/**
 <!-- Warning: \p .fl  does not work but <tt>.fl</tt>  does -->
 <!-- Warning: \p .h   does not work but <tt>.h</tt>   does -->
 <!-- Warning: \p .cxx does not work but <tt>.cxx</tt> does -->

 \page	fluid	Programming with FLUID

This chapter shows how to use the Fast Light User-Interface Designer
("FLUID") to create your GUIs.

Subchapters:

\li \ref fluid_what_is_fluid
\li \ref fluid_fluid_under_unix
\li \ref fluid_fluid_under_windows
\li \ref fluid_compiling_fl_files
\li \ref fluid_tutorial
\li \ref fluid_references
\li \ref fluid_i18n
\li \ref fluid_limitations

\section fluid_what_is_fluid What is FLUID?

The Fast Light User Interface Designer, or FLUID, is a
graphical editor that is used to produce FLTK source code. FLUID
edits and saves its state in <tt>.fl</tt> files. These files
are text, and you can (with care) edit them in a text editor,
perhaps to get some special effects.

FLUID can "compile" the <tt>.fl</tt> file into a
<tt>.cxx</tt> and a <tt>.h</tt> file. The <tt>.cxx</tt> file
defines all the objects from the <tt>.fl</tt> file and the
<tt>.h</tt> file declares all the global ones. FLUID also
supports localization (\ref fluid_i18n "Internationalization")
of label strings using message files and the GNU gettext or
POSIX catgets interfaces.

A simple program can be made by putting all your code (including a
\p main() function) into the <tt>.fl</tt> file and thus making the
<tt>.cxx</tt> file a
single source file to compile.  Most programs are more complex than
this, so you write other <tt>.cxx</tt> files that call the FLUID functions.
These <tt>.cxx</tt> files must
\p \#include
the <tt>.h</tt> file or they can
\p \#include
the <tt>.cxx</tt> file so it still appears to be a single source file.

 \image html fluid-org.png "Figure 9-1: FLUID organization"
 \image latex fluid-org.png "FLUID organization" width=12cm 

Normally the FLUID file defines one or more functions or classes which
output C++ code.  Each function defines one or more FLTK
windows, and all the widgets that go inside those windows.

Widgets created by FLUID are either "named", "complex named" or
"unnamed".  A named widget has a legal C++ variable identifier as its
name (i.e. only alphanumeric and underscore).  In this case FLUID
defines a global variable or class member that will point at the widget
after the function defining it is called.  A complex named object has
punctuation such as <tt>'.'</tt> or <tt>'->'</tt> or any other symbols
in its name.  In
this case FLUID assigns a pointer to the widget to the name, but does
not attempt to declare it.  This can be used to get the widgets into
structures.  An unnamed widget has a blank name and no pointer is stored.

Widgets may either call a named callback function that you write in
another source file, or you can supply a small piece of C++ source and
FLUID will write a private callback function into the <tt>.cxx</tt> file.

\section fluid_fluid_under_unix Running FLUID Under UNIX

To run FLUID under UNIX, type:

\code
fluid filename.fl &
\endcode

to edit the <tt>.fl</tt> file <tt>filename.fl</tt>.
If the file does not exist
you will get an error pop-up, but if you dismiss it you will be editing
a blank file of that name.  You can run FLUID without any name, in
which case you will be editing an unnamed blank setup (but you can use
save-as to write it to a file).

You can provide any of the standard FLTK switches before the filename: 

\code
-display host:n.n
-geometry WxH+X+Y
-title windowtitle
-name classname
-iconic
-fg color
-bg color
-bg2 color
-scheme schemename
\endcode

Changing the colors may be useful to see what your interface
will look at if the user calls it with the same switches.
Similarly, using "-scheme plastic" will show how the interface
will look using the "plastic" scheme.

In the current version, if you don't put FLUID into the
background with <tt>'&'</tt> then you will be able to abort FLUID by
typing <tt>CTRL-C</tt> on the terminal. It will exit
immediately, losing any changes.

\section fluid_fluid_under_windows Running FLUID Under Microsoft Windows

To run FLUID under WIN32, double-click on the \e FLUID.exe
file. You can also run FLUID from the Command Prompt window.
FLUID always runs in the background under WIN32.

\section fluid_compiling_fl_files Compiling .fl files

FLUID can also be called as a command-line
"compiler" to create the <tt>.cxx</tt> and <tt>.h</tt>
file from a <tt>.fl</tt> file.  To do this type:

\code
fluid -c filename.fl
\endcode

This will read the <tt>filename.fl</tt> file and write
<tt>filename.cxx</tt> and <tt>filename.h</tt>. Any leading
directory on <tt>filename.fl</tt> will be stripped, so they are
always written to the current directory. If there are any errors
reading or writing the files, FLUID will print the error and
exit with a non-zero code. You can use the following lines in a
makefile to automate the creation of the source and header
files:

\code
my_panels.h my_panels.cxx: my_panels.fl
	fluid -c my_panels.fl
\endcode

Most versions of make support rules that cause <tt>.fl</tt>
files to be compiled:

\code
.SUFFIXES: .fl .cxx .h
.fl.h .fl.cxx:
	fluid -c $<
\endcode

\section fluid_tutorial A Short Tutorial

FLUID is an amazingly powerful little program. However, this
power comes at a price as it is not always obvious how to
accomplish seemingly simple tasks with it. This tutorial will
show you how to generate a complete user interface class with
FLUID that is used for the CubeView program provided with FLTK.

\image html cubeview.png "Figure 9-2: CubeView demo"
\image latex cubeview.png "CubeView demo" width=10cm

The window is of class CubeViewUI, and is completely generated by FLUID,
including
class member functions. The central display of the cube is a separate
subclass of Fl_Gl_Window called CubeView. CubeViewUI manages CubeView
using callbacks from the various sliders and rollers to manipulate the
viewing angle and zoom of CubeView.

