=for rcs $Id: Window.pod,v 1.7 2003/08/01 10:05:26 dk Exp $

=head1 NAME

Prima::Window - top-level window management

=head1 DESCRIPTION 

Prima::Window is a descendant of Prima::Widget class.
It deals with top-level windows, the windows that
are specially treated by the system. Its major
difference from Prima::Widget is that instances of
Prima::Window can only be inferior by the
screen, not the other windows, and that the system or window manager add
decorations to these - usually menus, buttons and title 
bars. Prima::Window provides methods that communicate
with the system and hint these decorations.

=head1 USAGE

A typical program communicates with the user with aid
of widgets, collected upon one or more top-level windows.
Prima::Widget already has all functionality required for
these child-parent operations, so Prima::Window is not
special in respect of widget grouping and relationship.
Its usage therefore is straightforward:

   my $w = Prima::Window-> create( 
       size => [300,300],
       text => 'Startup window',
   );

There are more about Prima::Window in areas, that it is
specifically designed to - the system window management and
the dialog execution.

=head2 System window management

As noted before, top-level windows are special for the system,
not only in their 'look', but also in 'feel': the system adds
specific functions to the windows, aiding the user to navigate through
the desktop. The system ofter dictates the size and position for
windows, and some times these rules are hard or even impossible to 
circumvent. This document will be long if it would venture to describe the features
of different window management systems, and the task would be 
never accomplished - brand new window managers emerge every month,
and the old change their behavior in an unpredictable way. The only
golden rule is to never rely on the behavior of one window manager,
and test programs with at least two.

The Prima toolkit provides simple access to buttons, title bar
and borders of a window. Buttons and title bar are managed by
the C<::borderIcons> property, and borders by the C<::borderStyle> 
property. These operate with set of predefined constants, C<bi::XXX>
and C<bs::XXX>, correspondingly. The button constants can be combined with
each other, but not all combinations may be granted by the system.
The same is valid also for the border constant, except that they can
not be combined - the value of C<::borderStyle> is one of the integer constants.

There are other hints that the toolkit can set for a window manager.
The system can be supplied with an icon that a window is bound to; the icon
dimensions are much different, and although can be requested via
C<sv::XIcon> and C<sv::YIcon> system values, the C<::icon> property
scales the image automatically to the closest system-recognizable
dimension. The window icon is not shown by the toolkit, it is usually
resides in the window decorations and sometimes on a task bar, along
with the window's name. The system can be hinted to not reflect the window
on the task bar, by setting the C<::taskListed> property to 0.

Another issue is the window positioning. Usually, if no explicit
position was given, the window is positioned automatically
by the system. The same is valid for the size.  But some window
managers bend it to the extreme - for example, default CDE
setup force the user to set newly created windows' positions explicitly.
However, there is at least one point of certainty.
Typically, when the initial size and/or position of a top-level window 
are expected to be set by the system, the C<::originDontCare> and
C<::sizeDontCare> properties can be set to 1 during window creation.
If these set, the system is asked to size/position a window regarding
its own windowing policy. The reverse is not always true, unfortunately.
Either if these properties set to 0, or explicit size or positions are given,
the system is hinted to use these values instead, but this does not
always happen. Actually, this behavior is expected by the user and often does
not get even noticed as something special. Therefore it is a good practice to test
a top-level windowing code with several window managers.

There are different policies about window positioning and sizing; 
some window managers behave best when the position is given to the window
with the system-dependent decorations. It is hardly can be called a good
policy, since it is not possible to calculate the derived window coordinates
with certainty. This problem results in that it is impossible to
be sure about window position and size before these are set explicitly.
The only, not much efficient help the toolkit can provide is the property
pair C<::frameOrigin> and C<::frameSize>, which along with C<::origin>
and C<::size> reflect the position and size of a window, but taking into
account the system-dependent decorations.

=head2 Dialog execution

Method of Prima::Window, C<execute()> brings a window
in a modal state on top of other toolkit windows, and
returns after the window is dismissed in one or another way.
This method is special as it is an implicit event loop,
similar to 

  run Prima;

code. The event flow is not disrupted, but the windows and
widgets that do not belong to the currently executed, the
'modal' window group can not be activated. There can be many
modal windows on top of each other, but only one is accessible.
As an example a message box can be depicted, a window that prevents
the user to work with the application windows until dismissed.
There can be other message boxes on top of each other, preventing
the windows below from operation as well.
This scheme is called the 'exclusive' modality.

