[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>

1 files changed, 34 insertions, 2 deletions

diff --git a/src/include/ipxe/jumpscroll.h b/src/include/ipxe/jumpscroll.h
index 7a5b111c1..470f08e71 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 */