Fl_Button *button = new Fl_Button(x, y, width, height, "label"); Fl_Light_Button *lbutton = new Fl_Light_Button(x, y, width, height); Fl_Round_Button *rbutton = new Fl_Round_Button(x, y, width, height, "label");Each button has an associated type() which allows it to behave as a push button, toggle button, or radio button:
button->type(0); lbutton->type(FL_TOGGLE_BUTTON); rbutton->type(FL_RADIO_BUTTON);For toggle and radio buttons, the value() method returns the current button state (0 = off, 1 = on). The set() and clear() methods can be used on toggle buttons to turn a toggle button on or off, respectively. Radio buttons can be turned on with the setonly() method; this will also turn off other radio buttons in the current group.
The value() method is used to get or set the string that is displayed:
Fl_Input *input = new Fl_Input(x, y, width, height, "label");
input->value("Now is the time for all good men...");
The string is copied to the widget's own storage when you set the
value() of the widget.
Valuators
Unlike text widgets, valuators keep track of numbers instead of
strings. FLTK provides the following valuators:
The value()
method gets and sets the current value of the widget. The
minimum() and
maximum() methods set the range of values that are reported by
the widget.
Groups
The Fl_Group widget class is used as a general purpose
"container" widget. Besides grouping radio buttons, the groups are
used to encapsulate windows, tabs, and scrolled windows. The following
group classes are available with FLTK:
Setting the Size and Position of Widgets
The size and position of widgets is usually set when you create them.
You can access them with the x(), y(), w(),
and h() methods.
You can change the size and position by using the position(), resize(), and size() methods:
button->position(x, y); group->resize(x, y, width, height); window->size(width, height);If you change a widget's size or position after it is displayed you will have to call redraw() on the widget's parent.
There are symbols for naming some of the more common colors:
button->color(FL_RED);Similarly, the label color can be set using the labelcolor() method:
button->labelcolor(FL_WHITE);
The type Fl_Boxtype stored and returned in Fl_Widget::box() is an enumeration defined in <Enumerations.H>:
FL_NO_BOX means nothing is drawn at all, so whatever is already on the screen remains. The FL_..._FRAME types only draw their edges, leaving the center unchanged. In the above diagram the blue color is the area that is not drawn by the box.
void xyz_draw(int x, int y, int w, int h, Fl_Color c) {
...
}
A simple drawing function might fill a rectangle with the given color
and then draw a black outline:
void xyz_draw(int x, int y, int w, int h, Fl_Color c) {
fl_color(c);
fl_rectf(x, y, w, h);
fl_color(FL_BLACK);
fl_rect(x, y, w, h);
}
#define XYZ_BOX FL_FREE_BOXTYPE Fl::set_boxtype(XYZ_BOX, xyz_draw, 1, 1, 2, 2);The last 4 arguments to Fl::set_boxtype() are the offsets for the bounding box that should be subtracted when drawing the label inside the box.
void xyz_draw(Fl_Label *label, int x, int y, int w, int h, Fl_Align align) {
...
}
The label should be drawn inside this bounding box, even if
FL_ALIGN_INSIDE is not enabled. The function is not called if the
label value is NULL.
The measure function is called with a pointer to a Fl_Label structure and references to the width and height:
void xyz_measure(Fl_Label *label, int w int h {
...
}
It should measure the size of the label and set w and h
to the size it will occupy.
#define XYZ_LABEL FL_FREE_LABELTYPE Fl::set_labeltype(XYZ_LABEL, xyz_draw, xyz_measure);The label type number n can be any integer value starting at the constant FL_FREE_LABELTYPE. Once you have added the label type you can use the labeltype() method to select your label type.
The Fl::set_labeltype method can also be used to overload an existing label type such as FL_NORMAL_LABEL.
The FL_SYMBOL_LABEL label type uses the label() string to look up a small drawing procedure in a hash table. For historical reasons the string always starts with '@', if it starts with something else (or the symbol is not found) the label is drawn normally:
void xyz_callback(Fl_Widget *w, void *data) {
...
}
The callback() method sets the callback function for a
widget. You can optionally pass a pointer to some data needed for the
callback:
int xyz_data; button->callback(xyz_callback, data);Normally callbacks are performed only when the value of the widget changes. You can change this using the when() method:
button->when(FL_WHEN_NEVER); button->when(FL_WHEN_CHANGED); button->when(FL_WHEN_RELEASE); button->when(FL_WHEN_RELEASE_ALWAYS); button->when(FL_WHEN_ENTER_KEY); button->when(FL_WHEN_ENTER_KEY_ALWAYS); button->when(FL_WHEN_CHANGED | FL_WHEN_NOT_CHANGED);
button->shortcut(FL_Enter); button->shortcut(FL_SHIFT + 'b'); button->shortcut(FL_CTRL + 'b'); button->shortcut(FL_ALT + 'b'); button->shortcut(FL_CTRL + FL_ALT + 'b'); button->shortcut(0); // no shortcutThe shortcut value is the key event value (the ASCII value or one of the special keys like FL_Enter) combined with any modifiers (like shift, alt, and control).