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1 | =head1 NAME |
2 | ||
3 | Tk::DItem - Tix Display Items | |
4 | ||
5 | =for category Tix Extensions | |
6 | ||
7 | =head1 SYNOPSIS | |
8 | ||
9 | =head1 DESCRIPTION | |
10 | ||
11 | The Tix B<Display Items> and B<Display Types> are devised to | |
12 | solve a general problem: many Tix widgets (both existing and planned | |
13 | ones) display many items of many types simultaneously. | |
14 | ||
15 | For example, a hierarchical listbox widget (see L<Tk::HList>) can display | |
16 | items | |
17 | of images, plain text and subwindows in the form of a | |
18 | hierarchy. Another widget, the tabular listbox widget (see L<Tk::TList>) | |
19 | also displays items of the | |
20 | same types, although it arranges the items in a tabular form. Yet | |
21 | another widget, the spreadsheet widget (see L<Tk::TixGrid>), | |
22 | also displays similar types | |
23 | items, but in yet another format. | |
24 | ||
25 | In these examples, the display items in different widgets are only | |
26 | different in how they are arranged by the B<host widget>. In Tix, | |
27 | display items are clearly separated from the host widgets. The | |
28 | advantage is two-fold: first, the creation and configuration of | |
29 | display items become uniform across different host widgets. Second, | |
30 | new display item types can be added without the need to modify the | |
31 | existing host widgets. | |
32 | ||
33 | In a way, Tix display items are similar to the items inside Tk | |
34 | the canvas widget. However, unlike the Tix display items, the canvas | |
35 | items are not independent of the canvas widget; this makes it | |
36 | impossible to use the canvas items inside other types of TK widgets. | |
37 | ||
38 | The appearance of a display item is controlled by a set of | |
39 | I<attributes>. It is observed that each the attributes usually fall | |
40 | into one of two categroies: ``I<individual>'' or | |
41 | ``I<collective>''. For example, the text items inside a HList widget | |
42 | may all display a different text string; however, in most cases, the | |
43 | text items share the same color, font and spacing. Instead of keeping | |
44 | a duplicated version of the same attributes inside each display item, | |
45 | it will be advantageous to put the collective attributes in a | |
46 | special object called a B<display style>. First, there is the space | |
47 | concern: a host widget may have many thousands of items; keeping | |
48 | dupilcated attributes will be very wasteful. Second, when it becomes | |
49 | necessary to change a collective attribute, such as changing all the | |
50 | text items' foreground color to red, it will be more efficient to | |
51 | change only the display style object than to modify all the text | |
52 | items one by one. | |
53 | ||
54 | The attributes of the a display item are thus stored in two places: it | |
55 | has a set of B<item options> to store its individual attributes. Each | |
56 | display item is also associated with a I<display style>, which specifies | |
57 | the collective attributes of all items associated with itself. | |
58 | ||
59 | The division between the individual and collective attributes are | |
60 | fixed and cannot be changed. Thus, when it becomes necessary for some | |
61 | items to differ in their collective attributes, two or more B<display styles> | |
62 | can be used. For example, suppose you want to display two | |
63 | columns of text items inside an HList widget, one column in red and | |
64 | the other in blue. You can create a TextStyle object called ``$red'' | |
65 | which defines a red foreground, and another called ``$blue'', which | |
66 | defines a blue foreground. You can then associate all text items of | |
67 | the first column to ``$red'' and the second column to ``$blue'' | |
68 | ||
69 | =head1 DISPLAY ITEM TYPES AND OPTIONS | |
70 | ||
71 | Currently there are three types of display items: B<text>, | |
72 | B<imagetext> and I<window>. | |
73 | ||
74 | =head1 IMAGETEXT ITEMS | |
