focal (3) Tickit::Widget::Scroller.3pm.gz
NAME
"Tickit::Widget::Scroller" - a widget displaying a scrollable collection of items
SYNOPSIS
use Tickit;
use Tickit::Widget::Scroller;
use Tickit::Widget::Scroller::Item::Text;
my $tickit = Tickit->new;
my $scroller = Tickit::Widget::Scroller->new;
$scroller->push(
Tickit::Widget::Scroller::Item::Text->new( "Hello world" ),
Tickit::Widget::Scroller::Item::Text->new( "Here are some lines" ),
map { Tickit::Widget::Scroller::Item::Text->new( "<Line $_>" ) } 1 .. 50,
);
$tickit->set_root_widget( $scroller );
$tickit->run
DESCRIPTION
This class provides a widget which displays a scrollable list of items. The view of the items is
scrollable, able to display only a part of the list.
A Scroller widget stores a list of instances implementing the "Tickit::Widget::Scroller::Item" interface.
STYLE
The default style pen is used as the widget pen.
The following style pen prefixes are used:
indicator => PEN
The pen used for the scroll position indicators at the top or bottom of the display
KEYBINDINGS
The following keys are bound
• Down
Scroll one line down
• Up
Scroll one line up
• PageDown
Scroll half a window down
• PageUp
Scroll half a window up
• Ctrl-Home
Scroll to the top
• Ctrl-End
Scroll to the bottom
CONSTRUCTOR
new
$scroller = Tickit::Widget::Scroller->new( %args )
Constructs a new "Tickit::Widget::Scroller" object. The new object will start with an empty list of
items.
Takes the following named arguments:
gravity => STRING
Optional. If given the value "bottom", resize events and the "push" method will attempt to
preserve the item at the bottom of the screen. Otherwise, will preserve the top.
gen_top_indicator => CODE
gen_bottom_indicator => CODE
Optional. Generator functions for the top and bottom indicators. See also "set_gen_top_indicator"
and "set_gen_bottom_indicator".
METHODS
on_scrolled
set_on_scrolled
$on_scrolled = $scroller->on_scrolled
$scroller->set_on_scrolled( $on_scrolled )
Return or set the CODE reference to be called when the scroll position is adjusted.
$on_scrolled->( $scroller, $delta )
This is invoked by the "scroll" method, including the "scroll_to", "scroll_to_top" and
"scroll_to_bottom". In normal cases it will be given the delta offset that "scroll" itself was invoked
with, though this may be clipped if this would scroll past the beginning or end of the display.
push
$scroller->push( @items )
Append the given items to the end of the list.
If the Scroller is already at the tail (that is, the last line of the last item is on display) and the
gravity mode is "bottom", the newly added items will be displayed, possibly by scrolling downward if
required. While the scroller isn't adjusted by using any of the "scroll" methods, it will remain
following the tail of the items, scrolling itself downwards as more are added.
unshift
$scroller->unshift( @items )
Prepend the given items to the beginning of the list.
If the Scroller is already at the head (that is, the first line of the first item is on display) and the
gravity mode is "top", the newly added items will be displayed, possibly by scrolling upward if required.
While the scroller isn't adjusted by using any of the "scroll" methods, it will remain following the head
of the items, scrolling itself upwards as more are added.
shift
@items = $scroller->shift( $count )
Remove the given number of items from the start of the list and returns them.
If any of the items are on display, the Scroller will be scrolled upwards an amount sufficient to close
the gap, ensuring the first remaining item is now at the top of the display.
The returned items may be re-used by adding them back into the scroller again either by "push" or
"unshift", or may be discarded.
pop
@items = $scroller->pop( $count )
Remove the given number of items from the end of the list and returns them.
If any of the items are on display, the Scroller will be scrolled downwards an amount sufficient to close
the gap, ensuring the last remaining item is now at the bottom of the display.
The returned items may be re-used by adding them back into the scroller again either by "push" or
"unshift", or may be discarded.
scroll
$scroller->scroll( $delta )
Move the display up or down by the given $delta amount; with positive moving down. This will be a
physical count of displayed lines; if some items occupy multiple lines, then fewer items may be scrolled
than lines.
scroll_to
$scroller->scroll_to( $line, $itemidx, $itemline )
Moves the display up or down so that display line $line contains line $itemline of item $itemidx. Any of
these counts may be negative to count backwards from the display lines, items, or lines within the item.
scroll_to_top
$scroller->scroll_to_top( $itemidx, $itemline )
Shortcut for "scroll_to" to set the top line of display; where $line is 0. If $itemline is undefined, it
will be passed as 0. If $itemidx is also undefined, it will be passed as 0. Calling this method with no
arguments, therefore scrolls to the very top of the display.
scroll_to_bottom
$scroller->scroll_to_bottom( $itemidx, $itemline )
Shortcut for "scroll_to" to set the bottom line of display; where $line is -1. If $itemline is undefined,
it will be passed as -1. If $itemidx is also undefined, it will be passed as -1. Calling this method with
no arguments, therefore scrolls to the very bottom of the display.
line2item
$itemidx = $scroller->line2item( $line )
( $itemidx, $itemline ) = $scroller->line2item( $line )
Returns the item index currently on display at the given line of the window. In list context, also
returns the line number within item. If no window has been set, or there is no item on display at that
line, "undef" or an empty list are returned. $line may be negative to count backward from the last line
on display; the last line taking "-1".
item2line
$line = $scroller->item2line( $itemidx, $itemline )
( $line, $offscreen ) = $scroller->item2line( $itemidx, $itemline, $count_offscreen )
Returns the display line in the window of the given line of the item at the given index. $itemidx may be
given negative, to count backwards from the last item. $itemline may be negative to count backward from
the last line of the item.
In list context, also returns a value describing the offscreen nature of the item. For items fully on
display, this value is "undef". If the given line of the given item is not on display because it is
scrolled off either the top or bottom of the window, this value will be either "above" or "below"
respectively. If $count_offscreen is true, then the returned $line value will always be defined, even if
the item line is offscreen. This will be negative for items "above", and a value equal or greater than
the number of lines in the scroller's window for items "below".
lines_above
$count = $scroller->lines_above
Returns the number of lines of content above the scrolled display.
lines_below
$count = $scroller->lines_below
Returns the number of lines of content below the scrolled display.
set_gen_top_indicator
set_gen_bottom_indicator
$scroller->set_gen_top_indicator( $method )
$scroller->set_gen_bottom_indicator( $method )
Accessors for the generators for the top and bottom indicator text. If set, each should be a CODE
reference or method name on the scroller which will be invoked after any operation that changes the
contents of the window, such as scrolling or adding or removing items. It should return a text string
which, if defined and non-empty, will be displayed in an indicator window. This will be a small one-line
window displayed at the top right or bottom right corner of the Scroller's window.
$text = $scroller->$method()
The ability to pass method names allows subclasses to easily implement custom logic as methods without
having to capture a closure.
update_indicators
$scroller->update_indicators
Calls any defined generators for indicator text, and updates the indicator windows with the returned
text. This may be useful if the functions would return different text now.
TODO
• Abstract away the "item storage model" out of the actual widget. Implement more storage models, such
as database-driven ones.. more dynamic.
• Keybindings
AUTHOR
Paul Evans <leonerd@leonerd.org.uk>