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NAME

       Prima::Menu - pull-down and pop-up menu objects

SYNOPSIS

          use Prima;
          use Prima::Application;

          my $window = Prima::Window-> new(
               menuItems => [
                  [ '~File' => [
                     [ '~Open', 'Ctrl+O', '^O', \&open_file ],
                     [ '-save_file', '~Save', km::Ctrl | ord('S'), sub { save_file() } ],
                     [],
                     [ '~Exit', 'Alt+X', '@X', sub { exit } ],
                  ]],
                  [ '~Options' => [
                     [ '*option1' => 'Checkable option' => sub { $_[0]-> menu-> toggle( $_[1]) }],
                  ]],
                  [],
                  [ '~Help' => [
                     [ 'Show help' => sub { $::application-> open_help($0); }],
                  ]],
               ],
           );

           sub open_file
           {
               # enable 'save' menu item
               $window-> menu-> save_file-> enable;
           }

           $window-> popupItems( $window-> menuItems);

DESCRIPTION

       The document describes interfaces of Prima::AbstractMenu class, and its three descendants
       - Prima::Menu, Prima::Popup, and Prima::AccelTable, all aimed at different targets.
       Prima::AbstractMenu is a descendant of Prima::Component class, and its specialization is
       handling of menu items, held in a tree-like structure. Descendants of Prima::AbstractMenu
       are designed to be attached to widgets and windows, to serve as hints for the system-
       dependent pop-up and pull-down menus.

USAGE

   Menu items
       The central point of functionality in Prima::AbstractMenu-derived classes and their object
       instances ( further referred as 'menu classes' and 'menu objects'), is handling of a
       complex structure, contained in "::items" property. This property is special in that its
       structure is a tree-like array of scalars, each of whose is either a description of a menu
       item or a reference to an array.

       Parameters of an array must follow a special syntax, so the property input can be parsed
       and assigned correctly. In general, the syntax is

          $menu-> items( [
             [ menu item description ],
             [ menu item description ],
             ...
          ]);

       where 'menu item description' is an array of scalars, that can hold from 0 up to 6
       elements. Each menu item has six fields, that qualify a full description of a menu item;
       the shorter arrays are shortcuts, that imply default or special cases. These base six
       fields are:

       Menu item name
           A string identifier.  Menu items can be accessed individually by their names, and the
           following fields can be managed by calling elemental properties, that require an item
           name. If not given, or empty, item name is assigned a string in a form '#ID' where ID
           is the unique integer value within the menu object.

           IDs are set for each menu item, disregarding whether they have names or not.  Any menu
           item can be uniquely identifed by its ID value, by supplying the '#ID' string, in the
           same fashion as named menu items.  When creating or copying menu items, names in
           format '#ID' are not accepted, and treated as if an empty string is passed. When
           copying menu items to another menu object, all menu items to be copied change their
           IDs, but explicitly set names are preserved.  Since the anonymous menu items do not
           have name, their auto-generated names change also.

           If the name is prepended by '-' or '*' characters, or both, these are not treated as
           part of the name but as indicator that the item is disabled  ( '-' character ) or
           checked ( '*' character ).  This syntax is valid only for "::items" and "insert()"
           functions, not for "set_variable()" method.

       Menu text / menu image
           A non-separator menu item can be visualized either as a text string or an image. These
           options are exclusive to each other, and therefore occupy same field. Menu text is an
           arbitrary string, with with ~ ( tilde ) quoting for a shortcut character, that the
           system uses as a hot key during menu navigation.  Menu image is a Prima::Image object
           of no particular color space and dimensions.

           Menu text in menu item is accessible via the "::text" property, and menu image via the
           "::image" property. These can not accept or return sensible arguments simultaneously.

       Accelerator text
           An alternate text string, appearing together with a menu item or a menu image, usually
           serving as a description to the hot key, associated with a menu item. For example, if
           a hot key to a menu item is combination of 'enter' and 'control' keys, then usually
           accelerator text is 'Ctrl+Enter' string.

