FLTK Tutorial

Introduction Installation Widgets Handling Event System events Mouse events Keyboard events

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

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

Install FLTK http://www.fltk.org/software.php 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

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`

Widgets

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

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(); }

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

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);

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

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.

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(); }

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);

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

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);

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();

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);

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);

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();

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);

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

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

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

Keyboard Events Key Up/Down

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

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);