathName create line coordList ?option value option value ...?
1167 The arguments x1 through yn or coordList give the coordinates for a
1168 series of two or more points that describe a series of connected line
1169 segments. After the coordinates there may be any number of
1170 option-value pairs, each of which sets one of the configuration options
1171 for the item. These same option-value pairs may be used in itemconfig‐
1172 ure widget commands to change the item's configuration.
1173 The following standard options are supported by lines:
1174 -dash
1175 -activedash
1176 -disableddash
1177 -dashoffset
1178 -fill
1179 -activefill
1180 -disabledfill
1181 -stipple
1182 -activestipple
1183 -disabledstipple
1184 -state
1185 -tags
1186 -width
1187 -activewidth
1188 -disabledwidth
1189 The following extra options are supported for lines:
1190 -arrow where
1192 Indicates whether or not arrowheads are to be drawn at one or
1193 both ends of the line. Where must have one of the values none
1194 (for no arrowheads), first (for an arrowhead at the first point
1195 of the line), last (for an arrowhead at the last point of the
1196 line), or both (for arrowheads at both ends). This option
1197 defaults to none.
1198 -arrowshape shape
1200 This option indicates how to draw arrowheads. The shape argu‐
1201 ment must be a list with three elements, each specifying a dis‐
1202 tance in any of the forms described in the COORDINATES section
1203 above. The first element of the list gives the distance along
1204 the line from the neck of the arrowhead to its tip. The second
1205 element gives the distance along the line from the trailing
1206 points of the arrowhead to the tip, and the third element gives
1207 the distance from the outside edge of the line to the trailing
1208 points. If this option isn't specified then Tk picks a ``rea‐
1209 sonable'' shape.
1210 -capstyle style
1212 Specifies the ways in which caps are to be drawn at the end‐
1213 points of the line. Style may have any of the forms accepted by
1214 Tk_GetCapStyle (butt, projecting, or round). If this option
1215 isn't specified then it defaults to butt. Where arrowheads are
1216 drawn the cap style is ignored.
1217 -joinstyle style
1219 Specifies the ways in which joints are to be drawn at the ver‐
1220 tices of the line. Style may have any of the forms accepted by
1221 Tk_GetCapStyle (bevel, miter, or round). If this option isn't
1222 specified then it defaults to miter. If the line only contains
1223 two points then this option is irrelevant.
1224 -smooth smoothMethod
1226 smoothMethod must have one of the forms accepted by Tcl_Get‐
1227 Boolean or a line smoothing method. Only bezier is supported in
1228 the core, but more can be added at runtime. If a boolean false
1229 value or empty string is given, no smoothing is applied. A
1230 boolean truth value assume bezier smoothing. It indicates
1231 whether or not the line should be drawn as a curve. If so, the
1232 line is rendered as a set of parabolic splines: one spline is
1233 drawn for the first and second line segments, one for the second
1234 and third, and so on. Straight-line segments can be generated
1235 within a curve by duplicating the end-points of the desired line
1236 segment.
1237 -splinesteps number
1239 Specifies the degree of smoothness desired for curves: each
1240 spline will be approximated with number line segments. This
1241 option is ignored unless the -smooth option is true.
1242
1245 Items of type oval appear as circular or oval regions on the display.
1246 Each oval may have an outline, a fill, or both. Ovals are created with
1247 widget commands of the following form:
1248 pathName create oval x1 y1 x2 y2 ?option value option value ...?
1249 pathName create oval coordList ?option value option value ...?
1250 The arguments x1, y1, x2, and y2 or coordList give the coordinates of
1251 two diagonally opposite corners of a rectangular region enclosing the
1252 oval. The oval will include the top and left edges of the rectangle
1253 not the lower or right edges. If the region is square then the result‐
1254 ing oval is circular; otherwise it is elongated in shape. After the
1255 coordinates there may be any number of option-value pairs, each of
1256 which sets one of the configuration options for the item. These same
1257 option-value pairs may be used in itemconfigure widget commands to
1258 change the item's configuration.
1259 The following standard options are supported by ovals:
1260 -dash
1261 -activedash
1262 -disableddash
1263 -dashoffset
1264 -fill
1265 -activefill
1266 -disabledfill
1267 -offset
1268 -outline
1269 -activeoutline
1270 -disabledoutline
1271 -outlinestipple
1272 -activeoutlinestipple
1273 -disabledoutlinestipple
1274 -stipple
1275 -activestipple
1276 -disabledstipple
1277 -state
1278 -tags
1279 -width
1280 -activewidth
1281 -disabledwidth
1282
1284 Items of type polygon appear as polygonal or curved filled regions on
1285 the display. Polygon items support coordinate indexing operations
1286 using the canvas widget commands: dchars, index, insert. Polygons are
1287 created with widget commands of the following form:
1288 pathName create polygon x1 y1 ... xn yn ?option value option value ...?
