fltk/FL/Fl_Widget.H

//
// Widget header file for the Fast Light Tool Kit (FLTK).
//
// Copyright 1998-2023 by Bill Spitzak and others.
//
// This library is free software. Distribution and use rights are outlined in
// the file "COPYING" which should have been included with this file.  If this
// file is missing or damaged, see the license at:
//
//     https://www.fltk.org/COPYING.php
//
// Please see the following page on how to report bugs and issues:
//
//     https://www.fltk.org/bugs.php
//

/**
  \file FL/Fl_Widget.H
  \brief Fl_Widget and Fl_Label classes.
*/

#ifndef Fl_Widget_H
#define Fl_Widget_H

#include "Fl.H"

class Fl_Widget;
class Fl_Window;
class Fl_Group;
class Fl_Image;

/** Default callback type definition for all fltk widgets (by far the most used) */
typedef void (Fl_Callback )(Fl_Widget*, void*);
/** Default callback type pointer definition for all fltk widgets */
typedef Fl_Callback* Fl_Callback_p; // needed for BORLAND
/** One parameter callback type definition passing only the widget */
typedef void (Fl_Callback0)(Fl_Widget*);
/** Callback type definition passing the widget and a long data value */
typedef void (Fl_Callback1)(Fl_Widget*, long);

/** This struct stores all information for a text or mixed graphics label.

    \todo There is an aspiration that the Fl_Label type will become a widget by itself.
          That way we will be avoiding a lot of code duplication by handling labels in
          a similar fashion to widgets containing text. We also provide an easy
          interface for very complex labels, containing html or vector graphics.
          However, this re-factoring is not in place in this release.
 */
struct FL_EXPORT Fl_Label {
  /** label text */
  const char* value;
  /** optional image for an active label */
  Fl_Image* image;
  /** optional image for a deactivated label */
  Fl_Image* deimage;
  /** label font used in text */
  Fl_Font font;
  /** size of label font */
  Fl_Fontsize size;
  /** text color */
  Fl_Color color;
  /** alignment of label */
  Fl_Align align_;
  /** type of label. \see Fl_Labeltype */
  uchar type;

  /** Draws the label aligned to the given box */
  void draw(int,int,int,int, Fl_Align) const ;
  void measure(int &w, int &h) const ;
};


/** A class prototype that allows for additional data in callbacks.

 Users can extend this class and pass it to widget callbacks. Widgets can
 take ownership of the callback data, deleting the data when the widget
 itself is deleted.

 The destructor of this class is virtual, allowing for additional code to
 deallocate resources when the user data is deleted.

 \see FL_FUNCTION_CALLBACK_3, FL_METHOD_CALLBACK_1, FL_INLINE_CALLBACK_2
 \see Fl_Widget::callback(Fl_Callback*, Fl_Callback_User_Data*, bool)
 \see Fl_Widget::user_data(Fl_Callback_User_Data*, bool)
 */
class Fl_Callback_User_Data {
public:
  virtual ~Fl_Callback_User_Data() { }
};


/** Fl_Widget is the base class for all widgets in FLTK.

    You can't create one of these because the constructor is not public.
    However you can subclass it.

    All "property" accessing methods, such as color(), parent(), or argument()
    are implemented as trivial inline functions and thus are as fast and small
    as accessing fields in a structure. Unless otherwise noted, the property
    setting methods such as color(n) or label(s) are also trivial inline
    functions, even if they change the widget's appearance. It is up to the
    user code to call redraw() after these.
 */
class FL_EXPORT Fl_Widget {
  friend class Fl_Group;

  Fl_Group* parent_;
  Fl_Callback* callback_;
  void* user_data_;
  int x_,y_,w_,h_;
  Fl_Label label_;
  unsigned int flags_;
  Fl_Color color_;
  Fl_Color color2_;
  uchar type_;
  uchar damage_;
  uchar box_;
  uchar when_;

  const char *tooltip_;

  /** unimplemented copy ctor */
  Fl_Widget(const Fl_Widget &);
  /** unimplemented assignment operator */
  Fl_Widget& operator=(const Fl_Widget &);

protected:

  /** Creates a widget at the given position and size.

      The Fl_Widget is a protected constructor, but all derived widgets have a
      matching public constructor. It takes a value for x(), y(), w(), h(), and
      an optional value for label().

      \param[in] x, y the position of the widget relative to the enclosing window
      \param[in] w, h size of the widget in pixels
      \param[in] label optional text for the widget label
   */
  Fl_Widget(int x, int y, int w, int h, const char *label=0L);

