From 61c5769e3981825b5fef9aecf512679e94e0fc53 Mon Sep 17 00:00:00 2001
From: Jean-Marc Lasgouttes <lasgouttes@lyx.org>
Date: Mon, 8 Jan 2018 11:49:40 +0100
Subject: [PATCH] Fix ghost caret

This fixes a regression in e64ea357, where a test has been (badly)
tightened to avoid that two consecutive rows may be redrawn to get rid
of caret ghosts. The test prohibited empty rows from being redrawn.

Moreover, improve the test of cursor boundary to avoid the case where
cursor position is already 0.

Fixes bug #10952.

(cherry picked from commit 66c677b9463feb0687a8228603f86eddd4e859fd)
---
 src/BufferView.cpp | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/BufferView.cpp b/src/BufferView.cpp
index 23d0055221..36ac46cdde 100644
--- a/src/BufferView.cpp
+++ b/src/BufferView.cpp
@@ -2978,8 +2978,14 @@ namespace {
 
 bool sliceInRow(CursorSlice const & cs, Text const * text, Row const & row)
 {
+	/* The normal case is the last line. The previous line takes care
+	 * of empty rows (e.g. empty paragraphs). Cursor boundary issues
+	 * are taken care of when setting caret_slice_ in
+	 * BufferView::draw.
+	 */
 	return !cs.empty() && cs.text() == text && cs.pit() == row.pit()
-		&& row.pos() <= cs.pos() && cs.pos() < row.endpos();
+	       && ((row.pos() == row.endpos() && row.pos() == cs.pos())
+	          || (row.pos() <= cs.pos() && cs.pos() < row.endpos()));
 }
 
 }
@@ -3164,8 +3170,9 @@ void BufferView::draw(frontend::Painter & pain, bool paint_caret)
 	// Remember what has just been done for the next draw() step
 	if (paint_caret) {
 		d->caret_slice_ = d->cursor_.top();
-		if (d->cursor_.boundary()
-		    || d->cursor_.top().pos() == d->cursor_.top().lastpos())
+		if (d->caret_slice_.pos() > 0
+		    && (d->cursor_.boundary()
+		        || d->caret_slice_.pos() == d->caret_slice_.lastpos()))
 			--d->caret_slice_.pos();
 	} else
 		d->caret_slice_ = CursorSlice();