This appendix describes the operating system specific interfaces in FLTK.
All programs that need to access the operating system specific interfaces must include the following header file:
#include <FL/x.H>
Despite the name, this header file will define the appropriate interface for your environment. The pages that follow describe the functionality that is provided for each operating system.
| WARNING:
The interfaces provided by this header file may change radically in new FLTK releases. Use them only when an existing generic FLTK interface is not sufficient. |
The UNIX interface provides access to the X Window System state information and data structures.
Installs a function to parse unrecognized events. If FLTK cannot figure out what to do with an event, it calls each of these functions (most recent first) until one of them returns non-zero. If none of them returns non-zero then the event is ignored.
FLTK calls this for any X events it does not recognize, or X events with a window ID that FLTK does not recognize. You can look at the X event in the fl_xevent variable.
The argument is the FLTK event type that was not handled, or zero for unrecognized X events. These handlers are also called for global shortcuts and some other events that the widget they were passed to did not handle, for example FL_SHORTCUT.
This variable contains the most recent X event.
This variable contains the time stamp from the most recent X event that reported it; not all events do. Many X calls like cut and paste need this value.
Returns the XID for a window, or zero if not shown().
Returns the Fl_Window that corresponds to the given XID, or NULL if not found. This function uses a cache so it is slightly faster than iterating through the windows yourself.
This call allows you to supply the X events to FLTK, which may allow FLTK to cooperate with another toolkit or library. The return value is non-zero if FLTK understood the event. If the window does not belong to FLTK and the add_handler() functions all return 0, this function will return false.
Besides feeding events your code should call Fl::flush() periodically so that FLTK redraws its windows.
This function will call the callback functions. It will not return until they complete. In particular, if a callback pops up a modal window by calling fl_ask(), for instance, it will not return until the modal function returns.
The following global variables are set before Fl_Widget::draw() is called, or by Fl_Window::make_current():
extern Display *fl_display; extern Window fl_window; extern GC fl_gc; extern int fl_screen; extern XVisualInfo *fl_visual; extern Colormap fl_colormap;
You must use them to produce Xlib calls. Don't attempt to change them. A typical X drawing call is written like this:
XDrawSomething(fl_display, fl_window, fl_gc, ...);
Other information such as the position or size of the X window can be found by looking at Fl_Window::current(), which returns a pointer to the Fl_Window being drawn.
Returns the X pixel number used to draw the given FLTK color index or RGB color. This is the X pixel that fl_color() would use.
Points to the font selected by the most recent fl_font(). This is not necessarily the current font of fl_gc, which is not set until fl_draw() is called.
FLTK uses only a single display, screen, X visual, and X colormap. This greatly simplifies its internal structure and makes it much smaller and faster. You can change which it uses by setting global variables before the first Fl_Window::show() is called. You may also want to call Fl::visual(), which is a portable interface to get a full color and/or double buffered visual.
Set which X display to use. This actually does putenv("DISPLAY=...") so that child programs will display on the same screen if called with exec(). This must be done before the display is opened. This call is provided under MacOS and WIN32 but it has no effect.
The open X display. This is needed as an argument to most Xlib calls. Don't attempt to change it! This is NULL before the display is opened.
Opens the display. Does nothing if it is already open. This will make sure fl_display is non-zero. You should call this if you wish to do X calls and there is a chance that your code will be called before the first show() of a window.
This may call Fl::abort() if there is an error opening the display.
This closes the X connection. You do not need to call this to exit, and in fact it is faster to not do so! It may be useful to call this if you want your program to continue without the X connection. You cannot open the display again, and probably cannot call any FLTK functions.
Which screen number to use. This is set by fl_open_display() to the default screen. You can change it by setting this to a different value immediately afterwards. It can also be set by changing the last number in the Fl::display() string to "host:0.#".
