<FL/Fl.H>
. In addition the program must include a header file for each FLTK class it uses. Listing 1 shows a simple "Hello, World!" program that uses FLTK to display the window.
#include <FL/Fl.H> #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); box->labelsize(36); box->labelfont(FL_BOLD+FL_ITALIC); box->labeltype(FL_SHADOW_LABEL); window->end(); window->show(argc, argv); return Fl::run(); }
Then we create a box with the "Hello, World!" string in it. FLTK automatically adds the new box to window
, the current grouping widget.
Next, we set the type of box and the size, font, and style of the label:
box->box(FL_UP_BOX); box->labelsize(36); box->labelfont(FL_BOLD+FL_ITALIC); box->labeltype(FL_SHADOW_LABEL);
We tell FLTK that we will not add any more widgets to window
.
window->end();
Finally, we show the window and enter the FLTK event loop:
The resulting program will display the window in Figure 2-1. You can quit the program by closing the window or pressing the ESC
ape key.
Figure 2-1: The Hello, World! Window
new
operator. For most widgets the arguments to the constructor are:
Fl_Widget(x, y, width, height, label)
The x
and y
parameters determine where the widget or window is placed on the screen. In FLTK the top left corner of the window or screen is the origin (i.e. x = 0, y = 0
) and the units are in pixels.
The width
and height
parameters determine the size of the widget or window in pixels. The maximum widget size is typically governed by the underlying window system or hardware.
label
is a pointer to a character string to label the widget with or NULL
. If not specified the label defaults to NULL
. The label string must be in static storage such as a string constant because FLTK does not make a copy of it - it just uses the pointer.
myGroup->begin()
and myGroup->end()
. In this example, myGroup
would be the current group.
Newly created groups and their derived widgets implicitly call begin()
in the constructor, effectively adding all subsequently created widgets to itself until end()
is called.
Setting the current group to NULL
will stop automatic hierarchies. New widgets can now be added manually using Fl_Group::add(...)
and Fl_Group::insert(...)
.
box->box(FL_UP_BOX)
sets the type of box the Fl_Box draws, changing it from the default of FL_NO_BOX
, which means that no box is drawn. In our "Hello, World!" example we use FL_UP_BOX
, which means that a raised button border will be drawn around the widget. More details are available in the Box Types section.
You could examine the boxtype in by doing box->box()
. FLTK uses method name overloading to make short names for get/set methods. A "set" method is always of the form "void name(type)", and a "get" method is always of the form "type name() const".
redraw()
- you have to call it yourself. This greatly reduces code size and execution time. The only common exceptions are value()
which calls redraw()
and label()
which calls redraw_label()
if necessary.labelfont()
, labelsize()
, and labeltype()
methods.
The labelfont()
method sets the typeface and style that is used for the label, which for this example we are using FL_BOLD
and FL_ITALIC
. You can also specify typefaces directly.
The labelsize()
method sets the height of the font in pixels.
The labeltype()
method sets the type of label. FLTK supports normal, embossed, and shadowed labels internally, and more types can be added as desired.
A complete list of all label options can be found in the section on Labels and Label Types.
show()
method shows the widget or window. For windows you can also provide the command-line arguments to allow users to customize the appearance, size, and position of your windows.FLTK also supports idle, timer, and file pseudo-events that cause a function to be called when they occur. Idle functions are called when no user input is present and no timers or files need to be handled - in short, when the application is not doing anything. Idle callbacks are often used to update a 3D display or do other background processing.
Timer functions are called after a specific amount of time has expired. They can be used to pop up a progress dialog after a certain amount of time or do other things that need to happen at more-or-less regular intervals. FLTK timers are not 100% accurate, so they should not be used to measure time intervals, for example.
File functions are called when data is ready to read or write, or when an error condition occurs on a file. They are most often used to monitor network connections (sockets) for data-driven displays.
FLTK applications must periodically check (Fl::check()) or wait (Fl::wait()) for events or use the Fl::run() method to enter a standard event processing loop. Calling Fl::run() is equivalent to the following code:
while (Fl::wait());
Fl::run() does not return until all of the windows under FLTK control are closed by the user or your program.
-I
option:
CC -I/usr/local/include ... gcc -I/usr/local/include ...
The fltk-config
script included with FLTK can be used to get the options that are required by your compiler:
CC `fltk-config --cxxflags` ...
Similarly, when linking your application you will need to tell the compiler to use the FLTK library:
CC ... -L/usr/local/lib -lfltk -lXext -lX11 -lm gcc ... -L/usr/local/lib -lfltk -lXext -lX11 -lm
Aside from the "fltk" library, there is also a "fltk_forms" library for the XForms compatibility classes, "fltk_gl" for the OpenGL and GLUT classes, and "fltk_images" for the image file classes, Fl_Help_Dialog widget, and system icon support.
fltk-config
script included with FLTK can be used to get the options that are required by your linker:
CC ... `fltk-config --ldflags`
The forms, GL, and images libraries are included with the "--use-foo" options, as follows:
CC ... `fltk-config --use-forms --ldflags` CC ... `fltk-config --use-gl --ldflags` CC ... `fltk-config --use-images --ldflags` CC ... `fltk-config --use-forms --use-gl --use-images --ldflags`
Finally, you can use the fltk-config
script to compile a single source file as a FLTK program:
fltk-config --compile filename.cpp fltk-config --use-forms --compile filename.cpp fltk-config --use-gl --compile filename.cpp fltk-config --use-images --compile filename.cpp fltk-config --use-forms --use-gl --use-images --compile filename.cpp
Any of these will create an executable named filename
.
fltk-config
to build a program consisting of a single source file from the command line, and this is very convenient for small test programs. But fltk-config
can also be used to set the compiler and linker options as variables within a Makefile
that can be used to build programs out of multiple source files:
CXX = $(shell fltk-config --cxx) DEBUG = -g CXXFLAGS = $(shell fltk-config --use-gl --use-images --cxxflags ) -I. LDFLAGS = $(shell fltk-config --use-gl --use-images --ldflags ) LDSTATIC = $(shell fltk-config --use-gl --use-images --ldstaticflags ) LINK = $(CXX) TARGET = cube OBJS = CubeMain.o CubeView.o CubeViewUI.o SRCS = CubeMain.cxx CubeView.cxx CubeViewUI.cxx .SUFFIXES: .o .cxx %.o: %.cxx $(CXX) $(CXXFLAGS) $(DEBUG) -c $< all: $(TARGET) $(LINK) -o $(TARGET) $(OBJS) $(LDSTATIC) $(TARGET): $(OBJS) CubeMain.o: CubeMain.cxx CubeViewUI.h CubeView.o: CubeView.cxx CubeView.h CubeViewUI.h CubeViewUI.o: CubeViewUI.cxx CubeView.h clean: $(TARGET) $(OBJS) rm -f *.o 2> /dev/null rm -f $(TARGET) 2> /dev/null
You can build your Microsoft Windows applications as Console or WIN32 applications. If you want to use the standard C main()
function as the entry point, FLTK includes a WinMain()
function that will call your main()
function for you.
Note: The Visual C++ 5.0 optimizer is known to cause problems with many programs. We only recommend using the "Favor Small Code" optimization setting. The Visual C++ 6.0 optimizer seems to be much better and can be used with the "optimized for speed" setting.
Fl::foo()
or fl_foo()
.Fl_Foo
.FL_FOO
.<FL/...>
.
#include <FL/Fl_xyz.H>
#include <FL\Fl_xyz.H> #include <fl/fl_xyz.h> #include <Fl/fl_xyz.h>
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