WinSelector

This structure provides the gate of selectors.

Signature of WinSelector

List of Import References :
See BOOL
See Char
See Com
See DENOTATION
See Nat
See Option
See Pair
See Real
See Seq
See Set
See String
See Void
See WinInternal
See WinRegulator
See WinTclTk

SIGNATURE WinSelector[data]

$Date: 2010-09-30 18:24:17 +0200 (Do, 30. Sep 2010) $ ($Revision: 616 $)

SORT data

IMPORT  Com[selector]           ONLY com
        Com[void]               ONLY com
        Com[data]               ONLY com
        Void                    ONLY void

IMPORT  WinInternal             ONLY config:SORT
        WinRegulator            ONLY regulator:SORT

Gate of Selectors

A selector is a gate which represents a data value. Agents may set or get the value or may synchronize with value changes.

SORT selector

FUN  selector   : data  -> com[selector]

FUN  set        : selector ** data              -> com[void]
FUN  get        : selector                      -> com[data]
FUN  await      : selector ** (data -> bool)    -> com[data]

An agent may set or get the selectors values with the commands set and get. An agent may synchronize with value changes via the command await(Sel, Pred): this command is enabled whenever the given predicate on the value of the selector is true. It yields the current value of the selector.

Synchronization Configurations

A selector may be attached to a view or item such that each time a given predicate on the selectors value becomes true, one configuration is send to the view or item (the first argument of sync), and each time it becomes false another configuration is send.

FUN sync        : selector ** (data -> bool) 
                           ** config ** config          -> config

A specialzed version of sync, enable(Sel, Pred), enables the given view or item whenever the given predicate is true and disables it otherwise. It is simply defined as sync(Sel, Pred, state(normal), state(disabled)).

FUN  enable     : selector ** (data -> bool)            -> config

Selection Configurations

Views and menu-items such as check-buttons and radio-buttons support a special selection mechanism, which is controlled by the configuration below:

FUN  select             : selector ** (data -> bool) ** 
                                      (data -> data) ** (data -> data)
                                                     -> config

The configured view or menu-item will select and deselect itself (and display the selection state) according to whether the given predicate is true on the selectors value. Moreover, if the view is selected or deselected by the user, the transformer functions are applied to the selectors value (the first one if it is selected, the second one if it is deselected).

A typical use of select for check-buttons is with selectors which are instantiated with sets, such as in:

TYPE opt == opt1 opt2 ...

checkButton with 
   select(Sel : selector[set[opt, <]], opt1 in _, opt1 incl _, opt1 excl _)

Here, opt1 is automatically added or removed from the selectors set value according to the selection state of the check-button.

To implement a radio-button like behaviour, one would write:

TYPE mode == mode1 mode2 ...
radioButton with
   select(Sel : selector[mode], mode1?, \\ _ . mode1, \\ X. X)

A shortcut is provided which supports this usage:

FUN select : selector ** (data -> bool) ** data -> config

select(Sel, Pred, Val) is defined as select(Sel, Pred, \\ _ . Val, \\ X. X)

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