Class Hierarchy
Fl_Widget
|
+----Fl_Box, Fl_Browser, Fl_Button, Fl_Chart, Fl_Clock,
Fl_Free, Fl_Group, Fl_Input, Fl_Menu_, Fl_Positioner,
Fl_Timer, Fl_Valuator
Include Files
#include <FL/Fl_Widget.H>
Description
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.
Methods
Fl_Widget::Fl_Widget(int x, int y, int w, int h, const char* label=0);
This is the protected constructor for an Fl_Widget, but all derived
widgets have a matching public constructor. It takes a value for
x(), y(), w(), h(), and an optional value for label().
virtual Fl_Widget::~Fl_Widget();
Destroying single widgets is not very common. It is your
responsibility to either remove() them from any enclosing group, or to
destroy that group immediately after destroying the children.
uchar Fl_Widget::type() const;
This value is used for Forms compatability and to simulate RTTI.
The position of the upper-left corner of the widget in its enclosing
Fl_Window (not its parent if that is not an Fl_Window), and its
width and height.
Change the size or position of the widget. This is a virtual function
so the widget may implement it's own handling of resizing. The
default version does not do redraw(), that is the parent
widget's responsibility (this is because the parent may know a faster
way to update the display, such as scrolling from the old position).
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).
The initial size and position of the widget. This is a copy of the
arguments that the constructor was called with. This information is
used by Fl_Group to calculate new sizes of
the children when they are resized.
init_size() calls resize() with the passed sizes,
and then replaces the initial size with the new values. If this widget
is a group you will have to init_size all the children as well or
unpredictable results will occur.
Return a pointer to the Fl_Window
that this widget is in (it will skip any and all parent widgets between
this and the window). Returns NULL if none. Note: for an
Fl_Window, this returns it's parent window (if any),
not this window.
The box() identifies a routine that draws the background of the
widget. See Box Types for the available
types. The default depends on the widget, but is usually FL_NO_BOX
or FL_UP_BOX.
This color is passed to the box routine. Color is an index into an
internal table of rgb colors. For most widgets this defaults to
FL_GRAY. See the enumeration list
for predefined colors. Use
Fl::set_color() to redefine colors.
For Forms compatibility a second color is defined. This 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(a,b).
The label is printed somewhere on the widget or next to it. The
string is not copied, the passed pointer is stored unchanged in
the widget.
A labeltype identifies a routine that
draws the label of the widget. This can be used for special effects
such as emboss, or to use the label() pointer as another form
of data such as a bitmap. The value FL_NORMAL_LABEL prints
the label as text.
How the label is printed next to or inside the widget. The default
value is FL_ALIGN_CENTER, which centers the label. The value
can be any of these constants or'd together:
- FL_ALIGN_CENTER
- FL_ALIGN_TOP
- FL_ALIGN_BOTTOM
- FL_ALIGN_LEFT
- FL_ALIGN_RIGHT
- FL_ALIGN_INSIDE
- FL_ALIGN_CLIP
- FL_ALIGN_WRAP
This color is passed to the labeltype routine, and is typically the
color of the label text. This defaults to FL_BLACK.
Fonts are identified by small 8-bit indexes into a table. See the
enumeration list for predefined typefaces. The
default value uses a Helvetica typeface (Arial for Microsoft®
Windows®). The function Fl::set_font()
can define new typefaces.
Fonts are further identified by a point size. The default is 14.
Each widget has a single callback. You can set it or examine it with
these methods.
You can also just change the void * second argument to the callback
with the user_data methods.
For convenience you can also define the callback as taking a long
argument. This is implemented by casting this to a
Fl_Callback and casting the long to a void *
and may not be portable to some machines.
void Fl_Widget::callback(void (*)(Fl_Widget*))
For convenience you can also define the callback as taking only one
argument. This is implemented by casting this to a
Fl_Callback and may not be portable to some machines.
You can cause a widget to do its callback at any time, and even pass
arbitrary arguments.
Fl_Widget::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.
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.
The default callback, which puts a pointer to the widget on the queue
returned by Fl::readqueue(). You
may want to call this from your own callback.
An invisible widget never gets redrawn and does not get events. An
widget is really visible if visible() is true on it and all
it's parents. Changing it will send FL_SHOW or
FL_HIDE events to the widget. Do not change it if the
parent is not visible, as this will send false FL_SHOW or
FL_HIDE events to the widget. redraw() is called
if necessary on this or the parent.
Fl_Widget::active() returns whether the widget is active. An
inactive widget does not get any events, but it does get redrawn. A
widget is active if active() is true on it and all it's
parents. Changing this value will send FL_ACTIVATE or
FL_DEACTIVATE to the widget. Do not change it if the
parent is not active, as this will send false FL_ACTIVATE or
FL_DEACTIVATE events to the widget.
Currently you cannot deactivate Fl_Window widgets.
This is the same as active() && visible() but is faster.
Mark the widget as needing its draw() routine called.
Non-zero if draw() needs to be called. Actually this is a bit
field that the widget subclass can use to figure out what parts to
draw.
Returns a pointer to the parent widget. Usually this is a
Fl_Group or
int Fl_Widget::contains(Fl_Widget* b) const
Returns true if b is a child of this widget, or is equal to
this widget. Returns false if b is NULL.
Returns true if this is a child of a, or is equal to a.
Returns false if a is NULL.