Simplify scroll (#14)

cui/scroll.go

@@ -4,19 +4,26 @@ import (
 	"github.com/jroimartin/gocui"
 )
 
-func scroll(g *gocui.Gui, v *gocui.View, direction int) error {
+func scroll(v *gocui.View, direction int) error {
 	if v != nil {
 		ox, oy := v.Origin()
 		if oy+direction >= len(v.BufferLines())-1 {
+			// hit bottom
 			return nil
 		}
-		v.SetOrigin(ox, oy+direction)
+		if oy+direction < 0 {
+			// hit top
+			return nil
+		}
+		if err := v.SetOrigin(ox, oy+direction); err != nil {
+			return err
+		}
 	}
 	return nil
 }
 
 func cursorDown(g *gocui.Gui, v *gocui.View) error {
-	err := scroll(g, v, 1)
+	err := scroll(v, 1)
 	if g.CurrentView().Title == "Items" {
 		displayDescription(g, v)
 	}
@@ -24,7 +31,7 @@ func cursorDown(g *gocui.Gui, v *gocui.View) error {
 }
 
 func cursorUp(g *gocui.Gui, v *gocui.View) error {
-	err := scroll(g, v, -1)
+	err := scroll(v, -1)
 	if g.CurrentView().Title == "Items" {
 		displayDescription(g, v)
 	}