The toolkit also provides the shared modality scheme, where
there can be several stacks of modal windows, not interfering
with each other. Each window stack is distinct and contains its own windows.
An example analogy is when several independent applications run with 
modal message boxes being activated. This scheme, however, can not be achieved
with single execute()-like call without creating interlocking
conditions. The shared model call, C<execute_shared()>,
inserts the window into the shared modal stack, activates the window and returns immediately.

The both kinds of modal windows can coexist, but the exclusive
windows prevents the shared from operation; while there are
exclusive windows, the shared have same rights as the usual windows.

The stacking order for these two models is slightly different.
Any window, called execute() is set on top of the last exclusive
modal window. The same is valid for the shared model, but since
there can be many shared window stacks, a window enters same stack
as of its owner. Here introduced the 'modal horizon'
term. A modal horizon is a root of the shared window stack, 
and the default horizon is $::application's. The boolean C<::modalHorizon>
property is responsible whether the window serves as a horizon or not.

A window in modal state can return to its normal state by 
calling C<end_modal()> method. The window is then set hidden and disabled, 
and the windows below can be operated. If the window was in exclusive
modal state, the execute() call finished and returns an exit code, which
can be set through C<::modalResult> property. This property is an convenience
indicator of how the window was dismissed. There two methods, that 
dismiss the window with returning two basic 'ok' and 'not ok' code.
These are C<ok()> and C<cancel()> methods; the latter is identical to
when the user closes the modal window by the means of the system.
The values set to C<::modalResult> are C<mb::OK> and C<mb::Cancel>,
correspondingly. There are more C<mb::XXX> constants, but these represent
no special meaning; any integer value can be passed. Prima::MsgBox::message
method uses these so the message window can return up to four different
return codes.

=head2 Menu

A top-level window can be equipped with a menu bar. Its outlook
is system-dependent, but can be controlled by the toolkit up to
a certain level. The C<::menuItems> property, that manages the menu items
of a C<::menu> object of L<Prima::Menu> class, arrange the layout
of the menu. The syntax of the items-derived properties is described in
L<Prima::Menu>, but it must be reiterated that menu items contain only
hints, not requests for their exact representation. The same is valid for
the color and font properties, C<::menuColorIndex> and C<::menuFont>.

Only one menu at a time can be displayed in a top-level window, although
a window can be an owner for many menu objects. The key property is
C<Prima::Menu::selected> - if a menu object is selected on a widget
or a window object, it refers to the default menu actions, which, in
case of Prima::Window is being displayed as menu bar.

NB: A window can be an owner for several menu objects and still do not
have a menu bar displayed, if no menu objects are marked as selected.

=head2 Prima::Dialog

Prima::Dialog, a descendant from Prima::Window, introduces no
new functionality. It has its default values adjusted so
the colors use more appropriate system colors, and hints
the system that the outlook of a window is to be different,
to resemble the system dialogs on systems where such are
provided.

=head2 Prima::MainWindow

The class is a simple descendant of Prima::Window, which overloads
C<on_destroy> notification and calls C<$application-E<gt>close> inside it.
The purpose of declaration of a separate class for such a trifle difference
is that many programs are designed under a paradigm where these is a main
window, which is most 'important' to the user. As such consruct is used more
often than any other, it is considered an optimization to write

   Prima::MainWindow-> create( ... )

rather than

   Prima::Window-> create( ..., onDestroy => sub { $::application-> close })

, although these lines are equivalent.

=head1 API

=head2 Properties

=over

=item borderIcons INTEGER 

Hints the system about window's decorations, by
selecting the combination of C<bi::XXX> constants.
The constants are:

   bi::SystemMenu  - system menu button and/or close button 
                     ( usually with icon ) is shown
   bi::Minimize    - minimize button 
   bi::Maximize    - maximize ( and eventual restore )
   bi::TitleBar    - window title 
   bi::All         - all of the above

Not all systems respect these hints, and many systems
provide more navigating decoration controls than these.

=item borderStyle STYLE  

Hints the system about window's border style, by selecting
one of C<bs::XXX> constants. The constants are:

   bs::None      - no border
   bs::Single    - thin border
   bs::Dialog    - thick border
   bs::Sizeable  - thick border with interactive resize capabilities

C<bs::Sizeable> is an unique window mode. If selected, the user
can resize the window, not only by dragging the window borders with
the mouse but by other system-dependent means. The other border styles
disallow interactive resizing. 

Not all systems recognize all these hints, although many recognize
interactive resizing flag.

=item frameHeight HEIGHT

Maintains the height of a window, including 
the window decorations.

