class Fl
This appendix describes all of the fltk::foo()
functions. These functions mostly are concerned with event handling
and waiting for events. fltk:: should be considered a
C++ "namespace". However it is implemented as a class with no
instance variables and only static methods, in order to work with
older C++ compilers that do not handle namespaces.
FLTK also provides a number of global functions with
fltk::xyz names. The majority of these are concerned with
drawing or graphics state, and are described in the Drawing appendix. The others are a set of
modal popup utility functions for asking questions described in the Utility appendix.
Returns the version number of fltk. This can be compared to the value
of the fltk::VERSION macro to see if the shared library of fltk your
program linked with is up to date.
The FLTK version number is stored in a number of compile-time
constants:
- fltk::MAJOR_VERSION - The major release number, currently 2.
- fltk::MINOR_VERSION - The minor release number, currently 0.
- fltk::PATCH_VERSION - The patch release number, currently 1.
- fltk::VERSION - A combined floating-point version number
of the form M.mmpp where M is the major number, mm is the minor
number, and pp is the patch number, currently 2.0001.
Sets the X display to use for all windows. Actually this just sets
the environment variable $DISPLAY to the passed string, so this only
works before you show() the first window or otherwise open the display,
and does nothing useful under WIN32.
This call may be useful on multi-visual X servers to change from the
default to a more useful color mode. You must call this before you
show() any windows. The integer argument is an 'or' of the following:
- fltk::INDEX indicates that a colormapped visual is ok. This
call will normally fail if a TrueColor visual cannot be found.
- fltk::RGB this value is zero and may be passed to indicate
that fltk::INDEX is not wanted.
- fltk::RGB8 indicates that the TrueColor visual must have at
least 8 bits of red, green, and blue (Windows calls this "millions of
colors").
- fltk::DOUBLE indicates that hardware accelerated double
buffering is wanted. This will make fltk::DoubleBufferWindow work better.
This returns true if the system has the capabilities by default or
FLTK suceeded in turing them on. Your program will still work even if
this returns false (it just won't look as good). On non-X systems
this just returns true or false indicating if the system supports the
passed values.
This does the same thing as fltk::visual(int) but also requires OpenGL
drawing to work. Doing this on X will reduce colormap flashing at the
edges of fltk::GlWindows when
they are inside regular windows.
See fltk::GlWindow
for a list of additional values for the argument.
This function seems to have been renamed fltk::gl_visual(int).
Makes FLTK use its own colormap. This may make FLTK display better
and will reduce conflicts with other programs that want lots of colors.
However the colors may flash as you move the cursor between windows.
This does nothing if the current visual is not colormapped.
Return a structure of information describing the current state of the
screen. Currently this structure contains the following (this may be
added to in the future):
- int x left edge of work area
- int y top edge of work area
- int w width of work area
- int h height of work area
- int width full screen width in pixels
- int height full screen height in pixels
- int depth bits per pixel
- float dpi_x pixels per inch horizontally
- float dpi_y pixels per inch vertically
Same as fltk::wait(infinity). Call this repeatedly to "run"
your program. You can also check what happened each time after this
returns, which is quite useful for managing program state.
int fltk::wait(float time)
Waits until "something happens", or the given time interval passes.
It can return much sooner than the time if something happens.
What this really does is call all idle callbacks, all elapsed
timeouts, call fltk::flush() to get the screen to update, and
then wait some time (zero if there are idle callbacks, the shortest of
all pending timeouts, or the given time), for any events from the user
or any fltk::add_fd() callbacks. It then handles the events
and calls the callbacks and then returns.
The return value is non-zero if there are any visible windows (this
may change in future versions of fltk).
The return value is whatever the select() system call returned.
This will be negative if there was an error (this will happen on Unix
if a signal happens), zero if the timeout occurred, and positive if
any events or fd's came in.
On Win32 the return value is zero if nothing happened and
time is 0.0. Otherwise 1 is returned.
Same as fltk::wait(0). Calling this during a big calculation
will keep the screen up to date and the interface responsive:
while (!calculation_done()) {
calculate();
fltk::check();
if (user_hit_abort_button()) break;
}
This is similar to fltk::check() except this does not
call fltk::flush() and thus does not draw anything, and does
not read any events or call any callbacks. This returns true if fltk::check() would do anything (it will
continue to return true until you call fltk::check() or
fltk::wait()).