  /** Internal use only. Use position(int,int), size(int,int) or resize(int,int,int,int) instead. */
  void x(int v) {x_ = v;}
  /** Internal use only. Use position(int,int), size(int,int) or resize(int,int,int,int) instead. */
  void y(int v) {y_ = v;}
  /** Internal use only. Use position(int,int), size(int,int) or resize(int,int,int,int) instead. */
  void w(int v) {w_ = v;}
  /** Internal use only. Use position(int,int), size(int,int) or resize(int,int,int,int) instead. */
  void h(int v) {h_ = v;}
  /** Gets the widget flags mask */
  unsigned int flags() const {return flags_;}
  /** Sets a flag in the flags mask */
  void set_flag(unsigned int c) {flags_ |= c;}
  /** Clears a flag in the flags mask */
  void clear_flag(unsigned int c) {flags_ &= ~c;}
  /** flags possible values enumeration.
      See activate(), output(), visible(), changed(), set_visible_focus()
  */
  enum {
        INACTIVE        = 1<<0,   ///< the widget can't receive focus, and is disabled but potentially visible
        INVISIBLE       = 1<<1,   ///< the widget is not drawn, but can receive a few special events
        OUTPUT          = 1<<2,   ///< for output only
        NOBORDER        = 1<<3,   ///< don't draw a decoration (Fl_Window)
        FORCE_POSITION  = 1<<4,   ///< don't let the window manager position the window (Fl_Window)
        NON_MODAL       = 1<<5,   ///< this is a hovering toolbar window (Fl_Window)
        SHORTCUT_LABEL  = 1<<6,   ///< the label contains a shortcut we need to draw
        CHANGED         = 1<<7,   ///< the widget value changed
        OVERRIDE        = 1<<8,   ///< position window on top (Fl_Window)
        VISIBLE_FOCUS   = 1<<9,   ///< accepts keyboard focus navigation if the widget can have the focus
        COPIED_LABEL    = 1<<10,  ///< the widget label is internally copied, its destruction is handled by the widget
        CLIP_CHILDREN   = 1<<11,  ///< all drawing within this widget will be clipped (Fl_Group)
        MENU_WINDOW     = 1<<12,  ///< a temporary popup window, dismissed by clicking outside (Fl_Window)
        TOOLTIP_WINDOW  = 1<<13,  ///< a temporary popup, transparent to events, and dismissed easily (Fl_Window)
        MODAL           = 1<<14,  ///< a window blocking input to all other windows (Fl_Window)
        NO_OVERLAY      = 1<<15,  ///< window not using a hardware overlay plane (Fl_Menu_Window)
        GROUP_RELATIVE  = 1<<16,  ///< Reserved, not implemented. DO NOT USE.
        COPIED_TOOLTIP  = 1<<17,  ///< the widget tooltip is internally copied, its destruction is handled by the widget
        FULLSCREEN      = 1<<18,  ///< a fullscreen window (Fl_Window)
        MAC_USE_ACCENTS_MENU = 1<<19, ///< On the macOS platform, pressing and holding a key on the keyboard opens an accented-character menu window (Fl_Input_, Fl_Text_Editor)
        NEEDS_KEYBOARD  = 1<<20,  ///< set on touch screen devices if a widget needs a keyboard when it gets the focus. Reserved, not yet used in 1.4.0. \see Fl_Widget::needs_keyboard()
        IMAGE_BOUND     = 1<<21,  ///< binding the image to the widget will transfer ownership, so that the widget will delete the image when it is no longer needed
        DEIMAGE_BOUND   = 1<<22,  ///< bind the inactive image to the widget, so the widget deletes the image when it is no longer needed
        AUTO_DELETE_USER_DATA = 1<<23, ///< automatically call `delete` on the user_data pointer when destroying this widget; if set, user_data must point to a class derived from the class Fl_Callback_User_Data

        // Note to devs: add new FLTK core flags above this line (up to 1<<28).

        // Three more flags, reserved for user code

        USERFLAG3       = 1<<29,  ///< reserved for 3rd party extensions
        USERFLAG2       = 1<<30,  ///< reserved for 3rd party extensions
        USERFLAG1       = 1<<31   ///< reserved for 3rd party extensions
  };
  void draw_box() const;
  void draw_box(Fl_Boxtype t, Fl_Color c) const;
  void draw_box(Fl_Boxtype t, int x,int y,int w,int h, Fl_Color c) const;
  void draw_backdrop() const;

  /** Draws a focus rectangle around the widget.
    This method uses the widget's boxtype and coordinates and its
    background color color().
    \see Fl_Widget::draw_focus(Fl_Boxtype, int, int, int, int, Fl_Color) const
  */
  void draw_focus() const {
    draw_focus(box(), x(), y(), w(), h(), color());
  }

  /** Draws a focus rectangle around the widget.
    This method uses the given boxtype and coordinates and the widget's
    background color color().
    \see Fl_Widget::draw_focus(Fl_Boxtype, int, int, int, int, Fl_Color) const
  */
  void draw_focus(Fl_Boxtype t, int X, int Y, int W, int H) const {
    draw_focus(t, X, Y, W, H, color());

  }
  // See documentation in Fl_Widget.cxx
  void draw_focus(Fl_Boxtype t, int x, int y, int w, int h, Fl_Color bg) const;

  void draw_label() const;
  void draw_label(int, int, int, int) const;

public:

  /** Destroys the widget.
      Destroying single widgets is not very common. You almost always want to
      destroy the parent group instead, which will destroy all of the child widgets
      and groups in that group.

      \since FLTK 1.3, the widget's destructor removes the widget from its parent
      group, if it is member of a group.
   */
  virtual ~Fl_Widget();

  /** Draws the widget.
      Never call this function directly. FLTK will schedule redrawing whenever
      needed. If your widget must be redrawn as soon as possible, call redraw()
      instead.

      Override this function to draw your own widgets.

      If you ever need to call another widget's draw method <I>from within your
      own draw() method</I>, e.g. for an embedded scrollbar, you can do it
      (because draw() is virtual) like this:

      \code
        Fl_Widget *s = &scrollbar; // scrollbar is an embedded Fl_Scrollbar
        s->draw();                 // calls Fl_Scrollbar::draw()
      \endcode
   */
  virtual void draw() = 0;

  /** Handles the specified event.
      You normally don't call this method directly, but instead let FLTK do
      it when the user interacts with the widget.

      When implemented in a widget, this function must return 0 if the
      widget does not use the event or 1 otherwise.

      Most of the time, you want to call the inherited handle() method in
      your overridden method so that you don't short-circuit events that you
      don't handle. In this last case you should return the callee retval.

      \param[in] event the kind of event received
      \retval 0 if the event was not used or understood
      \retval 1 if the event was used and can be deleted
      \see Fl_Event
   */
  virtual int handle(int event);

  /** Returns whether the current label was assigned with copy_label().

      This can be useful for temporarily overwriting the widget's label
      and restoring it later.