=item frameOrigin X_OFFSET, Y_OFFSET

Maintains the left X and bottom Y boundaries of a window's
decorations relative to the screen.

=item frameSize WIDTH, HEIGHT

Maintains the width and height of a window, including 
the window decorations.

=item frameWidth WIDTH

Maintains the width of a window, including 
the window decorations.


=item icon OBJECT

Hints the system about an icon, associated with a window.
If OBJECT is C<undef>, the system-default icon is assumed.

See also: C<ownerIcon>

=item menu OBJECT

Manages a Prima::Menu object associated with a window. 
Prima::Window can host many Prima::Menu objects,
but only the one that is set in
C<::menu> property will be seen as a menu bar.

See also: C<Prima::Menu>, C<menuItems>

=item menuColorIndex INDEX, COLOR

Maintains eight color properties of a menu,
associated with a window. INDEX must be one of C<ci::XXX> constants
( see L<Prima::Widget>, I<colorIndex> section ). 

See also: C<menuItems>, C<menuFont>, C<menu>

=item menuColor COLOR

Basic foreground menu color.

See also: C<menuItems>, C<menuColorIndex>, C<menuFont>, C<menu>

=item menuBackColor COLOR

Basic background menu color.

See also: C<menuItems>, C<menuColorIndex>, C<menuFont>, C<menu>

=item menuDark3DColor COLOR

Color for drawing dark shadings in menus.

See also: C<menuItems>, C<menuColorIndex>, C<menuFont>, C<menu>

=item menuDisabledColor COLOR

Foreground color for disabled items in menus.

See also: C<menuItems>, C<menuColorIndex>, C<menuFont>, C<menu>

=item menuDisabledBackColor COLOR

Background color for disabled items in menus.

See also: C<menuItems>, C<menuColorIndex>, C<menuFont>, C<menu>

=item menuFont %FONT

Maintains the font of a menu, associated with a window.

See also: C<menuItems>, C<menuColorIndex>, C<menu>

=item menuHiliteColor COLOR

Foreground color for selected items in menus.

See also: C<menuItems>, C<menuColorIndex>, C<menuFont>, C<menu>

=item menuHiliteBackColor COLOR

Background color for selected items in menus.

See also: C<menuItems>, C<menuColorIndex>, C<menuFont>, C<menu>

=item menuItems [ ITEM_LIST ]

Manages items of a Prima::Menu object associated with a window.
The ITEM_LIST format is same as C<Prima::AbstractMenu::items>
and is described in L<Prima::Menu>.

See also: C<menu>, C<menuColorIndex>, C<menuFont>

=item menuLight3DColor COLOR

Color for drawing light shadings in menus.

See also: C<menuItems>, C<menuColorIndex>, C<menuFont>, C<menu>

=item modalHorizon BOOLEAN

Reflects whether a window is a root to the shared modal window stack
or is a non-root. A window with C<::modalHorizon> set to 1
in shared modal state groups its children windows in a separate
hierarchy from other shared modal hierarchies. The C<::modalHorizon>
is therefore useful only when several shared modal window stacks
are needed.

The property also serves as an additional grouping factor
for widgets and windows. For example, default keyboard navigation by
tab and arrow keys is limited to the windows and widgets of a horizon.

=item modalResult INTEGER

Maintains a custom integer value, returned by C<execute()>.
Historically it is one of C<mb::XXX> constants, but any 
integer value can be used. The most useful C<mb::> constants are:

   mb::OK, mb::Ok
   mb::Cancel
   mb::Yes
   mb::No
   mb::Abort
   mb::Retry
   mb::Ignore
   mb::Help

NB: These constants are defined so they can be bitwise-or'ed,
and I<Prima::MsgBox> package uses this feature, where one
of its functions parameters is a combination of C<mb::> constants.

=item ownerIcon BOOLEAN

If 1, the icon is synchronized with the owner's.
Automatically set to 0 if C<::icon> property is explicitly set.
Default value is 1, so assigning an icon to $::application
spawns the icon to all windows.

=item taskListed BOOLEAN

If set to 0, hints the system against
reflecting existence of a window into a system task bar, 
or a top-level window list, or otherwise lower the window's
value before the other windows. If 1, does not hint anything.

Default value: 1

=item windowState STATE

A three-state property, that governs the state of a window.
STATE can be one of three C<ws::XXX> constants:

   ws::Normal
   ws::Minimized
   ws::Maximized

There can be more or less, or other window states 
provided by the system, but these three were chosen as
a 'least common denominator'.  The property can be changed
either by explicit set-mode call or by the user. In either case,
a C<WindowState> notification is triggered.