This is useful if your program is in a state where such callbacks
are illegal, or because the expense of redrawing the screen is much
greater than the expense of your calculation.
while (!calculation_done()) {
calculate();
if (fltk::ready()) {
do_expensive_cleanup();
fltk::check();
if (user_hit_abort_button()) break;
}
}
Calls fltk::wait() as long as any windows are
not closed. When all the windows are hidden by fltk::Window::hide() (which is
normally called by the user closing them with the close box) this will
return with zero. A program can also exit by having a callback call
exit() or abort().
Most fltk programs will end
main() with return fltk::run();.
First thing: much of the time fltk::Window::exec() will do what
you want, so try using that.
This function sets the passed widget as the "modal widget". All
user events are directed to it or a child of it, preventing the user
from messing with other widgets. The modal widget does not have to be
visible or even a child of an fltk::Window for this to work (but if it
not visible, fltk::event_x() and fltk::event_y() are meaningless, use
fltk::event_x_root() and fltk::event_y_root()).
fltk::exit_modal() sets the
fltk::exit_modal_flag(). This may be used by user callbacks to
cancel modal state. The flag is also set by the destruction or hiding
of the modal widget, and on Windows by other applications taking the
focus when grab is on.
The calling code then loops calling fltk::wait() until fltk::exit_modal_flag() is set
or you otherwise decide to get out of the modal state. It is the
calling code's responsibility to monitor this flag and restore the
modal widget to it's previous value when it turns on.
fltk::modal() returns the current modal widget, or null if
there isn't one, and fltk::grab() returns the current value of
grab (this is always false if the modal widget is null). It is useful
to test these in timeouts and file descriptor callbacks in order to
block actions that should not happen while the modal window is up. You
also need these in order to save and restore the modal state.
grab indicates that the modal widget should get events from
anywhere on the screen. This is done by messing with the window
system. If fltk::exit_modal() is called in response to an
fltk::PUSH event (rather than waiting for the drag or release event) fltk
will "repost" the event so that it is handled after modal state is
exited. This may also be done for keystrokes in the future.
On both X and WIN32 grab will not work unless you have some
visible window because the system interface needs a visible window id.
On X be careful that your program does not enter an infinite loop
while grab() is on, it will lock up your screen!
Add a one-shot timeout callback. The function will be called by
fltk::wait() at t seconds after this function is called.
The optional void* argument is passed to the callback.
Inside a timeout callback you can call this to add another timeout.
Rather than the time being measured from "now", it is measured from
when the system call elapsed that caused this timeout to be called. This
will result in far more accurate spacing of the timeout callbacks, it
also has slightly less system call overhead. (It will also use all
your machine time if your timeout code and fltk's overhead take more
than t seconds, as the real timeout will be reduced to zero).
It is undefined what this does if called from outside a timeout
callback.
This code will print "TICK" each second on stdout, with a
fair degree of accuracy:
void callback(void*) {
printf("TICK\n");
fltk::repeat_timeout(1.0,callback);
}
main() {
fltk::add_timeout(1.0,callback);
for (;;) fltk::wait();
}
Returns true if the timeout exists and has not been called yet.
Removes a timeout callback. It is harmless to remove a timeout
callback that no longer exists.
Fltk will call this callback just before it flushes the display and
waits for events. This is different than an idle callback because it
is only called once, then fltk calls the system and tells it not to
return until an event happens.
This can be used by code that wants to monitor the
application's state, such as to keep a display up to date. The
advantage of using a check callback is that it is called only when no
events are pending. If events are coming in quickly, whole blocks of
them will be processed before this is called once. This can save
significant time and avoid the application falling behind the events.
Sample code:
bool state_changed; // anything that changes the display turns this on
void callback(void*) {
if (!state_changed) return;
state_changed = false;
do_expensive_calculation();
widget->redraw();
}
main() {
fltk::add_check(1.0,callback);
return fltk::run();
}
Returns true if the check exists and has not been called yet.
Removes a check callback. It is harmless to remove a check
callback that does not exist.