      \retval 0 current label was assigned with label().
      \retval 1 current label was assigned with copy_label().
  */
  int is_label_copied() const {return ((flags_ & COPIED_LABEL) ? 1 : 0);}

  /**
    Sets whether this widget needs a keyboard.

    Set this on touch screen devices if a widget needs a keyboard when it gets the focus.

    \note This flag can be set but is not yet \b used in FLTK 1.4.0. It is intended to be
      used in the future on real touch devices.

    \param[in]  needs   Set this to true or false

    \internal Needs implementations in screen driver methods:
      \see Fl::screen_driver()->request_keyboard();
      \see Fl::screen_driver()->release_keyboard();
  */
  void needs_keyboard(bool needs) {
    if (needs) set_flag(NEEDS_KEYBOARD);
    else clear_flag(NEEDS_KEYBOARD);
  }

  /**
    Returns whether this widget needs a keyboard.
    \return  true or false
    \see needs_keyboard(bool)
  */
  bool needs_keyboard() const {
    return (flags_ & NEEDS_KEYBOARD);
  }

  /** Returns a pointer to the parent widget.
      Usually this is a Fl_Group or Fl_Window.
      \retval NULL if the widget has no parent
      \see Fl_Group::add(Fl_Widget*)
   */
  Fl_Group* parent() const {return parent_;}

  /** Internal use only - "for hacks only".

      It is \em \b STRONGLY recommended not to use this method, because it
      short-circuits Fl_Group's normal widget adding and removing methods,
      if the widget is already a child widget of another Fl_Group.

      Use Fl_Group::add(Fl_Widget*) and/or Fl_Group::remove(Fl_Widget*) instead.
  */
  void parent(Fl_Group* p) {parent_ = p;} // for hacks only, use Fl_Group::add()

  /** Gets the widget type.
      Returns the widget type value, which gives some information about the derived widget class
      to which the object belongs. Noticeably, the condition <tt>type() >= FL_WINDOW</tt> indicates
      a widget is an Fl_Window or derived object.
   */
  uchar type() const {return type_;}

  /** Sets the widget type.
      \see type()
   */
  void type(uchar t) {type_ = t;}

  /** Gets the widget position in its window.
      \return the x position relative to the window
   */
  int x() const {return x_;}

  /** Gets the widget position in its window.
      \return the y position relative to the window
   */
  int y() const {return y_;}

  /** Gets the widget width.
      \return the width of the widget in pixels.
   */
  int w() const {return w_;}

  /** Gets the widget height.
      \return the height of the widget in pixels.
   */
  int h() const {return h_;}

  /** Changes the size or position of the widget.

      This is a virtual function so that the widget may implement its
      own handling of resizing. The default version does \e not
      call the redraw() method, but instead relies on the parent widget
      to do so because the parent may know a faster way to update the
      display, such as scrolling from the old position.

      Some window managers under X11 call resize() a lot more often
      than needed. Please verify that the position or size of a widget
      did actually change before doing any extensive calculations.

      position(X, Y) is a shortcut for resize(X, Y, w(), h()),
      and size(W, H) is a shortcut for resize(x(), y(), W, H).

      \param[in] x, y new position relative to the parent window
      \param[in] w, h new size
      \see position(int,int), size(int,int)
   */
  virtual void resize(int x, int y, int w, int h);

  /** Internal use only. */
  int damage_resize(int,int,int,int);

  /** Repositions the window or widget.

      position(X, Y) is a shortcut for resize(X, Y, w(), h()).

      \param[in] X, Y new position relative to the parent window
      \see resize(int,int,int,int), size(int,int)
   */
  void position(int X,int Y) {resize(X,Y,w_,h_);}

  /** Changes the size of the widget.

      size(W, H) is a shortcut for resize(x(), y(), W, H).

      \param[in] W, H new size
      \see position(int,int), resize(int,int,int,int)
   */
  void size(int W,int H) {resize(x_,y_,W,H);}

  /** Gets the label alignment.

      \return label alignment
      \see label(), align(Fl_Align), Fl_Align
   */
  Fl_Align align() const {return label_.align_;}

  /** Sets the label alignment.
      This controls how the label is displayed next to or inside the widget.
      The default value is FL_ALIGN_CENTER, which centers the label inside
      the widget.
      \param[in] alignment new label alignment
      \see align(), Fl_Align
   */
  void align(Fl_Align alignment) {label_.align_ = alignment;}

  /** Gets the box type of the widget.
      \return the current box type
      \see box(Fl_Boxtype), Fl_Boxtype
   */
  Fl_Boxtype box() const {return (Fl_Boxtype)box_;}

  /** Sets the box type for the widget.
      This identifies a routine that draws the background of the widget.
      See Fl_Boxtype for the available types. The default depends on the
      widget, but is usually FL_NO_BOX or FL_UP_BOX.
      \param[in] new_box the new box type
      \see box(), Fl_Boxtype
   */
  void box(Fl_Boxtype new_box) {box_ = new_box;}

  /** Gets the background color of the widget.
      \return current background color
      \see color(Fl_Color), color(Fl_Color, Fl_Color)
   */
  Fl_Color color() const {return color_;}

  /** Sets the background color of the widget.
      The color is passed to the box routine. The color is either an index into
      an internal table of RGB colors or an RGB color value generated using
      fl_rgb_color().

