[LyX/master] fix comment.

[Jean-Marc Lasgouttes]

commit f0b60d0b4e8998b25675317fa53c3279d57d0af7
Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
Date:   Wed Feb 8 12:28:01 2023 +0100

    fix comment.
---
 src/frontends/qt/GuiWorkArea.cpp |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/frontends/qt/GuiWorkArea.cpp b/src/frontends/qt/GuiWorkArea.cpp
index 31cfec1..cc1fdb5 100644
--- a/src/frontends/qt/GuiWorkArea.cpp
+++ b/src/frontends/qt/GuiWorkArea.cpp
@@ -1241,9 +1241,10 @@ void GuiWorkArea::paintEvent(QPaintEvent * ev)
 	// bug #10989). The second test triggers when in the middle of a
 	// dispatch operation.
 	if (view().busy() || d->buffer_view_->buffer().undo().activeUndoGroup()) {
-		// Since macOS has turned the screen black at this point, our
-		// backing store has to be copied to screen (this is a no-op
-		// except on macOS).
+		// Since the screen may have turned black at this point, our
+		// backing store has to be copied to screen. This is a no-op
+		// except when our drawing strategy is "backingstore" (macOS,
+		// Wayland, or set in prefs).
 		d->updateScreen(ev->rect());
 		// Ignore this paint event, but request a new one for later.
 		viewport()->update(ev->rect());