Add file descriptor fd to listen to. When the fd
becomes ready for reading fltk::wait() will
call the callback and then return. The callback is passed the
fd and the arbitrary void* argument.
The second version takes a when bitfield to indicate when
the callback should be done. You can or these together to make the
callback be called for multiple conditions:
- fltk::READ - Call the callback when there is data to be read.
- fltk::WRITE - Call the callback when data can be written without blocking.
- fltk::EXCEPT - Call the callback if an exception occurs on the file.
Under UNIX any file descriptor can be monitored (files,
devices, pipes, sockets, etc.) Due to limitations in Microsoft
Windows, WIN32 applications can only monitor sockets (? and is the
when value ignored?)
Remove all the callbacks (ie for all different when
values) for the given file descriptor. It is harmless to call this if
there are no callbacks for the file descriptor. If when is
given then those bits are removed from each callback for the file
descriptor, and the callback removed only if all of the bits turn off.
Adds a callback function that is called every time by
fltk::wait() and also makes it act as though the timeout is
zero (this makes fltk::wait() return immediately, so if it is
in a loop it is called repeatedly, and thus the idle fucntion is
called repeatedly). The idle function can be used to get background
processing done.
You can have multiple idle callbacks. To remove an idle callback use fltk::remove_idle().
fltk::wait() and fltk::check() call idle callbacks, but
fltk::ready() does not.
The idle callback can call any FLTK functions, including fltk::wait(), fltk::check(), and fltk::ready(). Fltk will not recursively call
the idle callback.
Returns true if the specified idle callback is currently installed.
Removes the specified idle callback, if it is installed.
True if any fltk::Widget::redraw() calls have
been done since the last flush().
Redraws all widgets. This is a good idea if you have made global
changes to the styles.
Causes all the windows that need it to be redrawn and graphics forced
out through the pipes. This is what wait() does before
looking for events.
Returns the id of some visible() window. If there is more than one,
the last one to receive an event is returned. This is useful for
setting the fltk::Window::child_of()
for dialog boxes that are used in multiple places in your program, and
is used by fltk::Window::exec() if no
other parent is specified.
If this window is visible, this removes it from wherever it is in the
list and inserts it at the top, as though it received an event. This
can be used to change the parent of dialog boxes run by fltk::Window::exec() or fltk::ask().
Returns the next visible() top-level window, returns NULL after the
last one. You can use this and first_window() to iterate through all
the visible windows.
Returns the most recent event handled, such as fltk::PUSH or
fltk::KEY. This is useful so callbacks can find out why
they were called.
Returns the mouse position of the event relative to the fltk::Window
it was passed to.
For fltk::MOUSEWHEEL events this is how many clicks the user
moved in the x and y directions (currently dx is always zero).
Returns the mouse position on the screen of the event. To find the
absolute position of an fltk::Window on the screen, use the
difference between event_x_root(),event_y_root() and
event_x(),event_y().
Returns the number of times the last mouse button or keyboard key
was pushed while fltk::event_is_click()
was true.
For a normal fltk::PUSH this is zero, if the user
"double-clicks" this is one, and it is N-1 for each subsequent
click. This is also used to see if the keyboard is repeating, if the
most recent fltk::KEY was caused by a repeating key this is
non-zero, and is N-1 for N repeats of the key.
Setting this value with fltk::event_clicks(n) can be used to
make callbacks think things were (or were not) double-clicked.
This is true if the time and mouse movement since the last
fltk::PUSH or fltk::KEY is short enough that the user is
intending to "click". After enough time or after enough mouse movement
this turns off.
The main use of this is to decide whether to increment fltk::event_clicks() when the user
clicks the mouse. But you can also test this on a fltk::RELEASE
or fltk::KEYUP event to decide if the user clicked quickly,
versus holding the mouse or key down.
You can set this to zero with fltk::event_is_click(0), this
can be used to prevent the next mouse click from being considered a
double click. It is not possible to set this true because the saved
time and position are inaccessible.
Returns which mouse button was last pushed or released. You can use
numerical constants or these values:
- fltk::LEFT_MOUSE 1
- fltk::MIDDLE_MOUSE 2
- fltk::RIGHT_MOUSE 3
This is a bitfield of what shift states were on and what mouse buttons
were held down during the most recent event. The second version
returns true if any of the passed bits are turned on. The legal
bits are:
- fltk::SHIFT - One of the shift keys is down.