At the completion of this tutorial you will (hopefully) understand
how to:

-# Use FLUID to create a complete user interface class, including
   constructor and any member functions necessary.
-# Use FLUID to set callbacks member functions of a custom widget
   classes.
-# Subclass an Fl_Gl_Window to suit your purposes.

\subsection fluid_cubeview The CubeView Class

The CubeView class is a subclass of Fl_Gl_Window. It has methods for
setting the zoom, the \e x and \e y pan, and the rotation angle
about the \e x and \e y axes.

You can safely skip this section as long as you realize that CubeView
is a sublass of Fl_Gl_Window and will respond to calls from
CubeViewUI, generated by FLUID.

\par The CubeView Class Definition

Here is the CubeView class definition, as given by its header file
"test/CubeView.h":

\code
class CubeView : public Fl_Gl_Window {
  public:
    CubeView(int x,int y,int w,int h,const char *l=0);
    // this value determines the scaling factor used to draw the cube.
    double size;
    /* Set the rotation about the vertical (y ) axis.
     *
     * This function is called by the horizontal roller in CubeViewUI
     * and the initialize button in CubeViewUI.
     */
    void v_angle(float angle){vAng=angle;};
    // Return the rotation about the vertical (y ) axis.
    float v_angle(){return vAng;};
    /* Set the rotation about the horizontal (x ) axis.
     *
     * This function is called by the vertical roller in CubeViewUI
       and the
     * initialize button in CubeViewUI.
     */
    void h_angle(float angle){hAng=angle;};
    // the rotation about the horizontal (x ) axis.
    float h_angle(){return hAng;};
    /* Sets the x shift of the cube view camera.
     *
     * This function is called by the slider in CubeViewUI and the
     * initialize button in CubeViewUI.
     */
    void panx(float x){xshift=x;};
    /* Sets the y shift of the cube view camera.
     *
     * This function is called by the slider in CubeViewUI and the
     * initialize button in CubeViewUI.
     */
    void pany(float y){yshift=y;};
    /* The widget class draw() override.
     * The draw() function initialize Gl for another round of
     * drawing then calls specialized functions for drawing each
     * of the entities displayed in the cube view.
     */
    void draw();

  private:
    /* Draw the cube boundaries
     * Draw the faces of the cube using the boxv[] vertices, using
     * GL_LINE_LOOP for the faces. The color is #defined by
     * CUBECOLOR.
     */
    void drawCube();
   
    float vAng,hAng; float xshift,yshift;

    float boxv0[3];float boxv1[3]; float boxv2[3];float boxv3[3];
    float boxv4[3];float boxv5[3]; float boxv6[3];float boxv7[3];
};
\endcode

\par The CubeView Class Implementation

Here is the CubeView implementation. It is very similar to the
"cube" demo included with FLTK.

\code
#include "CubeView.h"
#include <math.h>

CubeView::CubeView(int x,int y,int w,int h,const char *l)
            : Fl_Gl_Window(x,y,w,h,l)
{
    vAng = 0.0; hAng=0.0; size=10.0;
    /* The cube definition. These are the vertices of a unit cube
     * centered on the origin.*/
    boxv0[0] = -0.5; boxv0[1] = -0.5; boxv0[2] = -0.5; boxv1[0] = 0.5;
    boxv1[1] = -0.5; boxv1[2] = -0.5; boxv2[0] = 0.5; boxv2[1] = 0.5;
    boxv2[2] = -0.5; boxv3[0] = -0.5; boxv3[1] = 0.5; boxv3[2] = -0.5;
    boxv4[0] = -0.5; boxv4[1] = -0.5; boxv4[2] = 0.5; boxv5[0] = 0.5;
    boxv5[1] = -0.5; boxv5[2] = 0.5; boxv6[0] = 0.5; boxv6[1] = 0.5;
    boxv6[2] = 0.5; boxv7[0] = -0.5; boxv7[1] = 0.5; boxv7[2] = 0.5;
};

// The color used for the edges of the bounding cube.
#define CUBECOLOR 255,255,255,255

void CubeView::drawCube() {
/* Draw a colored cube */
#define ALPHA 0.5
    glShadeModel(GL_FLAT);

    glBegin(GL_QUADS);
      glColor4f(0.0, 0.0, 1.0, ALPHA);
      glVertex3fv(boxv0);
      glVertex3fv(boxv1);
      glVertex3fv(boxv2);
      glVertex3fv(boxv3);

      glColor4f(1.0, 1.0, 0.0, ALPHA);
      glVertex3fv(boxv0);
      glVertex3fv(boxv4);
      glVertex3fv(boxv5);
      glVertex3fv(boxv1);

      glColor4f(0.0, 1.0, 1.0, ALPHA);
      glVertex3fv(boxv2);
      glVertex3fv(boxv6);
      glVertex3fv(boxv7);
      glVertex3fv(boxv3);

      glColor4f(1.0, 0.0, 0.0, ALPHA);
      glVertex3fv(boxv4);
      glVertex3fv(boxv5);
      glVertex3fv(boxv6);
      glVertex3fv(boxv7);

      glColor4f(1.0, 0.0, 1.0, ALPHA);
      glVertex3fv(boxv0);
      glVertex3fv(boxv3);
      glVertex3fv(boxv7);
      glVertex3fv(boxv4);

      glColor4f(0.0, 1.0, 0.0, ALPHA);
      glVertex3fv(boxv1);
      glVertex3fv(boxv5);
      glVertex3fv(boxv6);
      glVertex3fv(boxv2);
    glEnd();