      The default for most widgets is FL_BACKGROUND_COLOR. Use Fl::set_color()
      to redefine colors in the color map.
      \param[in] bg background color
      \see color(), color(Fl_Color, Fl_Color), selection_color(Fl_Color)
   */
  void color(Fl_Color bg) {color_ = bg;}

  /** Gets the selection color.
      \return the current selection color
      \see selection_color(Fl_Color), color(Fl_Color, Fl_Color)
   */
  Fl_Color selection_color() const {return color2_;}

  /** Sets the selection color.
      The selection color is defined for Forms compatibility and is usually
      used to color the widget when it is selected, although some widgets
      use this color for other purposes. You can set both colors at once
      with color(Fl_Color bg, Fl_Color sel).
      \param[in] a the new selection color
      \see selection_color(), color(Fl_Color, Fl_Color)
   */
  void selection_color(Fl_Color a) {color2_ = a;}

  /** Sets the background and selection color of the widget.

      The two color form sets both the background and selection colors.
      \param[in] bg background color
      \param[in] sel selection color
      \see color(unsigned), selection_color(unsigned)
   */
  void color(Fl_Color bg, Fl_Color sel) {color_=bg; color2_=sel;}

  /** Gets the current label text.
      \return a pointer to the current label text
      \see label(const char *), copy_label(const char *)
   */
  const char* label() const {return label_.value;}

  /** Sets the current label pointer.

      The label is shown somewhere on or next to the widget.
      See \ref common_labels for details about what can be put in a label.
      The passed pointer is stored unchanged in the widget (the string is \em not copied), so if
      you need to set the label to a formatted value, make sure the buffer is
      static, global, or allocated. The copy_label() method can be used
      to make a copy of the label string automatically.
      \param[in] text pointer to new label text
      \see copy_label()
   */
  void label(const char* text);

  /** Sets the current label.
      Unlike label(), this method allocates a copy of the label
      string instead of using the original string pointer.

      The internal copy will automatically be freed whenever you assign
      a new label or when the widget is destroyed.

      \param[in] new_label the new label text
      \see label()
   */
  void copy_label(const char *new_label);

  /** Shortcut to set the label text and type in one call.
      \see label(const char *), labeltype(Fl_Labeltype)
   */
  void label(Fl_Labeltype a, const char* b) {label_.type = a; label_.value = b;}

  /** Gets the label type.
      \return the current label type.
      \see Fl_Labeltype
   */
  Fl_Labeltype labeltype() const {return (Fl_Labeltype)label_.type;}

  /** Sets the label type.
      The label type identifies the function that draws the label of the widget.
      This is generally used for special effects such as embossing or for using
      the label() pointer as another form of data such as an icon. The value
      FL_NORMAL_LABEL prints the label as plain text.
      \param[in] a new label type
      \see Fl_Labeltype
   */
  void labeltype(Fl_Labeltype a) {label_.type = a;}

  /** Gets the label color.
      The default color is FL_FOREGROUND_COLOR.
      \return the current label color
   */
  Fl_Color labelcolor() const {return label_.color;}

  /** Sets the label color.
      The default color is FL_FOREGROUND_COLOR.
      \param[in] c the new label color
   */
  void labelcolor(Fl_Color c) {label_.color=c;}

  /** Gets the font to use.
      Fonts are identified by indexes into a table. The default value
      uses a Helvetica typeface (Arial for Microsoft&reg; Windows&reg;).
      The function Fl::set_font() can define new typefaces.
      \return current font used by the label
      \see Fl_Font
   */
  Fl_Font labelfont() const {return label_.font;}

  /** Sets the font to use.
      Fonts are identified by indexes into a table. The default value
      uses a Helvetica typeface (Arial for Microsoft&reg; Windows&reg;).
      The function Fl::set_font() can define new typefaces.
      \param[in] f the new font for the label
      \see Fl_Font
   */
  void labelfont(Fl_Font f) {label_.font=f;}

  /** Gets the font size in pixels.
      The default size is 14 pixels.
      \return the current font size
   */
  Fl_Fontsize labelsize() const {return label_.size;}

  /** Sets the font size in pixels.
      \param[in] pix the new font size
      \see Fl_Fontsize labelsize()
   */
  void labelsize(Fl_Fontsize pix) {label_.size=pix;}

  /** Gets the image that is used as part of the widget label when in the active state.
      \return the current image
   */
  Fl_Image* image() {return label_.image;}

  /** Gets the image that is used as part of the widget label when in the active state.
      \return the current image
   */
  const Fl_Image* image() const {return label_.image;}

  /** Sets the image to use as part of the widget label when in the active state.

   The caller is responsible for making sure \p img is not deleted  while it's used by the widget,
   and, if appropriate, for deleting it after the widget's deletion.

   Calling image() with a new image will delete the old image if it
   was bound, and set the new image without binding it. If old and new are
   the same, the image will not be deleted, but it will be unbound.

   Calling image() with NULL will delete the old image if
   it was bound and not set a new image.

   \param[in] img the new image for the label
   \see bind_image(Fl_Image* img)
   */
  void image(Fl_Image* img);

  /** Sets the image to use as part of the widget label when in the active state.
   \param[in] img the new image for the label
   \see void image(Fl_Image* img)
   */
  void image(Fl_Image& img);

  /** Sets the image to use as part of the widget label when in the active state.

   The image will be bound to the widget. When the widget is deleted, the
   image will be deleted as well.

   Calling bind_image() with a new image will delete the old image if it
   was bound, and then set the new image, and bind that. If old and new image
   are the same, nothing happens.

   Calling bind_image() with NULL will delete the old image if
   it was bound and not set a new image.