1289 pathName create polygon coordList ?option value option value ...?
1290 The arguments x1 through yn or coordList specify the coordinates for
1291 three or more points that define a polygon. The first point should not
1292 be repeated as the last to close the shape; Tk will automatically close
1293 the periphery between the first and last points. After the coordinates
1294 there may be any number of option-value pairs, each of which sets one
1295 of the configuration options for the item. These same option-value
1296 pairs may be used in itemconfigure widget commands to change the item's
1297 configuration.
1298 The following standard options are supported by polygons:
1299 -dash
1300 -activedash
1301 -disableddash
1302 -dashoffset
1303 -fill
1304 -activefill
1305 -disabledfill
1306 -offset
1307 -outline
1308 -activeoutline
1309 -disabledoutline
1310 -outlinestipple
1311 -activeoutlinestipple
1312 -disabledoutlinestipple
1313 -stipple
1314 -activestipple
1315 -disabledstipple
1316 -state
1317 -tags
1318 -width
1319 -activewidth
1320 -disabledwidth
1321 The following extra options are supported for polygons:
1322 -joinstyle style
1324 Specifies the ways in which joints are to be drawn at the ver‐
1325 tices of the outline. Style may have any of the forms accepted
1326 by Tk_GetCapStyle (bevel, miter, or round). If this option
1327 isn't specified then it defaults to miter.
1328 -smooth boolean
1330 Boolean must have one of the forms accepted by Tcl_GetBoolean.
1331 It indicates whether or not the polygon should be drawn with a
1332 curved perimeter. If so, the outline of the polygon becomes a
1333 set of parabolic splines, one spline for the first and second
1334 line segments, one for the second and third, and so on.
1335 Straight-line segments can be generated in a smoothed polygon by
1336 duplicating the end-points of the desired line segment.
1337 -splinesteps number
1339 Specifies the degree of smoothness desired for curves: each
1340 spline will be approximated with number line segments. This
1341 option is ignored unless the -smooth option is true.
1342 Polygon items are different from other items such as rectangles, ovals
1344 and arcs in that interior points are considered to be ``inside'' a
1345 polygon (e.g. for purposes of the find closest and find overlapping
1346 widget commands) even if it is not filled. For most other item types,
1347 an interior point is considered to be inside the item only if the item
1348 is filled or if it has neither a fill nor an outline. If you would
1349 like an unfilled polygon whose interior points are not considered to be
1350 inside the polygon, use a line item instead.
1351
1353 Items of type rectangle appear as rectangular regions on the display.
1354 Each rectangle may have an outline, a fill, or both. Rectangles are
1355 created with widget commands of the following form:
1356 pathName create rectangle x1 y1 x2 y2 ?option value option value ...?
1357 pathName create rectangle coordList ?option value option value ...?
1358 The arguments x1, y1, x2, and y2 or coordList give the coordinates of
1359 two diagonally opposite corners of the rectangle (the rectangle will
1360 include its upper and left edges but not its lower or right edges).
1361 After the coordinates there may be any number of option-value pairs,
1362 each of which sets one of the configuration options for the item.
1363 These same option-value pairs may be used in itemconfigure widget com‐
1364 mands to change the item's configuration.
1365 The following standard options are supported by rectangles:
1366 -dash
1367 -activedash
1368 -disableddash
1369 -dashoffset
1370 -fill
1371 -activefill
1372 -disabledfill
1373 -offset
1374 -outline
1375 -activeoutline
1376 -disabledoutline
1377 -outlinestipple
1378 -activeoutlinestipple
1379 -disabledoutlinestipple
1380 -stipple
1381 -activestipple
1382 -disabledstipple
1383 -state
1384 -tags
1385 -width
1386 -activewidth
1387 -disabledwidth
1388
1390 A text item displays a string of characters on the screen in one or
1391 more lines. Text items support indexing and selection, along with the
1392 following text-related canvas widget commands: dchars, focus, icursor,
1393 index, insert, select. Text items are created with widget commands of
1394 the following form:
1395 pathName create text x y ?option value option value ...?
1396 pathName create text coordList ?option value option value ...?
1397 The arguments x and y or coordList specify the coordinates of a point
1398 used to position the text on the display (see the options below for
1399 more information on how text is displayed). After the coordinates
1400 there may be any number of option-value pairs, each of which sets one
1401 of the configuration options for the item. These same option-value
1402 pairs may be used in itemconfigure widget commands to change the item's
1403 configuration.