- fltk::CAPS_LOCK - The caps lock is on.
- fltk::CTRL - One of the ctrl keys is down.
- fltk::ALT - One of the alt keys is down.
- fltk::NUM_LOCK - The num lock is on.
- fltk::WIN - One of the Windows keys is down.
- fltk::SCROLL_LOCK - The scroll lock is on.
- fltk::BUTTON1 - Mouse button 1 is pushed.
- fltk::BUTTON2 - Mouse button 2 is pushed.
- fltk::BUTTON3 - Mouse button 3 is pushed.
- fltk::BUTTONS - Any mouse button is pushed.
- fltk::BUTTON(n) - Mouse button n is pushed.
X servers do not agree on shift states, so fltk::NUM_LOCK, fltk::WIN, and
fltk::SCROLL_LOCK may not work. The values were selected to match the
XFree86 server on Linux. In addition there is a bug in the way X
works so that the shift state is not correctly reported until the
first event after the shift key is pressed or released.
Returns which key on the keyboard was last pushed. fltk::FOCUS
events produced by the system, and mouse button events, set this to
values that cannot be confused with keys, to allow a widget to
determine if the focus is being changed due to a keystroke and what
keystroke that was.
Keys are identified by the unshifted values. FLTK defines a
set of symbols that should work on most modern machines for every key
on the keyboard:
- 'a' through 'z',
'0' through '9',
'`',
'-',
'=',
'[',
']',
'\\',
';',
'\'',
',',
'.',
'/' -
All keys on the main keyboard producing a printable ASCII
character use the value of that ASCII character (as though shift,
ctrl, and caps lock were not on).
- fltk::Space - The space key, same as ' ' or 32.
- fltk::BackSpace - The backspace key.
- fltk::Tab - The tab key.
- fltk::Enter - The enter key.
- fltk::Pause - The pause key.
- fltk::Scroll_Lock - The scroll lock key.
- fltk::Escape - The escape key.
- fltk::Home - The home key.
- fltk::Left - The left arrow key.
- fltk::Up - The up arrow key.
- fltk::Right - The right arrow key.
- fltk::Down - The down arrow key.
- fltk::Page_Up - The page-up key.
- fltk::Page_Down - The page-down key.
- fltk::End - The end key.
- fltk::Print - The print (or print-screen) key.
- fltk::Insert - The insert key.
- fltk::Menu - The menu key.
- fltk::Num_Lock - The num lock key.
- fltk::KP(c) - One of the keypad numbers, for instance
fltk::KP('5') is the 5 key
- fltk::KP_Enter - Same as fltk::KP('\r'), the enter key on the keypad.
- fltk::KP_Last - All keypad keys are in the range fltk::KP(0),fltk::KP_Last
- fltk::F(n) - A numbered function key, for instance
fltk::F(2) is the F2 key.
- fltk::F_Last - All function keys are in the range fltk::F(0),fltk::F_Last
- fltk::Shift_L - The lefthand shift key.
- fltk::Shift_R - The righthand shift key.
- fltk::Control_L - The lefthand control key.
- fltk::Control_R - The righthand control key.
- fltk::Caps_Lock - The caps lock key.
- fltk::Alt_L - The left alt key.
- fltk::Alt_R - The right alt key.
- fltk::Win_L - The left Windows key.
- fltk::Win_R - The right Windows key.
- fltk::Delete - The delete key.
- On X systems any unrecognized keys are reported as their X keysym
value.
Returns true if the given key was held down (or pressed)
during the last event. This is constant until the next event
is read from the server. The possible values for the key are listed
above.
On Win32 fltk::event_key_state(fltk::KP_Enter) does not work.
Returns the ASCII text (in the future this may be UTF-8) produced by
the last fltk::KEY or fltk::PASTE or possibly other
event. A zero-length string is returned for any keyboard function keys
that do not produce text. This pointer points at a static buffer and is
only valid until the next event is processed.
Under X this is the result of calling XLookupString().
Returns the length of the text in fltk::event_text(). There will always be
a nul at this position in the text. However there may be a nul before
that if the keystroke translates to a nul character or you paste a nul
character.