           Accelerator text in menu item is accessible via "::accel" property.

           NB: There is "Prima::KeySelector::describe" function, that converts a key value to a
           string in human-readable format.

       Hot key
           An integer value, combined from either "kb::XXX" constant or a character index with
           modificator key values ( "km::XXX" constant ).  This representation format is not that
           informative as three-integer key event format (CODE,KEY,MOD), described in
           Prima::Widget.  However, these formats are easily converted to each other:
           CODE,KEY,MOD is translated to INTEGER format by "translate_key()" method. The reverse
           operation is not needed for "Prima::AbstractMenu" functionality and is performed by
           "Prima::KeySelector::translate_codes" method.

           The integer value can be given in a some more readable format when submitting to
           "::items". Character and F-keys (from F1 to F16) can be used literally, without "kb::"
           prepending, and the modificator keys can be hinted as prefix characters: km::Shift as
           '#', km::Ctrl as '^' and km::Alt as '@'. This way, combination of 'control' and 'G'
           keys can be expressed as '^G' literal, and 'control'+'shift'+'F10' - as '^#F10'.

           Hot key in menu item is accessible via "::key" property. The property does accept
           literal key format, described above.

           A literal key string can be converted to an integer value by "translate_shortcut"
           method.

           When the user presses the key combination, that matches to hot key entry in a menu
           item, its action is triggered.

       Action
           Every non-separator and non-submenu item is destined to perform an action. The action
           can be set either as an anonymous sub, or as string with name of a method on the owner
           of a menu object. Both have their niche of usage, and both are supplied with three
           parameters, when called - the owner of a menu object, the menu object itself and the
           name of a menu item, that triggered the action.

           Action scalar in menu item is accessible via "::action" property.

       User data
           At last, a non-separator and non-submenu menu item can hold an arbitrary scalar value,
           the 'user data' field.  The toolkit does not use this field, leaving that to the
           programmer.

           User data scalar in menu item is accessible via "::data" property.

       Syntax of "::items" does not provide 'disabled' and 'checked' states for a menu item as
       separate fields. These states can be set by using '-' and '*' prefix characters, as
       described above, in "Menu item name". They also can be assigned on per-item basis via
       "::enabled" and "::checked" properties.

       All these fields qualify a most common menu item, that has text, shortcut key and an
       action - a 'text item'.  However, there are also two other types of menu items - a sub-
       menu and separator. The type of a menu items can not be changed except by full menu item
       tree change functions ( "::items", "remove()", "insert()".

       Sub-menu item can hold same references as text menu item does, except the action field.
       Instead, the action field is used for a sub-menu reference scalar, pointing to another set
       of menu item description arrays. From that point of view, syntax of "::items" can be more
       elaborated and shown as

          $menu-> items( [
             [ text menu item description ],
             [ sub-menu item description [

                [ text menu item description ],
                [ sub-menu item description [
                    [ text menu item description ],
                    ...
                ]
                [ text menu item description ],
                ...
             ] ],
             ...
          ]);

       Separator items do not hold any fields, except name.  Their purpose is to hint a logical
       division of menu items by the system, which visualizes them usually as non-selectable
       horizontal lines.

       In menu bars, the first separator item met by parser is treated differently. It serves as
       a hint, that the following items must be shown in the right corner of a menu bar, contrary
       to the left-adjacent default layout. Subsequent separator items in a menu bar declaration
       can be either shown as a vertical division bars, or ignored.

