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
             ->set_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

   new
          $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
          $vextent = $scrollbox->vextent

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

   hextent
          $hextent = $scrollbox->hextent

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

METHODS

   scroll
          $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).

   scroll_to
          $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 child must indicate the range of its scrolling ability by using the "set_total" method
       on the extent object it is given.

   $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>