jumpscroll.c

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/*
 * Copyright (C) 2015 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

/**
 * Jump scrolling
 *
 */

#include <assert.h>
#include <ipxe/keys.h>
#include <ipxe/jumpscroll.h>

/**
 * Handle keypress
 *
 * @v scroll            Jump scroller
 * @v key               Key pressed by user
 * @ret move            Scroller movement, or zero
 */
unsigned int jump_scroll_key ( struct jump_scroller *scroll, int key ) {
        unsigned int flags = 0;
        int16_t delta;

        /* Sanity checks */
        assert ( scroll->rows != 0 );
        assert ( scroll->count != 0 );
        assert ( scroll->current < scroll->count );
        assert ( scroll->first < scroll->count );
        assert ( scroll->first <= scroll->current );
        assert ( scroll->current < ( scroll->first + scroll->rows ) );

        /* Handle key, if applicable */
        switch ( key ) {
        case KEY_UP:
                delta = -1;
                break;
        case TAB:
                flags = SCROLL_WRAP;
                /* fall through */
        case KEY_DOWN:
                delta = +1;
                break;
        case KEY_PPAGE:
                delta = ( scroll->first - scroll->current - 1 );
                break;
        case KEY_NPAGE:
                delta = ( scroll->first - scroll->current + scroll->rows );
                break;
        case KEY_HOME:
                delta = -( scroll->count );
                break;
        case KEY_END:
                delta = +( scroll->count );
                break;
        default:
                delta = 0;
                break;
        }

        return ( SCROLL ( delta ) | flags );
}

/**
 * Move scroller
 *
 * @v scroll            Jump scroller
 * @v move              Scroller movement
 * @ret move            Continuing scroller movement (if applicable)
 */
unsigned int jump_scroll_move ( struct jump_scroller *scroll,
                                unsigned int move ) {
        int16_t delta = SCROLL_DELTA ( move );
        int current = scroll->current;
        int last = ( scroll->count - 1 );

        /* Sanity checks */
        assert ( move != 0 );
        assert ( scroll->count != 0 );

        /* Move to the new current item */
        current += delta;

        /* Default to continuing movement in the same direction */
        delta = ( ( delta >= 0 ) ? +1 : -1 );

        /* Check for start/end of list */
        if ( ( current >= 0 ) && ( current <= last ) ) {
                /* We are still within the list.  Update the current
                 * item and continue moving in the same direction (if
                 * applicable).
                 */
                scroll->current = current;
        } else {
                /* We have attempted to move outside the list.  If we
                 * are wrapping around, then continue in the same
                 * direction (if applicable), otherwise reverse.
                 */
                if ( ! ( move & SCROLL_WRAP ) )
                        delta = -delta;

                /* Move to start or end of list as appropriate */
                if ( delta >= 0 ) {
                        scroll->current = 0;
                } else {
                        scroll->current = last;
                }
        }

        return ( SCROLL ( delta ) | ( move & SCROLL_FLAGS ) );
}

/**
 * Jump scroll to new page (if applicable)
 *
 * @v scroll            Jump scroller
 * @ret jumped          Jumped to a new page
 */
int jump_scroll ( struct jump_scroller *scroll ) {
        unsigned int index;

        /* Sanity checks */
        assert ( scroll->rows != 0 );
        assert ( scroll->count != 0 );
        assert ( scroll->current < scroll->count );
        assert ( scroll->first < scroll->count );

        /* Do nothing if we are already on the correct page */
        index = ( scroll->current - scroll->first );
        if ( index < scroll->rows )
                return 0;

        /* Move to required page */
        while ( scroll->first < scroll->current )
                scroll->first += scroll->rows;
        while ( scroll->first > scroll->current )
                scroll->first -= scroll->rows;

        return 1;
}