       With these menu items types and fields, it is possible to construct the described above
       menu description arrays.  An item description array can hold from 0 to 6 scalars, and each
       combination is treated differently.

       six - [ NAME, TEXT/IMAGE, ACCEL, KEY, ACTION/SUBMENU, DATA ]
           Six-scalar array is a fully qualified text-item description.  All fields correspond to
           the described above scalars.

       five [ NAME, TEXT/IMAGE, ACCEL, KEY, ACTION/SUBMENU ]
           Same as six-scalar syntax, but without DATA field.  If DATA is skipped it is "undef"
           by default.

       four [ TEXT/IMAGE, ACCEL, KEY, ACTION/SUBMENU ]
           Same as five-scalar syntax, but without NAME field.  When NAME is skipped it is
           assigned to an unique string within menu object.

       three [ NAME, TEXT/IMAGE, ACTION/SUBMENU ]
           Same as five-scalar syntax, but without ACCEL and KEY fields.  KEY is "kb::NoKey" by
           default, so no keyboard combination is bound to the item. Default ACCEL value is an
           empty string.

       two [ TEXT/IMAGE, ACTION/SUBMENU ]
           Same as three-scalar syntax, but without NAME field.

       one and zero [ ]
           Both empty and 1-scalar arrays indicate a separator menu item. In case of 1-scalar
           syntax, the scalar value is ignored.

       As an example of all above said, a real-life piece of code is exemplified:

          $img = Prima::Image-> create( ... );
          ...
          $menu-> items( [
             [ "~File" => [
                 [ "Anonymous" => "Ctrl+D" => '^d' => sub { print "sub\n";}],   # anonymous sub
                 [ $img => sub {
                    my $img = $_[0]-> menu-> image( $_[1]);
                    my @r = @{$img-> palette};
                    $img-> palette( [reverse @r]);
                    $_[0]->menu->image( $_[1], $img);
                 }],                         # image
                 [],                         # division line
                 [ "E~xit" => "Exit"    ]    # calling named function of menu owner
             ]],
             [ ef => "~Edit" => [                  # example of system commands usage
                ...
                [ "Pa~ste" => sub { $_[0]->foc_action('paste')} ],
                ...
                ["~Duplicate menu"=>sub{ TestWindow->create( menu=>$_[0]->menu)}],
             ]],
             ...
             [],                             # divisor in main menu opens
             [ "~Clusters" => [              # right-adjacent part
               [ "*".checker =>  "Checking Item"   => "Check"     ],
               [],
               [ "-".slave   =>  "Disabled state"   => "PrintText"],
               ...
             ]]
          ] );

       The code is stripped from 'menu.pl' from 'examples' directory in the toolkit installation.
       The reader is advised to run the example and learn the menu mechanics.

   Prima::MenuItem
       As described above, text and sub-menu items can be managed by elemental properties -
       "::accel", "::text", "::image", "::checked", "::enabled", "::action", "::data".  All
       these, plus some other methods can be called in an alternative way, resembling name-based
       component calls of Prima::Object. A code

         $menu-> checked('CheckerMenuItem', 1);

       can be re-written as

         $menu-> CheckerMenuItem-> checked(1);

       Name-based call substitutes Prima::MenuItem object, created on the fly. Prima::MenuItem
       class shares same functions of Prima::AbstractMenu, that handle individual menu items.

   Prima::Menu
       Objects, derived from Prima::Menu class are used to tandem Prima::Window objects, and
       their items to be shown as menu bar on top of the window.

       Prima::Menu is special in that its top-level items visualized horizontally, and in
       behavior of the top-level separator items ( see above, "Menu items" ).

       If "::selected" is set to 1, then a menu object is visualized in a window, otherwise it is
       not.  This behavior allows window to host multiple menu objects without clashing.  When a
       Prima::Menu object gets 'selected', it displaces the previous 'selected' menu Prima::Menu
       object, and its items are installed into the visible menu bar. Prima::Window property
       "::menu" then points to the menu object, and "::menuItems" is an alias for "::items" menu
       class property.  Prima::Window's properties "::menuFont" and "::menuColorIndex" are used
       as visualization hints.

       Prima::Menu provide no new methods or properties.

   Prima::Popup
       Objects, derived from Prima::Popup class are used together with Prima::Widget objects.
       Menu items are visualized when the user pressed the pop-up key or mouse buttons
       combination, in response to Prima::Widget's "Popup" notification.

