1. FLTK Tutorial

2. Introduction Installation Widgets Handling Event System events
Mouse events
Keyboard events

3. Introduction
The Fast Light Tool Kit (“FLTK”, pronounced “fulltick”) is a cross-platform C++ GUI toolkit
FLTK was originally developed by Mr. Bill Spitzak
FLTK website:
Documentation:

4. Why FLTK ? It’s Free Open Source Software It’s cross platform
It supports OpenGL
It has a graphical user interface builder called FLUID

5. Install FLTK
get source code and unzip it
Linux/ Unix/ Mac OSX
./configure && make && make install
Mac Xcode
Xcode project file can be found in fltk-source/ide/
Windows Visual Studio
Open fltk-source/ide/VisualC/fltk.sln and build
In fltk-source copy FL folder to vc/include
In fltk-source/lib copy all files to vc/lib

6. Linking Visual Studio Linux/ Unix
Add fltk.lib, wsock32.lib, comctl32.lib,fltkgl.lib, fltkforms.lib, and fltkimages.lib (or fltkd.lib, etc.) to linker input
Linux/ Unix
`fltk-config --use-gl --use-images --use-forms --cxxflags –ldflags`

7. Widgets

8. Common FLTK Widgets Buttons Text box Valuators Groups
Includes radio buttons and check boxes
Text box
Display and receive strings
Valuators
Display and receive numbers
Groups
Containers such as tabs and group boxes
Also includes windows and OpenGL windows

9. FLTK Hello World #include <FL/Fl.H> //FLTK global class
180
300 20 40
260
100
#include <FL/Fl.H>
//FLTK global class
#include <FL/Fl_Window.H>
#include <FL/Fl_Box.H>
Int main(int argc, char **argv) {
Fl_Window *window = new Fl_Window(300, 180);
Fl_Box *box = new Fl_Box(20, 40, 260, 100,
"Hello World");
box->box(FL_UP_BOX);
//tell FLTK that we will not add any more widgets to window
window->end();
//show the window and enter the FLTK event loop:
window->show(argc, argv);
return Fl::run(); }

10. FLTK Callbacks
Sets a functions to call when the value of a widget changes
void functionName(Fl_Widget*, void*)
Called function passed pointer to the widget that changed and optional pointer to data
Can be activated by keyboard shortcut

11. Callback Demo void button_cb(Fl_Widget *widget, void *data) {
Fl_Button *button = (Fl_Button*)widget;
button->label("Thank you"); }
Int main(int argc, char **argv)
...
Fl_Button *button = new Fl_Button(50, 70, 200, 40, "Click Me");
button->callback(button_cb);

12. Custom Widgets Subclass an existing widget
hold a list of child widgets and handle them together

13. Custom Widget Composite widget Slider and text box
When the value of one changes the other is updated
Will use slider internally to store data
Easier because already has min, max, etc.

14. Main function #include <FL/Fl.H> #include <FL/Fl_Window.H>
#include "CustomWidget.h"
int main(int argc, char **argv) {
Fl_Window *window = new Fl_Window(300, 120);
CustomWidget *customWidget = new CustomWidget(50, 50, 200, 20);
window->end();
window->show(argc, argv);
return Fl::run(); }

15. Widget is a composition so we will inherit Fl_Group
Class CustomWidget : Fl_Group {
Constructor with default FLTK parameters
public:
CustomWidget(int x, int y, int w, int h, char *l =0) : Fl_Group(x, y, w, h, l);

16. Slider will store our data
Our two widgets
private:
Fl_Int_Input*input;
Fl_Slider*slider;
Slider will store our data
Current value
Bounds
Step size

17. Common slider properties
public:
int value();
void value(intv);
int minimum();
void minimum(int min);
int maximum();
void maximum(int max);
void bounds(int min, int max);

18. Internal callbacks
static void input_cb(Fl_Widget *w, void *d);
static void slider_cb(Fl_Widget *w, void *d);
void input_cb2();
void slider_cb2();

19. Constructor: Layout
Int const in_w = 40;
input = new Fl_Int_Input(x, y, in_w,
h);
slider = new Fl_Slider(x + in_w, y,
w- in_w, h);
slider->type(FL_HOR_SLIDER);

20. Constructor: Data
bounds(1, 100);
value(1);
Constructor: Callbacks
//The callback is done each time the text is changed by the user
input->when(FL_WHEN_CHANGED);
input->callback(input_cb, this);
slider->callback(slider_cb, this);

21. Static callbacks
void CustomWidget::input_cb(Fl_Widget *w,
void *d) {
((CustomWidget*)d)->input_cb2(); }
void CustomWidget::slider_cb(Fl_Widget *w,
((CustomWidget*)d)->slider_cb2();

22. Callbacks: Update the other widget
void CustomWidget::input_cb2() {
Int val;
sscanf(input->value(), "%d", &val);
slider->value(val); }
void CustomWidget::slider_cb2()
char val[16];
sprintf(val, "%d", (int)(slider->value() + 0.5));
input->value(val);

23. Properties
Int CustomWidget::value() {
return (int)(slider->value() + 0.5); }
void CustomWidget::value(intv)
slider->value(v);
slider_cb2();

24. System Events Focus events Clipboard events Widget events
Mouse enters/leaves program
Program gains/loses focus
Clipboard events
Widget events
Activation/deactivation
Show/hide

25. Mouse Events Button pushed down
Mouse moved while button pressed (drag)
Button release
Mouse moved
Mouse wheel

26. Keyboard Events
Key Up/Down

27. FLTK Events Override int handle(int event)
Return 0 if event unused
Event will continue to be passed around
Return 1 if event used
Event is consumed
Slider responds to up/down keys

28. Int CustomWidget::handle(int event){
if ( event == FL_KEYDOWN )
if ( Fl::event_key() == FL_Up )
value(value() + 1);
return 1; }
else if ( Fl::event_key() == FL_Down )
value(value() - 1);
return Fl_Group::handle(event);