The property has three convenience wrappers: C<maximize()>,
C<minimize()> and C<restore()>.

See also: C<WindowState>

=back

=head2 Methods

=over

=item cancel

A standard method to dismiss a modal window with C<mb::Cancel>
result. The effect of calling this method is equal to when
the user selects a 'close window' action with system-provided
menu, button or other tool.

See also: C<ok>, C<modalResult>, C<execute>, C<execute_shared>


=item end_modal

If a window is in modal state, the C<EndModal>
notification is activated.
Then the window is returned from the modal state, 
gets hidden and disabled.
If the window was on top in the exclusive modal state,
the last called C<execute()> function finishes.
If the window was not on top in the exclusive modal state, 
the corresponding C<execute()> function finishes after
all subsequent execute() calls are finished.

=item execute INSERT_BEFORE = undef

A window is turned to the exclusive modal state
and is put on top of non-modal and shared-modal windows.
By default, if INSERT_BEFORE object is undef, the window
is also put on top of other exclusive-modal windows;
if INSERT_BEFORE is one of the exclusive-modal windows
the window is placed in queue before the INSERT_BEFORE window.
The window is showed and enabled, if necessary, and
C<Execute> notification is triggered.

The function is returned when a window is dismissed,
or if the system-dependent 'exit'-event is triggered by the
user ( the latter case falls through all execute() calls
and terminates C<run Prima;> call, exiting gracefully).

=item execute_shared INSERT_BEFORE = undef

A window is turned to the shared modal state
and is put on top of non-modal windows in the stack
of its C<::modalHorizon>. A window with C<::modalHorizon>
set to 1 starts its own stack, independent of all other
window stacks.

By default, if INSERT_BEFORE object is undef, the window
is also put on top of other shared-modal windows in its stack.
If INSERT_BEFORE is one of the shared-modal windows in its stack,
the window is placed in queue before the INSERT_BEFORE window.

The window is showed and enabled, if necessary, and
C<Execute> notification is triggered.

The function is returned immediately.

=item get_default_menu_font

Returns the default font for a Prima::Menu class.

=item get_modal

Returns one of three constants, reflecting the modal
state of a window:

   mt::None
   mt::Shared
   mt::Exclusive

Value of C<mt::None> is 0, so result of get_modal() can be 
also treated as a boolean value, if only the fact of modality
is needed to check.

=item get_modal_window MODALITY_TYPE = mt::Exclusive, NEXT = 1

Returns a modal window, that is next to the given window in the
modality chain. MODALITY_TYPE selects the chain, and can be either
C<mt::Exclusive> or C<mt::Shared>. NEXT is a boolean flag, selecting
the lookup direction; if it is 1, the 'upper' window is returned,
if 0, the 'lower' one ( in a simple case when window A is made modal
(executed) after modal window B, the A window is the 'upper' one ).

If a window has no immediate modal relations,  C<undef> is returned.

=item maximize

Maximizes window. A shortcut for C<windowState(ws::Maximized)>.

=item minimize

Minimizes window. A shortcut for C<windowState(ws::Minimized)>.

=item ok

A standard method to dismiss a modal window with C<mb::OK>
result. Typically the effect of calling this method is equal to when
the user presses the enter key of a modal window, signaling that
the default action is to be taken.

See also: C<cancel>, C<modalResult>, C<execute>, C<execute_shared>


=item restore

Restores window to normal state from
minimized or maximized state. A shortcut for C<windowState(ws::Normal)>.

=back

=head2 Events

=over 

=item Activate

Triggered when a window is activated by the user.
Activation mark is usually resides on a window that
contains keyboard focus, and is usually reflected by
highlighted system decorations.

The toolkit does not provide standalone activation
functions; C<select()> call is used instead.

=item Deactivate

Triggered when a window is deactivated by the user.
Window is usually marked inactive, when it contains
no keyboard focus.

The toolkit does not provide standalone de-activation
functions; C<deselect()> call is used instead.

=item EndModal

Called before a window leaves modal state.

=item Execute

Called after a window enters modal state.

=item WindowState STATE

Triggered when window state is changed, either by
an explicit C<windowState()> call, or by the user.
STATE is the new window state, one of three C<ws::XXX>
constants.

=back

=head1 AUTHOR

Dmitry Karasik, E<lt>dmitry@karasik.eu.orgE<gt>.


=head1 SEE ALSO

L<Prima>, L<Prima::Object>, L<Prima::Drawable>,
L<Prima::Widget>.


