From e6b54ea4d2e28d55565699ded45da971278b23bf Mon Sep 17 00:00:00 2001
From: Jean-Marc Lasgouttes <lasgouttes@lyx.org>
Date: Sun, 14 Jul 2019 23:20:29 +0200
Subject: [PATCH] Fix assertion in caret display code

It is not a good idea to call caretPosAndHeight when the caret is in a
paragraph that is not in cached metrics. This can happen when not
using "cursor follows scrollbar".

This commit refactor things a bit so that testing is done in
BufferView.

This bug is not in 2.3.x.
---
 src/BufferView.cpp                | 11 ++++++++---
 src/BufferView.h                  |  4 ++--
 src/frontends/qt4/GuiWorkArea.cpp | 15 +++++----------
 3 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/src/BufferView.cpp b/src/BufferView.cpp
index 2068f050cf..97adab820c 100644
--- a/src/BufferView.cpp
+++ b/src/BufferView.cpp
@@ -3044,11 +3044,16 @@ void BufferView::caretPosAndHeight(Point & p, int & h) const
 }
 
 
-bool BufferView::cursorInView(Point const & p, int h) const
+bool BufferView::caretInView() const
 {
-	Cursor const & cur = cursor();
+	if (!paragraphVisible(cursor()))
+		return false;
+	Point p;
+	int h;
+	caretPosAndHeight(p, h);
+
 	// does the cursor touch the screen ?
-	if (p.y_ + h < 0 || p.y_ >= workHeight() || !paragraphVisible(cur))
+	if (p.y_ + h < 0 || p.y_ >= workHeight())
 		return false;
 	return true;
 }
diff --git a/src/BufferView.h b/src/BufferView.h
index 45928f256e..40dd0d29c3 100644
--- a/src/BufferView.h
+++ b/src/BufferView.h
@@ -307,8 +307,8 @@ public:
 	Point getPos(DocIterator const & dit) const;
 	/// is the paragraph of the cursor visible ?
 	bool paragraphVisible(DocIterator const & dit) const;
-	/// is the cursor currently visible in the view
-	bool cursorInView(Point const & p, int h) const;
+	/// is the caret currently visible in the view
+	bool caretInView() const;
 	/// get the position and height of the caret
 	void caretPosAndHeight(Point & p, int & h) const;
 
diff --git a/src/frontends/qt4/GuiWorkArea.cpp b/src/frontends/qt4/GuiWorkArea.cpp
index 02c56c2fdb..6a7c995da9 100644
--- a/src/frontends/qt4/GuiWorkArea.cpp
+++ b/src/frontends/qt4/GuiWorkArea.cpp
@@ -439,11 +439,8 @@ void GuiWorkArea::startBlinkingCaret()
 	if (view().busy())
 		return;
 
-	Point p;
-	int h = 0;
-	d->buffer_view_->caretPosAndHeight(p, h);
 	// Don't start blinking if the cursor isn't on screen.
-	if (!d->buffer_view_->cursorInView(p, h))
+	if (!d->buffer_view_->caretInView())
 		return;
 
 	d->showCaret();
@@ -583,10 +580,7 @@ void GuiWorkArea::Private::resizeBufferView()
 	// Warn our container (GuiView).
 	p->busy(true);
 
-	Point point;
-	int h = 0;
-	buffer_view_->caretPosAndHeight(point, h);
-	bool const caret_in_view = buffer_view_->cursorInView(point, h);
+	bool const caret_in_view = buffer_view_->caretInView();
 	buffer_view_->resize(p->viewport()->width(), p->viewport()->height());
 	if (caret_in_view)
 		buffer_view_->scrollToCursor();
@@ -610,11 +604,12 @@ void GuiWorkArea::Private::resizeBufferView()
 
 void GuiWorkArea::Private::updateCaretGeometry()
 {
+	if (!buffer_view_->caretInView())
+		return;
+
 	Point point;
 	int h = 0;
 	buffer_view_->caretPosAndHeight(point, h);
-	if (!buffer_view_->cursorInView(point, h))
-		return;
 
 	// RTL or not RTL
 	bool l_shape = false;