75 | ||
76 | Display items of the type B<imagetext> are used to display an image | |
77 | together with a text string. Imagetext items support the following options: | |
78 | ||
79 | =head2 Imagetext Item Options | |
80 | ||
81 | =over 4 | |
82 | ||
83 | =item Name: B<bitmap> | |
84 | ||
85 | =item Class: B<Bitmap> | |
86 | ||
87 | =item Switch: B<-bitmap> | |
88 | ||
89 | Specifies the bitmap to display in the item. | |
90 | ||
91 | =item Name: B<image> | |
92 | ||
93 | =item Class: B<Image> | |
94 | ||
95 | =item Switch: B<-image> | |
96 | ||
97 | Specifies the image to display in the item. When both the | |
98 | B<-bitmap> and B<-image> options are specified, only the image | |
99 | will be displayed. | |
100 | ||
101 | =item Name: B<imageTextStyle> | |
102 | ||
103 | =item Class: B<ImageTextStyle> | |
104 | ||
105 | =item Switch: B<-style> | |
106 | ||
107 | Specifies the display style to use for this item. Must be the | |
108 | name of a B<imagetext> display style that has already be created with | |
109 | B<ItemStyle>. | |
110 | ||
111 | =item Name: B<showImage> | |
112 | ||
113 | =item Class: B<ShowImage> | |
114 | ||
115 | =item Switch: B<-showimage> | |
116 | ||
117 | A Boolean value that specifies whether the image/bitmap should be | |
118 | displayed. | |
119 | ||
120 | =item Name: B<showText> | |
121 | ||
122 | =item Class: B<ShowText> | |
123 | ||
124 | =item Switch: B<-showtext> | |
125 | ||
126 | A Boolean value that specifies whether the text string should be | |
127 | displayed. | |
128 | ||
129 | =item Name: B<text> | |
130 | ||
131 | =item Class: B<Text> | |
132 | ||
133 | =item Switch: B<-text> | |
134 | ||
135 | Specifies the text string to display in the item. | |
136 | ||
137 | =item Name: B<underline> | |
138 | ||
139 | =item Class: B<Underline> | |
140 | ||
141 | =item Switch: B<-underline> | |
142 | ||
143 | Specifies the integer index of a character to underline in the text | |
144 | string in the item. 0 corresponds to the first character of the text | |
145 | displayed in the widget, 1 to the next character, and so on. | |
146 | ||
147 | =back | |
148 | ||
149 | =head2 Imagetext Style Options | |
150 | ||
151 | The style information of B<imagetext> items are stored in the | |
152 | B<imagetext> display style. The following options are supported: | |
153 | ||
154 | B<STANDARD OPTIONS> | |
155 | ||
156 | B<-activebackground> B<-activeforeground> | |
157 | B<-anchor> B<-background> | |
158 | B<-disabledbackground> B<-disabledforeground> | |
159 | B<-foreground> B<-font> | |
160 | B<-justify> B<-padx> | |
161 | B<-pady> B<-selectbackground> | |
162 | B<-selectforeground> B<-wraplength> | |
163 | ||
164 | See L<Tk::options> for details of the standard options. | |
165 | ||
166 | B<STYLE-SPECIFIC OPTIONS> | |
167 | ||
168 | =over 4 | |
169 | ||
170 | =item Name: B<gap> | |
171 | ||
172 | =item Class: B<Gap> | |
173 | ||
174 | =item Switch: B<-gap> | |
175 | ||
176 | Specifies the distance between the bitmap/image and the text string, | |
177 | in number of pixels. | |
178 | ||
179 | =item Name: B<textAnchor> | |
180 | ||
181 | =item Class: B<TextAnchor> | |
182 | ||
183 | =item Switch: B<-textanchor> | |
184 | ||
185 | The anchor position on the image to which text part is attached. | |
186 | This is a perl/Tk addition. Defaults to B<e> for compatibility with standard | |
187 | Tix. The interesting cases are | |
188 | ||
189 | =over 8 | |
190 | ||
191 | =item B<n> | |
192 | ||
193 | Text is centred above the image. | |
194 | ||
195 | =item B<s> | |
196 | ||
197 | Text is centred below the image | |
198 | ||
199 | =item B<e> | |
200 | ||
201 | Text is centred to right of the image. | |
202 | ||
203 | =item B<w> | |
204 | ||
205 | Text is centred to left of the image. | |
206 | ||
207 | =item B<c> | |
208 | ||
209 | Text is centred over the image. | |
210 | ||
211 | =back | |
212 | ||
213 | The B<sw>, B<se>, B<ne>, and b<nw> cases look rather odd. | |
214 | ||
215 | To get items to line up correctly it will usually be necessary | |
