1[manpage_begin uevent n 0.2]
2[copyright {2007 Andreas Kupries <andreas_kupries@users.sourceforge.net>}]
3[moddesc   {User events}]
4[titledesc {User events}]
5[category  {Programming tools}]
6[require Tcl 8.4]
7[require uevent [opt 0.2]]
8[require logger]
9[keywords event bind unbind {generate event}]
10[description]
11
12This package provides a general facility for the handling of user
13events. Allows the binding of arbitrary commands to arbitrary events
14on arbitrary tags, removal of bindings, and event generation.
15
16[para]
17
18The main difference to the event system built into the Tcl/Tk core is
19that the latter can generate only virtual events, and only for
20widgets. It is not possible to use the builtin facilities to bind to
21events on arbitrary (pseudo-)objects, nor is it able to generate
22events for such.
23
24[para]
25
26Here we can, by assuming that each object in question is represented
27by its own tag. Which is possible as we allow arbitrary tags.
28
29[para]
30
31More differences:
32
33[list_begin enumerated]
34[enum]
35
36The package uses only a two-level hierarchy, tags and events, to
37handle everything, whereas the Tcl/Tk system uses three levels, i.e.
38objects, tags, and events, with a n:m relationship between objects and
39tags.
40
41[enum]
42This package triggers all bound commands for a tag/event combination,
43and they are independent of each other. A bound command cannot force
44the event processing core to abort the processing of command coming
45after it.
46
47[list_end]
48
49[section API]
50
51The package exports three commands, as specified below:
52
53[list_begin definitions]
54
55[call [cmd ::uevent::bind] [arg tag] [arg event] [arg command]]
56
57Using this command registers the [arg command] prefix to be triggered
58when the [arg event] occurs for the [arg tag]. The result of the
59command is an opaque token representing the binding. Note that if the
60same combination of <[arg tag],[arg event],[arg command]> is used
61multiple times the same token is returned by every call.
62
63[para]
64
65The signature of the [arg command] prefix is
66
67[list_begin definitions]
68[call [cmd command] [arg tag] [arg event] [arg details]]
69[list_end]
70[para]
71
72where [arg details] contains the argument(s) of the event. Its
73contents are event specific and have to be agreed upon between actual
74event generator and consumer. This package simply transfers the
75information and does not perform any processing beyond that.
76
77
78[call [cmd ::uevent::unbind] [arg token]]
79
80This command releases the event binding represented by the
81[arg token]. The token has to be the result of a call to
82[cmd ::uevent::bind]. The result of the command is the empty string.
83
84
85[call [cmd ::uevent::generate] [arg tag] [arg event] [opt [arg details]]]
86
87This command generates an [arg event] for the [arg tag], triggering
88all commands bound to that combination. The [arg details] argument is
89simply passed unchanged to all event handlers. It is the
90responsibility of the code generating and consuming the event to have
91an agreement about the format and contents of the information carried
92therein. The result of the command is the empty string.
93
94[para]
95
96Note that all bound commands are triggered, independently of each
97other. The event handlers cannot assume a specific order. They are
98also [emph not] called synchronously with the invokation of this
99command, but simply put into the event queue for processing when the
100system returns to the event loop.
101
102[para]
103
104Generating an event for an unknown tag, or for a
105<[arg tag],[arg event]> combination which has no commands bound to it
106is allowed, such calls will be ignored.
107
108
109[call [cmd ::uevent::list]]
110
111In this form the command returns a list containing the names of all
112tags which have events with commands bound to them.
113
114
115[call [cmd ::uevent::list] [arg tag]]
116
117In this format the command returns a list containing the names of all
118events for the [arg tag] with commands bound to them. Specifying an
119unknown tag, i.e. a tag without event and commands, will cause the
120command to throw an error.
121
122
123[call [cmd ::uevent::list] [arg tag] [arg event]]
124
125In this format the command returns a list containing all commands
126bound to the [arg event] for the [arg tag]. Specifying an unknown tag
127or unknown event, will cause the command to throw an error.
128
129[list_end]
130
131[section {BUGS, IDEAS, FEEDBACK}]
132
133This document, and the package it describes, will undoubtedly contain
134bugs and other problems.
135
136Please report such in the category [emph uevent] of the
137[uri {http://sourceforge.net/tracker/?group_id=12883} {Tcllib SF Trackers}].
138
139Please also report any ideas for enhancements you may have for either
140package and/or documentation.
141
142[manpage_end]
143