Ubuntu Manpage: persistentSelection - Enhanced PRIMARY selection

Provided by: tklib_0.8~20230222-1_all

NAME

       persistentSelection - Enhanced PRIMARY selection

SYNOPSIS

       package require Tcl  8.5

       package require Tk  8.5

       package require persistentSelection  ?1.0?

       persistentSelection::fixText

       persistentSelection::getClassicPrimarySel ?displayOf? ?withOthers?

       persistentSelection::getPrimarySel ?displayOf?

       persistentSelection::report type pathName

________________________________________________________________________________________________________________

DESCRIPTION

       Consider  a  Tk  widget  that  sets  its  -exportselection  option to boolean true, thereby exporting its
       selection.  When the selection in the widget  is  canceled,  by  default  Tk  also  cancels  the  PRIMARY
       selection.   In  this  situation,  an attempt to read the PRIMARY selection, e.g. by a <<PasteSelection>>
       event, will fail.

       The persistentSelection package offers  more  convenient  behavior.   It  will  sustain  as  the  PRIMARY
       selection  the  last  non-empty  value  set  by  any  Tk  widget that it monitors, as long as the PRIMARY
       selection is not claimed by another process, or by a widget that it does not monitor.

       The persistentSelection package works by binding to the <<Selection>> event on the widgets  of  interest,
       and  using  this binding to monitor any change of the selection in the widget.  Its commands are confined
       to the namespace ::persistentSelection.

COMMANDS

       persistentSelection::fixText
              Call this command once to resolve problems with text widgets that use  the  default  Text  bindtag
              (rather than Ntext).  See Text widgets for an explanation.

              The command adjusts some Text bindings to generate <<Selection>> events; and it re-orders calls to
              the  text  widget  tag  command  in  the  private command ::tk::TextSelectTo, so that this command
              cooperates better with persistentSelection.

              These   adjustments   are   needed   only   to   older    versions    of    Tk.     The    command
              persistentSelection::fixText  has  no  effect  on  sufficiently recent releases.  It can safely be
              called for any version of Tk.

       persistentSelection::getClassicPrimarySel ?displayOf? ?withOthers?

              •      displayOf - a Tk window path on the display to be interrogated (optional, default {.})

              •      withOthers - whether to return the PRIMARY selection if it is owned by another  process  or
                     interpreter (optional, boolean, default false)

              A  command to return the classic (non-persistent) form of the PRIMARY selection.  If the selection
              does not exist, or is sustained only by persistentSelection, the command returns the empty string.

       persistentSelection::getPrimarySel ?displayOf?

              •      displayOf - a Tk window on the display to be interrogated (optional, default {.})

              A command to return the value of the PRIMARY selection.  If the  selection  does  not  exist,  the
              command  returns  the  empty string.  The usual Tk commands are perfectly valid, but they raise an
              error if the selection does not exist.

       persistentSelection::report type pathName

              •      type - (value text or entry) classification of the widget whose selection has changed

              •      pathName - the Tk window path of the widget whose selection has changed

              To make package  persistentSelection  monitor  a  widget,  this  command  must  be  bound  to  the
              <<Selection>>  event  on  that widget.  The command records changes in the widget's selection, and
              uses the information to sustain a non-empty PRIMARY selection on each display.

USAGE

SCRIPT REQUIREMENTS
For each widget that will be monitored by persistentSelection, the command persistentSelection::report
must be bound to event <<Selection>> in one of the widget's binding tags.

For example, the developer may wish to use persistentSelection with every text and entryPlus widget in an
application: this can be achieved by adding the <<Selection>> binding to the Text and EntryPlus bindtags.
See EXAMPLES.

If persistentSelection is not required for all widgets of a particular class, the binding can be added to
per-widget bindtags. See EXAMPLES.

WIDGET REQUIREMENTS
To be capable of being monitored by persistentSelection, a widget must satisfy three conditions:

• It must have an -exportselection option that allows it to export its selection to the PRIMARY
selection.

• It must generate a <<Selection>> event whenever its selection changes.

• its bindings to other events should be suitable - specifically, in versions of Tk older than
8.6.6, a GUI event that extends or reduces the selection from one non-empty value to another
should not use an intermediate state that has an empty selection, because this confuses
persistentStore.

