akbasic/src/input_akgl.c

/**
 * @file input_akgl.c
 * @brief Wires the input backend record to libakgl's keystroke ring.
 *
 * The thinnest of the four adaptors, and the one whose *shape* carries the
 * design: akgl_controller_poll_key() reads a ring that
 * akgl_controller_handle_event() fills as the **host** pumps SDL events. The
 * interpreter therefore answers "is there a key waiting" without owning an event
 * loop, which is the whole of goal 3 for input.
 *
 * The caveat a host needs, repeated here because this is the file that causes
 * it: that ring is process-global and the host's own control maps read the same
 * events. A script sitting in a GET loop drains keystrokes the game will then
 * never see. Withhold the backend, or supply a filtered one.
 */

#include <akerror.h>

#include <akgl/controller.h>
#include <akgl/error.h>

#include <akbasic/akgl.h>
#include <akbasic/error.h>

static akerr_ErrorContext *in_poll_key(akbasic_InputBackend *self, int *keycode, bool *available)
{
    PREPARE_ERROR(errctx);

    (void)self;
    /*
     * An empty ring comes back as success with available false, both here and
     * upstream. Passed through unchanged: GET reports it as the empty string,
     * which is ordinary BASIC rather than a failure.
     */
    PASS(errctx, akgl_controller_poll_key(keycode, available));
    SUCCEED_RETURN(errctx);
}

static akerr_ErrorContext *in_flush_keys(akbasic_InputBackend *self)
{
    PREPARE_ERROR(errctx);

    (void)self;
    PASS(errctx, akgl_controller_flush_keys());
    SUCCEED_RETURN(errctx);
}

akerr_ErrorContext *akbasic_input_init_akgl(akbasic_InputBackend *obj)
{
    PREPARE_ERROR(errctx);

    FAIL_ZERO_RETURN(errctx, (obj != NULL), AKERR_NULLPOINTER,
		     "NULL backend in input_init_akgl");
    PASS(errctx, akgl_error_init());

    obj->self		= NULL;	/* the ring is libakgl's, not ours */
    obj->poll_key	= in_poll_key;
    obj->flush_keys	= in_flush_keys;
    SUCCEED_RETURN(errctx);
}