1 files changed, 43 insertions, 0 deletions
diff --git a/src/listnav.c b/src/listnav.c
new file mode 100644
index 0000000..707a973
--- /dev/null
+++ b/src/listnav.c
@@ -0,0 +1,43 @@
+#include "listnav.h"
+#include "util.h"
+
+#include <string.h>
+
+void
+listnav_init(struct listnav *nav)
+{
+	memset(nav, 0, sizeof(struct listnav));
+}
+
+void
+listnav_update_bounds(struct listnav *nav, int min, int max)
+{
+	nav->min = min;
+	nav->max = max;
+	nav->wmin = MAX(nav->wmin, nav->min);
+	nav->wmax = MIN(nav->wmin + nav->wlen, nav->max);
+	nav->sel = MIN(MAX(nav->sel, nav->wmin), nav->wmax - 1);
+}
+
+void
+listnav_update_wlen(struct listnav *nav, int wlen)
+{
+	nav->wlen = wlen;
+	nav->wmax = MIN(nav->wmin + nav->wlen, nav->max);
+	nav->sel = MIN(MAX(nav->sel, nav->wmin), nav->wmax - 1);
+}
+
+void
+listnav_update_sel(struct listnav *nav, int sel)
+{
+	nav->sel = MAX(MIN(sel, nav->max - 1), nav->min);
+
+	if (nav->sel >= nav->wmax) {
+		nav->wmax = nav->sel + 1;
+		nav->wmin = MAX(nav->min, nav->wmax - nav->wlen);
+	} else if (nav->sel < nav->wmin) {
+		nav->wmin = nav->sel;
+		nav->wmax = MIN(nav->wmin + nav->wlen, nav->max);
+	}
+}
+