pod::Prima::Window(3)

NAME
Prima::Window - top-level window management

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.

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.

  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 "::borderIcons" property, and borders by the "::borderStyle" property. These operate with set of predefined constants, "bi::XXX" and "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 "::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 "sv::XIcon" and "sv::YIcon" system values, the "::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 "::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 "::originDontCare" and "::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 "::frameOrigin" and "::frameSize", which along with "::origin" and "::size" reflect the position and size of a window, but taking into account the system-dependent decorations.

  Dialog execution
Method of Prima::Window, "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, "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 "::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 "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 "::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 "ok()" and "cancel()" methods; the latter is identical to when the user closes the modal window by the means of the system. The values set to "::modalResult" are "mb::OK" and "mb::Cancel", correspondingly. There are more "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.

  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 "::menuItems" property, that manages the menu items of a "::menu" object of Prima::Menu class, arrange the layout of the menu. The syntax of the items-derived properties is described in 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, "::menuColorIndex" and "::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 "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.

  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.

  Prima::MainWindow
The class is a simple descendant of Prima::Window, which overloads "on_destroy" notification and calls "$application->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.

API

  Properties

borderIcons INTEGER
    Hints the system about window's decorations, by selecting the combination of "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.

borderStyle STYLE
    Hints the system about window's border style, by selecting one of "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

    "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.

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

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

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

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

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

    See also: "ownerIcon"

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 "::menu" property will be seen as a menu bar.

    See also: "Prima::Menu", "menuItems"

menuColorIndex INDEX, COLOR
    Maintains eight color properties of a menu, associated with a window. INDEX must be one of "ci::XXX" constants ( see Prima::Widget, colorIndex section ).

    See also: "menuItems", "menuFont", "menu"

menuColor COLOR
    Basic foreground menu color.

    See also: "menuItems", "menuColorIndex", "menuFont", "menu"

menuBackColor COLOR
    Basic background menu color.

    See also: "menuItems", "menuColorIndex", "menuFont", "menu"

menuDark3DColor COLOR
    Color for drawing dark shadings in menus.

    See also: "menuItems", "menuColorIndex", "menuFont", "menu"

menuDisabledColor COLOR
    Foreground color for disabled items in menus.

    See also: "menuItems", "menuColorIndex", "menuFont", "menu"

menuDisabledBackColor COLOR
    Background color for disabled items in menus.

    See also: "menuItems", "menuColorIndex", "menuFont", "menu"

menuFont %FONT
    Maintains the font of a menu, associated with a window.

    See also: "menuItems", "menuColorIndex", "menu"

menuHiliteColor COLOR
    Foreground color for selected items in menus.

    See also: "menuItems", "menuColorIndex", "menuFont", "menu"

menuHiliteBackColor COLOR
    Background color for selected items in menus.

    See also: "menuItems", "menuColorIndex", "menuFont", "menu"

menuItems [ ITEM_LIST ]
    Manages items of a Prima::Menu object associated with a window. The ITEM_LIST format is same as "Prima::AbstractMenu::items" and is described in Prima::Menu.

    See also: "menu", "menuColorIndex", "menuFont"

menuLight3DColor COLOR
    Color for drawing light shadings in menus.

    See also: "menuItems", "menuColorIndex", "menuFont", "menu"

modalHorizon BOOLEAN
    Reflects whether a window is a root to the shared modal window stack or is a non-root. A window with "::modalHorizon" set to 1 in shared modal state groups its children windows in a separate hierarchy from other shared modal hierarchies. The "::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.

modalResult INTEGER
    Maintains a custom integer value, returned by "execute()". Historically it is one of "mb::XXX" constants, but any integer value can be used. The most useful "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 Prima::MsgBox package uses this feature, where one of its functions parameters is a combination of "mb::" constants.

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

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

windowState STATE
    A three-state property, that governs the state of a window. STATE can be one of three "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 "WindowState" notification is triggered.

    The property has three convenience wrappers: "maximize()", "minimize()" and "restore()".

    See also: "WindowState"

  Methods

cancel
    A standard method to dismiss a modal window with "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: "ok", "modalResult", "execute", "execute_shared"

end_modal
    If a window is in modal state, the "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 "execute()" function finishes. If the window was not on top in the exclusive modal state, the corresponding "execute()" function finishes after all subsequent execute() calls are finished.

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 "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 "run Prima;" call, exiting gracefully).

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 "::modalHorizon". A window with "::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 "Execute" notification is triggered.

    The function is returned immediately.

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

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

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

    Value of "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.

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 "mt::Exclusive" or "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, "undef" is returned.

maximize
    Maximizes window. A shortcut for "windowState(ws::Maximized)".

minimize
    Minimizes window. A shortcut for "windowState(ws::Minimized)".

ok  A standard method to dismiss a modal window with "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: "cancel", "modalResult", "execute", "execute_shared"

restore
    Restores window to normal state from minimized or maximized state. A shortcut for "windowState(ws::Normal)".

  Events

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; "select()" call is used instead.

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; "deselect()" call is used instead.

EndModal
    Called before a window leaves modal state.

Execute
    Called after a window enters modal state.

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

AUTHOR
Dmitry Karasik, <dmitry@karasik.eu.org>.

SEE ALSO
Prima, Prima::Object, Prima::Drawable, Prima::Widget.