FLTK 1.3.3
|
Base class of all widgets that have a menu in FLTK. More...
#include <Fl_Menu_.H>
Public Member Functions | |
int | add (const char *, int shortcut, Fl_Callback *, void *=0, int=0) |
Adds a new menu item. More... | |
int | add (const char *a, const char *b, Fl_Callback *c, void *d=0, int e=0) |
See int Fl_Menu_::add(const char* label, int shortcut, Fl_Callback*, void *user_data=0, int flags=0) | |
int | add (const char *) |
This is a Forms (and SGI GL library) compatible add function, it adds many menu items, with '|' separating the menu items, and tab separating the menu item names from an optional shortcut string. More... | |
void | clear () |
Same as menu(NULL), set the array pointer to null, indicating a zero-length menu. More... | |
int | clear_submenu (int index) |
Clears the specified submenu pointed to by index of all menu items. More... | |
void | copy (const Fl_Menu_Item *m, void *user_data=0) |
Sets the menu array pointer with a copy of m that will be automatically deleted. More... | |
Fl_Boxtype | down_box () const |
This box type is used to surround the currently-selected items in the menus. More... | |
void | down_box (Fl_Boxtype b) |
See Fl_Boxtype Fl_Menu_::down_box() const. | |
Fl_Color | down_color () const |
For back compatibility, same as selection_color() | |
void | down_color (unsigned c) |
For back compatibility, same as selection_color() | |
int | find_index (const char *name) const |
Find the menu item index for a given menu pathname , such as "Edit/Copy". More... | |
int | find_index (const Fl_Menu_Item *item) const |
Find the index the menu array for given item . More... | |
int | find_index (Fl_Callback *cb) const |
Find the index into the menu array for a given callback cb . More... | |
const Fl_Menu_Item * | find_item (const char *name) |
Find the menu item for a given menu pathname , such as "Edit/Copy". More... | |
const Fl_Menu_Item * | find_item (Fl_Callback *) |
Find the menu item for the given callback cb . More... | |
Fl_Menu_ (int, int, int, int, const char *=0) | |
Creates a new Fl_Menu_ widget using the given position, size, and label string. More... | |
void | global () |
Make the shortcuts for this menu work no matter what window has the focus when you type it. More... | |
int | insert (int index, const char *, int shortcut, Fl_Callback *, void *=0, int=0) |
Inserts a new menu item at the specified index position. More... | |
int | insert (int index, const char *a, const char *b, Fl_Callback *c, void *d=0, int e=0) |
See int Fl_Menu_::insert(const char* label, int shortcut, Fl_Callback*, void *user_data=0, int flags=0) | |
int | item_pathname (char *name, int namelen, const Fl_Menu_Item *finditem=0) const |
Get the menu 'pathname' for the specified menuitem. More... | |
const Fl_Menu_Item * | menu () const |
Returns a pointer to the array of Fl_Menu_Items. More... | |
void | menu (const Fl_Menu_Item *m) |
Sets the menu array pointer directly. More... | |
void | mode (int i, int fl) |
Sets the flags of item i. More... | |
int | mode (int i) const |
Gets the flags of item i. More... | |
const Fl_Menu_Item * | mvalue () const |
Returns a pointer to the last menu item that was picked. More... | |
const Fl_Menu_Item * | picked (const Fl_Menu_Item *) |
When user picks a menu item, call this. More... | |
void | remove (int) |
Deletes item i from the menu. More... | |
void | replace (int, const char *) |
Changes the text of item i . More... | |
void | shortcut (int i, int s) |
Changes the shortcut of item i to n. More... | |
int | size () const |
This returns the number of Fl_Menu_Item structures that make up the menu, correctly counting submenus. More... | |
void | size (int W, int H) |
const Fl_Menu_Item * | test_shortcut () |
Returns the menu item with the entered shortcut (key value). More... | |
const char * | text () const |
Returns the title of the last item chosen. More... | |
const char * | text (int i) const |
Returns the title of item i. More... | |
Fl_Color | textcolor () const |
Get the current color of menu item labels. More... | |
void | textcolor (Fl_Color c) |
Sets the current color of menu item labels. More... | |
Fl_Font | textfont () const |
Gets the current font of menu item labels. More... | |
void | textfont (Fl_Font c) |