   \param[in] img the new image for the label
   \see void image(Fl_Image* img)
   */
  void bind_image(Fl_Image* img);

  /** Bind the image to the widget, so the widget will delete the image when it is no longer needed.
   \param f 1: mark the image as bound, 0: mark the image as managed by the user
   \see image_bound(), bind_deimage()
   */
  void bind_image(int f) { if (f) set_flag(IMAGE_BOUND); else clear_flag(IMAGE_BOUND); }

  /** Returns whether the image is managed by the widget.
   \retval 0 if the image is not bound to the widget
   \retval 1 if the image will be deleted when the widget is deleted
   \see deimage_bound(), bind_image()
   */
  int image_bound() const {return ((flags_ & IMAGE_BOUND) ? 1 : 0);}

  /** Gets the image that is used as part of the widget label when in the inactive state.
      \return the current image for the deactivated widget
   */
  Fl_Image* deimage() {return label_.deimage;}

  /** Gets the image that is used as part of the widget label when in the inactive state.
      \return the current image for the deactivated widget
   */
  const Fl_Image* deimage() const {return label_.deimage;}

  /** Sets the image to use as part of the widget label when in the inactive state.
   \param[in] img the new image for the deactivated widget
   \note The caller is responsible for making sure \p img is not deleted  while it's used by the widget,
   and, if appropriate, for deleting it after the widget's deletion.
   \see void bind_deimage(Fl_Image* img)
   */
  void deimage(Fl_Image* img);

  /** Sets the image to use as part of the widget label when in the inactive state.
   \param[in] img the new image for the deactivated widget
   \see void deimage(Fl_Image* img)
   */
  void deimage(Fl_Image& img);

  /** Sets the image to use as part of the widget label when in the inactive state.
   \param[in] img the new image for the deactivated widget
   \note The image will be bound to the widget. When the widget is deleted, the
   image will be deleted as well.
   \see void deimage(Fl_Image* img)
   */
  void bind_deimage(Fl_Image* img);

  /** Returns whether the inactive image is managed by the widget.
   \retval 0 if the image is not bound to the widget
   \retval 1 if the image will be deleted when the widget is deleted
   \see image_bound(), bind_deimage()
   */
  int deimage_bound() const {return ((flags_ & DEIMAGE_BOUND) ? 1 : 0);}

  /** Bind the inactive image to the widget, so the widget will delete the image when it is no longer needed.
   \param f 1: mark the image as bound, 0: mark the image as managed by the user
   \see deimage_bound(), bind_image()
   */
  void bind_deimage(int f) { if (f) set_flag(DEIMAGE_BOUND); else clear_flag(DEIMAGE_BOUND); }

  /** Gets the current tooltip text.
      \return a pointer to the tooltip text or NULL
      \see tooltip(const char*), copy_tooltip(const char*)
   */
  const char *tooltip() const {return tooltip_;}

  void tooltip(const char *text);               // see Fl_Tooltip
  void copy_tooltip(const char *text);          // see Fl_Tooltip

  /** Gets the current callback function for the widget.
      Each widget has a single callback.
      \return current callback
   */
  Fl_Callback_p callback() const {return callback_;}

  /** Sets the current callback function and data for the widget.
      Each widget has a single callback.
      \param[in] cb new callback
      \param[in] p user data
   */
  void callback(Fl_Callback* cb, void* p) {
    callback_ = cb;
    user_data(p);
  }

  /** Sets the current callback function and managed user data for the widget.
   Setting auto_free will transfer ownership of the callback user data to the
   widget. Deleting the widget will then also delete the user data.
   \param[in] cb new callback
   \param[in] p user data
   \param[in] auto_free if set, the widget will free user data when destroyed
   */
  void callback(Fl_Callback* cb, Fl_Callback_User_Data* p, bool auto_free) {
    callback_ = cb;
    user_data(p, auto_free);
  }

  /** Sets the current callback function for the widget.
      Each widget has a single callback.
      \param[in] cb new callback
   */
  void callback(Fl_Callback* cb) {callback_ = cb;}

  /** Sets the current callback function for the widget.
      Each widget has a single callback.
      \param[in] cb new callback
   */
  void callback(Fl_Callback0* cb) {
    callback_ = (Fl_Callback*)(fl_intptr_t)(cb);
  }

  /** Sets the current callback function for the widget.
      Each widget has a single callback.
      \param[in] cb new callback
      \param[in] p user data
   */
  void callback(Fl_Callback1* cb, long p = 0) {
    callback_ = (Fl_Callback*)(fl_intptr_t)(cb);
    user_data((void*)(fl_intptr_t)p);
  }

  /** Gets the user data for this widget.
      Gets the current user data (void *) argument that is passed to the callback function.
      \return user data as a pointer
   */
  void* user_data() const {return user_data_;}

  /** \brief Sets the user data for this widget. */
  void user_data(void* v);

  /** \brief Sets the user data for this widget. */
  void user_data(Fl_Callback_User_Data* v, bool auto_free);

  /** Gets the current user data (long) argument that is passed to the callback function.

    \note On platforms with <tt>sizeof(long) \< sizeof(void*)</tt>, particularly
          on Windows 64-bit platforms, this method can truncate stored addresses
          \p (void*) to the size of a \p long value. Use with care and only
          if you are sure that the stored user_data value fits in a \p long
          value because it was stored with argument(long) or another method
          using only \p long values. You may want to use user_data() instead.

    \see user_data()
  */
  long argument() const {return (long)(fl_intptr_t)user_data_;}

  /** Sets the current user data (long) argument that is passed to the callback function.

    \see argument()
   */
  void argument(long v) {user_data((void*)(fl_intptr_t)v);}

  /** Returns the conditions under which the callback is called.

      You can set the flags with when(uchar), the default value is
      FL_WHEN_RELEASE.

      \return set of flags
      \see when(uchar), Fl_When, do_callback(), Fl::callback_reason()
   */
  Fl_When when() const {return (Fl_When)when_;}

  /** Sets the flags used to decide when a callback is called.