    glColor3f(1.0, 1.0, 1.0);
    glBegin(GL_LINES);
      glVertex3fv(boxv0);
      glVertex3fv(boxv1);

      glVertex3fv(boxv1);
      glVertex3fv(boxv2);

      glVertex3fv(boxv2);
      glVertex3fv(boxv3);

      glVertex3fv(boxv3);
      glVertex3fv(boxv0);

      glVertex3fv(boxv4);
      glVertex3fv(boxv5);

      glVertex3fv(boxv5);
      glVertex3fv(boxv6);

      glVertex3fv(boxv6);
      glVertex3fv(boxv7);

      glVertex3fv(boxv7);
      glVertex3fv(boxv4);

      glVertex3fv(boxv0);
      glVertex3fv(boxv4);

      glVertex3fv(boxv1);
      glVertex3fv(boxv5);

      glVertex3fv(boxv2);
      glVertex3fv(boxv6);

      glVertex3fv(boxv3);
      glVertex3fv(boxv7);
    glEnd();
};//drawCube

void CubeView::draw() {
    if (!valid()) {
        glLoadIdentity(); glViewport(0,0,w(),h());
        glOrtho(-10,10,-10,10,-20000,10000); glEnable(GL_BLEND);
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    }

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glPushMatrix(); glTranslatef(xshift, yshift, 0);
    glRotatef(hAng,0,1,0); glRotatef(vAng,1,0,0);
    glScalef(float(size),float(size),float(size)); drawCube();
    glPopMatrix();
};
\endcode

\subsection fluid_cubevieui The CubeViewUI Class

We will completely construct a window to display and control the
CubeView defined in the previous section using FLUID.

\par Defining the CubeViewUI Class

Once you have started FLUID, the first step in defining a class is to
create a new class within FLUID using the <b>New->Code->Class</b>
menu item. Name the class "CubeViewUI" and leave the
subclass blank. We do not need any inheritance for this
window. You should see the new class declaration in the FLUID
browser window.

\image html fluid1.png "Figure 9-3: FLUID file for CubeView"
\image latex fluid1.png "FLUID file for CubeView" width=10cm

\par Adding the Class Constructor

Click on the CubeViewUI class in the FLUID window and add a new method
by selecting <b>New->Code->Function/Method.</b> The name of the
function will also be CubeViewUI. FLUID will understand that this will
be the constructor for the class and will generate the appropriate
code. Make sure you declare the constructor public.

Then add a window to the CubeViewUI class. Highlight the name of
the constructor in the FLUID browser window and click on
<b>New->Group->Window</b>. In a similar manner add the
following to the CubeViewUI constructor:

\li A horizontal roller named \p hrot
\li A vertical roller named \p vrot
\li A horizontal slider named \p xpan
\li A vertical slider named \p ypan
\li A horizontal value slider named \p zoom

None of these additions need be public. And they shouldn't be
unless you plan to expose them as part of the interface for
CubeViewUI.

When you are finished you should have something like this:

\image html fluid2.png "Figure 9-4: FLUID window containing CubeView demo"
\image latex fluid2.png "FLUID window containing CubeView demo" width=10cm

We will talk about the \p show() method that is highlighted
shortly.

\par Adding the CubeView Widget

What we have is nice, but does little to show our cube. We have already
defined the CubeView class and we would like to show it within the
CubeViewUI.

The CubeView class inherits the Fl_Gl_Window class, which
is created in the same way as a Fl_Box widget. Use
<b>New->Other->Box</b> to add a square box to the main window.
This will be no ordinary box, however.

The Box properties window will appear. The key to letting CubeViewUI
display CubeView is to enter CubeView in the <b>Class:</b> text
entry box. This tells FLUID that it is not an Fl_Box, but a
similar widget with the same constructor. 

In the <b>Extra Code:</b> field enter <tt>\#include "CubeView.h"</tt>

This \p \#include is important, as we have just included
CubeView as a member of CubeViewUI, so any public CubeView methods are
now available to CubeViewUI.

\image html fluid3-cxx.png "Figure 9-5: CubeView methods"
\image latex fluid3-cxx.png "CubeView methods" width=10cm

\par Defining the Callbacks

Each of the widgets we defined before adding CubeView can have
callbacks that call CubeView methods. You can call an external
function or put in a short amount of code in the <b>Callback</b>
field of the widget panel. For example, the callback for the
\p ypan slider is:

\code
cube->pany(((Fl_Slider *)o)->value());
cube->redraw();
\endcode

We call <tt>cube->redraw()</tt> after changing the value to update
the CubeView window. CubeView could easily be modified to do this, but
it is nice to keep this exposed. In the case where you may want to do
more than one view change only redrawing once saves a lot of time.

There is no reason to wait until after you have added CubeView to
enter these callbacks. FLUID assumes you are smart enough not to refer
to members or functions that don't exist.

\par Adding a Class Method

You can add class methods within FLUID that have nothing to do with the
GUI. As an example add a show function so that CubeViewUI can actually
appear on the screen.

Make sure the top level CubeViewUI is selected and select
<b>New->Code->Function/Method</b>. Just use the name
\p show(). We don't need a return value here, and since we will
not be adding any widgets to this method FLUID will assign it a return
type of \p void.

\image html fluid4.png "Figure 9-6: CubeView constructor"
\image latex fluid4.png "CubeView constructor" width=10cm

Once the new method has been added, highlight its name and select
<b>New->Code->Code.</b> Enter the method's code in the code window.

\subsection fluid_addconst Adding Constructor Initialization Code

If you need to add code to initialize a class, for example setting
initial values of the horizontal and vertical angles in the
CubeView, you can simply highlight the constructor and select
<b>New->Code->Code</b>. Add any required code.

