implement nano-like page up/page down functionality

internal/action/actions.go

@@ -1696,31 +1696,26 @@ func (h *BufPane) SelectPageDown() bool {
 	return true
 }
 
-// CursorPageUp places the cursor a page up
+// CursorPageUp scrolls the view up a page,
+// keeping the cursor at the same relative position in the view
 func (h *BufPane) CursorPageUp() bool {
-	h.Cursor.Deselect(true)
-
-	if h.Cursor.HasSelection() {
-		h.Cursor.Loc = h.Cursor.CurSelection[0]
-		h.Cursor.ResetSelection()
-		h.Cursor.StoreVisualX()
-	}
-	h.MoveCursorUp(h.BufView().Height)
-	h.Relocate()
+	scrollmargin := int(h.Buf.Settings["scrollmargin"].(float64))
+	pageOffset := h.BufView().Height - scrollmargin
+	h.Buf.ClearCursors()
+	h.ScrollUp(pageOffset)
+	h.MoveCursorUp(pageOffset)
 	return true
 }
 
-// CursorPageDown places the cursor a page up
+// CursorPageDown scrolls the view down a page,
+// keeping the cursor at the same relative position in the view
 func (h *BufPane) CursorPageDown() bool {
-	h.Cursor.Deselect(false)
-
-	if h.Cursor.HasSelection() {
-		h.Cursor.Loc = h.Cursor.CurSelection[1]
-		h.Cursor.ResetSelection()
-		h.Cursor.StoreVisualX()
-	}
-	h.MoveCursorDown(h.BufView().Height)
-	h.Relocate()
+	scrollmargin := int(h.Buf.Settings["scrollmargin"].(float64))
+	pageOffset := h.BufView().Height - scrollmargin
+	h.Buf.ClearCursors()
+	h.ScrollDown(pageOffset)
+	h.ScrollAdjust()
+	h.MoveCursorDown(pageOffset)
 	return true
 }
 

internal/display/softwrap.go

@@ -291,13 +291,7 @@ func (w *BufWindow) diff(s1, s2 SLoc) int {
 // within the buffer boundaries.
 func (w *BufWindow) Scroll(s SLoc, n int) SLoc {
 	if !w.Buf.Settings["softwrap"].(bool) {
-		s.Line += n
-		if s.Line < 0 {
-			s.Line = 0
-		}
-		if s.Line > w.Buf.LinesNum()-1 {
-			s.Line = w.Buf.LinesNum() - 1
-		}
+		s.Line = util.Clamp(s.Line + n, 0, w.Buf.LinesNum()-1)
 		return s
 	}
 	return w.scroll(s, n)