Sets the current font of menu item labels. More... | |
Fl_Fontsize | textsize () const |
Gets the font size of menu item labels. More... | |
void | textsize (Fl_Fontsize c) |
Sets the font size of menu item labels. More... | |
int | value () const |
Returns the index into menu() of the last item chosen by the user. More... | |
int | value (const Fl_Menu_Item *) |
The value is the index into menu() of the last item chosen by the user. More... | |
int | value (int i) |
The value is the index into menu() of the last item chosen by the user. More... | |
Public Member Functions inherited from Fl_Widget | |
void | _clear_fullscreen () |
void | _set_fullscreen () |
void | activate () |
Activates the widget. More... | |
unsigned int | active () const |
Returns whether the widget is active. More... | |
int | active_r () const |
Returns whether the widget and all of its parents are active. More... | |
Fl_Align | align () const |
Gets the label alignment. More... | |
void | align (Fl_Align alignment) |
Sets the label alignment. More... | |
long | argument () const |
Gets the current user data (long) argument that is passed to the callback function. | |
void | argument (long v) |
Sets the current user data (long) argument that is passed to the callback function. More... | |
virtual class Fl_Gl_Window * | as_gl_window () |
Returns an Fl_Gl_Window pointer if this widget is an Fl_Gl_Window. More... | |
virtual Fl_Group * | as_group () |
Returns an Fl_Group pointer if this widget is an Fl_Group. More... | |
virtual Fl_Window * | as_window () |
Returns an Fl_Window pointer if this widget is an Fl_Window. More... | |
Fl_Boxtype | box () const |
Gets the box type of the widget. More... | |
void | box (Fl_Boxtype new_box) |
Sets the box type for the widget. More... | |
Fl_Callback_p | callback () const |
Gets the current callback function for the widget. More... | |
void | callback (Fl_Callback *cb, void *p) |
Sets the current callback function for the widget. More... | |
void | callback (Fl_Callback *cb) |
Sets the current callback function for the widget. More... | |
void | callback (Fl_Callback0 *cb) |
Sets the current callback function for the widget. More... | |
void | callback (Fl_Callback1 *cb, long p=0) |
Sets the current callback function for the widget. More... | |
unsigned int | changed () const |
Checks if the widget value changed since the last callback. More... | |
void | clear_active () |
Marks the widget as inactive without sending events or changing focus. More... | |
void | clear_changed () |
Marks the value of the widget as unchanged. More... | |
void | clear_damage (uchar c=0) |
Clears or sets the damage flags. More... | |
void | clear_output () |
Sets a widget to accept input. More... | |
void | clear_visible () |
Hides the widget. More... | |
void | clear_visible_focus () |
Disables keyboard focus navigation with this widget. More... | |
Fl_Color | color () const |
Gets the background color of the widget. More... | |
void | color (Fl_Color bg) |
Sets the background color of the widget. More... | |
void | color (Fl_Color bg, Fl_Color sel) |
Sets the background and selection color of the widget. More... | |
Fl_Color | color2 () const |
For back compatibility only. More... | |
void | color2 (unsigned a) |
For back compatibility only. More... | |
int | contains (const Fl_Widget *w) const |
Checks if w is a child of this widget. More... | |
void | copy_label (const char *new_label) |
Sets the current label. More... | |
void | copy_tooltip (const char *text) |
Sets the current tooltip text. More... | |
uchar | damage () const |
Returns non-zero if draw() needs to be called. More... | |
void | damage (uchar c) |
Sets the damage bits for the widget. More... | |
void | damage (uchar c, int x, int y, int w, int h) |
Sets the damage bits for an area inside the widget. More... | |
int | damage_resize (int, int, int, int) |
Internal use only. More... | |
void | deactivate () |
Deactivates the widget. More... | |
Fl_Image * | deimage () |
Gets the image that is used as part of the widget label. More... | |
const Fl_Image * | deimage () const |
void | deimage (Fl_Image *img) |
Sets the image to use as part of the widget label. More... | |
void | deimage (Fl_Image &img) |
Sets the image to use as part of the widget label. More... | |
