Prima::Window - top-level window management

Properties
Methods
Events

AUTHOR
SEE ALSO

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::Widget can never be clipped by anything but the screen, 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 time these rules are hard or even impossible to circumvent. It will be a long document, describing 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 as many as possible.

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 constants.

There are other hints, that the toolkit can specify for a window. 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 operating the ::taskListed property.

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. But 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 it is closed. There can be other message boxes on top of each other, preventing the lower window from operation as well. This is an exclusive modality.

The toolkit also provides the shared modality model, where there can be several stacks of modal windows, not interfering in operation. Each stack is exclusive for its own windows. An example can be several independent applications with their message boxes activated. This model, however, can not be achieved with single execute()-like call without creating interlocking conditions. The shared model call, execute_shared(), 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 be dismissed in several ways.

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 the Prima::Menu manpage class, arrange the layout of the menu. The syntax of the items-derived properties is described in the Prima::Menu manpage, but it must be reiterated that menu item records only hint, not request their exact representation. The same is valid for the color and font properties, ::menuColorIndex and ::menuFont.

Only one menu at a time can be set on a top-level window, although a window can be 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 default menu actions.

NB: A window can be owner for several menu objects and still do not have a menu bar, 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, and resemble the system dialogs - on systems where they are provided.

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.

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>.