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<H1 ALIGN=RIGHT>2 - FLTK Basics</H1>
This chapter will teach you the basics of compiling programs that use
FLTK.
<H2>Naming</H2>
All public symbols in FLTK start with the characters 'F' and 'L':
<ul>
<li>Functions are either <tt>Fl::foo()</tt> or <tt>fl_foo()</tt>.
<li>Class and type names are capitalized: <tt>Fl_Foo</tt>.
<li><a href=#Enumerations>Constants and enumerations</a> are
uppercase: <tt>FL_FOO</tt>.
<li>All header files start with <tt><FL/...></tt>.
</ul>
<H2>Header Files</H2>
The proper way to include FLTK header files is:
<ul><pre>
#include <FL/Fl_xyz.H>
</pre></ul>
<b>Microsoft Windows developers please note:</b> case *is* significant
under other operating systems, and the C standard uses the forward
slash (/) to separate directories. The following <tt>#include</tt>
directives are *not* recommended for portability reasons:
<ul><pre>
#include <fl\fl_xyz.h>
#include <fl/fl_xyz.h>
#include <FL\Fl_xyz.H>
</pre></ul>
<H2>Compiling Programs with Standard Compilers</H2>
Under UNIX (and under Microsoft Windows when using the GNU development tools)
you will probably need to tell the compiler where to find the header files.
This is usually done using the <tt>-I</tt> option:
<ul><pre>
CC -I/usr/local/include ...
gcc -I/usr/local/include ...
</pre></ul>
Similarly, when linking your application you will need to tell the compiler
to use the FLTK library:
<ul><pre>
CC ... -L/usr/local/lib -lfltk -lXext -lX11 -lm
gcc ... -L/usr/local/lib -lfltk -lXext -lX11 -lm
</pre></ul>
<H2>Compiling Programs with Microsoft Visual C++</H2>
In Visual C++ you will need to tell the compiler where to find the FLTK
header files. This can be done by selecting "Settings" from the
"Project" menu and then changing the "Preprocessor" settings under the
"C/C++" tab. Similarly, you will need to add the FLTK library to the
"Link" settings.
<p>You can build your Microsoft Windows applications as Console or
WIN32 applications. If you want to use the standard C <tt>main()</tt>
function as the entry point, FLTK includes a <tt>WinMain()</tt> function
that will call your <tt>main()</tt> function for you.
<p><i>Note: The Visual C++ optimizer is known to cause problems with
many programs. We only recommend using the "Favor Small Code"
optimization setting.
<H2>Writing Your First FLTK Program</H2>
All programs must include the file <tt><FL/Fl.H></tt>. 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.
<ul>
<i>Listing 1 - "hello.cxx"</i>
<br>
<pre>
#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(FL_UP_BOX,20,40,260,100,"Hello, World!");
box->labelsize(36);
box->labelfont(FL_BOLD+FL_ITALIC);
box->labeltype(FL_SHADOW_LABEL);
window->end();
window->show(argc, argv);
return Fl::run();
}
</pre></ul>
After including the required header files, the program then creates a
window:
<ul><pre>
Fl_Window *window = new <a href="#Fl_Window">Fl_Window</a>(300,180);
</pre></ul>
and a box with the "Hello, World!" string in it:
<ul><pre>
Fl_Box *box = new <a href="#Fl_Box">Fl_Box</a>(FL_UP_BOX,20,40,260,100,"Hello, World!");
</pre></ul>
Next, we set the size, font, and style of the label:
<ul><pre>
box-><a href="#Fl_Widget.labelsize">labelsize</a>(36);
box-><a href="#Fl_Widget.labelfont">labelfont</a>(FL_BOLD+FL_ITALIC);
box-><a href="#Fl_Widget.labeltype">labeltype</a>(FL_SHADOW_LABEL);
</pre></ul>
Finally, we show the window and enter the FLTK event loop:
<ul><pre>
window-><a href="#Fl_Group.end">end</a>();
window-><a href="#Fl_Window.show">show</a>(argc, argv);
return <a href="#run">Fl::run</a>();
</pre></ul>
The resulting program will display the window below. You can quit
the program by closing the window or pressing the ESCape key.
<center><img src=hello.C.gif></center>
<H3>Creating the Widgets</H3>
The widgets are created using the C++ <tt>new</tt> operator; the arguments
to the constructors are usually one of the following:
<ul><pre>
Fl_Widget(boxtype, x, y, width, height)
Fl_Widget(x, y, width, height)
Fl_Widget(width, height)
</pre></ul>
The <tt>boxtype</tt> value is the style of the box that is drawn around
the widget. Usually this is <tt>FL_NO_BOX</tt>, which means that no
box is drawn. In our "Hello, World!" example we use <tt>FL_UP_BOX</tt>,
which means that a raised button border will be drawn around the
widget. You can learn more about boxtypes in <a href="#boytypes">Chapter
3</a>.
<p>The <tt>x</tt> and <tt>y</tt> 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.
<p>The <tt>width</tt> and <tt>height</tt> 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.
<H3>Labels</H3>
All widgets support labels. In the case of window widgets, the label
is used for the label in the title bar. Our example program calls the
<a href="#Fl_Widget.labelfont"><tt>labelfont</tt></a>,
<a href="#Fl_Widget.labelsize"><tt>labelsize</tt></a>, and
<a href="#Fl_Widget.labeltype"><tt>labeltype</tt></a> methods.
<p>The <tt>labelfont</tt> method sets the typeface and style that is
used for the label, which for this example we are using
<tt>FL_BOLD</tt> and <tt>FL_ITALIC</tt>. You can also specify typefaces
directly.
<p>The <tt>labelsize</tt> method sets the height of the font in pixels.
<p>The <tt>labeltype</tt> method sets the type of label. FLTK supports
normal, embossed, shadowed, symbol, and image labels.
<p>A complete list of all label options can be found in <a href="#labels">
Chapter 3</a>.
<H3>Showing the Window</H3>
The <tt>show()</tt> 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.
<H3>The Main Event Loop</H3>
FLTK provides the <a href="#run"><tt>Fl:run()</tt></a> method to enter
a standard event processing loop. This is equivalent to the following
code:
<ul><pre>
while (Fl::wait());
</pre></ul>
<tt>Fl::run()</tt> does not return until all of the windows under FLTK control
are closed (either by the user or your program).
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