[hci] Allow tab key to be used to cycle through UI elements

Add support for wraparound scrolling and allow the tab key to be used
to move forward through a list of elements, wrapping back around to
the beginning of the list on overflow.

This is mildly useful for a menu, and likely to be a strong user
expectation for an interactive form.

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

4 files changed, 86 insertions, 33 deletions

diff --git a/src/hci/jumpscroll.c b/src/hci/jumpscroll.c
index dd6bcac..641f781 100644
--- a/src/hci/jumpscroll.c
+++ b/src/hci/jumpscroll.c
@@ -39,7 +39,9 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
  * @v key		Key pressed by user
  * @ret move		Scroller movement, or zero
  */
-int jump_scroll_key ( struct jump_scroller *scroll, int key ) {
+unsigned int jump_scroll_key ( struct jump_scroller *scroll, int key ) {
+	unsigned int flags = 0;
+	int16_t delta;
 
 	/* Sanity checks */
 	assert ( scroll->rows != 0 );
@@ -52,20 +54,32 @@ int jump_scroll_key ( struct jump_scroller *scroll, int key ) {
 	/* Handle key, if applicable */
 	switch ( key ) {
 	case KEY_UP:
-		return -1;
+		delta = -1;
+		break;
+	case TAB:
+		flags = SCROLL_WRAP;
+		/* fall through */
 	case KEY_DOWN:
-		return +1;
+		delta = +1;
+		break;
 	case KEY_PPAGE:
-		return ( scroll->first - scroll->current - 1 );
+		delta = ( scroll->first - scroll->current - 1 );
+		break;
 	case KEY_NPAGE:
-		return ( scroll->first - scroll->current + scroll->rows );
+		delta = ( scroll->first - scroll->current + scroll->rows );
+		break;
 	case KEY_HOME:
-		return -( scroll->count );
+		delta = -( scroll->count );
+		break;
 	case KEY_END:
-		return +( scroll->count );
+		delta = +( scroll->count );
+		break;
 	default:
-		return 0;
+		delta = 0;
+		break;
 	}
+
+	return ( SCROLL ( delta ) | flags );
 }
 
 /**
@@ -75,7 +89,9 @@ int jump_scroll_key ( struct jump_scroller *scroll, int key ) {
  * @v move		Scroller movement
  * @ret move		Continuing scroller movement (if applicable)
  */
-int jump_scroll_move ( struct jump_scroller *scroll, int move ) {
+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 );
 
@@ -84,30 +100,35 @@ int jump_scroll_move ( struct jump_scroller *scroll, int move ) {
 	assert ( scroll->count != 0 );
 
 	/* Move to the new current item */
-	current += move;
+	current += delta;
+
+	/* Default to continuing movement in the same direction */
+	delta = ( ( delta >= 0 ) ? +1 : -1 );
 
 	/* 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).
+	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 = last;
-		return -1;
+		scroll->current = current;
 	} else {
-		/* Update the current item and continue moving in the
-		 * same direction (if applicable).
+		/* We have attempted to move outside the list.  If we
+		 * are wrapping around, then continue in the same
+		 * direction (if applicable), otherwise reverse.
 		 */
-		scroll->current = current;
-		return ( ( move > 0 ) ? +1 : -1 );
+		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 ) );
 }
 
 /**
diff --git a/src/hci/tui/menu_ui.c b/src/hci/tui/menu_ui.c
index cac61a7..067e2d8 100644
--- a/src/hci/tui/menu_ui.c
+++ b/src/hci/tui/menu_ui.c
@@ -175,9 +175,9 @@ static int menu_loop ( struct menu_ui *ui, struct menu_item **selected ) {
 	struct menu_item *item;
 	unsigned long timeout;
 	unsigned int previous;
+	unsigned int move;
 	int key;
 	int i;
-	int move;
 	int chosen = 0;
 	int rc = 0;
 
@@ -192,7 +192,7 @@ static int menu_loop ( struct menu_ui *ui, struct menu_item **selected ) {
 		ui->timeout -= timeout;
 
 		/* Get key */
-		move = 0;
+		move = SCROLL_NONE;
 		key = getkey ( timeout );
 		if ( key < 0 ) {
 			/* Choose default if we finally time out */
@@ -228,7 +228,7 @@ static int menu_loop ( struct menu_ui *ui, struct menu_item **selected ) {
 					if ( item->name ) {
 						chosen = 1;
 					} else {
-						move = +1;
+						move = SCROLL_DOWN;
 					}
 				}
 				break;
diff --git a/src/hci/tui/settings_ui.c b/src/hci/tui/settings_ui.c
index 10c9423..bc08750 100644
--- a/src/hci/tui/settings_ui.c
+++ b/src/hci/tui/settings_ui.c
@@ -381,8 +381,8 @@ static void select_settings ( struct settings_ui *ui,
 static int main_loop ( struct settings *settings ) {
 	struct settings_ui ui;
 	unsigned int previous;
+	unsigned int move;
 	int redraw = 1;
-	int move;
 	int key;
 	int rc;
 
diff --git a/src/include/ipxe/jumpscroll.h b/src/include/ipxe/jumpscroll.h
index 7a5b111..470f08e 100644
--- a/src/include/ipxe/jumpscroll.h
+++ b/src/include/ipxe/jumpscroll.h
@@ -9,6 +9,8 @@
 
 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
+#include <stdint.h>
+
 /** A jump scroller */
 struct jump_scroller {
 	/** Maximum number of visible rows */
@@ -22,6 +24,35 @@ struct jump_scroller {
 };
 
 /**
+ * Construct scroll movement
+ *
+ * @v delta		Change in scroller position
+ * @ret move		Scroll movement
+ */
+#define SCROLL( delta ) ( ( unsigned int ) ( uint16_t ) ( int16_t ) (delta) )
+
+/**
+ * Extract change in scroller position
+ *
+ * @v move		Scroll movement
+ * @ret delta		Change in scroller position
+ */
+#define SCROLL_DELTA( scroll ) ( ( int16_t ) ( (scroll) & 0x0000ffffUL ) )
+
+/** Scroll movement flags */
+#define SCROLL_FLAGS	0xffff0000UL
+#define SCROLL_WRAP	0x80000000UL	/**< Wrap around scrolling */
+
+/** Do not scroll */
+#define SCROLL_NONE SCROLL ( 0 )
+
+/** Scroll up by one line */
+#define SCROLL_UP SCROLL ( -1 )
+
+/** Scroll down by one line */
+#define SCROLL_DOWN SCROLL ( +1 )
+
+/**
  * Check if jump scroller is currently on first page
  *
  * @v scroll		Jump scroller
@@ -43,8 +74,9 @@ static inline int jump_scroll_is_last ( struct jump_scroller *scroll ) {
 	return ( ( scroll->first + scroll->rows ) >= scroll->count );
 }
 
-extern int jump_scroll_key ( struct jump_scroller *scroll, int key );
-extern int jump_scroll_move ( struct jump_scroller *scroll, int move );
+extern unsigned int jump_scroll_key ( struct jump_scroller *scroll, int key );
+extern unsigned int jump_scroll_move ( struct jump_scroller *scroll,
+				       unsigned int move );
 extern int jump_scroll ( struct jump_scroller *scroll );
 
 #endif /* _IPXE_JUMPSCROLL_H */