Add Horizontal Scroll Actions

internal/action/actions.go

@@ -35,6 +35,22 @@ func (h *BufPane) ScrollDown(n int) {
 	h.SetView(v)
 }
 
+// ScrollLeft is not an action
+func (h *BufPane) ScrollLeft(n int) bool {
+	v := h.GetView()
+	v.StartCol = h.HScroll(v.StartCol, -n)
+	h.SetView(v)
+	return true
+}
+
+// ScrollRight is not an action
+func (h *BufPane) ScrollRight(n int) bool {
+	v := h.GetView()
+	v.StartCol = h.HScroll(v.StartCol, n)
+	h.SetView(v)
+	return true
+}
+
 // ScrollAdjust can be used to shift the view so that the last line is at the
 // bottom if the user has scrolled past the last line.
 func (h *BufPane) ScrollAdjust() {
@@ -159,6 +175,18 @@ func (h *BufPane) ScrollDownAction() bool {
 	return true
 }
 
+// ScrollDownAction scrolls the view left
+func (h *BufPane) ScrollLeftAction() bool {
+	h.ScrollLeft(util.IntOpt(h.Buf.Settings["scrollspeed"]))
+	return true
+}
+
+// ScrollUpAction scrolls the view right
+func (h *BufPane) ScrollRightAction() bool {
+	h.ScrollRight(util.IntOpt(h.Buf.Settings["scrollspeed"]))
+	return true
+}
+
 // Center centers the view on the cursor
 func (h *BufPane) Center() bool {
 	v := h.GetView()

internal/action/bufpane.go

@@ -838,6 +838,8 @@ var BufKeyActions = map[string]BufKeyAction{
 	"Suspend":                   (*BufPane).Suspend,
 	"ScrollUp":                  (*BufPane).ScrollUpAction,
 	"ScrollDown":                (*BufPane).ScrollDownAction,
+	"ScrollLeft":                (*BufPane).ScrollLeftAction,
+	"ScrollRight":               (*BufPane).ScrollRightAction,
 	"SpawnMultiCursor":          (*BufPane).SpawnMultiCursor,
 	"SpawnMultiCursorUp":        (*BufPane).SpawnMultiCursorUp,
 	"SpawnMultiCursorDown":      (*BufPane).SpawnMultiCursorDown,

internal/display/infowindow.go

@@ -83,6 +83,7 @@ func (i *InfoWindow) BufView() View {
 	}
 }
 
+func (i *InfoWindow) HScroll(sc, n int) int            { return sc }
 func (i *InfoWindow) Scroll(s SLoc, n int) SLoc        { return s }
 func (i *InfoWindow) Diff(s1, s2 SLoc) int             { return 0 }
 func (i *InfoWindow) SLocFromLoc(loc buffer.Loc) SLoc  { return SLoc{0, 0} }

internal/display/softwrap.go

@@ -60,6 +60,7 @@ type VLoc struct {
 }
 
 type SoftWrap interface {
+	HScroll(sc, n int) int
 	Scroll(s SLoc, n int) SLoc
 	Diff(s1, s2 SLoc) int
 	SLocFromLoc(loc buffer.Loc) SLoc
@@ -297,6 +298,30 @@ func (w *BufWindow) Scroll(s SLoc, n int) SLoc {
 	return w.scroll(s, n)
 }
 
+// HScroll returns the column after moving n columns relative to sc
+// i.e. the result of scrolling n columns left/right. n can be negative,
+// which means scrolling left. The returned column is guaranteed to be
+// within the buffer boundaries.
+func (w *BufWindow) HScroll(sc, n int) int {
+	if w.Buf.Settings["softwrap"].(bool) {
+		return sc
+	}
+	if n <= 0 {
+		return util.Max(0, sc+n)
+	}
+
+	lw := 0 // longest line width
+	for i := 0; i < w.Buf.LinesNum(); i++ {
+		cc := util.CharacterCount(w.Buf.LineBytes(i))
+		lw = util.Max(lw, cc)
+	}
+
+	OFFSET := 3
+	maxSc := lw - w.BufView().Width + OFFSET
+
+	return util.Min(sc+n, maxSc)
+}
+
 // Diff returns the difference (the vertical distance) between two SLocs.
 func (w *BufWindow) Diff(s1, s2 SLoc) int {
 	if !w.Buf.Settings["softwrap"].(bool) {