NAME

       "Tickit::Window" - a window for drawing operations

SYNOPSIS

        use Tickit;
        use Tickit::Pen;

        my $tickit = Tickit->new;

        my $rootwin = $tickit->rootwin;

        $rootwin->bind_event( expose => sub {
           my ( $win, undef, $info ) = @_;

           my $rb = $info->rb;

           $rb->clear;

           $rb->text_at(
              int( $win->lines / 2 ), int( ($win->cols - 12) / 2 ),
              "Hello, world"
           );
        });
        $rootwin->bind_event( geomchange => sub { shift->expose } );
        $rootwin->set_pen( Tickit::Pen->new( fg => "white" ) );

        $rootwin->expose;
        $tickit->run;

DESCRIPTION

       Provides coordination of widget drawing activities. A "Window" represents a region of the
       screen that a widget occupies.

       Windows cannot directly be constructed. Instead they are obtained by sub-division of other
       windows, ultimately coming from the root window associated with the terminal.

       Normally all windows are visible, but a window may be hidden by calling the "hide" method.
       After this, the window will not respond to any of the drawing methods, until it is made
       visible again with the "show" method. A hidden window will not receive focus or input
       events. It may still receive geometry change events if it is resized.

   Sub Windows
       A division of a window made by calling "make_sub" or "make_float" obtains a window that
       represents some portion of the drawing area of the parent window.  Child windows are
       stored in order; "make_sub" adds a new child to the end of the list, and "make_float" adds
       one at the start.

       Higher windows (windows more towards the start of the list), will always handle input
       events before lower siblings. The extent of windows also obscures lower windows; drawing
       on lower windows may not be visible because higher windows are above it.

   Deferred Child Window Operations
       In order to minimise the chances of ordering-specific bugs in window event handlers that
       cause child window creation, reordering or deletion, the actual child window list is only
       mutated after the event processing has finished, by using a Tickit "later" block.

METHODS

   close
          $win->close

       Removes the window from its parent and clears any event handlers set using bind_event.
       Also recursively closes any child windows.

       Currently this is an optional method, as child windows are stored as weakrefs, so should
       be destroyed when the last reference to them is dropped. Widgets should make sure to call
       this method anyway, because this will be changed in a future version.

   make_sub
          $sub = $win->make_sub( $top, $left, $lines, $cols )

       Constructs a new sub-window of the given geometry, and places it at the end of the child
       window list; below any other siblings.

   make_hidden_sub
          $sub = $win->make_hidden_sub( $top, $left, $lines, $cols )

       Constructs a new sub-window like "make_sub", but the window starts initially hidden. This
       avoids having to call "hide" separately afterwards.

   make_float
          $float = $win->make_float( $top, $left, $lines, $cols )

       Constructs a new sub-window of the given geometry, and places it at the start of the child
       window list; above any other siblings.

   make_popup
          $popup = $win->make_popup( $top, $left, $lines, $cols )

       Constructs a new floating popup window starting at the given coordinates relative to this
       window. It will be sized to the given limits.

       This window will have the root window as its parent, rather than the window the method was
       called on. Additionally, a popup window will steal all keyboard and mouse events that
       happen, regardless of focus or mouse position. It is possible that, if the window has an
       "on_mouse" handler, that it may receive mouse events from outwide the bounds of the
       window.

   bind_event
          $id = $win->bind_event( $ev, $code, $data )

       Installs a new event handler to watch for the event specified by $ev, invoking the $code
       reference when it occurs. $code will be invoked with the given window, the event name, an
       event information object, and the $data value it was installed with. "bind_event" returns
       an ID value that may be used to remove the handler by calling "unbind_event_id".

        $ret = $code->( $win, $ev, $info, $data )

       The type of $info will depend on the kind of event that was received, as indicated by $ev.
       The information structure types are documented in Tickit::Event.

   bind_event (with flags)
          $id = $win->bind_event( $ev, $flags, $code, $data )

       The $code argument may optionally be preceded by an integer of flag values. This should be
       zero to apply default semantics, or a bitmask of constants. The constants are documented
       in "bind_event (with flags)" in Tickit::Term.

   unbind_event_id
          $win->unbind_event_id( $id )

       Removes an event handler that returned the given $id value.

   raise
          $win->raise

   lower
          $win->lower

       Moves the order of the window in its parent one higher or lower relative to its siblings.

   raise_to_front
          $win->raise_to_front

       Moves the order of the window in its parent to be the front-most among its siblings.

   lower_to_back
          $win->lower_to_back

       Moves the order of the window in its parent to be the back-most among its siblings.

   parent
          $parentwin = $win->parent

       Returns the parent window; i.e. the window on which "make_sub" or "make_float" was called
       to create this one

   subwindows
          @windows = $win->subwindows

       Returns a list of the subwindows of this one. They are returned in order, highest first.

   root
          $rootwin = $win->root

       Returns the root window

   term
          $term = $win->term

       Returns the Tickit::Term instance of the terminal on which this window lives.