216 | to specify B<-anchor> as well. e.g. with default B<e> then anchoring | |
217 | item as a whole B<w> lines images up down left with text stuck to right side. | |
218 | ||
219 | =back | |
220 | ||
221 | =head1 TEXT ITEMS | |
222 | ||
223 | Display items of the type B<text> are used to display a text string | |
224 | in a widget. Text items support the following options: | |
225 | ||
226 | =head2 Text Item Options | |
227 | ||
228 | =over 4 | |
229 | ||
230 | =item Name: B<textStyle> | |
231 | ||
232 | =item Class: B<TextStyle> | |
233 | ||
234 | =item Switch: B<-style> | |
235 | ||
236 | Specifies the display style to use for this text item. Must be the | |
237 | name of a B<text> display style that has already be created with | |
238 | B<ItemStyle>. | |
239 | ||
240 | =item Name: B<text> | |
241 | ||
242 | =item Class: B<Text> | |
243 | ||
244 | =item Switch: B<-text> | |
245 | ||
246 | Specifies the text string to display in the item. | |
247 | ||
248 | =item Name: B<underline> | |
249 | ||
250 | =item Class: B<Underline> | |
251 | ||
252 | =item Switch: B<-underline> | |
253 | ||
254 | Specifies the integer index of a character to underline in the item. | |
255 | 0 corresponds to the first character of the text displayed in the | |
256 | widget, 1 to the next character, and so on. | |
257 | ||
258 | =back | |
259 | ||
260 | =head2 Text Style Options | |
261 | ||
262 | B<STANDARD OPTIONS> | |
263 | ||
264 | B<-activebackground> B<-activeforeground> | |
265 | B<-anchor> B<-background> | |
266 | B<-disabledbackground> B<-disabledforeground> | |
267 | B<-foreground> B<-font> | |
268 | B<-justify> B<-padx> | |
269 | B<-pady> B<-selectbackground> | |
270 | B<-selectforeground> B<-wraplength> | |
271 | ||
272 | See L<Tk::options> for details of the standard options. | |
273 | ||
274 | =head1 WINDOW ITEMS | |
275 | ||
276 | Display items of the type I<window> are used to display a | |
277 | sub-window in a widget. B<Window> items support the following | |
278 | options: | |
279 | ||
280 | =head2 Window Item Options | |
281 | ||
282 | =over 4 | |
283 | ||
284 | =item Name: B<windowStyle> | |
285 | ||
286 | =item Class: B<WindowStyle> | |
287 | ||
288 | =item Switch: B<-style> | |
289 | ||
290 | Specifies the display style to use for this window item. Must be the | |
291 | name of a I<window> display style that has already be created with | |
292 | the B<ItemStyle> method. | |
293 | ||
294 | =item Name: B<window> | |
295 | ||
296 | =item Class: B<Window> | |
297 | ||
298 | =item Switch: B<-window> | |
299 | ||
300 | =item Alias: B<-widget> | |
301 | ||
302 | Specifies the sub-window to display in the item. | |
303 | ||
304 | =back | |
305 | ||
306 | =head2 Window Style Options | |
307 | ||
308 | B<STYLE STANDARD OPTIONS> | |
309 | ||
310 | B<-anchor> B<-padx> B<-pady> | |
311 | ||
312 | See L<Tk::options> for details of the standard options. | |
313 | ||
314 | =head1 CREATING DISPLAY ITEMS | |
315 | ||
316 | Display items do not exist on their and thus they cannot be created | |
317 | independently of the widgets they reside in. As a rule, display items | |
318 | are created by special methods of their ``host'' widgets. For | |
319 | example, the HList widgets has a method B<item> which can be used | |
320 | to create new display items. The following code creates a new text | |
321 | item at the third column of the entry foo inside an HList widget: | |
322 | ||
323 | my $hlist = $parent->HList(-columns=>3); | |
324 | $hlist->add('foo'); | |
325 | $hlist->itemCreate('foo', 2, -itemtype=>'text', -text=>'Hello'); | |
326 | ||
327 | The B<itemCreate> method of the HList widget accepts a variable | |
328 | number of arguments. The special argument B<-itemtype> specifies | |
329 | which type of display item to create. Options that are valid for this | |
330 | type of display items can then be specified by one or more | |
331 | I<option-value> pairs. | |
332 | ||
333 | After the display item is created, they can then be configured or | |
334 | destroyed using the methods provided by the host widget. For example, | |
