[LyX/2.3.x] Introduce BufferView::caretInView()

[Jean-Marc Lasgouttes]

commit 64e5a8c01660051a8c5831f6b0f8ef4c66866034
Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
Date:   Sun Jul 14 23:20:29 2019 +0200

    Introduce BufferView::caretInView()
    
    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.
    
    (cherry picked from commit e6b54ea4d2e28d55565699ded45da971278b23bf)
---
 src/BufferView.cpp                |   11 ++++++++---
 src/BufferView.h                  |    4 ++--
 src/frontends/qt4/GuiWorkArea.cpp |   25 ++++++++-----------------
 3 files changed, 18 insertions(+), 22 deletions(-)

diff --git a/src/BufferView.cpp b/src/BufferView.cpp
index e7e69f6..0788036 100644
--- a/src/BufferView.cpp
+++ b/src/BufferView.cpp
@@ -3060,11 +3060,16 @@ 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 1089781..886d3c8 100644
--- a/src/BufferView.h
+++ b/src/BufferView.h
@@ -303,8 +303,8 @@ 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;
 	/// set the ascent and descent of the caret
 	void setCaretAscentDescent(int asc, int des);
 	/// get the position and height of the caret
diff --git a/src/frontends/qt4/GuiWorkArea.cpp b/src/frontends/qt4/GuiWorkArea.cpp
index 046199d..e8cb4c4 100644
--- a/src/frontends/qt4/GuiWorkArea.cpp
+++ b/src/frontends/qt4/GuiWorkArea.cpp
@@ -443,16 +443,11 @@ void GuiWorkArea::startBlinkingCaret()
 	if (view().busy())
 		return;
 
-	// we cannot update geometry if not ready and we do not need to if
-	// caret is not in view.
-	if (!d->buffer_view_->buffer().undo().activeUndoGroup()) {
-		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))
-			return;
-	}
+	// Don't start blinking if the cursor isn't on screen, unless we
+	// are not ready to know whether the cursor is on screen.
+	if (!d->buffer_view_->buffer().undo().activeUndoGroup()
+	    && !d->buffer_view_->caretInView())
+		return;
 
 	d->showCaret();
 
@@ -588,10 +583,7 @@ 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();
@@ -617,14 +609,13 @@ void GuiWorkArea::Private::updateCaretGeometry()
 {
 	// we cannot update geometry if not ready and we do not need to if
 	// caret is not in view.
-	if (buffer_view_->buffer().undo().activeUndoGroup())
+	if (buffer_view_->buffer().undo().activeUndoGroup()
+	    || !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;