The visual and colormap that FLTK will use for all windows. These are set by fl_open_display() to the default visual and colormap. You can change them before calling show() on the first window. Typical code for changing the default visual is:
Fl::args(argc, argv); // do this first so $DISPLAY is set
fl_open_display();
fl_visual = find_a_good_visual(fl_display, fl_screen);
if (!fl_visual) Fl::abort("No good visual");
fl_colormap = make_a_colormap(fl_display, fl_visual->visual, fl_visual->depth);
// it is now ok to show() windows:
window->show(argc, argv);
FLTK can manage an X window on a different screen, visual and/or colormap, you just can't use FLTK's drawing routines to draw into it. But you can write your own draw() method that uses Xlib (and/or OpenGL) calls only.
FLTK can also manage XID's provided by other libraries or programs, and call those libraries when the window needs to be redrawn.
To do this, you need to make a subclass of Fl_Window and override some of these virtual functions:
If the window is already shown() this must cause it to be raised, this can usually be done by calling Fl_Window::show(). If not shown() your implementation must call either Fl_X::set_xid() or Fl_X::make_xid().
An example:
void MyWindow::show() {
if (shown()) {Fl_Window::show(); return;} // you must do this!
fl_open_display(); // necessary if this is first window
// we only calcualte the necessary visual colormap once:
static XVisualInfo *visual;
static Colormap colormap;
if (!visual) {
visual = figure_out_visual();
colormap = XCreateColormap(fl_display, RootWindow(fl_display,fl_screen),
vis->visual, AllocNone);
}
Fl_X::make_xid(this, visual, colormap);
}
Allocate a hidden structure called an Fl_X, put the XID into it, and set a pointer to it from the Fl_Window. This causes Fl_Window::shown() to return true.
This static method does the most onerous parts of creating an X window, including setting the label, resize limitations, etc. It then does Fl_X::set_xid() with this new window and maps the window.
This virtual function is called by Fl::flush() to update the window. For FLTK's own windows it does this by setting the global variables fl_window and fl_gc and then calling the draw() method. For your own windows you might just want to put all the drawing code in here.
The X region that is a combination of all damage() calls done so far is in Fl_X::i(this)->region. If NULL then you should redraw the entire window. The undocumented function fl_clip_region(XRegion) will initialize the FLTK clip stack with a region or NULL for no clipping. You must set region to NULL afterwards as fl_clip_region() will own and delete it when done.
If damage() & FL_DAMAGE_EXPOSE then only X expose events have happened. This may be useful if you have an undamaged image (such as a backing buffer) around.
Here is a sample where an undamaged image is kept somewhere:
void MyWindow::flush() {
fl_clip_region(Fl_X::i(this)->region);
Fl_X::i(this)->region = 0;
if (damage() != 2) {... draw things into backing store ...}
... copy backing store to window ...
}
Destroy the window server copy of the window. Usually you will destroy contexts, pixmaps, or other resources used by the window, and then call Fl_Window::hide() to get rid of the main window identified by xid(). If you override this, you must also override the destructor as shown:
void MyWindow::hide() {
if (mypixmap) {
XFreePixmap(fl_display,mypixmap);
mypixmap = 0;
}
Fl_Window::hide(); // you must call this
}
Because of the way C++ works, if you override hide() you must override the destructor as well (otherwise only the base class hide() is called):
MyWindow::~MyWindow() {
hide();
}
FLTK currently supports setting a window's icon *before* it is shown using the Fl_Window::icon() method.
Sets the icon for the window to the passed pointer. You will need to cast the icon Pixmap to a char * when calling this method. To set the icon using a bitmap compiled with your application use:
#include "icon.xbm"
Pixmap p = XCreateBitmapFromData(fl_display, DefaultRootWindow(fl_display),
icon_bits, icon_width, icon_height);
window->icon((char *)p);
| NOTE:
You must call Fl_Window::show(argc, argv) for the icon to be used. The Fl_Window::show() method does not bind the icon to the window. |
The Windows interface provides access to the WIN32 GDI state information and data structures.
By default a single WNDCLASSEX called "FLTK" is created. All Fl_Window's are of this class unless you use Fl_Window::xclass(). The window class is created the first time Fl_Window::show() is called.