\subsection fluid_gencode Generating the Code

Now that we have completely defined the CubeViewUI, we have to generate
the code. There is one last trick to ensure this all works. Open the
preferences dialog from <b>Edit->Preferences</b>.

At the bottom of the preferences dialog box is the key:
<b>"Include Header from Code"</b>.
Select that option and set your desired file
extensions and you are in business. You can include the CubeViewUI.h
(or whatever extension you prefer) as you would any other C++ class.

<!-- NEW PAGE -->

\section fluid_references FLUID Reference

The following sections describe each of the windows in FLUID.

\subsection fluid_browser The Widget Browser

The main window shows a menu bar and a scrolling browser of
all the defined widgets. The name of the <tt>.fl</tt> file being
edited is shown in the window title.

The widgets are stored in a hierarchy.  You can open and close a
level by clicking the "triangle" at the left of a widget.
The leftmost widgets are the \e parents, and all the widgets
listed below them are their \e children.  Parents don't have to have
any children.

The top level of the hierarchy is composed of \e functions and
\e classes.  Each of these will produce a single C++ public
function or class in the output <tt>.cxx</tt> file.  Calling the function or
instantiating the class will create all of the child widgets.

The second level of the hierarchy contains the \e windows.
Each of these produces an instance of class Fl_Window.

Below that are either \e widgets (subclasses of Fl_Widget) or
\e groups of widgets (including other groups).  Plain groups are for
layout, navigation, and resize purposes. <i>Tab groups</i> provide the
well-known file-card tab interface.

Widgets are shown in the browser by either their \e name (such
as "main_panel" in the example), or by their \e type
and \e label (such as "Button "the green"").

You \e select widgets by clicking on their names, which highlights
them (you can also select widgets from any displayed window).  You can
select many widgets by dragging the mouse across them, or by using
Shift+Click to toggle them on and off.  To select no widgets, click in
the blank area under the last widget.  Note that hidden children may
be selected even when there is no visual indication of this.

You \e open widgets by double-clicking on them, or (to open several
widgets you have picked) by typing the F1 key.  A control panel will appear
so you can change the widget(s).

\subsection fluid_menu_items Menu Items

The menu bar at the top is duplicated as a pop-up menu on any
displayed window.  The shortcuts for all the menu items work in any
window.  The menu items are: 

\par File/Open... (Ctrl+o)

\par
Discards the current editing session and reads in a different
<tt>.fl</tt> file. You are asked for confirmation if you have
changed the current file.

\par
FLUID can also read <tt>.fd</tt> files produced by the Forms
and XForms "fdesign" programs. It is best to
File/Merge them instead of opening them. FLUID does not
understand everything in a <tt>.fd</tt> file, and will print a
warning message on the controlling terminal for all data it does
not understand. You will probably need to edit the resulting
setup to fix these errors. Be careful not to save the file
without changing the name, as FLUID will write over the
<tt>.fd</tt> file with its own format, which fdesign cannot
read! 

\par File/Insert... (Ctrl+i)

\par
Inserts the contents of another <tt>.fl</tt> file, without
changing the name of the current <tt>.fl</tt> file.  All the
functions (even if they have the same names as the current ones)
are added, and you will have to use cut/paste to put the widgets
where you want.

\par File/Save (Ctrl+s)

\par
Writes the current data to the <tt>.fl</tt> file.  If the
file is unnamed then FLUID will ask for a filename.

\par File/Save As... (Ctrl+Shift+S)

\par
Asks for a new filename and saves the file.

\par File/Write Code (Ctrl+Shift+C)

\par
"Compiles" the data into a <tt>.cxx</tt> and <tt>.h</tt>
file. These are exactly the same as the files you get when you run
FLUID with the \c -c switch.

\par
The output file names are the same as the <tt>.fl</tt> file, with
the leading  directory and trailing ".fl" stripped, and
".h" or ".cxx" appended.

\par File/Write Strings (Ctrl+Shift+W)

\par
Writes a message file for all of the text labels defined in
the current file.

\par
The output file name is the same as the <tt>.fl</tt> file,
with the leading  directory and trailing ".fl"
stripped, and ".txt", ".po", or ".msg" appended depending on the
\ref fluid_i18n "Internationalization Mode".

\par File/Quit (Ctrl+q)

\par
Exits FLUID. You are asked for confirmation if you have
changed the current file.

\par Edit/Undo (Ctrl+z)

\par
This isn't implemented yet. You should do save often so you can
recover from any mistakes you make.

\par Edit/Cut (Ctrl+x)

\par
Deletes the selected widgets and all of their children. 
These are saved to a "clipboard" file and can be
pasted back into any FLUID window.

\par Edit/Copy (Ctrl+c)

\par
Copies the selected widgets and all of their children to the
"clipboard" file.

\par Edit/Paste (Ctrl+c)

\par
Pastes the widgets from the clipboard file.

\par
If the widget is a window, it is added to whatever function
is selected, or contained in the current selection.

\par
If the widget is a normal widget, it is added to whatever
window or group is selected.  If none is, it is added to the
window or group that is the parent of the current selection.

\par
To avoid confusion, it is best to select exactly one widget
before doing a paste.

\par
Cut/paste is the only way to change the parent of a
widget.

\par Edit/Select All (Ctrl+a)

\par
Selects all widgets in the same group as the current selection.

\par
If they are all selected already then this selects all
widgets in that group's parent.  Repeatedly typing Ctrl+a will
select larger and larger groups of widgets until everything is
selected.

\par Edit/Open... (F1 or double click)

\par
Displays the current widget in the attributes panel. If the
widget is a window and it is not visible then the window is
shown instead.