       If "::selected" is set to 1, then a menu object is visualized in the system pop-up menu,
       otherwise it is not.  This behavior allows widget to host multiple menu objects without
       clashing.  When a Prima::Popup object gets 'selected', it displaces the previous
       'selected' menu Prima::Popup object.  Prima::Widget property "::popup" then points to the
       menu object, and "::popupItems" is an alias for "::items" menu class property.
       Prima::Widget's properties "::popupFont" and "::popupColorIndex" are used as visualization
       hints.

       A Prima::Popup object can be visualized explicitly, by means of "popup" method. The
       implicit visualization by the user is happened only if the "::autoPopup" property is set
       to 1.

       Prima::Popup provides new "popup" method and new "::autoPopup" property.

   Prima::AccelTable
       This class is destined for a more limited functionality than Prima::Menu and Prima::Popup,
       primarily for mapping key strokes to predefined actions.  Prima::AccelTable objects are
       never visualized, and consume no system resources, although full menu item management
       syntax is supported.

       If "::selected" is set to 1, then it displaces the previous 'selected' menu
       Prima::AccelTable object.  Prima::Widget property "::accelTable" then points to the menu
       object, and "::accelItems" is an alias for "::items" menu class property.

       Prima::AccelTable provide no new methods or properties.

API

   Properties
       accel NAME, STRING / Prima::MenuItem::accel STRING
           Manages accelerator text for a menu item.  NAME is name of the menu item.

       action NAME, SCALAR / Prima::MenuItem::action SCALAR.
           Manages action for a menu item.  NAME is name of the menu item.  SCALAR can be either
           an anonymous sub or a method name, defined in the menu object owner's name space.
           Both called with three parameters - the owner of a menu object, the menu object itself
           and the name of the menu item.

       autoPopup BOOLEAN
           Only in Prima::Popup

           If set to 1 in selected state, calls "popup()" action in response to "Popup"
           notification, when the user presses the default key or mouse button combination.

           If 0, the pop-up menu can not be executed implicitly.

           Default value: 1

       checked NAME, BOOLEAN / Prima::MenuItem::checked BOOLEAN
           Manages 'checked' state of a menu item. If 'checked', a menu item visualized with a
           distinct check-mark near the menu item text or image. Its usage with sub-menu items is
           possible, although discouraged.

           NAME is name of the menu item.

       data NAME, SCALAR / Prima::MenuItem::data SCALAR
           Manages the user data scalar.

           NAME is name of the menu item.  SCALAR can be any scalar value, the toolkit does not
           use this property internally.

       enabled NAME, BOOLEAN / Prima::MenuItem::enabled BOOLEAN
           Manages 'enabled' state of a menu item. If 'enabled' is 0, a menu item visualized with
           grayed or otherwise dimmed color palette. If a sub-menu item is disabled, whole sub-
           menu is inaccessible.

           NAME is name of the menu item.

       image NAME, OBJECT / Prima::MenuItem::image OBJECT
           Manages the image, bound with a menu item. OBJECT is a non-null Prima::Image object
           reference, with no particular color space or dimensions ( because of dimensions, its
           usage in top-level Prima::Menu items is discouraged ).

           "::image" and "::text" are mutually exclusive menu item properties, and can not be set
           together, but a menu item can change between image and text representation at run time
           by calling these properties.

           NAME is name of the menu item.

       items SCALAR
           Manages the whole menu items tree. SCALAR is a multi-level anonymous array structure,
           with syntax described in "Menu items".

           "::items" is an ultimate tool for reading and writing the menu items tree, but often
           it is too powerful, so there are elemental properties "::accel", "::text", "::image",
           "::checked", "::enabled", "::action", "::data" declared, that handle menu items
           individually.

       key NAME, KEY / Prima::MenuItem::key KEY
           Manages the hot key combination, bound with a menu item.  Internally KEY is kept as an
           integer value, and get-mode call returns integers only, but set-mode accepts the
           literal key format - like, '^C', 'F5' strings.

