Avoid showing vertical scroll mark when not necessary

Now the mark if only shown when editable text is outside of the row.

Fixes bug #9807.

src/Row.cpp

@@ -259,6 +259,35 @@ ostream & operator<<(ostream & os, Row const & row)
 }
 
 
+int Row::left_x() const
+{
+	double x = left_margin;
+	const_iterator const end = elements_.end();
+	const_iterator cit = elements_.begin();
+	while (cit != end && cit->isVirtual()) {
+		x += cit->full_width();
+		++cit;
+	}
+	return int(x + 0.5);
+}
+
+
+int Row::right_x() const
+{
+	double x = dim_.wid;
+	const_iterator const begin = elements_.begin();
+	const_iterator cit = elements_.end();
+	while (cit != begin) {
+		--cit;
+		if (cit->isVirtual())
+			x -= cit->full_width();
+		else
+			break;
+	}
+	return int(x + 0.5);
+}
+
+
 int Row::countSeparators() const
 {
 	int n = 0;

src/Row.h

@@ -170,6 +170,11 @@ public:
 	///
 	int descent() const { return dim_.des; }
 
+	/// The offset of the left-most cursor position on the row
+	int left_x() const;
+	/// The offset of the right-most cursor position on the row
+	int right_x() const;
+
 	// Return the number of separators in the row
 	int countSeparators() const;
 	// Set the extra spacing for every separator in STRING elements

src/TextMetrics.cpp

@@ -1956,8 +1956,8 @@ void TextMetrics::drawParagraph(PainterInfo & pi, pit_type const pit, int const
 			rp.paintLast();
 		if (i == 0 && is_rtl)
 			rp.paintFirst();
-		rp.paintTooLargeMarks(row_x < 0,
-				      row_x + row.width() > bv_->workWidth());
+		rp.paintTooLargeMarks(row_x < row.left_x(),
+				      row_x + row.right_x() > bv_->workWidth());
 		y += row.descent();
 
 		// Restore full_repaint status.