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

       Paul Evans <leonerd@leonerd.org.uk>

perl v5.40.0                                       2024-10-20                                Tickit::Window(3pm)

       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.

   SubWindows
       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.

   DeferredChildWindowOperations
       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.

       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.

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(withflags)
          $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.

   getctlsetctl
          $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.

   topbottomleftright
          $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_topabs_left
          $top  = $win->abs_top

          $left = $win->abs_left

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

   colslines
          $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

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

        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;