update view cursor when selecting new line in patch explorer view

vendor/github.com/jesseduffield/gocui/gui.go

@@ -1226,8 +1226,10 @@ func (g *Gui) onKey(ev *GocuiEvent) error {
 				newCx = lastCharForLine
 			}
 		}
-		if err := v.SetCursor(newCx, newCy); err != nil {
-			return err
+		if !IsMouseScrollKey(ev.Key) {
+			if err := v.SetCursor(newCx, newCy); err != nil {
+				return err
+			}
 		}
 
 		if IsMouseKey(ev.Key) {
@@ -1289,6 +1291,19 @@ func IsMouseKey(key interface{}) bool {
 	}
 }
 
+func IsMouseScrollKey(key interface{}) bool {
+	switch key {
+	case
+		MouseWheelUp,
+		MouseWheelDown,
+		MouseWheelLeft,
+		MouseWheelRight:
+		return true
+	default:
+		return false
+	}
+}
+
 // execKeybindings executes the keybinding handlers that match the passed view
 // and event. The value of matched is true if there is a match and no errors.
 func (g *Gui) execKeybindings(v *View, ev *GocuiEvent) (matched bool, err error) {

vendor/github.com/jesseduffield/gocui/view.go

@@ -418,9 +418,10 @@ func (v *View) setRune(x, y int, ch rune, fgColor, bgColor Attribute) error {
 		if err != nil {
 			return err
 		}
-		_, rcy, err = v.realPosition(v.cx, v.cy)
-		if err != nil {
-			return err
+		_, rrcy, err := v.realPosition(v.cx, v.cy)
+		// if error is not nil, then the cursor is out of bounds, which is fine
+		if err == nil {
+			rcy = rrcy
 		}
 	}
 
@@ -460,6 +461,22 @@ func (v *View) SetCursor(x, y int) error {
 	return nil
 }
 
+func (v *View) SetCursorX(x int) {
+	maxX, _ := v.Size()
+	if x < 0 || x >= maxX {
+		return
+	}
+	v.cx = x
+}
+
+func (v *View) SetCursorY(y int) {
+	_, maxY := v.Size()
+	if y < 0 || y >= maxY {
+		return
+	}
+	v.cy = y
+}
+
 // Cursor returns the cursor position of the view.
 func (v *View) Cursor() (x, y int) {
 	return v.cx, v.cy
@@ -1349,11 +1366,12 @@ func (v *View) OverwriteLines(y int, content string) {
 }
 
 func (v *View) ScrollUp(amount int) {
-	newOy := v.oy - amount
-	if newOy < 0 {
-		newOy = 0
+	if amount > v.oy {
+		amount = v.oy
 	}
-	v.oy = newOy
+
+	v.oy -= amount
+	v.cy += amount
 }
 
 // ensures we don't scroll past the end of the view's content
@@ -1361,6 +1379,7 @@ func (v *View) ScrollDown(amount int) {
 	adjustedAmount := v.adjustDownwardScrollAmount(amount)
 	if adjustedAmount > 0 {
 		v.oy += adjustedAmount
+		v.cy -= adjustedAmount
 	}
 }