     This controls when callbacks are done. The following values are useful,
     the default value is FL_WHEN_RELEASE:

     \li 0: The callback is not done, but changed() is turned on.
     \li FL_WHEN_CHANGED: The callback is done each time the text is
         changed by the user.
     \li FL_WHEN_RELEASE: The callback will be done when this widget loses
         the focus, including when the window is unmapped. This is a useful
         value for text fields in a panel where doing the callback on every
         change is wasteful. However the callback will also happen if the
         mouse is moved out of the window, which means it should not do
         anything visible (like pop up an error message).
         You might do better setting this to zero, and scanning all the
         items for changed() when the OK button on a panel is pressed.
     \li FL_WHEN_ENTER_KEY: If the user types the Enter key, the entire
         text is selected, and the callback is done if the text has changed.
         Normally the Enter key will navigate to the next field (or insert
         a newline for a Fl_Multiline_Input) - this changes the behavior.
     \li FL_WHEN_ENTER_KEY|FL_WHEN_NOT_CHANGED: The Enter key will do the
         callback even if the text has not changed. Useful for command fields.
     \li \ref FL_WHEN_CLOSED : If the user requests that the widget is closed,
         the callback is called with \ref FL_REASON_CLOSED. The \ref Fl_Tabs
         widget checks this flag on its children to determine whether to display
         a close button on the tab of that widget.

      Fl_Widget::when() is a set of bitflags used by subclasses of
      Fl_Widget to decide when to do the callback.

      If the value is zero then the callback is never done. Other values
      are described  in the individual widgets. This field is in the base
      class so that you can scan a panel and do_callback() on all the ones
      that don't do their own callbacks in response to an "OK" button.
      \param[in] i set of flags
      \see Fl_When, do_callback(), Fl::callback_reason()
   */
  void when(uchar i) {when_ = i;}

  /** Returns whether a widget is visible.
      \retval 0 if the widget is not drawn and hence invisible.
      \see show(), hide(), visible_r()
   */
  unsigned int visible() const {return !(flags_&INVISIBLE);}

  /** Returns whether a widget and all its parents are visible.
      \retval 0 if the widget or any of its parents are invisible.
      \see show(), hide(), visible()
   */
  int visible_r() const;

  /** Makes a widget visible.

      An invisible widget never gets redrawn and does not get keyboard
      or mouse events, but can receive a few other events like FL_SHOW.

      The visible() method returns true if the widget is set to be
      visible. The visible_r() method returns true if the widget and
      all of its parents are visible. A widget is only visible if
      visible() is true on it <I>and all of its parents</I>.

      Changing it will send FL_SHOW or FL_HIDE events to the widget.
      <I>Do not change it if the parent is not visible, as this
      will send false FL_SHOW or FL_HIDE events to the widget</I>.
      redraw() is called if necessary on this or the parent.

      \see hide(), visible(), visible_r()
   */
  virtual void show();

  /** Makes a widget invisible.
      \see show(), visible(), visible_r()
   */
  virtual void hide();

  /** Makes the widget visible.
      You must still redraw the parent widget to see a change in the
      window. Normally you want to use the show() method instead.
   */
  void set_visible() {flags_ &= ~INVISIBLE;}

  /** Hides the widget.
      You must still redraw the parent to see a change in the window.
      Normally you want to use the hide() method instead.
   */
  void clear_visible() {flags_ |= INVISIBLE;}

  /** Returns whether the widget is active.
      \retval 0 if the widget is inactive
      \see active_r(), activate(), deactivate()
   */
  unsigned int active() const {return !(flags_&INACTIVE);}

  /** Returns whether the widget and all of its parents are active.
      \retval 0 if this or any of the parent widgets are inactive
      \see active(), activate(), deactivate()
   */
  int active_r() const;

  /** Activates the widget.
      Changing this value will send FL_ACTIVATE to the widget if
      active_r() is true.
      \see active(), active_r(), deactivate()
   */
  void activate();

  /** Deactivates the widget.
      Inactive widgets will be drawn "grayed out", e.g. with less contrast
      than the active widget. Inactive widgets will not receive any keyboard
      or mouse button events. Other events (including FL_ENTER, FL_MOVE,
      FL_LEAVE, FL_SHORTCUT, and others) will still be sent. A widget is
      only active if active() is true on it <I>and all of its parents</I>.

      Changing this value will send FL_DEACTIVATE to the widget if
      active_r() is true.

      Currently you cannot deactivate Fl_Window widgets.

      \see activate(), active(), active_r()
   */
  void deactivate();

  /** Returns if a widget is used for output only.
      output() means the same as !active() except it does not change how the
      widget is drawn. The widget will not receive any events. This is useful
      for making scrollbars or buttons that work as displays rather than input
      devices.
      \retval 0 if the widget is used for input and output
      \see set_output(), clear_output()
   */
  unsigned int output() const {return (flags_&OUTPUT);}

  /** Sets a widget to output only.
      \see output(), clear_output()
   */
  void set_output() {flags_ |= OUTPUT;}

  /** Sets a widget to accept input.
      \see set_output(), output()
   */
  void clear_output() {flags_ &= ~OUTPUT;}

  /** Returns if the widget is able to take events.
      This is the same as (active() && !output() && visible())
      but is faster.
      \retval 0 if the widget takes no events
   */
  unsigned int takesevents() const {return !(flags_&(INACTIVE|INVISIBLE|OUTPUT));}

  /**
      Checks if the widget value changed since the last callback.

      "Changed" is a flag that is turned on when the user changes the value
      stored in the widget. This is only used by subclasses of Fl_Widget that
      store values, but is in the base class so it is easier to scan all the
      widgets in a panel and do_callback() on the changed ones in response
      to an "OK" button.

      Most widgets turn this flag off when they do the callback, and when
      the program sets the stored value.

      \note do_callback() turns this flag off after the callback.

