FLTK Tutorial

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: http://www.fltk.org/index.php • Documentation: http://www.fltk.org/documentation.php

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 • http://www.fltk.org/software.phpget 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 • 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 • 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 40 20 180 100 #include <FL/Fl.H> //FLTK global class #include <FL/Fl_Window.H> #include <FL/Fl_Box.H> Int main(intargc, 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(); } 260 300

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(intargc, 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(intargc, 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. 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 Intconstin_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, void *d) { ((CustomWidget*)d)->slider_cb2(); }

22. Callbacks: Update the other widget void CustomWidget::input_cb2() { Intval; 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 IntCustomWidget::value() { return (int)(slider->value() + 0.5); } void CustomWidget::value(intv) { slider->value(v); slider_cb2(); }

24. System Events • Focus 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(intevent) • 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. IntCustomWidget::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 1; } } return Fl_Group::handle(event); }