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<HTML>
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<BODY>
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<H1 ALIGN=RIGHT>2 - FLTK Basics</H1>
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This chapter will teach you the basics of compiling programs that use
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FLTK.
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<H2>Naming</H2>
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All public symbols in FLTK start with the characters 'F' and 'L':
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<ul>
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<li>Functions are either <tt>Fl::foo()</tt> or <tt>fl_foo()</tt>.
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<li>Class and type names are capitalized: <tt>Fl_Foo</tt>.
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<li><a href=#Enumerations>Constants and enumerations</a> are
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uppercase: <tt>FL_FOO</tt>.
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<li>All header files start with <tt><FL/...></tt>.
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</ul>
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<H2>Header Files</H2>
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The proper way to include FLTK header files is:
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<ul><pre>
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#include <FL/Fl_xyz.H>
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</pre></ul>
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Microsoft Windows developers please note: case *is* significant
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under other operating systems, and the C standard uses the forward
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slash (/) to separate directories. The following <tt>#include</tt>
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directives are *not* recommended for portability reasons:
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<ul><pre>
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#include <fl\fl_xyz.h>
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#include <fl/fl_xyz.h>
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#include <FL\Fl_xyz.H>
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</pre></ul>
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<H2>Compiling Programs with Standard Compilers</H2>
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Under UNIX (and under Microsoft Windows when using the GNU development tools)
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you will probably need to tell the compiler where to find the header files.
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This is usually done using the <tt>-I</tt> option:
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<ul><pre>
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CC -I/usr/local/include ...
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gcc -I/usr/local/include ...
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</pre></ul>
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Similarly, when linking your application you will need to tell the compiler
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to use the FLTK library:
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<ul><pre>
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CC ... -L/usr/local/lib -lfltk -lXext -lX11 -lm
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gcc ... -L/usr/local/lib -lfltk -lXext -lX11 -lm
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</pre></ul>
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<H2>Compiling Programs with Microsoft Visual C++</H2>
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In Visual C++ you will need to tell the compiler where to find the FLTK
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header files. This can be done by selecting "Settings" from the
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"Project" menu and then changing the "Preprocessor" settings under the
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"C/C++" tab. Similarly, you will need to add the FLTK library to the
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"Link" settings.
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<p>You can build your Microsoft Windows applications as Console or
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WIN32 applications. If you want to use the standard C <tt>main()</tt>
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function as the entry point, enter the name <tt>mainCRTStartup</tt> in
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the "Entry-point symbol" field in the "Output" settings under the
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"Link" tab.
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<p><i>Note: The Visual C++ optimizer is known to cause problems with
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many programs. We only recommend using the "Favor Small Code"
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optimization setting.
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<H2>Writing Your First FLTK Program</H2>
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All programs must include the file <tt><FL/Fl.H></tt>. In
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addition the program must include a header file for each FLTK class it
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uses. Listing 1 shows a simple "Hello, World!" program that uses
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FLTK to display the window.
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<ul>
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<i>Listing 1 - "hello.cxx"</i>
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<br>
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<pre>
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#include <FL/Fl.H>
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#include <FL/Fl_Window.H>
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#include <FL/Fl_Box.H>
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int main(int argc, char **argv) {
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Fl_Window *window = new Fl_Window(300,180);
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Fl_Box *box = new Fl_Box(FL_UP_BOX,20,40,260,100,"Hello, World!");
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box->labelsize(36);
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box->labelfont(FL_BOLD+FL_ITALIC);
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box->labeltype(FL_SHADOW_LABEL);
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window->end();
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window->show(argc, argv);
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return Fl::run();
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}
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</pre></ul>
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After including the required header files, the program then creates a
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window:
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<ul><pre>
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Fl_Window *window = new <a href="#Fl_Window">Fl_Window</a>(300,180);
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</pre></ul>
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and a box with the "Hello, World!" string in it:
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<ul><pre>
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Fl_Box *box = new <a href="#Fl_Box">Fl_Box</a>(FL_UP_BOX,20,40,260,100,"Hello, World!");
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</pre></ul>
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Next, we set the size, font, and style of the label:
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<ul><pre>
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box-><a href="#Fl_Widget.labelsize">labelsize</a>(36);
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box-><a href="#Fl_Widget.labelfont">labelfont</a>(FL_BOLD+FL_ITALIC);
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box-><a href="#Fl_Widget.labeltype">labeltype</a>(FL_SHADOW_LABEL);
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</pre></ul>
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Finally, we show the window and enter the FLTK event loop:
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<ul><pre>
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window-><a href="#Fl_Group.end">end</a>();
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window-><a href="#Fl_Window.show">show</a>(argc, argv);
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return <a href="#run">Fl::run</a>();
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</pre></ul>
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The resulting program will display the window below. You can quit
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the program by closing the window or pressing the ESCape key.
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<center><img src=hello.C.gif></center>
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<H3>Creating the Widgets</H3>
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The widgets are created using the C++ <tt>new</tt> operator; the arguments
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to the constructors are usually one of the following:
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<ul><pre>
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Fl_Widget(boxtype, x, y, width, height)
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Fl_Widget(x, y, width, height)
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Fl_Widget(width, height)
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</pre></ul>
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The <tt>boxtype</tt> value is the style of the box that is drawn around
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the widget. Usually this is <tt>FL_NO_BOX</tt>, which means that no
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box is drawn. In our "Hello, World!" example we use <tt>FL_UP_BOX</tt>,
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which means that a raised button border will be drawn around the
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widget. You can learn more about boxtypes in <a href="#common">Chapter
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3</a>.
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<p>The <tt>x</tt> and <tt>y</tt> parameters determine where the widget
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or window is placed on the screen. In FLTK the top left corner of the
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window or screen is the origin (i.e. x = 0, y = 0) and the units are in
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pixels.
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<p>The <tt>width</tt> and <tt>height</tt> parameters determine the size
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of the widget or window in pixels. The maximum widget size is typically
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governed by the underlying window system or hardware.
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<H3>Labels</H3>
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All widgets support labels. In the case of window widgets, the label
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is used for the label in the title bar. Our example program calls the
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<a href="#Fl_Widget.labelfont"><tt>labelfont</tt></a>,
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<a href="#Fl_Widget.labelsize"><tt>labelsize</tt></a>, and
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<a href="#Fl_Widget.labeltype"><tt>labeltype</tt></a> methods.
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<p>The <tt>labelfont</tt> method sets the typeface and style that is
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used for the label, which for this example we are using
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<tt>FL_BOLD</tt> and <tt>FL_ITALIC</tt>. You can also specify typefaces
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directly.
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<p>The <tt>labelsize</tt> method sets the height of the font in pixels.
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<p>The <tt>labeltype</tt> method sets the type of label. FLTK supports
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normal, embossed, shadowed, symbol, and image labels.
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<p>A complete list of all label options can be found in <a href="#common">
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Chapter 3</a>.
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<H3>Showing the Window</H3>
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The <tt>show()</tt> method shows the widget or window. For windows you can
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also provide the command-line arguments to allow users to customize the
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appearance, size, and position of your windows.
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<H3>The Main Event Loop</H3>
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FLTK provides the <a href="#run"><tt>Fl:run()</tt></a> method to enter
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a standard event processing loop. This is equivalent to the following
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code:
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<ul><pre>
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while (Fl::wait());
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</pre></ul>
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<tt>Fl::run()</tt> does not return until all of the windows under FLTK control
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are closed (either by the user or your program).
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</BODY>
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</HTML>
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