Returns non-zero if the current fltk::event_x()
and fltk::event_y()
put it inside the passed box. You should always call this rather than
doing your own comparison so you are consistent about edge effects.
Test the current event, which must be an fltk::KEY or
fltk::SHORTCUT, against a shortcut value (described in fltk::Button).
Returns non-zero if there is a match. Not to be confused with fltk::Widget::test_shortcut().
Unparse a key name (as returned by fltk::event_key()) or a shortcut value
(as used by fltk::Button
or Fl_Menu_Item) into a
human-readable string like "Alt+N". If the shortcut is zero an empty
string is returned. The return value points at a static buffer that
is overwritten with each call.
Use of this function is very simple. Any text editing widget should
call this for each fltk::KEY event.
If true is returned, then it has modified the fltk::event_text() and fltk::event_length() to a set of
bytes to insert (it may be of zero length!). It will also set
the del parameter to the number of bytes to the left of
the cursor to delete, this is used to delete the results of the
previous call to fltk::compose().
If false is returned, the keys should be treated as
function keys. You could insert the text anyways, if you don't know
what else to do, del is set to zero and the fltk::event_text() and fltk::event_length() are left unchanged,
length is zero for any function keys.
Though the current implementation returns immediately, future
versions may take quite awhile, as they may pop up a window or do
other user-interface things to allow characters to be selected.
If the user moves the cursor, be sure to call fltk::compose_reset().
The next call to fltk::compose() will start out in an initial state. In
particular it will not set "del" to non-zero. This call is very fast
so it is ok to call it many times and in many places.
Returns true if the given key is held down now. Under X
this requires a round-trip to the server and is much slower
than fltk::event_key_state(int).
On Win32 fltk::get_key_state(fltk::KP_Enter) does not work.
Return where the mouse is on the screen by doing a round-trip query to
the server. You should use fltk::event_x_root() and fltk::event_y_root() if possible, but
this is necessary if you are not sure if a mouse event has been
processed recently (such as to position your first window). If the
display is not open, this will open it.
Install 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.
Currently there are only two uses for this:
1. If there is a keystroke that no widgets are interested in, this
is called with fltk::SHORTCUT. You can use this to implement
global shortcut keys.
2. On X, if FLTK does not recognize an X event or the window id the
event is sent to, this is called with zero. You can then use system specific code to access the event
data and figure out what to do. (this is not done on Win32 due to the
enormous number of bogus events sent, it was much to slow to
search the handler list for every one).
Ignore any other values this is called with. We have not figured
out what the rules for these are yet.
Get the widget that is below the mouse. This is the last widget to
respond to an fltk::ENTER event as long as the mouse is still
pointing at it. This is for highlighting buttons and bringing up
tooltips. It is not used to send fltk::PUSH or fltk::MOVE
directly, for several obscure reasons, but those events typically go
to this widget.
void fltk::belowmouse(fltk::Widget*)
Change the fltk::belowmouse()
widget, the previous one and all parents (that don't contain the new
widget) are sent fltk::LEAVE events. Changing this does
not send fltk::ENTER to this or any widget, because
sending fltk::ENTER is supposed to test if the widget
wants the mouse (by it returning non-zero from handle()).
Get the widget that is being pushed. fltk::DRAG or
fltk::RELEASE (and any more fltk::PUSH) events will be sent to
this widget. This is null if no mouse button is being held down, or if
no widget responded to the fltk::PUSH event.
void fltk::pushed(fltk::Widget*)
Change the fltk::pushed() widget, the
previous one and all parents (that don't contain the new widget) are
sent fltk::RELEASE events. Changing this does not send
fltk::PUSH to this or any widget, because sending
fltk::PUSH is supposed to test if the widget wants the
mouse (by it returning non-zero from handle()).
Returns the widgets that will receive fltk::KEY
events. This is NULL if the application does not have focus now, or if
no widgets accepted focus.
void fltk::focus(fltk::Widget *)
Change fltk::focus() to the given widget,
the previous widget and all parents (that don't contain the new
widget) are sent fltk::UNFOCUS events, the new widget and all
parents that don't contain the old widget are sent fltk::FOCUS
events. fltk::focus() is set whether or not the applicaton has the
focus or if the widgets accept the focus. You may want to use fltk::Widget::take_focus() instead, it
will test first.