           NAME is name of the menu item, KEY is an integer value.

       selected BOOLEAN
           If set to 1, menu object is granted extra functionality from a window or widget owner
           object. Different Prima::AbstractMenu descendant provided with different extra
           functionalities.  In Usage section, see Prima::Menu, Prima::Popup and
           Prima::AccelTable.

           Within each menu class, only one menu object can be selected for its owner.

           If set to 0, the only actions performed are implicit hot-key lookup when on "KeyDown"
           event.

           Default value: 1

       text NAME, STRING / Prima::MenuItem::text STRING
           Manages the text, bound with a menu item. STRING is an arbitrary string, with '~' (
           tilde ) quotation of a hot key character. The hot key character is only used when
           keyboard navigation of a pop-up or a pull-down menu is performed; it has no influence
           outside menu sessions.

           "::text" and "::image" are mutually exclusive menu item properties, and can not be set
           together, but a menu item can change between image and text representation at run time
           by calling these properties.

   Methods
       check NAME / Prima::MenuItem::check
           Alias for checked(1).  Sets menu item in checked state.

       disable NAME / Prima::MenuItem::disable
           Alias for enabled(0).  Sets menu item in disabled state.

       enabled NAME / Prima::MenuItem::enabled
           Alias for enabled(1).  Sets menu item in enabled state.

       get_handle
           Returns a system-dependent menu handle.

           NB: Prima::AccelTable use no system resources, and this method returns its object
           handle instead.

       has_item NAME
           Returns boolean value, whether the menu object has a menu item with name NAME.

       insert ITEMS, ROOT_NAME, INDEX
           Inserts menu item inside existing item tree.  ITEMS has same syntax as "::items".
           ROOT_NAME is the name of a menu item, where the insertion must take place; if
           ROOT_NAME is an empty string, the insertion is performed to the top level items.
           INDEX is an offset, which the newly inserted items would possess after the insertion.
           INDEX 0 indicates the beginning, thus.

           Returns no value.

       popup X_OFFSET, Y_OFFSET, [ LEFT = 0, BOTTOM = 0, RIGHT = 0, TOP = 0 ]
           Only in Prima::Popup

           Executes the system-driven pop-up menu, in location near (X_OFFSET,Y_OFFSET) pixel on
           the screen, with items from "::items" tree. The pop-up menu is hinted to be positioned
           so that the rectangle, defined by (LEFT,BOTTOM) - (RIGHT,TOP) coordinates is not
           covered by the first-level menu. This is useful when a pop-up menu is triggered by a
           button widget, for example.

           If during the execution the user selects a menu item, then its associated action is
           executed ( see "action" ).

           The method returns immediately and returns no value.

       remove NAME / Prima::MenuItem::remove
           Deletes a menu item from the items tree, and its sub-menus if the item is a sub-menu
           item.

       select
           Alias for selected(1).  Sets menu object in selected state.

       set_command KEY, ENABLED
           Disables or enables menu items, associated with key combinations KEY.

       set_variable NAME, NEW_NAME
           Changes the name of a menu item with NAME to NEW_NAME.  NEW_NAME must not be an empty
           string and must not be in a '#integer' form.

       toggle NAME / Prima::MenuItem::toggle
           Toggles the checked state of a menu item and returns the new state.

       translate_accel TEXT
           Locates a '~' ( tilde ) - escaped character in a TEXT string and returns its index (
           as ord(lc())), or 0 if no escaped characters were found.

           The method can be called with no object.

       translate_key CODE, KEY, MOD
           Translates three-integer key representation into the one-integer format and returns
           the integer value.  The three-integer format is used in "KeyDown" and "KeyUp"
           notifications for Prima::Widget.

           See Prima::Widget

           The method can be called with no object.

       translate_shortcut KEY
           Converts literal-represented KEY string into the integer format and returns the
           integer value.

           The method can be called with no object.

       uncheck NAME / Prima::MenuItem::uncheck
           Alias for checked(0).  Sets menu item in unchecked state.

AUTHOR

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

SEE ALSO

       Prima, Prima::Object, Prima::Widget, Prima::Window