pod::Prima::Menu(3)

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

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
    An unique string, assigned to every menu item. 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. The name itself can be dynamically changed by set_variable() method. If the menu name was not given explicitly, it is formed by sprintf("MenuItem_%d", unique number) string automatically.

    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 the Prima::Image manpage 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 the Prima::Widget manpage. 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 the section on 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 the Prima::Object manpage. 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, the section on 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 the section on 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 the Prima::Menu manpage, the Prima::Popup manpage and the Prima::AccelTable manpage.

    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.

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 the Prima::Widget manpage

    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
the Prima manpage, the Prima::Object manpage, the Prima::Widget manpage, the Prima::Window manpage