1999-01-13 22:28:54 +03:00
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1999-01-13 20:48:12 +03:00
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<H1 ALIGN=RIGHT><A NAME=basics>2 - FLTK Basics</A></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>. </LI>
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<LI>Class and type names are capitalized: <TT>Fl_Foo</TT>. </LI>
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<LI><A href=enumerations.html#Enumerations>Constants and enumerations</A>
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are uppercase: <TT>FL_FOO</TT>. </LI>
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<LI>All header files start with <TT><FL/...></TT>. </LI>
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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>
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<PRE>
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#include <FL/Fl_xyz.H>
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</PRE>
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</UL>
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<B>Microsoft Windows developers please note:</B> 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. <i>Do not do any of the following:</i>
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<UL>
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<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>
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</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
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tools) you will probably need to tell the compiler where to find the
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header files. This is usually done using the <TT>-I</TT> option:
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<UL>
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<PRE>
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CC -I/usr/local/include ...
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gcc -I/usr/local/include ...
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</PRE>
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</UL>
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Similarly, when linking your application you will need to tell the
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compiler to use the FLTK library:
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<UL>
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<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>
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</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
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FLTK 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. You will also need to add the FLTK and WinSock (WSOCK32.LIB)
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libraries to the "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, FLTK includes a <TT>WinMain()</TT>
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function that will call your <TT>main()</TT> function for you. </P>
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<P><I>Note: The Visual C++ 5.0 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.</I> The Visual C++ 6.0 optimizer seems to be much
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better and can be used with the "optimized for speed" setting.</P>
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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 addition the
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program must include a header file for each FLTK class it uses.
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Listing 1 shows a simple "Hello, World!" program that uses FLTK to
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display the window.
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<UL><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(20,40,260,100,"Hello, World!");
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box->box(FL_UP_BOX);
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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>
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</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>
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<PRE>
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Fl_Window *window = new <A href=Fl_Window.html#Fl_Window>Fl_Window</A>(300,180);
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</PRE>
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</UL>
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and a box with the "Hello, World!" string in it:
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<UL>
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<PRE>
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Fl_Box *box = new <A href=Fl_Box.html#Fl_Box>Fl_Box</A>(20,40,260,100,"Hello, World!");
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</PRE>
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</UL>
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Next, we set the type of box and the size, font, and style of the label:
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<UL>
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<PRE>
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box->box(FL_UP_BOX);
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box-><A href=Fl_Widget.html#Fl_Widget.labelsize>labelsize</A>(36);
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box-><A href=Fl_Widget.html#Fl_Widget.labelfont>labelfont</A>(FL_BOLD+FL_ITALIC);
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box-><A href=Fl_Widget.html#Fl_Widget.labeltype>labeltype</A>(FL_SHADOW_LABEL);
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</PRE>
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</UL>
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Finally, we show the window and enter the FLTK event loop:
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<UL>
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<PRE>
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window-><A href=Fl_Group.html#Fl_Group.end>end</A>();
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window-><A href=Fl_Window.html#Fl_Window.show>show</A>(argc, argv);
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return <A href=functions.html#run>Fl::run</A>();
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</PRE>
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</UL>
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The resulting program will display the window below. You can quit the
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program by closing the window or pressing the ESCape key.
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<P ALIGN=CENTER><IMG src=./hello.C.gif></P>
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<H3>Creating the Widgets</H3>
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The widgets are created using the C++ <TT>new</TT> operator. For
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most widgets the arguments to the constructor are:
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<UL>
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<PRE>
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Fl_Widget(x, y, width, height)
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</PRE>
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</UL>
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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. </P>
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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
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typically governed by the underlying window system or hardware. </P>
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<p><tt>label</tt> is a pointer to a character string to label the
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widget with or <tt>NULL</tt>. If not specified the label defaults to
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<tt>NULL</tt>. The label string must be in static storage (such as a
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string constant) because FLTK does not make a copy of it (it just uses
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the pointer).
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<H3>Get/Set Methods</H3>
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<tt>box->box(FL_UP_BOX)</tt> sets the type of box the
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Fl_Box draws, changing it from the default of <tt>FL_NO_BOX</tt>, which means
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that no box is drawn. In our "Hello, World!" example we use <TT>
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FL_UP_BOX</TT>, which means that a raised button border will be drawn
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around the widget. You can learn more about boxtypes in <A href=#boytypes>
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Chapter 3</A>.
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<p>You could examine the boxtype in by doing
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<tt>box->box()</tt>. Fltk uses method name overloading to make
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short names for get/set methods. A "set" method is always of the form
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"void name(type)", and a "get" method is always of the form
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"type name() const".
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<p>Almost all of these set/get pairs are very fast and short inline
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functions and thus very efficient. However, <i>the "set" methods do
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not call redraw()</i>, you have to call it yourself. This greatly
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reduces code size and execution time. The only common exception is
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<tt>value()</tt>, this does redraw() if necessary.
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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 <A href=Fl_Widget.html#Fl_Widget.labelfont>
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<TT>labelfont</TT></A>, <A href=Fl_Widget.html#Fl_Widget.labelsize><TT>
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labelsize</TT></A>, and <A href=Fl_Widget.html#Fl_Widget.labeltype><TT>
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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 <TT>FL_BOLD</TT>
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and <TT>FL_ITALIC</TT>. You can also specify typefaces directly. </P>
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<P>The <TT>labelsize</TT> method sets the height of the font in pixels. </P>
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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. </P>
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<P>A complete list of all label options can be found in <A href=common.html#labels>
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Chapter 3</A>. </P>
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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
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you can also provide the command-line arguments to allow users to
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customize the 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=functions.html#run><TT>Fl:run()</TT></A>
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method to enter a standard event processing loop. This is equivalent
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to the following code:
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<UL>
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<PRE>
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while (Fl::wait());
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</PRE>
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</UL>
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<TT>Fl::run()</TT> does not return until all of the windows under FLTK
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control are closed (either by the user or your program). </TT></BODY></HTML>
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