      \retval 0 if the value did not change
      \see set_changed(), clear_changed()
      \see do_callback(Fl_Widget *widget, void *data)
   */
  unsigned int changed() const {return flags_ & CHANGED;}

  /** Marks the value of the widget as changed.
      \see changed(), clear_changed()
   */
  void set_changed() {flags_ |= CHANGED;}

  /** Marks the value of the widget as unchanged.
      \see changed(), set_changed()
   */
  void clear_changed() {flags_ &= ~CHANGED;}

  /** Marks the widget as inactive without sending events or changing focus.
      This is mainly for specialized use, for normal cases you want deactivate().
      \see deactivate()
   */
  void clear_active() {flags_ |= INACTIVE;}

  /** Marks the widget as active without sending events or changing focus.
      This is mainly for specialized use, for normal cases you want activate().
      \see activate()
   */
  void set_active() {flags_ &= ~INACTIVE;}

  /** Gives the widget the keyboard focus.
      Tries to make this widget be the Fl::focus() widget, by first sending
      it an FL_FOCUS event, and if it returns non-zero, setting
      Fl::focus() to this widget. You should use this method to
      assign the focus to a widget.
      \return true if the widget accepted the focus.
   */
  int take_focus();

  /** Enables keyboard focus navigation with this widget.
      Note, however, that this will not necessarily mean that the widget
      will accept focus, but for widgets that can accept focus, this method
      enables it if it has been disabled.
      \see visible_focus(), clear_visible_focus(), visible_focus(int)
   */
  void set_visible_focus() { flags_ |= VISIBLE_FOCUS; }

  /** Disables keyboard focus navigation with this widget.
      Normally, all widgets participate in keyboard focus navigation.
      \see set_visible_focus(), visible_focus(), visible_focus(int)
   */
  void clear_visible_focus() { flags_ &= ~VISIBLE_FOCUS; }

  /** Modifies keyboard focus navigation.
      \param[in] v set or clear visible focus
      \see set_visible_focus(), clear_visible_focus(), visible_focus()
   */
  void visible_focus(int v) { if (v) set_visible_focus(); else clear_visible_focus(); }

  /** Checks whether this widget has a visible focus.
      \retval 0 if this widget has no visible focus.
      \see visible_focus(int), set_visible_focus(), clear_visible_focus()
   */
  unsigned int visible_focus() const { return flags_ & VISIBLE_FOCUS; }

  /** The default callback for all widgets that don't set a callback.

    This callback function puts a pointer to the widget on the queue
    returned by Fl::readqueue(). This is the default for all widgets
    if you don't set a callback.

    You can avoid the overhead of this default handling if you set the
    callback to \p NULL explicitly.

    Relying on the default callback and reading the callback queue with
    Fl::readqueue() is not recommended. If you need a callback, you should
    set one with Fl_Widget::callback(Fl_Callback *cb, void *data)
    or one of its variants.

    \param[in] widget the Fl_Widget given to the callback
    \param[in] data user data associated with that callback

    \see callback(), Fl::readqueue()
    \see do_callback(Fl_Widget *widget, void *data)
   */
  static void default_callback(Fl_Widget *widget, void *data);

  /** Calls the widget callback function with default arguments.

    This is the same as calling
    \code
      do_callback(this, user_data(), reason);
    \endcode

    \param[in] reason give a reason to why this callback was called, defaults to \ref FL_REASON_UNKNOWN

    \see callback()
    \see do_callback(Fl_Widget *widget, void *data, Fl_Callback_Reason reason), Fl_Callback_Reason
  */
  void do_callback(Fl_Callback_Reason reason=FL_REASON_UNKNOWN) {do_callback(this, user_data_, reason);}

  /** Calls the widget callback function with arbitrary arguments.
    \param[in] widget call the callback with \p widget as the first argument
    \param[in] arg call the callback with \p arg as the user data (second) argument
    \param[in] reason give a reason to why this callback was called, defaults to \ref FL_REASON_UNKNOWN
    \see callback()
    \see do_callback(Fl_Widget *widget, void *data), Fl_Callback_Reason
  */
  void do_callback(Fl_Widget *widget, long arg, Fl_Callback_Reason reason=FL_REASON_UNKNOWN) {
    do_callback(widget, (void*)(fl_intptr_t)arg, reason);
  }

  void do_callback(Fl_Widget *widget, void *arg = 0, Fl_Callback_Reason reason=FL_REASON_UNKNOWN);

  /* Internal use only. */
  int test_shortcut();
  /* Internal use only. */
  static unsigned int label_shortcut(const char *t);
  /* Internal use only. */
  static int test_shortcut(const char*, const bool require_alt = false);
  /* Internal use only. */
  void _set_fullscreen() {flags_ |= FULLSCREEN;}
  void _clear_fullscreen() {flags_ &= ~FULLSCREEN;}

  /** Checks if w is a child of this widget.
      \param[in] w potential child widget
      \return Returns 1 if \p w is a child of this widget, or is
      equal to this widget. Returns 0 if \p w is NULL.
   */
  int contains(const Fl_Widget *w) const ;

  /** Checks if this widget is a child of \p wgt.
      Returns 1 if this widget is a child of \p wgt, or is
      equal to \p wgt. Returns 0 if \p wgt is NULL.
      \param[in] wgt the possible parent widget.
      \see contains()
   */
  int inside(const Fl_Widget *wgt) const {return wgt ? wgt->contains(this) : 0;}

  /** Schedules the drawing of the widget.
      Marks the widget as needing its draw() routine called.
   */
  void redraw();

  /** Schedules the drawing of the label.
     Marks the widget or the parent as needing a redraw for the label area
     of a widget.
   */
  void redraw_label();

  /** Returns non-zero if draw() needs to be called.
      The damage value is actually a bit field that the widget
      subclass can use to figure out what parts to draw.
      \return a bitmap of flags describing the kind of damage to the widget
      \see damage(uchar), clear_damage(uchar)
   */
  uchar damage() const {return damage_;}

  /** Clears or sets the damage flags.
      Damage flags are cleared when parts of the widget drawing is repaired.