       Note that it is not guaranteed that this method will return the same Perl-level terminal
       instance that the root window was constructed with. In particular, if the root window in
       fact lives on a mock terminal created by Tickit::Test::MockTerm this method may "forget"
       this fact, returning an object instance simply in the "Tickit::Term" class instead. While
       the instance will still be useable as a terminal, the fact it was a mock terminal may get
       forgotten.

   tickit
          $tickit = $win->tickit

       Returns the Tickit instance with which this window is associated.

   show
          $win->show

       Makes the window visible. Allows drawing methods to output to the terminal.  Calling this
       method also exposes the window, invoking the "on_expose" handler. Shows the cursor if this
       window currently has focus.

   hide
          $win->hide

       Makes the window invisible. Prevents drawing methods outputting to the terminal. Hides the
       cursor if this window currently has focus.

   is_visible
          $visible = $win->is_visible

       Returns true if the window is currently visible.

   resize
          $win->resize( $lines, $cols )

       Change the size of the window.

   reposition
          $win->reposition( $top, $left )

       Move the window relative to its parent.

   change_geometry
          $win->change_geometry( $top, $left, $lines, $cols )

       A combination of "resize" and "reposition", to atomically change all the coordinates of
       the window. Will only invoke "on_geom_changed" once, rather than twice as would be the
       case calling the above methods individually.

   expose
          $win->expose( $rect )

       Marks the given region of the window as having been exposed, to invoke the "on_expose"
       event handler on itself, and all its child windows. The window's own handler will be
       invoked first, followed by all the child windows, in screen order (top to bottom, then
       left to right).

       If $rect is not supplied it defaults to exposing the entire window area.

       The "on_expose" event handler isn't invoked immediately; instead, the "Tickit" "later"
       method is used to invoke it at the next round of IO event handling. Until then, any other
       window could be exposed. Duplicates are suppressed; so if a window and any of its
       ancestors are both queued for expose, the actual handler will only be invoked once per
       unique region of the window.

   getctl
   setctl
          $value = $win->getctl( $ctl )

          $success = $win->setctl( $ctl, $value )

       Accessor and mutator for window control options. $ctl should be one of the following
       options:

       cursor-blink (bool)
       cursor-shape (int)
       cursor-visible (bool)
           Cursor properties to set for the terminal cursor when this window has input focus.

       focus-child-notify (bool)
           Whether the window will also receive focus events about child windows.

       steal-input (bool)
           Whether the window is currently stealing input from its siblings.

   set_focus_child_notify
          $win->set_focus_child_notify( $notify )

       If set to a true value, the "on_focus" event handler will also be invoked when descendent
       windows gain or lose focus, in addition to when it gains or loses focus itself. Defaults
       to false; meaning the "on_focus" handler only receives notifications about the window
       itself.

   top
   bottom
   left
   right
          $top    = $win->top

          $bottom = $win->bottom

          $left   = $win->left

          $right  = $win->right

       Returns the coordinates of the start of the window, relative to the parent window.

   abs_top
   abs_left
          $top  = $win->abs_top

          $left = $win->abs_left

       Returns the coordinates of the start of the window, relative to the root window.

   cols
   lines
          $cols  = $win->cols

          $lines = $win->lines

       Obtain the size of the window

   selfrect
          $rect = $win->selfrect

       Returns a Tickit::Rect containing representing the window's extent within itself. This
       will have "top" and "left" equal to 0.

   rect
          $rect = $win->rect

       Returns a Tickit::Rect containing representing the window's extent relative to its parent

   pen
          $pen = $win->pen

       Returns the current Tickit::Pen object associated with this window

   set_pen
          $win->set_pen( $pen )

       Replace the current Tickit::Pen object for this window with a new one. The object
       reference will be stored, allowing it to be shared with other objects.  If "undef" is set,
       then a new, blank pen will be constructed.

   getpenattr
          $val = $win->getpenattr( $attr )

       Returns a single attribue from the current pen

   get_effective_pen
          $pen = $win->get_effective_pen

       Returns a new Tickit::Pen containing the effective pen attributes for the window, combined
       by those of all its parents.

   get_effective_penattr
          $val = $win->get_effective_penattr( $attr )

       Returns the effective value of a pen attribute. This will be the value of this window's
       attribute if set, or the effective value of the attribute from its parent.

   scrollrect
          $success = $win->scrollrect( $rect, $downward, $rightward )

          $success = $win->scrollrect( $top, $left, $lines, $cols, $downward, $rightward )

          $success = $win->scrollrect( ..., $pen )

          $success = $win->scrollrect( ..., %attrs )

       Attempt to scroll the rectangle of the window (either given by a "Tickit::Rect" or defined
       by the first four parameters) by an amount given by the latter two. Since most terminals
       cannot perform arbitrary rectangle scrolling, this method returns a boolean to indicate if
       it was successful.  The caller should test this return value and fall back to another
       drawing strategy if the attempt was unsuccessful.

       Optionally, a "Tickit::Pen" instance or hash of pen attributes may be provided, to
       override the background colour used for erased sections behind the scroll.

       The cursor may move as a result of calling this method; its location is undefined if this
       method returns successful. The terminal pen, in particular the background colour, may be
       modified by this method even if it fails to scroll the terminal (and returns false).

