.\"Copyright 2010 (c) EPFL
.TH DTK_PROCESS_EVENTS 3 2010 "EPFL" "Draw Toolkit manual"
.SH NAME
dtk_process_events, dtk_set_event_handler - Events processing
.SH SYNOPSIS
.LP
.B #include <dtk_event.h>
.sp
.BI "typedef int (*DTKEvtProc)(dtk_hwnd, int, const union dtk_event*);"
.sp
.BI "void dtk_set_event_handler(dtk_hwnd " wnd ", DTKEvtProc " handler ");"
.br
.BI "int dtk_process_events(dtk_hwnd " wnd ");"
.br
.SH DESCRIPTION
.LP
\fBdtk_set_event_handler\fP() set \fIhandler\fP as the current event handler
for the window \fIwnd\fP. \fIhandler\fP is a function that has arguments in
the following order:
.IP " *" 3
a reference of type \fBdtk_hwnd\fP to the window that has received the
event.
.IP " *" 3
the type ID of the event.
.IP " *" 3
a pointer to a \fBunion dtk_event\fP holding event-specific data (if not
\fBNULL\fP) defined as follows:
.sp
.in +4n
.nf
union dtk_event {
    struct dtk_keyevent key;
    struct dtk_mouseevent mouse;
};
.fi
.in
.LP
\fBdtk_process_events\fP() processes pending events in the event queues
associated to the window referenced by \fIwnd\fP, i.e.  for each event in
the queue, it calls the event handler that has been set by
\fBdtk_set_event_handler\fP(). \fBdtk_process_events\fP() returns if a event
handler has returned 0 or if there is no more pending event in the queue.
.LP
If \fBdtk_set_event_handler\fP() has never been called or called with
\fIhandle\fP as NULL, it use a minimalistic event handler that returns 0
(i.e. stop the loop) when pressing the close button on the window.
.LP
The type ID of the event can be one of the following:
.TP
.B DTK_EVT_REDRAW
This event indicates that the whole window or parts of it must be redrawn.
This may be caused by another window has been overlapped it or the window
has been resized. If such an event is received, the event pointer passed to
the handler will be \fBNULL\fP.
.TP
.B DTK_EVT_QUIT
This event indicates that the close button of the window has been clicked.
The event pointer passed will be \fBNULL\fP.
.TP
.B DTK_EVT_KEYBOARD
Indicates that a key of the keyboard has been pressed or released. If such
an event is received, the meaningfull member of the \fBunion dtk_event\fP
will be \fIkey\fP which is defined as follows:
.sp
.in +4n
.nf
struct dtk_keyevent {
    unsigned int state;  /* pressed or released */
    unsigned int sym;    /* Symbolic code of the key */
    unsigned int mod;    /* modifiers key */
};
.fi
.in
.TP
.B DTK_EVT_MOUSEBUTTON
This event indicates that one of the mouse buttons has been pressed or
released. If such an event is received, the meaningfull member of the
\fBunion dtk_event\fP will be \fImouse\fP which is defined as follows:
.sp
.in +4n
.nf
struct dtk_mouseevent {
    unsigned int button; /* button identifier */
    unsigned int state;  /* pressed or realeased */
    unsigned int x;   /* x-coordinate of the mouse position */
    unsigned int y;   /* y-coordinate of the mouse position */
};
.fi
.in
.TP
.B DTK_EVT_MOUSEMOTION
This is similar to the \fBDTK_EVT_MOUSEBUTTON\fP but indicates that the
mouse has moved. Event data should also be accessed through \fImouse\fP
member but its \fIbutton\fP and \fIstate\fP members will be meaningless.
.SH "RETURN VALUE"
.LP
\fBdtk_set_event_handler\fP() does not return value.
.LP
\fBdtk_process_events\fP() returns 1 if there is no more pending event in the
queue.  It returns 0 if the processing loop has been interrupted by an event
handler, i.e. the last event handler has returned 0.