void | do_callback () |
Calls the widget callback. More... | |
void | do_callback (Fl_Widget *o, long arg) |
Calls the widget callback. More... | |
void | do_callback (Fl_Widget *o, void *arg=0) |
Calls the widget callback. More... | |
virtual void | draw ()=0 |
Draws the widget. More... | |
void | draw_label (int, int, int, int, Fl_Align) const |
Draws the label in an arbitrary bounding box with an arbitrary alignment. More... | |
int | h () const |
Gets the widget height. More... | |
virtual int | handle (int event) |
Handles the specified event. More... | |
virtual void | hide () |
Makes a widget invisible. More... | |
Fl_Image * | image () |
Gets the image that is used as part of the widget label. More... | |
const Fl_Image * | image () const |
void | image (Fl_Image *img) |
Sets the image to use as part of the widget label. More... | |
void | image (Fl_Image &img) |
Sets the image to use as part of the widget label. More... | |
int | inside (const Fl_Widget *wgt) const |
Checks if this widget is a child of wgt . More... | |
const char * | label () const |
Gets the current label text. More... | |
void | label (const char *text) |
Sets the current label pointer. More... | |
void | label (Fl_Labeltype a, const char *b) |
Shortcut to set the label text and type in one call. More... | |
Fl_Color | labelcolor () const |
Gets the label color. More... | |
void | labelcolor (Fl_Color c) |
Sets the label color. More... | |
Fl_Font | labelfont () const |
Gets the font to use. More... | |
void | labelfont (Fl_Font f) |
Sets the font to use. More... | |
Fl_Fontsize | labelsize () const |
Gets the font size in pixels. More... | |
void | labelsize (Fl_Fontsize pix) |
Sets the font size in pixels. More... | |
Fl_Labeltype | labeltype () const |
Gets the label type. More... | |
void | labeltype (Fl_Labeltype a) |
Sets the label type. More... | |
void | measure_label (int &ww, int &hh) const |
Sets width ww and height hh accordingly with the label size. More... | |
unsigned int | output () const |
Returns if a widget is used for output only. More... | |
Fl_Group * | parent () const |
Returns a pointer to the parent widget. More... | |
void | parent (Fl_Group *p) |
Internal use only - "for hacks only". More... | |
void | position (int X, int Y) |
Repositions the window or widget. More... | |
void | redraw () |
Schedules the drawing of the widget. More... | |
void | redraw_label () |
Schedules the drawing of the label. More... | |
virtual void | resize (int x, int y, int w, int h) |
Changes the size or position of the widget. More... | |
Fl_Color | selection_color () const |
Gets the selection color. More... | |
void | selection_color (Fl_Color a) |
Sets the selection color. More... | |
void | set_active () |
Marks the widget as active without sending events or changing focus. More... | |
void | set_changed () |
Marks the value of the widget as changed. More... | |
void | set_output () |
Sets a widget to output only. More... | |
void | set_visible () |
Makes the widget visible. More... | |
void | set_visible_focus () |
Enables keyboard focus navigation with this widget. More... | |
virtual void | show () |
Makes a widget visible. More... | |
void | size (int W, int H) |
Changes the size of the widget. More... | |
int | take_focus () |
Gives the widget the keyboard focus. More... | |
unsigned int | takesevents () const |
Returns if the widget is able to take events. More... | |
int | test_shortcut () |
Returns true if the widget's label contains the entered '&x' shortcut. More... | |
const char * | tooltip () const |
Gets the current tooltip text. More... | |
void | tooltip (const char *text) |
Sets the current tooltip text. More... | |
Fl_Window * | top_window () const |
Returns a pointer to the top-level window for the widget. More... | |
Fl_Window * | top_window_offset (int &xoff, int &yoff) const |
Finds the x/y offset of the current widget relative to the top-level window. More... | |
uchar | type () const |
Gets the widget type. More... | |
void | type (uchar t) |
Sets the widget type. More... | |
int | use_accents_menu () |
Returns non zero if MAC_USE_ACCENTS_MENU flag is set, 0 otherwise. | |
void * | user_data () const |
Gets the user data for this widget. More... | |
void | user_data (void *v) |