      The optional argument \p c specifies the bits that <b>are set</b>
      after the call (default: 0) and \b not the bits that are cleared!

      \note Therefore it is possible to set damage bits with this method, but
      this should be avoided. Use damage(uchar) instead.

      \param[in] c new bitmask of damage flags (default: 0)
      \see damage(uchar), damage()
   */
  void clear_damage(uchar c = 0) {damage_ = c;}

  /** Sets the damage bits for the widget.
      Setting damage bits will schedule the widget for the next redraw.
      \param[in] c bitmask of flags to set
      \see damage(), clear_damage(uchar)
   */
  void damage(uchar c);

  /** Sets the damage bits for an area inside the widget.
      Setting damage bits will schedule the widget for the next redraw.
      \param[in] c bitmask of flags to set
      \param[in] x, y, w, h size of damaged area
      \see damage(), clear_damage(uchar)
   */
  void damage(uchar c, int x, int y, int w, int h);

  void draw_label(int, int, int, int, Fl_Align) const;

  /** Sets width ww and height hh accordingly with the label size.
      Labels with images will return w() and h() of the image.

      This calls fl_measure() internally. For more information about
      the arguments \p ww and \p hh and word wrapping
      \see fl_measure(const char*, int&, int&, int)
   */
  void measure_label(int& ww, int& hh) const {label_.measure(ww, hh);}

  Fl_Window* window() const ;
  Fl_Window* top_window() const;
  Fl_Window* top_window_offset(int& xoff, int& yoff) const;

  /** Returns an Fl_Group pointer if this widget is an Fl_Group.

      Use this method if you have a widget (pointer) and need to
      know whether this widget is derived from Fl_Group. If it returns
      non-NULL, then the widget in question is derived from Fl_Group,
      and you can use the returned pointer to access its children
      or other Fl_Group-specific methods.

      Example:
      \code
      void my_callback (Fl_Widget *w, void *) {
        Fl_Group *g = w->as_group();
        if (g)
          printf ("This group has %d children\n", g->children());
        else
          printf ("This widget is not a group!\n");
      }
      \endcode

      \retval NULL if this widget is not derived from Fl_Group.
      \note This method is provided to avoid dynamic_cast.
      \see Fl_Widget::as_window(), Fl_Widget::as_gl_window()
   */
  virtual Fl_Group* as_group() { return NULL; }
  virtual Fl_Group const* as_group() const { return NULL; }

  /** Returns an Fl_Window pointer if this widget is an Fl_Window.

      Use this method if you have a widget (pointer) and need to
      know whether this widget is derived from Fl_Window. If it returns
      non-NULL, then the widget in question is derived from Fl_Window,
      and you can use the returned pointer to access its children
      or other Fl_Window-specific methods.

      \retval NULL if this widget is not derived from Fl_Window.
      \note This method is provided to avoid dynamic_cast.
      \see Fl_Widget::as_group(), Fl_Widget::as_gl_window()
   */
  virtual Fl_Window* as_window() { return 0; }
  virtual Fl_Window const* as_window() const { return NULL; }

  /** Returns an Fl_Gl_Window pointer if this widget is an Fl_Gl_Window.

      Use this method if you have a widget (pointer) and need to
      know whether this widget is derived from Fl_Gl_Window. If it returns
      non-NULL, then the widget in question is derived from Fl_Gl_Window.

      \retval NULL if this widget is not derived from Fl_Gl_Window.
      \note This method is provided to avoid dynamic_cast.
      \see Fl_Widget::as_group(), Fl_Widget::as_window()
   */
  virtual class Fl_Gl_Window* as_gl_window() { return NULL; }
  virtual class Fl_Gl_Window const* as_gl_window() const { return NULL; }

  /** Returns non zero if MAC_USE_ACCENTS_MENU flag is set, 0 otherwise.
   */
  int use_accents_menu() { return flags() & MAC_USE_ACCENTS_MENU; }

  /** For back compatibility only.
      \deprecated Use selection_color() instead.
  */
  Fl_Color color2() const {return (Fl_Color)color2_;}

  /** For back compatibility only.
      \deprecated Use selection_color(unsigned) instead.
  */
  void color2(unsigned a) {color2_ = a;}

  /** Sets whether the widget's label uses '&' to indicate shortcuts.
   By default, all objects of classes Fl_Menu_ (and derivatives), Fl_Button (and derivatives),
   Fl_Text_Display, Fl_Value_Input, and Fl_Input_ (and derivatives)
   use character '&' in their label, unless '&' is repeated,
   to indicate shortcuts: '&' does not appear in the drawn label,
   the next character after '&' in the label is drawn underlined, and typing this character
   triggers the corresponding menu window, button, or other widget. If the label contains 2 consecutive '&',
   only one is drawn and the next character is not underlined and not used as a shortcut.
   If \p value is set to 0, all these labels don't process character '&' as indicating a shortcut:
   '&' is drawn in the label, the next character is not underlined and does not define a shortcut.
   */
  void shortcut_label(int value) {
    if (value)
      set_flag(SHORTCUT_LABEL);
    else
      clear_flag(SHORTCUT_LABEL);
  }

  /** Returns whether the widget's label uses '&' to indicate shortcuts.
   \see void shortcut_label(int value) */
  int shortcut_label() const { return flags_ & SHORTCUT_LABEL; }
};

/**
    Reserved type numbers (necessary for my cheapo RTTI) start here.
    Grep the header files for "RESERVED_TYPE" to find the next available
    number.
*/
#define FL_RESERVED_TYPE 100

#endif