You can probably combine FLTK with other libraries that make their own WIN32 window classes. The easiest way is to call Fl::wait(), as it will call DispatchMessage for all messages to the other windows. If necessary you can let the other library take over as long as it calls DispatchMessage(), but you will have to arrange for the function Fl::flush() to be called regularly so that widgets are updated, timeouts are handled, and the idle functions are called.
This variable contains the most recent message read by GetMessage, which is called by Fl::wait(). This may not be the most recent message sent to an FLTK window, because silly WIN32 calls the handle procedures directly for some events (sigh).
Installs a function to parse unrecognized messages sent to FLTK windows. If FLTK cannot figure out what to do with a message, it calls each of these functions (most recent first) until one of them returns non-zero. The argument passed to the functions is the FLTK event that was not handled or zero for unknown messages. If all the handlers return zero then FLTK calls DefWindowProc().
Returns the window handle for a Fl_Window, or zero if not shown().
Returns the Fl_Window that corresponds to the given window handle, or NULL if not found. This function uses a cache so it is slightly faster than iterating through the windows yourself.
When the virtual function Fl_Widget::draw() is called, FLTK stores all the silly extra arguments you need to make a proper GDI call in some global variables:
extern HINSTANCE fl_display; extern HWND fl_window; extern HDC fl_gc; COLORREF fl_RGB(); HPEN fl_pen(); HBRUSH fl_brush();
These global variables are set before draw() is called, or by Fl_Window::make_current(). You can refer to them when needed to produce GDI calls, but don't attempt to change them. The functions return GDI objects for the current color set by fl_color() and are created as needed and cached. A typical GDI drawing call is written like this:
DrawSomething(fl_gc, ..., fl_brush());
It may also be useful to refer to Fl_Window::current() to get the window's size or position.
FLTK currently supports setting a window's icon *before* it is shown using the Fl_Window::icon() method.
Sets the icon for the window to the passed pointer. You will need to cast the HICON handle to a char * when calling this method. To set the icon using an icon resource compiled with your application use:
window->icon((char *)LoadIcon(fl_display, MAKEINTRESOURCE(IDI_ICON)));
You can also use the LoadImage() and related functions to load specific resolutions or create the icon from bitmap data.
| NOTE:
You must call Fl_Window::show(argc, argv) for the icon to be used. The Fl_Window::show() method does not bind the icon to the window. |
WIN32 has a really stupid mode switch stored in the executables that controls whether or not to make a console window.
To always get a console window you simply create a console application (the "/SUBSYSTEM:CONSOLE" option for the linker). For a GUI-only application create a WIN32 application (the "/SUBSYSTEM:WINDOWS" option for the linker).
FLTK includes a WinMain() function that calls the ANSI standard main() entry point for you. This function creates a console window when you use the debug version of the library.
WIN32 applications without a console cannot write to stdout or stderr, even if they are run from a console window. Any output is silently thrown away. Additionally, WIN32 applications are run in the background by the console, although you can use "start /wait program" to run them in the foreground.
The following is a list of known bugs and problems in the WIN32 version of FLTK:
FLTK supports MacOS 8.6, MacOS 9 and MacOS X using the Apple Carbon library. When compiled with MPW or MetroWerks' CodeWarrior, application binaries in CFM format will run on all the above systems without changes. The OS X GNU (gcc) compiler, however, creates Mach-O binaries which are not supported by MacOS 9 and earlier.
Returns the window reference for an Fl_Window, or NULL if the window has not been shown.
Returns the Fl_Window that corresponds to the give window handle, or NULL if not found. FLTK windows that are children of top-level windows share the WindowRef of the top-level window.
When the virtual function Fl_Widget::draw() is called, FLTK has prepared the Window and CGrafPort for drawing. Clipping and offsets are prepared to allow correct subwindow drawing.
OS X doublebuffers all windows automatically. On OS X, Fl_Window and Fl_Double_Window are handled internally in the same way.
FLTK does not access the resource fork of an application. However, a minimal resource fork must be created for OS 8 and OS X applications.
FLTK uses UNIX-style filenames and paths.
The following is a list of known bugs and problems in the MacOS version of FLTK: