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git-svn-id: file:///fltk/svn/fltk/branches/branch-1.1@1934 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
287 lines
9.8 KiB
HTML
287 lines
9.8 KiB
HTML
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<H1 ALIGN=RIGHT><A NAME=basics>2 - FLTK Basics</A></H1>
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<P>This chapter teaches you the basics of compiling programs
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that use FLTK.</P>
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<H2>Writing Your First FLTK Program</H2>
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<P>All programs must include the file <TT><FL/Fl.H></TT>.
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In addition the program must include a header file for each
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FLTK class it uses. Listing 1 shows a simple "Hello,
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World!" program that uses FLTK to display the window.</P>
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<UL>
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<P><I>Listing 1 - "hello.cxx"</I>
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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></UL>
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<P>After including the required header files, the program then creates a
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window:</P>
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<UL><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></UL>
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<P>and a box with the "Hello, World!" string in it:</P>
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<UL><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></UL>
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<P>Next, we set the type of box and the size, font, and style of the label:</P>
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<UL><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></UL>
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<P>Finally, we show the window and enter the FLTK event loop:</P>
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<UL><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="Fl.html#Fl.run">Fl::run</A>();
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</PRE></UL>
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<P>The resulting program will display the window in Figure 2-1.
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You can quit the program by closing the window or pressing the
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<KBD>ESC</KBD>ape key.</P>
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<P ALIGN="CENTER"><IMG src="hello.C.gif" alt="Hello, World! Window"><BR>
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<I>Figure 2-1: The Hello, World! Window</I></P>
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<H3>Creating the Widgets</H3>
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<P>The widgets are created using the C++ <TT>new</TT> operator. For
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most widgets the arguments to the constructor are:</P>
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<UL><PRE>
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Fl_Widget(x, y, width, height, label)
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</PRE></UL>
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<P>The <TT>x</TT> and <TT>y</TT> parameters determine where the
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widget or window is placed on the screen. In FLTK the top left
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corner of the window or screen is the origin (i.e. x = 0, y =
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0) and the units are in pixels.</P>
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<P>The <TT>width</TT> and <TT>height</TT> parameters determine
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the size of the widget or window in pixels. The maximum widget
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size is typically governed by the underlying window system or
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hardware.</P>
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<P><tt>label</tt> is a pointer to a character string to label
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the widget with or <tt>NULL</tt>. If not specified the label
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defaults to <tt>NULL</tt>. The label string must be in static
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storage such as a string constant because FLTK does not make a
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copy of it - it just uses the pointer.</P>
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<H3>Get/Set Methods</H3>
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<P><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
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<tt>FL_NO_BOX</tt>, which means that no box is drawn. In our
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"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
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the widget. You can learn more about boxtypes in
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<A href="common.html#boxtypes">Chapter 3</A>.</P>
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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
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the form "void name(type)", and a "get" method is always
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of the form "type name() const".</P>
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<H3>Redrawing After Changing Attributes</H3>
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<P>Almost all of the set/get pairs are very fast, short inline
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functions and thus very efficient. However, <i>the "set"
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methods do not call <TT>redraw()</TT></i> - you have to call it
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yourself. This greatly reduces code size and execution time.
