Next: Example, Up: Part I Free Objects [Contents][Index]
To add a free object to a form use the call
FL_OBJECT *fl_add_free(int type, FL_Coord x, FL_Coord y,
FL_Coord w, FL_Coord h,
const char *label, int (*handle)());
type indicates the type of free object, see below for a list
and their meaning. x, y, w and h are the
bounding box. The label is normally not drawn unless the
handle routine takes care of this. handle is the routine
that does the redrawing and handles the interaction with the free
object. The application program must supply this routine.
This routine handle is called by the library whenever
an action has to be performed. The routine should have the form:
int handle(FL_OBJECT *obj, int event, FL_Coord mx, FL_Coord my,
int key, void *xev);
where obj is the object to which the event applies.
event indicates what has to happen to the object. See below for
a list of possible events. mx and my indicate the
position of the mouse (only meaningful with mouse related events)
relative to the form origin and key is the KeySym of the key
typed in by the user (only for FL_KEYPRESS events). xev
is the (cast) XEvent that causes the invocation of this handler.
event and xev->type can both be used to obtain the event
types. The routine should return whether the status of the object has
changed, i.e., whether fl_do_forms() or
fl_check_forms() should return this object.
The following types of events exist for which the routine must take action:
FL_DRAWThe object has to be redrawn. To figure out the size of the object you
can use the fields obj->x, obj->y, obj->w and
obj->h. Some other aspects might also influence the way the
object has to be drawn. E.g., you might want to draw the object
differently when the mouse is on top of it or when the mouse is
pressed on it. This can be figured out as follows. The field
obj->belowmouse indicates whether the object is below the
mouse. The field obj->pushed indicates whether the object is
currently being pushed with the mouse. Finally, obj->focus
indicates whether input focus is directed towards this object. When
required, the label should also be drawn. This label can be found in
the field obj->label. The drawing should be done such that it
works correctly in the visual/depth the current form is in. Complete
information is available on the state of the current form as well as
several routines that will help you to tackle the trickiest (also the
most tedious) part of X programming. In particular, the return value
of fl_get_vclass() can be used as an index into a table
of structures, fl_state[], from which all information
about current active visual can be obtained. See Drawing Objects, for details on drawing objects and the
routines.
FL_DRAWLABELThis event is not always generated. It typically follows
FL_DRAW and indicates the object label needs to be (re)drawn.
You can ignore this event if (a) the object handler always draws the
label upon receiving FL_DRAW or (b) the object label is not
drawn at all9.
FL_ENTERThis event is sent when the mouse has entered the bounding box. This
might require some action. Note that also the
field belowmouse in the object is being set. If
entering only changes the appearance redrawing the object normally
suffices. Don’t do this directly! Always redraw the object using the
routine fl_redraw_object(). It will
send an FL_DRAW event to the object but also does
some other things (like setting window id’s, taking care of double
buffering and some other bookkeeping tasks).
FL_LEAVEThe mouse has left the bounding box. Again, normally a redraw is enough (or nothing at all).
FL_MOTIONA motion event is sent between FL_ENTER and FL_LEAVE
events when the mouse position changes on the object. The mouse
position is given with the routine.
FL_PUSHThe user has pushed a mouse button in the object. Normally this requires some action.
FL_RELEASEThe user has released the mouse button. This event is only sent if a
FL_PUSH event was sent earlier.
FL_DBLCLICKThe user has pushed a mouse button twice within a certain time limit
(FL_CLICK_TIMEOUT), which by default is about 400 msec.
FL_TRPLCLICKThe user has pushed a mouse button three times within a certain time
window between each push. This event is sent after a
FL_DBLCLICK, FL_PUSH, FL_RELEASE sequence.
FL_UPDATEThe mouse position has changed. This event is sent to an object
between an FL_PUSH and an FL_RELEASE event (actually
this event is sent periodically, even if mouse has not moved). The
mouse position is given as the parameter mx and my and
action can be taken based on the position.
FL_FOCUSInput got focussed to this object. This event and the next two are
only sent to a free object of type FL_INPUT_FREE (see below).
FL_UNFOCUSInput is no longer focussed on this object.
FL_KEYPRESSA key was pressed. The KeySym is given with the routine. This event
only happens between FL_FOCUS and FL_UNFOCUS events.
FL_STEPA step event is sent all the time (at most 50 times per second but
often less because of time consuming redraw operations) to a free
object of type FL_CONTINUOUS_FREE such that it can update its
state or appearance.
FL_SHORTCUTHotkeys for the object have been triggered. Typically this should result in the returning of the free object.
FL_FREEMEMUpon receiving this event, the handler should free all object class specific memory allocated.
FL_OTHERSome other events typically caused by window manager events or
inter-client events. All information regarding the details of the
events is in xev.
Many of these events might make it necessary to (partially) redraw the
object. Always do this using the routine
fl_redraw_object().
As indicated above not all events are sent to all free objects. It
depends on their types. The following types exist (all objects are sent
FL_OTHER when it occurs):
FL_NORMAL_FREEThe object will receive the events FL_DRAW, FL_ENTER,
FL_LEAVE, FL_MOTION, FL_PUSH, FL_RELEASE
and FL_MOUSE.
FL_INACTIVE_FREEThe object only receives FL_DRAW events. This should be used
for objects without interaction (e.g., a picture).
FL_INPUT_FREESame as FL_NORMAL_FREE but the object also receives
FL_FOCUS, FL_UNFOCUS and FL_KEYPRESS events. The
obj->wantkey is by default set to FL_KEY_NORMAL, i.e.,
the free object will receive all normal keys (0-255) except
<Tab> and <Return> key. If you’re interested in
<Tab> or <Return> key, you need to change
obj->wantkey to FL_KEY_TAB or FL_KEY_ALL.
See Events, for details.
FL_CONTINUOUS_FREESame as FL_NORMAL_FREE but the object also receives
FL_STEP events. This should be used for objects that change
themselves continuously.
FL_ALL_FREEThe object receives all types of events.
See free1.c for a (terrible) example of the use of free objects. See also freedraw.c, which is a nicer example of the use of free objects.
Free objects provide all the generality you want from the Forms Library. Because free objects behave a lot like new object classes it is recommended that you also read part IV of this documentation before designing free objects.
Label for free objects can’t be drawn outside of the bounding box because of the clippings by the dispatcher.
Next: Example, Up: Part I Free Objects [Contents][Index]