[menu] Abstract out the generic concept of a jump scroller

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/hci/jumpscroll.c

@@ -0,0 +1,140 @@
+/*
+ * 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
+ */
+int jump_scroll_key ( struct jump_scroller *scroll, int key ) {
+
+	/* 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:
+		return -1;
+	case KEY_DOWN:
+		return +1;
+	case KEY_PPAGE:
+		return ( scroll->first - scroll->current - 1 );
+	case KEY_NPAGE:
+		return ( scroll->first - scroll->current + scroll->rows );
+	case KEY_HOME:
+		return -( scroll->count );
+	case KEY_END:
+		return +( scroll->count );
+	default:
+		return 0;
+	}
+}
+
+/**
+ * Move scroller
+ *
+ * @v scroll		Jump scroller
+ * @v move		Scroller movement
+ * @ret move		Continuing scroller movement (if applicable)
+ */
+int jump_scroll_move ( struct jump_scroller *scroll, int 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 += move;
+
+	/* Check for start/end of list */
+	if ( current < 0 ) {
+		/* We have attempted to move before the start of the
+		 * list.  Move to the start of the list and continue
+		 * moving forwards (if applicable).
+		 */
+		scroll->current = 0;
+		return +1;
+	} else if ( current > last ) {
+		/* We have attempted to move after the end of the
+		 * list.  Move to the end of the list and continue
+		 * moving backwards (if applicable).
+		 */
+		scroll->current = last;
+		return -1;
+	} else {
+		/* Update the current item and continue moving in the
+		 * same direction (if applicable).
+		 */
+		scroll->current = current;
+		return ( ( move > 0 ) ? +1 : -1 );
+	}
+}
+
+/**
+ * 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;
+}