\par Edit/Sort

\par
Sorts the selected widgets into left to right, top to bottom
order.  You need to do this to make navigation keys in FLTK work
correctly.  You may then fine-tune the sorting with
"Earlier" and "Later".  This does not affect
the positions of windows or functions.

\par Edit/Earlier (F2)

\par
Moves all of the selected widgets one earlier in order among
the children of their parent (if possible).  This will affect
navigation order, and if the widgets overlap it will affect how
they draw, as the later widget is drawn on top of the earlier
one.  You can also use this to reorder functions, classes, and
windows within functions.

\par Edit/Later (F3)

\par
Moves all of the selected widgets one later in order among
the children of their parent (if possible).

\par Edit/Group (F7)

\par
Creates a new Fl_Group and make all the currently
selected widgets children of it.

\par Edit/Ungroup (F8)

\par
Deletes the parent group if all the children of a group are
selected.

\par Edit/Overlays on/off (Ctrl+Shift+O)

\par
Toggles the display of the red overlays off, without changing
the selection.  This makes it easier to see box borders and how
the layout looks.  The overlays will be forced back on if you
change the selection.

\par Edit/Project Settings... (Ctrl+p)

\par
Displays the project settings panel.
The output filenames control the extensions or names of the files that
are generated by FLUID. If you check the "Include Header from Code"
button the code file will include the header file automatically.

\par
The \ref fluid_i18n "internationalization" options are described
later in this chapter.

\image html fluid_prefs.png "Figure 9-7: FLUID Preferences Window"
\image latex fluid_prefs.png "FLUID Preferences Window" width=10cm

\par Edit/Project Settings... (Shift+Ctrl+p)

\par
Displays the project settings ("Preferences") panel. This panel is used
to control the user interface settings.

\par New/Code/Function

\par
Creates a new C function.  You will be asked for a name for
the function.  This name should be a legal C++ function
template, without the return type.  You can pass arguments which
can be referred to by code you type into the individual widgets.

\par
If the function contains any unnamed windows, it will be
declared as  returning a Fl_Window pointer.  The unnamed window
will be returned from it  (more than one unnamed window is
useless).  If the function contains  only named windows, it will
be declared as returning nothing (\c void ).

\par
It is possible to make the <tt>.cxx</tt> output be a
self-contained program  that can be compiled and executed.  This
is done by deleting the  function name so
\p main(argc,argv) is used.  The function will call
\p show() on all the windows it creates and then call
\p Fl::run().  This can also be used to test resize
behavior or other parts of the user  interface.

\par
You can change the function name by double-clicking on the
function.

\par New/Window

\par
Creates a new Fl_Window widget.  The window is added
to the currently selected  function, or to the function
containing the currently selected item.  The window will appear,
sized to 100x100. You can resize it to whatever size you
require.

\par
The widget panel will also appear and is described later in
this chapter.

\par New/...

\par
All other items on the New menu are subclasses of
Fl_Widget.  Creating them will add them to the
currently selected group or window, or the group or window
containing the currently selected widget.  The initial
dimensions and position are chosen by copying the current
widget, if possible.

\par
When you create the widget you will get the widget's control
panel, which is described later in this chapter.

\par Layout/Align/... 

\par
Align all selected widgets to the first widget in the selection.

\par Layout/Space Evenly/... 

\par
Space all selected widgets evenly inside the selected space.
Widgets will be sorted from first to last.

\par Layout/Make Same Size/... 

\par
Make all selected widgets the same size as the first selected widget.

\par Layout/Center in Group/... 

\par
Center all selected widgets relative to their parent widget

\par Layout/Grid... (Ctrl+g)

\par
Displays the grid settings panel. 
This panel
controls the grid that all widgets snap to when you move and
resize them, and for the "snap" which is how far a widget has to
be dragged from its original position to actually change.

\par Shell/Execute Command... (Alt+x)

\par
Displays the shell command panel. The shell command
is commonly used to run a 'make' script to compile the FLTK output.

\par Shell/Execute Again (Alt+g)

\par
Run the shell command again.

\par Help/About FLUID

\par
Pops up a panel showing the version of FLUID.

\par Help/On FLUID

\par
Shows this chapter of the manual.

\par Help/Manual

\par
Shows the contents page of the manual

\subsection fluid_widget_panel The Widget Panel

When you double-click on a widget or a set of widgets you
will get the "widget attribute panel".

When you change attributes using this panel, the changes are
reflected immediately in the window. It is useful to hit the
"no overlay" button (or type Ctrl+Shift+O) to hide the
red overlay so you can see the widgets more accurately,
especially when setting the box type.

If you have several widgets selected, they may have different
values for the fields.  In this case the value for \e one of
the widgets is shown.  But if you change this value, \e all
of the selected widgets are changed to the new value.

Hitting "OK" makes the changes permanent. 
Selecting a different widget also makes the changes permanent. 
FLUID checks for simple syntax errors such as mismatched
parenthesis in any code before saving any text.

"Revert" or "Cancel" put everything back
to when you last brought up the panel or hit OK.  However in the
current version of FLUID, changes to "visible"
attributes (such as the color, label, box) are not undone by
revert or cancel.  Changes to code like the callbacks are
undone, however.

<!-- NEW PAGE -->

\image html fluid_widget_gui.png "Figure 9-8: The FLUID widget GUI attributes"
\image latex fluid_widget_gui.png "The FLUID widget GUI attributes" width=10cm

\section fluid_widget_attributes GUI Attributes

\par Label (text field)

\par
String to print next to or inside the button. You can put
newlines into the string to make multiple lines. The easiest way
is by typing Ctrl+j.

\par
\ref common_labels "Symbols"
can be added to the label using the at sign ("@").

\par Label (pull down menu)

\par
How to draw the label.  Normal, shadowed, engraved, and
embossed change the appearance of the text.