Sets the user data for this widget. More... | |
unsigned int | visible () const |
Returns whether a widget is visible. More... | |
void | visible_focus (int v) |
Modifies keyboard focus navigation. More... | |
unsigned int | visible_focus () |
Checks whether this widget has a visible focus. More... | |
int | visible_r () const |
Returns whether a widget and all its parents are visible. More... | |
int | w () const |
Gets the widget width. More... | |
Fl_When | when () const |
Returns the conditions under which the callback is called. More... | |
void | when (uchar i) |
Sets the flags used to decide when a callback is called. More... | |
Fl_Window * | window () const |
Returns a pointer to the nearest parent window up the widget hierarchy. More... | |
int | x () const |
Gets the widget position in its window. More... | |
int | y () const |
Gets the widget position in its window. More... | |
virtual | ~Fl_Widget () |
Destroys the widget. More... | |
Protected Attributes | |
uchar | alloc |
uchar | down_box_ |
Fl_Color | textcolor_ |
Fl_Font | textfont_ |
Fl_Fontsize | textsize_ |
Additional Inherited Members | |
Static Public Member Functions inherited from Fl_Widget | |
static void | default_callback (Fl_Widget *cb, void *d) |
Sets the default callback for all widgets. More... | |
static unsigned int | label_shortcut (const char *t) |
Returns the Unicode value of the '&x' shortcut in a given text. More... | |
static int | test_shortcut (const char *, const bool require_alt=false) |
Returns true if the given text t contains the entered '&x' shortcut. More... | |
Protected Types inherited from Fl_Widget | |
enum | { INACTIVE = 1<<0, INVISIBLE = 1<<1, OUTPUT = 1<<2, NOBORDER = 1<<3, FORCE_POSITION = 1<<4, NON_MODAL = 1<<5, SHORTCUT_LABEL = 1<<6, CHANGED = 1<<7, OVERRIDE = 1<<8, VISIBLE_FOCUS = 1<<9, COPIED_LABEL = 1<<10, CLIP_CHILDREN = 1<<11, MENU_WINDOW = 1<<12, TOOLTIP_WINDOW = 1<<13, MODAL = 1<<14, NO_OVERLAY = 1<<15, GROUP_RELATIVE = 1<<16, COPIED_TOOLTIP = 1<<17, FULLSCREEN = 1<<18, MAC_USE_ACCENTS_MENU = 1<<19, USERFLAG3 = 1<<29, USERFLAG2 = 1<<30, USERFLAG1 = 1<<31 } |
flags possible values enumeration. More... | |
Protected Member Functions inherited from Fl_Widget | |
void | clear_flag (unsigned int c) |
Clears a flag in the flags mask. | |
void | draw_backdrop () const |
If FL_ALIGN_IMAGE_BACKDROP is set, the image or deimage will be drawn. | |
void | draw_box () const |
Draws the widget box according its box style. | |
void | draw_box (Fl_Boxtype t, Fl_Color c) const |
Draws a box of type t, of color c at the widget's position and size. More... | |
void | draw_box (Fl_Boxtype t, int x, int y, int w, int h, Fl_Color c) const |
Draws a box of type t, of color c at the position X,Y and size W,H. More... | |
void | draw_focus () |
draws a focus rectangle around the widget | |
void | draw_focus (Fl_Boxtype t, int x, int y, int w, int h) const |
Draws a focus box for the widget at the given position and size. | |
void | draw_label () const |
Draws the widget's label at the defined label position. More... | |
void | draw_label (int, int, int, int) const |
Draws the label in an arbitrary bounding box. More... | |
Fl_Widget (int x, int y, int w, int h, const char *label=0L) | |
Creates a widget at the given position and size. More... | |
unsigned int | flags () const |
Gets the widget flags mask. | |
void | h (int v) |
Internal use only. More... | |
void | set_flag (unsigned int c) |
Sets a flag in the flags mask. | |
void | w (int v) |
Internal use only. More... | |
void | x (int v) |
Internal use only. More... | |
void | y (int v) |
Internal use only. More... | |
Base class of all widgets that have a menu in FLTK.
Currently FLTK provides you with Fl_Menu_Button, Fl_Menu_Bar, and Fl_Choice.
The class contains a pointer to an array of structures of type Fl_Menu_Item. The array may either be supplied directly by the user program, or it may be "private": a dynamically allocated array managed by the Fl_Menu_.
Fl_Menu_::Fl_Menu_ | ( | int | X, |
int | Y, | ||
int | W, | ||
int | H, | ||
const char * | l = 0 |
||
) |
int Fl_Menu_::add | ( | const char * | label, |
int | shortcut, | ||
Fl_Callback * | callback, | ||
void * | userdata = 0 , |
||
int | flags = 0 |
||
) |
Adds a new menu item.
