From 8abea3b7e94414ce15211590daf193c20d1d7350 Mon Sep 17 00:00:00 2001
From: Richard Kimberly Heck <rikiheck@lyx.org>
Date: Wed, 25 Apr 2018 23:46:13 -0400
Subject: [PATCH] Try to fix bug #10989.

The problem is that popping dialogs during reload can cause paint
events for which we are not ready. If this does not work, then we
can introduce a new flag, besides 'busy', for that case. But busy
does not seem to be used very widely, so hopefully this works.

Note that when paintEvent is triggered on macOS, the least we can do
is to copy our backing store to the screen.

(cherry picked from commit 19e6977b5b527ec8311da35d8f0a40d6fd509080)
(cherry picked from commit d03deeca0c666256ea68087c5c70b8de73b66edc)
---
 src/frontends/qt4/GuiWorkArea.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/frontends/qt4/GuiWorkArea.cpp b/src/frontends/qt4/GuiWorkArea.cpp
index 7a856ae90d..d68185c4b6 100644
--- a/src/frontends/qt4/GuiWorkArea.cpp
+++ b/src/frontends/qt4/GuiWorkArea.cpp
@@ -1244,6 +1244,16 @@ void GuiWorkArea::Private::paintPreeditText(GuiPainter & pain)
 
 void GuiWorkArea::paintEvent(QPaintEvent * ev)
 {
+	// Do not trigger the painting machinery if we are not ready (see
+	// bug #10989). However, since macOS has turned the screen black at
+	// this point, our backing store has to be copied to screen.
+	if (view().busy()) {
+		// this is a no-op except on macOS.
+		d->updateScreen(ev->rect());
+		ev->accept();
+		return;
+	}
+
 	// LYXERR(Debug::PAINTING, "paintEvent begin: x: " << rc.x()
 	//	<< " y: " << rc.y() << " w: " << rc.width() << " h: " << rc.height());