\par Image

\par
The active image for the widget. Click on the
\b Browse... button to pick an image file using the file
chooser.

\par Inactive

\par
The inactive image for the widget. Click on the
\b Browse... button to pick an image file using the file
chooser.

\par Alignment (buttons)

\par
Where to draw the label.  The arrows put it on that side of the
widget, you can combine them to put it in the corner. The "box"
button puts the label inside the widget, rather than outside.

\par
The \b clip button clips the label to the widget box, the
\b wrap button wraps any text in the label, and the
<b>text image</b> button puts the text over the image instead of under
the image.

\par Position (text fields)

\par
The position fields show the current position and size of the
widget box. Enter new values to move and/or resize a widget.

\par Values (text fields)

\par
The values and limits of the current widget. Depending on the
type of widget, some or all of these fields may be inactive.

\par Shortcut

\par
The shortcut key to activate the widget. Click on the
shortcut button and press any key sequence to set the shortcut.

\par Attributes (buttons)

\par
The \b Visible button controls whether the widget is
visible (on) or hidden (off) initially.  Don't change this for
windows or for the immediate children of a Tabs group.

\par
The \b Active button controls whether the widget is
activated (on) or deactivated (off) initially. Most widgets
appear greyed out when deactivated.

\par
The \b Resizable button controls whether the window is
resizeable. In addition all the size changes of a window or
group will go "into" the resizable child.  If you have
a large data display surrounded by buttons, you probably want
that data area to be resizable. You can get more complex
behavior by making invisible boxes the resizable widget, or by
using hierarchies of groups.  Unfortunately the only way to test
it is to compile the program.  Resizing the FLUID window is
\e not the same as what will happen in the user program.

\par
The \b Hotspot button causes the parent window to be
positioned with that widget centered on the mouse.  This
position is determined <i>when the FLUID function is called</i>,
so you should call it immediately before showing the window.  If
you want the window to hide and then reappear at a new position,
you should have your program set the hotspot itself just before
\p show().

\par
The \b Border button turns the window manager border on
or off. On most window managers you will have to close the
window and reopen it to see the effect.

\par X Class (text field)

\par
The string typed into here is passed to the X window manager
as the class. This can change the icon or window decorations. 
On most (all?) window managers you will have to close the window
and reopen it to see the effect.

\image html fluid_widget_style.png "Figure 9-9: The FLUID widget Style attributes"
\image latex fluid_widget_style.png "The FLUID widget Style attributes" width=10cm

\subsection fluid_style_attributes Style Attributes

\par Label Font (pulldown menu)

\par
Font to draw the label in.  Ignored by symbols, bitmaps, and
pixmaps. Your program can change the actual font used by these
"slots" in case you want some font other than the 16
provided.

\par Label Size (pulldown menu)

\par
Pixel size (height) for the font to draw the label in. 
Ignored by symbols, bitmaps, and pixmaps.  To see the result
without dismissing the panel, type the new number and then Tab.

\par Label Color (button)

\par
Color to draw the label.  Ignored by pixmaps (bitmaps,
however, do use this color as the foreground color).

\par Box (pulldown menu)

\par
The boxtype to draw as a background for the widget.

\par
Many widgets will work, and draw faster, with a
"frame" instead of a "box".  A frame does
not draw the colored interior, leaving whatever was already
there visible.  Be careful, as FLUID may draw this ok but the
real program may leave unwanted stuff inside the widget.

\par
If a window is filled with child widgets, you can speed up
redrawing by changing the window's box type to
"NO_BOX".  FLUID will display a checkerboard for any
areas that are not colored in by boxes. Note that this
checkerboard is not drawn by the resulting program. Instead
random garbage will be displayed.

\par Down Box (pulldown menu)

\par
The boxtype to draw when a button is pressed or for some
parts of other widgets like scrollbars and valuators.

\par Color (button)

\par
The color to draw the box with.

\par Select Color (button)

\par
Some widgets will use this color for certain parts.  FLUID
does not always show the result of this: this is the color
buttons draw in when pushed down, and the color of input fields
when they have the focus.

\par Text Font, Size, and Color

\par
Some widgets display text, such as input fields, pull-down
menus, and browsers.

\image html fluid_widget_cxx.png "Figure 9-10: The FLUID widget C++ attributes"
\image latex fluid_widget_cxx.png "The FLUID widget C++ attributes" width=10cm

\subsection fluid_cpp_attributes C++ Attributes

\par Class

\par
This is how you use your own subclasses of
Fl_Widget.  Whatever identifier you type in here will
be the class that is instantiated.

\par
In addition, no \p \#include header file is put in the
<tt>.h</tt> file.  You must provide a \p \#include line as
the first line of the "Extra Code" which declares your
subclass.

\par
The class must be similar to the class you are spoofing.  It
does not have to be a subclass.  It is sometimes useful to
change this to another FLTK class. Currently the only way to get
a double-buffered window is to change this field for the window
to "Fl_Double_Window" and to add
\code #include <FL/Fl_Double_Window.h> \endcode
to the extra code.

\par Type (upper-right pulldown menu)

\par
Some classes have subtypes that modify their appearance or behavior.
You pick the subtype off of this menu.

\par Name (text field)

\par
Name of a variable to declare, and to store a pointer to this
widget into.  This variable will be of type "<class>*".  If the name is
blank then no variable is created.

\par
You can name several widgets with "name[0]", "name[1]", "name[2]",
etc.  This will cause FLUID to declare an array of pointers.  The array
is big enough that the highest number found can be stored.  All widgets
in the array must be the same type.

\par Public (button)

\par
Controls whether the widget is publicly accessible. When
embedding widgets in a C++ class, this controls whether the
widget is \p public or \p private in the class.
Otherwise it controls whether the widget is declared
\p static or global (\p extern ).

