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}
SEE ALSO
bindtags, ntext, text, widgetPlus