Change the current selection. The block of text is
copied to an internal buffer by FLTK (be careful if doing this in
response to an fltk::PASTE as this may be the same buffer
returned by event_text()).
The block of text may be retrieved (from this program or whatever
program last set it) with fltk::paste().
There are actually two buffers. If clipboard is true then
the text goes into the user-visible selection that is moved around
with cut/copy/paste commands (on X this is the CLIPBOARD
selection). If clipboard is false then the text goes into a
less-visible buffer used for temporarily selecting text with the mouse
and for drag & drop (on X this is the XA_PRIMARY selection).
Copying the buffer every time the selection is changed is
obviously wasteful, especially for large selections. An interface will
probably be added in a future version to allow the selection to be made
by a callback function. The current interface will be emulated on top
of this.
This is what a widget does when a "paste" command (like Ctrl+V or the
middle mouse click) is done to it. Cause an fltk::PASTE event to be sent to
the receiver with the contents of the current selection in the
fltk::event_text(). The selection can
be set by fltk::copy().
There are actually two buffers. If clipboard is true then
the text is from the user-visible selection that is moved around
with cut/copy/paste commands (on X this is the CLIPBOARD
selection). If clipboard is false then the text goes into a
less-visible buffer used for temporarily selecting text with the mouse
and for drag & drop (on X this is the XA_PRIMARY selection).
The reciever should be prepared to be called directly by
this, or for it to happen later, or possibly not at all.
This allows the window system to take as long as necessary to retrieve
the paste buffer (or even to screw up completely) without complex and
error-prone synchronization code most toolkits require.
Drag and drop the data set by the most recent fltk::copy() (with the clipboard
argument false). Returns true if the data was dropped on something
that accepted it.
By default only blocks of text are dragged. You can use system-specific variables to change the type of
data.
Blocks the current thread until it can safely access FLTK widgets and
data. Child threads should call this method prior to updating any
widgets or accessing data. The main thread must call
fltk::lock() to initialize the threading support in FLTK before
calling fltk::wait() or fltk::run().
Child threads must call fltk::unlock()
when they are done accessing FLTK. They may want to call fltk::awake() first if the display needs to
change.
This is a "recursive lock". If you call fltk::lock() more
than once, the subsequent calls return immediately. But you must call
fltk::unlock() the same number of times as you called
fltk::lock() before the lock is released.
When the wait() method is waiting for
input or timeouts, child threads are given access to FLTK. Similarly,
when the main thread receives events and needs to do processing, it
will wait until all child threads have called unlock() before processing the events and
doing callbacks.
See the file <fltk/Threads.h> for a simple
portable recursive lock object you can use in your own code for
locking other objects. However there is no requirement that you use
this, you can use pthreads or any other library that is compatable
with your system.
Releases the lock that was set using the fltk::lock() method. Child threads should call
this method as soon as they are finished accessing FLTK. If some other
thread is waiting for fltk::lock() to return, it will get
control.
Make the main thread (the one that is calling fltk::wait()) wake up. The main purpose of
this is to get the main thread to redraw the screen, but it will
also cause fltk::wait() to return so the
program's code can do something.
Due to obscure race problems you must call this after you
call fltk::unlock(). If you call this
while things are locked both the X and Win32 implementations can deadlock.
The message argument can be retrieved by the other thread
using fltk::thread_message().
Returns an argument sent to an fltk::awake()
call, or returns null if none. The current implementation
only has a one-entry queue and only returns the most recent value!
FLTK will call these to print messages when unexpected conditions
occur.
fltk::warning means that there was a recoverable problem,
the display may be messed up but the user can probably keep working.
(all X protocol errors call this).
fltk::error means there is a recoverable error, but the
display is so messed up it is unlikely the user can continue (very
little calls this now).
fltk::fatal must not return, as FLTK is in an unusable
state, however your version may be able to use longjmp or an
exception to continue, as long as it does not call FLTK again.
The default versions on Unix print messages to stderr, while on
Windows they use MessageBox(). fltk::error and
fltk::fatal call abort(). You can override the
behavior by setting the function pointers to your own routines.