The Tk and Ttk widgets that can export their selection are text, entry, listbox, spinbox, ttk::entry,
ttk::spinbox, and ttk::combobox.

TEXT WIDGETS
In versions of Tk older than 8.6.9, the text widget does not generate <<Selection>> events in a few
"corner cases" in which its selection changes. These omissions can be corrected by changes to the Text
bindings, in order to satisfy the second condition of Widget requirements.

In addition, versions of Tk older than 8.6.6 process selection events slightly differently from newer
versions, and in combination with the Text bindings this confuses persistentStore. If an upgrade to the
current version of Tcl/Tk is not feasible, this problem can be resolved by making a slight modification
to the widget bindings, in order to satisfy the third condition of Widget requirements.

Either the script should call the command persistentSelection::fixText to adjust the Text bindings and
the commands that they call; or the widget can use the Ntext binding tag (for ntext version 1.0 or above)
instead of the default Text bindtag.

In either case, the argument type supplied to command persistentSelection::report should have the value
text.

ENTRY, SPINBOX, TTK::ENTRY, TTK::SPINBOX, AND TTK::COMBOBOX WIDGETS
The entry, spinbox, ttk::entry, ttk::spinbox, and ttk::combobox widgets do not generate a <<Selection>>
event when their selection changes, and therefore require modification.

The package widgetPlus provides snit wrappers widgetPlus::entryPlus, widgetPlus::spinboxPlus,
widgetPlus::ttkEntryPlus, widgetPlus::ttkSpinboxPlus, and widgetPlus::ttkComboboxPlus respectively. Each
widgetPlus widget generates the required <<Selection>> events.

In all these cases, the argument type supplied to command persistentSelection::report should have the
value entry. This argument determines how persistentSelection will inspect the widget's selection, and
the commands that do so are the same for all these widgets.

LISTBOX WIDGETS
A similar wrapper has not been created for the listbox widget, which has the complication of permitting
multiple selections.

TO DO

       •      Test on a system with multiple displays.

BUGS

       This version of persistentSelection is intended to be compatible with all releases of Tk 8.5 and 8.6, and
       with the branches core-8-5-branch, core-8-6-branch, revised_text, and trunk in the source code repository
       for Tk.  Any incompatibility with any of these versions, for any Tk windowing system, should be  reported
       as   a   bug.   Please   report   such   in  the  category  persistentSelection  of  the  Tklib  Trackers
       [http://core.tcl.tk/tklib/reportlist].

EXAMPLES

       Each example uses persistentSelection to retain the last non-empty value  of  the  selection  in  certain
       widgets.  Each example also includes the creation of sample widgets.

       Monitor all entryPlus widgets.

              package require widgetPlus
              widgetPlus::entryPlus .ep
              pack .ep

              package require persistentSelection
              bind EntryPlus <<Selection>> {::persistentSelection::report entry %W}

       Monitor all text widgets that use the default Text bindings.

              text .t
              pack .t

              package require persistentSelection
              ::persistentSelection::fixText
              bind Text <<Selection>> {::persistentSelection::report text %W}

       Monitor all text widgets that use the default Text bindings, and all entryPlus widgets.

              text .t
              pack .t

              package require widgetPlus
              widgetPlus::entryPlus .ep
              pack .ep

              package require persistentSelection
              ::persistentSelection::fixText
              bind Text <<Selection>> {::persistentSelection::report text %W}
              bind EntryPlus <<Selection>> {::persistentSelection::report entry %W}

       Monitor all text widgets that use Ntext bindings.

              text .t
              pack .t

              package require ntext
              bindtags .t {.t Ntext . all}

              package require persistentSelection
              bind Ntext <<Selection>> {::persistentSelection::report text %W}

       Monitor a single entryPlus widget .ep

              package require widgetPlus
              widgetPlus::entryPlus .ep
              pack .ep

              package require persistentSelection
              bind .ep <<Selection>> {::persistentSelection::report entry %W}

       Monitor a single text widget .t

              text .t
              pack .t

              package require persistentSelection
              bind .t <<Selection>> {::persistentSelection::report text %W}