NAME

Tickit::Widget::ScrollBox - allow a single child widget to be scrolled

SYNOPSIS

 use Tickit;
 use Tickit::Widget::ScrollBox;
 use Tickit::Widget::Static;

 my $scrollbox = Tickit::Widget::ScrollBox->new(
    child => Tickit::Widget::Static->new(
       text => join( "\n", map { "The content for line $_" } 1 .. 100 ),
    ),
 );

 Tickit->new( root => $scrollbox )->run;

DESCRIPTION

This container widget draws a scrollbar beside a single child widget and allows a portion of it to be displayed by scrolling.

STYLE

Th following style pen prefixes are used:

scrollbar => PEN

The pen used to render the background of the scroll bar

scrollmark => PEN

The pen used to render the active scroll position in the scroll bar

arrow => PEN

The pen used to render the scrolling arrow buttons

The following style keys are used:

arrow_up => STRING

arrow_down => STRING

arrow_left => STRING

arrow_right => STRING

Each should be a single character to use for the scroll arrow buttons.

The following style actions are used:

up_1 (<Up>)

down_1 (<Down>)

left_1 (<Left>)

right_1 (<Right>)

Scroll by 1 line

up_half (<PageUp>)

down_half (<PageDown>)

left_half (<C-Left>)

right_half (<C-Right>)

Scroll by half of the viewport

to_top (<C-Home>)

to_bottom (<C-End>)

to_leftmost (<Home>)

to_rightmost (<End>)

Scroll to the edge of the area

CONSTRUCTOR

$scrollbox = Tickit::Widget::ScrollBox->new( %args )

Constructs a new Tickit::Widget::ScrollBox object.

Takes the following named arguments in addition to those taken by the base Tickit::SingleChildWidget constructor:

vertical => BOOL or "on_demand"

horizontal => BOOL or "on_demand"

Whether to apply a scrollbar in the vertical or horizontal directions. If not given, these default to vertical only.

If given as the string on_demand then the scrollbar will be optionally be displayed only if needed; if the space given to the widget is smaller than the child content necessary to display.

ACCESSORS

$vextent = $scrollbox->vextent

Returns the Tickit::Widget::ScrollBox::Extent object representing the box's vertical scrolling extent.

$hextent = $scrollbox->hextent

Returns the Tickit::Widget::ScrollBox::Extent object representing the box's horizontal scrolling extent.

METHODS

$scrollbox->scroll( $downward, $rightward )

Requests the content be scrolled downward a number of lines and rightward a number of columns (either of which which may be negative).

$scrollbox->scroll_to( $top, $left )

Requests the content be scrolled such that the given line and column number of the child's content is the topmost visible in the container.

SMART SCROLLING

If the child widget declares it supports smart scrolling, then the ScrollBox will not implement content scrolling on its behalf. Extra methods are used to co-ordinate the scroll position between the scrolling-aware child widget and the containing ScrollBox. This is handled by the following methods on the child widget.

If smart scrolling is enabled for the child, then its window will be set to the viewport directly, and the child widget must offset its content within the window as appropriate. The lines and cols methods will continue to be called, and will continue to be used to query the child on how much content it has that requires scrolling (for setting the total of the extent objects).

$smart = $child->CAN_SCROLL

If this method exists and returns a true value, the ScrollBox will use smart scrolling. This method must return a true value for this to work, allowing the method to itself be a proxy, for example, to proxy scrolling information through a single child widget container.

$child->set_scrolling_extents( $vextent, $hextent )

Gives the child widget the vertical and horizontal scrolling extents. The child widget should save thes values, and inspect the start value of them any time it needs these to implement content offset position when rendering.

$child->scrolled( $downward, $rightward, $h_or_v )

Informs the child widget that one of the scroll positions has changed. It passes the delta (which may be negative) of each position, and a string which will be either "h" or "v" to indicate whether it was an adjustment of the horizontal or vertical scrollbar. The extent objects will already have been updated by this point, so the child may also inspect the start value of them to obtain the new absolute offsets.

TODO

• Choice of left/right and top/bottom bar positions.

• Click-and-hold on arrow buttons for auto-repeat

• Allow smarter cooperation with a scrolling-aware child widget; likely by setting extent objects on the child if it declares to be supported, and use that instead of an offset child window.

AUTHOR

Paul Evans <leonerd@leonerd.org.uk>

cpanm Tickit::Widget::ScrollBox

perl -MCPAN -e shell
install Tickit::Widget::ScrollBox