Transcript FLTK Tutorial by Xu

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


Mac Xcode


./configure && make && make install
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


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


Display and receive strings
Valuators


Includes radio buttons and check boxes
Display and receive numbers
Groups

Containers such as tabs and group boxes

Also includes windows and OpenGL windows
FLTK Hello World
40
#include <FL/Fl.H>
20
180
//FLTK global class
100
#include <FL/Fl_Window.H>
#include <FL/Fl_Box.H>
260
Int main(int argc, char **argv)
{
300
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);

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,
void *d)
{
((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

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


Return 1 if event used


Event will continue to be passed around
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 1;
}
}
return Fl_Group::handle(event);
}