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The only common exception is <tt>value()</tt> which calls
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<TT>redraw()</TT> if necessary.</P>
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<H3>Labels</H3>
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<P>All widgets support labels. In the case of window widgets,
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the label is used for the label in the title bar. Our example
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program calls the <A href=Fl_Widget.html#Fl_Widget.labelfont>
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<TT>labelfont</TT></A>,
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<A href=Fl_Widget.html#Fl_Widget.labelsize><TT> labelsize</TT></A>,
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and <A href=Fl_Widget.html#Fl_Widget.labeltype><TT>labeltype</TT></A>
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methods.</P>
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<P>The <TT>labelfont</TT> method sets the typeface and style
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that is 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
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typefaces directly. </P> <P>The <TT>labelsize</TT> method sets
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the height of the font in pixels. </P> <P>The <TT>labeltype</TT>
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method sets the type of label. FLTK supports normal, embossed,
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and shadowed labels internally, and more types can be added as
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desired.</P>
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<P>A complete list of all label options can be found in
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<A href="common.html#labels">Chapter 3</A>.</P>
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<H3>Showing the Window</H3>
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<P>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.</P>
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<H3>The Main Event Loop</H3>
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<P>All FLTK applications (and most GUI applications in general)
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are based on a simple event processing model. User actions such
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as mouse movement, button clicks, and keyboard activity generate
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events that are sent to an application. The application may then
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ignore the events or respond to the user, typically by redrawing
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a button in the "down" position, adding the text to an input
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field, and so forth.</P>
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<P>FLTK also supports idle, timer, and file pseudo-events that
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cause a function to be called when they occur. Idle functions
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are called when no user input is present and no timers or files
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need to be handled - in short, when the application is not doing
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anything. Idle callbacks are often used to update a 3D display
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or do other background processing.</P>
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<P>Timer functions are called after a specific amount of time
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has expired. They can be used to pop up a progress dialog after
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a certain amount of time or do other things that need to happen
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at more-or-less regular intervals. FLTK timers are not 100%
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accurate, so they should not be used to measure time intervals,
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for example.</P>
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<P>File functions are called when data is ready to read or
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write, or when an error condition occurs on a file. They are
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most often used to monitor network connections (sockets) for
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data-driven displays.</P>
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<P>FLTK applications must periodically check
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(<TT>Fl::check()</TT>) or wait (<TT>Fl::wait()</TT>) for events
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or use the <A href="Fl.html#Fl.run"><TT>Fl::run()</TT></A>
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method to enter a standard event processing loop. Calling
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<TT>Fl::run()</TT> is equivalent to the following code:</P>
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<UL><PRE>
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while (Fl::wait());
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</PRE></UL>
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<P><TT>Fl::run()</TT> does not return until all of the windows
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under FLTK control are closed by the user or your program.</P>
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<H2>Compiling Programs with Standard Compilers</H2>
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<P>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:</P>
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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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<P>The <TT>fltk-config</TT> script included with FLTK can be
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used to get the options that are required by your compiler:</P>
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<UL><PRE>
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CC `fltk-config --cxxflags` ...
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</PRE></UL>
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<P>Similarly, when linking your application you will need to tell the
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compiler to use the FLTK library:</P>
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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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<P>The <TT>fltk-config</TT> script included with FLTK can be
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used to get the options that are required by your linker:</P>
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<UL><PRE>
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CC ... `fltk-config --ldflags`
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</PRE></UL>
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<H2>Compiling Programs with Microsoft Visual C++</H2>
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<P>In Visual C++ you will need to tell the compiler where to
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find the FLTK header files. This can be done by selecting
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"Settings" from the "Project" menu and then
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changing the "Preprocessor" settings under the
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"C/C++" tab. You will also need to add the FLTK and
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WinSock (WSOCK32.LIB) libraries to the "Link"
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settings.</P>
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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>Naming</H2>
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<P>All public symbols in FLTK start with the characters 'F' and 'L':</P>
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<UL>
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<LI>Functions are either <TT>Fl::foo()</TT> or
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<TT>fl_foo()</TT>.</LI>
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<LI>Class and type names are capitalized:
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<TT>Fl_Foo</TT>.</LI>
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<LI><A href="enumerations.html">Constants and
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enumerations</A> are uppercase: <TT>FL_FOO</TT>.</LI>
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<LI>All header files start with <TT><FL/...></TT>.
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</LI>
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</UL>
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<H2>Header Files</H2>
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<P>The proper way to include FLTK header files is:</P>
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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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<P><B>Microsoft Windows developers please note:</B> case *is*
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significant under other operating systems, and the C standard
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uses the forward slash (/) to separate directories. <i>Do not
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use any of the following include lines:</i></P>
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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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</BODY>
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</HTML>
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