[in] | label | The text label for the menu item. |
[in] | shortcut | Optional keyboard shortcut that can be an int or string; (FL_CTRL+'a') or "^a". Default 0 if none. |
[in] | callback | Optional callback invoked when user clicks the item. Default 0 if none. |
[in] | userdata | Optional user data passed as an argument to the callback. Default 0 if none. |
[in] | flags | Optional flags that control the type of menu item; see below. Default is 0 for none. |
Detailed Description of Parameters
[#+^]<ascii_value> e.g. "97", "^97", "+97", "#97" [#+^]<ascii_char> e.g. "a", "^a", "+a", "#a"
# - Alt + - Shift ^ - Control
int Fl_Menu_::add | ( | const char * | str | ) |
This is a Forms (and SGI GL library) compatible add function, it adds many menu items, with '|' separating the menu items, and tab separating the menu item names from an optional shortcut string.
The passed string is split at any '|' characters and then add(s,0,0,0,0) is done with each section. This is often useful if you are just using the value, and is compatible with Forms and other GL programs. The section strings use the same special characters as described for the long version of add().
No items must be added to a menu during a callback to the same menu.
str | string containing multiple menu labels as described above |
void Fl_Menu_::clear | ( | ) |
Same as menu(NULL), set the array pointer to null, indicating a zero-length menu.
Menus must not be cleared during a callback to the same menu.
int Fl_Menu_::clear_submenu | ( | int | index | ) |
Clears the specified submenu pointed to by index
of all menu items.
This method is useful for clearing a submenu so that it can be re-populated with new items. Example: a "File/Recent Files/..." submenu that shows the last few files that have been opened.
The specified index
must point to a submenu.
The submenu is cleared with remove(). If the menu array was directly set with menu(x), then copy() is done to make a private array.
Example:
index | The index of the submenu to be cleared |
void Fl_Menu_::copy | ( | const Fl_Menu_Item * | m, |
void * | ud = 0 |
||
) |
Sets the menu array pointer with a copy of m that will be automatically deleted.
If userdata ud
is not NULL, then all user data pointers are changed in the menus as well. See void Fl_Menu_::menu(const Fl_Menu_Item* m).
|
inline |
This box type is used to surround the currently-selected items in the menus.
If this is FL_NO_BOX then it acts like FL_THIN_UP_BOX and selection_color() acts like FL_WHITE, for back compatibility.
int Fl_Menu_::find_index | ( | const char * | pathname | ) | const |
Find the menu item index for a given menu pathname
, such as "Edit/Copy".
This method finds a menu item's index position for the given menu pathname, also traversing submenus, but not submenu pointers.
To get the menu item pointer for a pathname, use find_item()
pathname | The path and name of the menu item index to find |
int Fl_Menu_::find_index | ( | const Fl_Menu_Item * | item | ) | const |
Find the index the menu array for given item
.
A way to convert a menu item pointer into an index.
Current implementation is fast and not expensive.
item | The *item to be found |
int Fl_Menu_::find_index | ( | Fl_Callback * | cb | ) | const |
Find the index into the menu array for a given callback cb
.
This method finds a menu item's index position, also traversing submenus, but not submenu pointers. This is useful if an application uses internationalisation and a menu item can not be found using its label. This search is also much faster.
cb | Find the first item with this callback |
const Fl_Menu_Item * Fl_Menu_::find_item | ( | const char * | pathname | ) |
Find the menu item for a given menu pathname
, such as "Edit/Copy".
This method finds a menu item in the menu array, also traversing submenus, but not submenu pointers.
To get the menu item's index, use find_index(const char*)
Example:
pathname | The path and name of the menu item |
const Fl_Menu_Item * Fl_Menu_::find_item | ( | Fl_Callback * | cb | ) |
Find the menu item for the given callback cb
.
This method finds a menu item in a menu array, also traversing submenus, but not submenu pointers. This is useful if an application uses internationalisation and a menu item can not be found using its label. This search is also much faster.
cb | find the first item with this callback |
void Fl_Menu_::global | ( | ) |
Make the shortcuts for this menu work no matter what window has the focus when you type it.
This is done by using Fl::add_handler(). This Fl_Menu_ widget does not have to be visible (ie the window it is in can be hidden, or it does not have to be put in a window at all).
