[LyX/master] Avoid showing vertical scroll mark when not necessary

[Jean-Marc Lasgouttes]

commit 32edb65985a8e63340c0421d76c00956bf846fd2
Author: Jean-Marc Lasgouttes <lasgout...@lyx.org>
Date:   Sun Oct 25 23:58:58 2015 +0100

    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.

diff --git a/src/Row.cpp b/src/Row.cpp
index e3e8a34..5bdcbe0 100644
--- a/src/Row.cpp
+++ b/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;
diff --git a/src/Row.h b/src/Row.h
index a51e3ce..e03e4c9 100644
--- a/src/Row.h
+++ b/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
diff --git a/src/TextMetrics.cpp b/src/TextMetrics.cpp
index 15ecafe..73bd4f8 100644
--- a/src/TextMetrics.cpp
+++ b/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.