1404 The following standard options are supported by text items:
1405 -fill
1406 -activefill
1407 -disabledfill
1408 -stipple
1409 -activestipple
1410 -disabledstipple
1411 -state
1412 -tags
1413 The following extra options are supported for text items:
1414 -anchor anchorPos
1416 AnchorPos tells how to position the text relative to the posi‐
1417 tioning point for the text; it may have any of the forms
1418 accepted by Tk_GetAnchor. For example, if anchorPos is center
1419 then the text is centered on the point; if anchorPos is n then
1420 the text will be drawn such that the top center point of the
1421 rectangular region occupied by the text will be at the position‐
1422 ing point. This option defaults to center.
1423 -font fontName
1425 Specifies the font to use for the text item. FontName may be
1426 any string acceptable to Tk_GetFont. If this option isn't spec‐
1427 ified, it defaults to a system-dependent font.
1428 -justify how
1430 Specifies how to justify the text within its bounding region.
1431 How must be one of the values left, right, or center. This
1432 option will only matter if the text is displayed as multiple
1433 lines. If the option is omitted, it defaults to left.
1434 -text string
1436 String specifies the characters to be displayed in the text
1437 item. Newline characters cause line breaks. The characters in
1438 the item may also be changed with the insert and delete widget
1439 commands. This option defaults to an empty string.
1440 -width lineLength
1442 Specifies a maximum line length for the text, in any of the
1443 forms described in the COORDINATES section above. If this
1444 option is zero (the default) the text is broken into lines only
1445 at newline characters. However, if this option is non-zero then
1446 any line that would be longer than lineLength is broken just
1447 before a space character to make the line shorter than line‐
1448 Length; the space character is treated as if it were a newline
1449 character.
1450
1452 Items of type window cause a particular window to be displayed at a
1453 given position on the canvas. Window items are created with widget
1454 commands of the following form:
1455 pathName create window x y ?option value option value ...?
1456 pathName create window coordList ?option value option value ...?
1457 The arguments x and y or coordList specify the coordinates of a point
1458 used to position the window on the display (see the -anchor option
1459 below for more information on how bitmaps are displayed). After the
1460 coordinates there may be any number of option-value pairs, each of
1461 which sets one of the configuration options for the item. These same
1462 option-value pairs may be used in itemconfigure widget commands to
1463 change the item's configuration.
1464 The following standard options are supported by window items:
1465 -state
1466 -tags
1467 The following extra options are supported for window items:
1468 -anchor anchorPos
1470 AnchorPos tells how to position the window relative to the posi‐
1471 tioning point for the item; it may have any of the forms
1472 accepted by Tk_GetAnchor. For example, if anchorPos is center
1473 then the window is centered on the point; if anchorPos is n
1474 then the window will be drawn so that its top center point is at
1475 the positioning point. This option defaults to center.
1476 -height pixels
1478 Specifies the height to assign to the item's window. Pixels may
1479 have any of the forms described in the COORDINATES section
1480 above. If this option isn't specified, or if it is specified as
1481 an empty string, then the window is given whatever height it
1482 requests internally.
1483 -width pixels
1485 Specifies the width to assign to the item's window. Pixels may
1486 have any of the forms described in the COORDINATES section
1487 above. If this option isn't specified, or if it is specified as
1488 an empty string, then the window is given whatever width it
1489 requests internally.
1490 -window pathName
1492 Specifies the window to associate with this item. The window
1493 specified by pathName must either be a child of the canvas wid‐
1494 get or a child of some ancestor of the canvas widget. PathName
1495 may not refer to a top-level window.
1496 Note: due to restrictions in the ways that windows are managed, it is
1498 not possible to draw other graphical items (such as lines and images)
1499 on top of window items. A window item always obscures any graphics
1500 that overlap it, regardless of their order in the display list.
1501
1503 It is possible for individual applications to define new item types for
1504 canvas widgets using C code. See the documentation for Tk_CreateItem‐
1505 Type.
1506
1508 In the current implementation, new canvases are not given any default
1509 behavior: you'll have to execute explicit Tcl commands to give the
1510 canvas its behavior.
1511
1513 Tk's canvas widget is a blatant ripoff of ideas from Joel Bartlett's
1514 ezd program. Ezd provides structured graphics in a Scheme environment
1515 and preceded canvases by a year or two. Its simple mechanisms for
1516 placing and animating graphical objects inspired the functions of can‐
1517 vases.
1518
1521 bind(n), font(n), image(n), scrollbar(n)
1522
1525 canvas, widget
1526Tk 8.3 canvas(n)