Currently there can be only one global()menu. Setting a new one will replace the old one. There is no way to remove the global() setting (so don't destroy the widget!)
int Fl_Menu_::insert | ( | int | index, |
const char * | label, | ||
int | shortcut, | ||
Fl_Callback * | callback, | ||
void * | userdata = 0 , |
||
int | flags = 0 |
||
) |
Inserts a new menu item at the specified index
position.
If index
is -1, the menu item is appended; same behavior as add().
To properly insert a menu item, label
must be the name of the item (eg. "Quit"), and not a 'menu pathname' (eg. "File/Quit"). If a menu pathname is specified, the value of index
is ignored, the new item's position defined by the pathname.
For more details, see add(). Except for the index
parameter, add() has more detailed information on parameters and behavior, and is functionally equivalent.
[in] | index | The menu array's index position where the new item is inserted. If -1, behavior is the same as add(). |
[in] | label | The text label for the menu item. If the label is a menu pathname, index is ignored, and the pathname indicates the position of the new item. |
[in] | shortcut | Optional keyboard shortcut. Can be an int (FL_CTRL+'a') or a string ("^a"). Default is 0. |
[in] | callback | Optional callback invoked when user clicks the item. Default 0 if none. |
[in] | userdata | Optional user data passed as an argument to the callback. Default 0 if none. |
[in] | flags | Optional flags that control the type of menu item; see add() for more info. Default is 0 for none. |
int Fl_Menu_::item_pathname | ( | char * | name, |
int | namelen, | ||
const Fl_Menu_Item * | finditem = 0 |
||
) | const |
Get the menu 'pathname' for the specified menuitem.
If finditem==NULL, mvalue() is used (the most recently picked menuitem).
Example:
|
inline |
Returns a pointer to the array of Fl_Menu_Items.
This will either be the value passed to menu(value) or the private copy.
Example: How to walk the array:
void Fl_Menu_::menu | ( | const Fl_Menu_Item * | m | ) |
|
inline |
Sets the flags of item i.
For a list of the flags, see Fl_Menu_Item.
|
inline |
Gets the flags of item i.
For a list of the flags, see Fl_Menu_Item.
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inline |
Returns a pointer to the last menu item that was picked.
const Fl_Menu_Item * Fl_Menu_::picked | ( | const Fl_Menu_Item * | v | ) |
When user picks a menu item, call this.
It will do the callback. Unfortunately this also casts away const for the checkboxes, but this was necessary so non-checkbox menus can really be declared const...
void Fl_Menu_::remove | ( | int | i | ) |
Deletes item i
from the menu.
If the menu array was directly set with menu(x) then copy() is done to make a private array.
No items must be removed from a menu during a callback to the same menu.
i | index into menu array |
void Fl_Menu_::replace | ( | int | i, |
const char * | str | ||
) |
|
inline |
Changes the shortcut of item i to n.
int Fl_Menu_::size | ( | ) | const |
This returns the number of Fl_Menu_Item structures that make up the menu, correctly counting submenus.
This includes the "terminator" item at the end. To copy a menu array you need to copy size()*sizeof(Fl_Menu_Item) bytes. If the menu is NULL this returns zero (an empty menu will return 1).
|
inline |
Returns the menu item with the entered shortcut (key value).
This searches the complete menu() for a shortcut that matches the entered key value. It must be called for a FL_KEYBOARD or FL_SHORTCUT event.
If a match is found, the menu's callback will be called.
|
inline |
Returns the title of the last item chosen.
|
inline |
Returns the title of item i.
|
inline |
Get the current color of menu item labels.
|
inline |
Sets the current color of menu item labels.
|
inline |
Gets the current font of menu item labels.
|
inline |
Sets the current font of menu item labels.
|
inline |
Gets the font size of menu item labels.
|
inline |
Sets the font size of menu item labels.
|
inline |
Returns the index into menu() of the last item chosen by the user.
It is zero initially.
int Fl_Menu_::value | ( | const Fl_Menu_Item * | m | ) |
The value is the index into menu() of the last item chosen by the user.
It is zero initially. You can set it as an integer, or set it with a pointer to a menu item. The set routines return non-zero if the new value is different than the old one.
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inline |
The value is the index into menu() of the last item chosen by the user.
It is zero initially. You can set it as an integer, or set it with a pointer to a menu item. The set routines return non-zero if the new value is different than the old one.