335 | the HList widget has the methods B<itemConfigure>, B<itemCget> | |
336 | and B<itemDelete> for accessing the display items. | |
337 | ||
338 | =head1 CREATING AND MANIPULATING ITEM STYLES | |
339 | ||
340 | Item styles are created with B<ItemStyle>: | |
341 | ||
342 | =head1 SYNOPSIS | |
343 | ||
344 | S< >I<$widget>-E<gt>B<ItemStyle>(I<itemType> ?,B<-stylename>=E<gt>I<name>? ?,B<-refwindow>=E<gt>I<pathName>? ?,I<option>=E<gt>I<value>, ...>?); | |
345 | ||
346 | I<itemType> must be one of the existing display items types such as | |
347 | B<text>, B<imagetext>, B<window> or any new types added by | |
348 | the user. Additional arguments can be given in one or more | |
349 | I<option-value> pairs. I<option> can be any of the valid option | |
350 | for this display style or any of the following: | |
351 | ||
352 | =over 4 | |
353 | ||
354 | =item B<-stylename> =E<gt> I<name> | |
355 | ||
356 | Specifies a name for this style. If unspecified, then a default name | |
357 | will be chosen for this style. | |
358 | ||
359 | =item B<-refwindow> =E<gt> I<$otherwidget> | |
360 | ||
361 | Specifies a window to use for determine the default values of the | |
362 | display type. If unspecified, the I<$widget> will be used. Default | |
363 | values for the display types can be set via the options database. The | |
364 | following example sets the B<-disablebackground> and | |
365 | B<-disabledforeground> options of a B<text> display style via | |
366 | the option database: | |
367 | ||
368 | $widget->optionAdd('*table.list*disabledForeground' => 'blue'); | |
369 | $widget->optionAdd('*table.list*disabledBackground' => 'darkgray'); | |
370 | $widget->ItemStyle('text', -refwindow => $table_list, -fg => 'red'); | |
371 | ||
372 | By using the option database to set the options of the display styles, | |
373 | we can advoid hard-coding the option values and give the user more | |
374 | flexibility in customization. See L<Tk::option> for a detailed description | |
375 | of the option database. | |
376 | ||
377 | =back | |
378 | ||
379 | =head1 STYLE METHODS | |
380 | ||
381 | The B<ItemStyle> method creates an object. | |
382 | This object supports the B<configure> and B<cget> methods | |
383 | described in L<Tk::options> which can be used to enquire and | |
384 | modify the options described above. | |
385 | ||
386 | The following additional methods are available for item styles: | |
387 | ||
388 | =over 4 | |
389 | ||
390 | =item I<$style>-E<gt>B<delete> | |
391 | ||
392 | Destroy this display style object. | |
393 | ||
394 | =back | |
395 | ||
396 | =head1 EXAMPLE | |
397 | ||
398 | The following example creates two columns of data in a HList | |
399 | widget. The first column is in red and the second column in blue. The | |
400 | colors of the columns are controlled by two different B<text> | |
401 | styles. Also, the anchor and font of the second column is chosen so | |
402 | that the income data is aligned properly. | |
403 | ||
404 | use strict; | |
405 | use Tk; | |
406 | use Tk::HList; | |
407 | use Tk::ItemStyle; | |
408 | ||
409 | my $mw = MainWindow->new(); | |
410 | ||
411 | my $hlist = $mw->HList(-columns=>2)->pack; | |
412 | ||
413 | my $red = $hlist->ItemStyle('text', -foreground=>'#800000'); | |
414 | my $blue = $hlist->ItemStyle('text', -foreground=>'#000080', -anchor=>'e'); | |
415 | ||
416 | my $e; | |
417 | foreach ([Joe => '$10,000'], [Peter => '$20,000'], | |
418 | [Raj => '$90,000'], [Zinh => '$0']) { | |
419 | $e = $hlist->addchild(""); | |
420 | $hlist->itemCreate($e, 0, -itemtype=>'text', | |
421 | -text=>$_->[0], -style=>$red ); | |
422 | $hlist->itemCreate($e, 1, -itemtype=>'text', | |
423 | -text=>$_->[1], -style=>$blue); | |
424 | } | |
425 | ||
426 | Tk::MainLoop; | |
427 | ||
428 | =head1 SEE ALSO | |
429 | ||
430 | L<Tk::HList|Tk::HList> | |
431 | L<Tk::TixGrid|Tk::TixGrid> | |
432 | L<Tk::TList|Tk::TList> | |
433 | ||
434 | =head1 KEYWORDS | |
435 | ||
436 | display item, display style, item style | |
437 | ||
438 | =cut | |
439 |