\par Extra Code (text fields)

\par
These four fields let you type in literal lines of code to
dump into the <tt>.h</tt> or <tt>.cxx</tt> files.

\par
If the text starts with a <tt>\#</tt> or the word
\p extern then FLUID thinks this is an "include"
line, and it is written to the <tt>.h</tt> file. If the same
include line occurs several times then only one copy is
written.

\par
All other lines are "code" lines.  The current
widget is pointed to by the local variable \p o.  The
window being constructed is pointed to by the local variable
\p w.  You can also access any arguments passed to the
function here, and any named widgets that are before this
one.

\par
FLUID will check for matching parenthesis, braces, and
quotes, but does not do much other error checking.  Be careful
here, as it may be hard to figure out what widget is producing
an error in the compiler. If you need more than four lines you
probably should call a function in your own <tt>.cxx</tt>
code.

\par Callback (text field)

\par
This can either be the name of a function, or a small snippet
of code. If you enter anything other than letters, numbers, and the
underscore then FLUID treats it as code.

\par
A name refers to a function in your own code.  It must be
declared as <tt>void name(<class>*,void*)</tt>.

\par
A code snippet is inserted into a static function in the
<tt>.cxx</tt> output  file.  The function prototype is
<tt>void name(class *o, void *v)</tt>
so that you can refer to the widget as \p o and the \p user_data()
as \p v.  FLUID will check for matching  parenthesis, braces,
and quotes, but does not do much other error  checking.  Be
careful here, as it may be hard to figure out what widget  is
producing an error in the compiler.

\par
If the callback is blank then no callback is set.

\par User Data (text field)

\par
This is a value for the \p user_data() of the widget. 
If blank the default value of zero is used.  This can be any
piece of C code that can be cast to a \p void pointer.

\par Type (text field)

\par
The \p void* in the callback function prototypes is
replaced with this. You may want to use \p long for old
XForms code.  Be warned that anything other than \p void*
is not guaranteed to work! However on most architectures other
pointer types are ok, and \p long is usually ok, too.

\par When (pulldown menu)

\par
When to do the callback. This can be \b Never,
\b Changed, \b Release, or \b Enter Key. The value of
<b>Enter Key</b> is only useful for text input fields.

\par
There are other rare but useful values for the
\p when() field that are not in the menu. You should use
the extra code fields to put these values in.

\par No Change (button)

\par
The <b>No Change</b> button means the callback is done on the
matching event even if the data is not changed.

\section fluid_selecting_moving Selecting and Moving Widgets

Double-clicking a window name in the browser will display it,
if not displayed yet.  From this display you can select widgets,
sets of widgets, and move or resize them.  To close a window
either double-click it or type \c ESC.

To select a widget, click it. To select several widgets drag
a rectangle around them.  Holding down shift will toggle the
selection of the widgets instead.

You cannot pick hidden widgets.  You also cannot choose some
widgets if they are completely overlapped by later widgets.  Use
the browser to select these widgets.

The selected widgets are shown with a red "overlay"
line around them.  You can move the widgets by dragging this
box.  Or you can resize them by dragging the outer edges and
corners.  Hold down the Alt key while dragging the mouse to
defeat the snap-to-grid effect for fine positioning.

If there is a tab box displayed you can change which child is
visible by clicking on the file tabs.  The child you pick is
selected.

The arrow, tab, and shift+tab keys "navigate" the
selection.  Left, right, tab, or shift+tab move to the next or
previous widgets in the hierarchy.  Hit the right arrow enough
and you will select every widget in the window.  Up/down widgets
move to the previous/next widgets that overlap horizontally.  If
the navigation does not seem to work you probably need to
"Sort" the widgets.  This is important if you have
input fields, as FLTK uses the same rules when using arrow keys
to move between input fields.

To "open" a widget, double click it.  To open
several widgets select them and then type F1 or pick
"Edit/Open" off the pop-up menu.

Type Ctrl+o to temporarily toggle the overlay off without
changing the selection, so you can see the widget borders.

You can resize the window by using the window manager border
controls.  FLTK will attempt to round the window size to the
nearest multiple of the grid size and makes it big enough to
contain all the widgets (it does this using illegal X methods,
so it is possible it will barf with some window managers!). 
Notice that the actual window in your program may not be
resizable, and if it is, the effect on child widgets may be
different.

The panel for the window (which you get by double-clicking
it) is almost identical to the panel for any other Fl_Widget. 
There are three extra items:

\section fluid_images Image Labels

The \e contents of the image files in the \b Image
and \b Inactive text fields are written to the <tt>.cxx</tt>
file. If many widgets share the same image then only one copy is
written. Since the image data is embedded in the generated
source code, you need only distribute the C++ code and not the
image files themselves.

However, the \e filenames are stored in the <tt>.fl</tt>
file so you will need the image files as well to read the
<tt>.fl</tt> file. Filenames are relative to the location of the
<tt>.fl</tt> file and not necessarily the current directory. We
recommend you either put the images in the same directory as the
<tt>.fl</tt> file, or use absolute path names.

\par Notes for All Image Types

\par
FLUID runs using the default visual of your X server. This
may be 8 bits, which will give you dithered images. You may get
better results in your actual program by adding the code
"Fl::visual(FL_RGB)" to your code right before the
first window is displayed.

\par
All widgets with the same image on them share the same code
and source X pixmap. Thus once you have put an image on a
widget, it is nearly free to put the same image on many other
widgets.

\par
If you edit an image at the same time you are using it in FLUID,
the only way to convince FLUID to read the image file again is to
remove the image from all widgets that are using it or re-load the
<tt>.fl</tt> file.

