1option(n) [incr Tcl] option(n)
2______________________________________________________________________________
6
8 itcl::option - define options for extendedclass, widget or widgetadap‐
9 tor
10 Parts of this description are "borrowed" from Tcl extension [snit], as
12 the functionality is mostly identical.
13
15 This is new functionality in [incr Tcl] where the API can still
16 change!!
17
19 option optionSpec ?defaultValue?
20 option optionSpec ?options?
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22
25 The option command is used inside an [incr Tcl] extendedclass/wid‐
26 get/widgetadaptor definition to define options.
27 In the first form defines an option for instances of this type, and
29 optionally gives it an initial value. The initial value defaults to the
30 empty string if no defaultValue is specified.
31 An option defined in this way is said to be locally defined. The
33 optionSpec is a list defining the option's name, resource name, and
34 class name, e.g.:
35 option {-font font Font} {Courier 12}
37 The option name must begin with a hyphen, and must not contain any
39 upper case letters. The resource name and class name are optional; if
40 not specified, the resource name defaults to the option name, minus the
41 hyphen, and the class name defaults to the resource name with the first
42 letter capitalized. Thus, the following statement is equivalent to the
43 previous example:
44 option -font {Courier 12}
46 See The Tk Option Database for more information about resource and
48 class names.
49 Options are normally set and retrieved using the standard instance
51 methods configure and cget; within instance code (method bodies, etc.),
52 option values are available through the options array:
53 set myfont $itcl_options(-font)
55 In the second form you can define option handlers (e.g., -config‐
57 uremethod), then it should probably use configure and cget to access
58 its options to avoid subtle errors.
59 The option statement may include the following options:
61 -default defvalue
63 Defines the option's default value; the option's default value
64 will be "" otherwise.
65 -readonly
67 The option is handled read-only -- it can only be set using con‐
68 figure at creation time, i.e., in the type's constructor.
69 -cgetmethod methodName
71 Every locally-defined option may define a -cgetmethod; it is
72 called when the option's value is retrieved using the cget
73 method. Whatever the method's body returns will be the return
74 value of the call to cget.
75 The named method must take one argument, the option name. For
77 example, this code is equivalent to (though slower than) Itcl's
78 default handling of cget:
79 option -font -cgetmethod GetOption
81 method GetOption {option} {
82 return $itcl_options($option)
83 }
84 Note that it's possible for any number of options to share a
86 -cgetmethod.
87 -cgetmethodvar varName
89 That is very similar to -cgetmethod, the only difference is, one
90 can define a variable, where to find the cgetmethod during run‐
91 time.
92 -configuremethod methodName
94 Every locally-defined option may define a -configuremethod; it
95 is called when the option's value is set using the configure or
96 configurelist methods. It is the named method's responsibility
97 to save the option's value; in other words, the value will not
98 be saved to the itcl_options() array unless the method saves it
99 there.
100 The named method must take two arguments, the option name and
102 its new value. For example, this code is equivalent to (though
103 slower than) Itcl's default handling of configure:
104 option -font -configuremethod SetOption
106 method SetOption {option value} {
107 set itcl_options($option) $value
108 }
109 Note that it's possible for any number of options to share a
111 single -configuremethod.
112 -configuremethodvar varName
114 That is very similar to -configuremethod, the only difference
115 is, one can define a variable, where to find the configuremethod
116 during runtime.
117 -validatemethod methodName
119 Every locally-defined option may define a -validatemethod; it is
120 called when the option's value is set using the configure or
121 configurelist methods, just before the -configuremethod (if
122 any). It is the named method's responsibility to validate the
123 option's new value, and to throw an error if the value is
124 invalid.
125 The named method must take two arguments, the option name and
127 its new value. For example, this code verifies that -flag's
128 value is a valid Boolean value:
129 option -font -validatemethod CheckBoolean
131 method CheckBoolean {option value} {
132 if {![string is boolean -strict $value]} {
133 error "option $option must have a boolean value."
134 }
135 }
136 Note that it's possible for any number of options to share a
138 single -validatemethod.
139 -validatemethodvar varName
141 That is very similar to -validatemethod, the only difference is,
142 one can define a variable, where to find the validatemethod dur‐
143 ing runtime.
144
147 option, widget, widgetadaptor, extendedclass
148itcl 4.0 option(n)