       This method will enqueue all of the required expose requests before returning, so in this
       case the return value is not interesting.

   scroll
          $success = $win->scroll( $downward, $rightward )

       A shortcut for calling "scrollrect" on the entire region of the window.

   scroll_with_children
          $win->scroll_with_children( $downward, $rightward )

       Similar to "scroll" but ignores child windows of this one, moving all of the terminal
       content paying attention only to obscuring by newer siblings of ancestor windows.

       This method is experimental, intended only for use by Tickit::Widget::ScrollBox. After
       calling this method, the terminal content will have moved and the windows drawing them
       will be confused unless the window position was also updated. "ScrollBox" takes care to do
       this.

   cursor_at
          $win->cursor_at( $line, $col )

       Sets the position in the window at which the terminal cursor will be placed if this window
       has focus. This method does not force the window to take the focus though; for that see
       "take_focus".

   cursor_visible
          $win->cursor_visible( $visible )

       Sets whether the terminal cursor is visible on the window when it has focus.  Normally it
       is, but passing a false value will make the cursor hidden even when the window is focused.

   cursor_shape
          $win->cursor_shape( $shape )

       Sets the shape that the terminal cursor will have if this window has focus.  This method
       does not force the window to take the focus though; for that see "take_focus". Valid
       values for $shape are the various "CURSORSHAPE_*" constants from Tickit::Term.

   take_focus
          $win->take_focus

       Causes this window to take the input focus, and updates the cursor position to the stored
       active position given by "cursor_at".

   focus
          $win->focus( $line, $col )

       A convenient shortcut combining "cursor_at" with "take_focus"; setting the focus cursor
       position and taking the input focus.

   is_focused
          $focused = $win->is_focused

       Returns true if this window currently has the input focus

   is_steal_input
          $steal = $win->is_steal_input

       Returns true if this window is currently stealing input from its siblings

   set_steal_input
          $win->set_steal_input( $steal )

       Controls whether this window is currently stealing input from its siblings

EVENTS

       The following event types are emitted and may be observed by "bind_event".

   key
       Emitted when a key on the keyboard is pressed while this window or one of its child
       windows has the input focus, or is set to steal input anyway.

       The event handler should return a true value if it considers the keypress dealt with, or
       false to pass it up to its parent window.

       Before passing it to its parent, a window will also try any other non-focused sibling
       windows of the currently-focused window in order of creation (though note this order is
       not necessarily the order the child widgets that own those windows were created or added
       to their container).

       If no window actually handles the keypress, then every window will eventually be consulted
       about it, preferring windows closer to the focused one.

       This broadcast-like behaviour allows widgets to handle keypresses that should make sense
       even though their window does not actually have the keyboard focus.  This feature should
       be used sparingly, to only capture one or two keypresses that really make sense; for
       example to capture the "PageUp" and "PageDown" keys in a scrolling list, or a numbered
       function key that performs some special action.

   mouse
       Emitted when a mouse button is pressed or released, the cursor moved while a button is
       held (a dragging event), or the wheel is scrolled.

       The following event names may be observed:

       press   A mouse button has been pressed down on this cell

       drag_start
               The mouse was moved while a button was held, and was initially in the given cell

       drag    The mouse was moved while a button was held, and is now in the given cell

       drag_outside
               The mouse was moved outside of the window that handled the "drag_start" event, and
               is still being dragged.

       drag_drop
               A mouse button was released after having been moved, while in the given cell

       drag_stop
               The drag operation has finished. This event is always given directly to the window
               that handled the "drag_start" event, rather than the window on which the mouse
               release event happened.

       release A mouse button was released after being pressed

       wheel   The mouse wheel was moved. "button" will indicate the wheel direction as a string
               "up" or "down".

       The invoked code should return a true value if it considers the mouse event dealt with, or
       false to pass it up to its parent window.

       Once a dragging operation has begun via "drag_start", the window that handled the event
       will always receive "drag", "drag_outside", and an eventual "drag_stop" event even if the
       mouse moves outside that window. No other window will receive a "drag_outside" or
       "drag_stop" event than the one that started the operation.

   geomchange
       Emitted when the window is resized or repositioned; i.e. whenever its geometry changes.

   expose
       Emitted when a region of the window is exposed by the expose method, or implicitly because
       it or another window has changed size, been shown or hidden, or the stacking order has
       been changed.

       When invoked, render buffer passed in the event will have its origin set to that of the
       window, and its clipping will be set to the damage rectangle.

       If any child windows overlap the region, these will be exposed first, before the
       containing window.

   focus
       Emitted when the window gains or loses input focus.

       If the "focus-child-notify" behavior is enabled, this callback is also invoked for changes
       of focus on descendent windows. In this case, it is passed an additional argument, being
       the immediate child window in which the focus chain has now changed (which may or may not
       be the focused window directly; it could itself be another ancestor).

       When a window gains focus, any of its ancestors that have "focus-child-notify" enabled
       will be informed first, from the outermost inwards, before the window itself. When one
       loses focus, it is notified first, and then its parents from the innermost outwards.

AUTHOR

       Paul Evans <leonerd@leonerd.org.uk>