\par
Don't rely on how FLTK crops images that are outside the
widget, as this may change in future versions! The cropping of
inside labels will probably be unchanged.

\par
To more accurately place images, make a new "box"
widget and put the image in that as the label.

\par XBM (X Bitmap) Files

\par
FLUID reads X bitmap files which use C source code to define
a bitmap. Sometimes they are stored with the ".h" or
".bm" extension rather than the standard
".xbm" extension.

\par
FLUID writes code to construct an Fl_Bitmap image and use it
to label the widget. The '1' bits in the bitmap are drawn using
the label color of the widget. You can change this color in the
FLUID widget attributes panel. The '0' bits are transparent.

\par
The program "bitmap" on the X distribution does an
adequate job of editing bitmaps.

\par XPM (X Pixmap) Files

\par
FLUID reads X pixmap files as used by the \p libxpm
library. These files use C source code to define a pixmap. The
filenames usually have the ".xpm" extension.

\par
FLUID writes code to construct an Fl_Pixmap image and use it
to label the widget. The label color of the widget is ignored,
even for 2-color images that could be a bitmap. XPM files can
mark a single color as being transparent, and FLTK uses this
information to generate a transparency mask for the image.

\par
We have not found any good editors for small iconic pictures.
For pixmaps we have used
<A href="http://home.worldonline.dk/~torsten/xpaint/index.html">XPaint</A>
and the KDE icon editor.

\par BMP Files

\par
FLUID reads Windows BMP image files which are often used in
WIN32 applications for icons. FLUID converts BMP files into
(modified) XPM format and uses a Fl_BMP_Image image to label the
widget. Transparency is handled the same as for XPM files. All
image data is uncompressed when written to the source file, so
the code may be much bigger than the <tt>.bmp</tt> file.

\par GIF Files

\par
FLUID reads GIF image files which are often used in HTML
documents to make icons. FLUID converts GIF files into
(modified) XPM format and uses a Fl_GIF_Image image to label the
widget. Transparency is handled the same as for XPM files. All
image data is uncompressed when written to the source file, so
the code may be much bigger than the <tt>.gif</tt> file. Only
the first image of an animated GIF file is used.

\par JPEG Files

\par
If FLTK is compiled with JPEG support, FLUID can read JPEG
image files which are often used for digital photos. FLUID uses
a Fl_JPEG_Image image to label the widget, and writes
uncompressed RGB or grayscale data to the source file.

\par PNG (Portable Network Graphics) Files

\par
If FLTK is compiled with PNG support, FLUID can read PNG
image files which are often used in HTML documents. FLUID uses a
Fl_PNG_Image image to label the widget, and writes uncompressed
RGB or grayscale data to the source file. PNG images can provide
a full alpha channel for partial transparency, and FLTK supports
this as best as possible on each platform.

\section fluid_i18n Internationalization with FLUID

FLUID supports internationalization (I18N for short) of label
strings used by widgets. The preferences window
(<tt>Ctrl+p</tt>) provides access to the I18N options.

\subsection fluid_i18n_methods I18N Methods

FLUID supports three methods of I18N: use none, use GNU
gettext, and use POSIX catgets. The "use none" method is the
default and just passes the label strings as-is to the widget
constructors.

The "GNU gettext" method uses GNU gettext (or a similar
text-based I18N library) to retrieve a localized string before
calling the widget constructor.

The "POSIX catgets" method uses the POSIX catgets function to
retrieve a numbered message from a message catalog before
calling the widget constructor.

\subsection fluid_gettext_i18n Using GNU gettext for I18N

FLUID's code support for GNU gettext is limited to calling a
function or macro to retrieve the localized label; you still
need to call \p setlocale() and \p textdomain() or
\p bindtextdomain() to select the appropriate language and
message file.

To use GNU gettext for I18N, open the preferences window and
choose "GNU gettext" from the \b Use: chooser. Two new input
fields will then appear to control the include file and
function/macro name to use when retrieving the localized label
strings.

 \image html fluid-gettext.png "Figure 9-11: Internationalization using GNU gettext"
 \image latex fluid-gettext.png "Internationalization using GNU gettext" width=10cm

The \b \#include
field controls the header file to include for
I18N; by default this is \b <libintl.h>, the
standard I18N file for GNU gettext.

The \b Function: field controls the function (or macro) that
will retrieve the localized message; by default the
\p gettext function will be called.

\subsection fluid_catgets_i18n Using POSIX catgets for I18N

FLUID's code support for POSIX catgets allows you to use a
global message file for all interfaces or a file specific to
each <tt>.fl</tt> file; you still need to call
\p setlocale() to select the appropriate language.

To use POSIX catgets for I18N, open the preferences window
and choose "POSIX catgets" from the \b Use: chooser. Three new
input fields will then appear to control the include file,
catalog file, and set number for retrieving the localized label
strings.

 \image html fluid-catgets.png "Figure 9-12: Internationalization using POSIX catgets"
 \image latex fluid-catgets.png "Internationalization using POSIX catgets" width=10cm

The \b \#include
field controls the header file to include for
I18N; by default this is \b <nl_types.h>, the
standard I18N file for POSIX catgets.

The \b File: field controls the name of the catalog file
variable to use when retrieving localized messages; by default
the file field is empty which forces a local (static) catalog
file to be used for all of the windows defined in your
<tt>.fl</tt> file.

The \b Set: field controls the set number in the catalog file.
The default set is 1 and rarely needs to be changed.

\section fluid_limitations Known limitations

Declaration Blocks can be used to temporarily block out already
designed code using <tt>\#if 0</tt> and <tt>\#endif</tt>
type construction. This will effectively avoid compilation of
blocks of code. However, static code and data generated by this
segment (menu items, images, include statements, etc.) will still
be generated and likely cause compile-time warnings.


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