Handle negative values gracefully.

It may happen (for example with on the fly spell checking) that
GuiFontMetrics::pos2x is called with a negative pos value. Add a
special case for this situation.

Fixes bug #10506

diff --git a/src/frontends/qt4/GuiFontMetrics.cpp b/src/frontends/qt4/GuiFontMetrics.cpp
index 77cda8043409223c62a0b4dc39a24d57ec1025d6..d3c89f1a593b6d9ae8f3b4dc3e08d574b62ffa2c 100644 (file)
--- a/src/frontends/qt4/GuiFontMetrics.cpp
+++ b/src/frontends/qt4/GuiFontMetrics.cpp
@@ -205,6 +205,8 @@ GuiFontMetrics::getTextLayout(docstring const & s, QFont font,
 int GuiFontMetrics::pos2x(docstring const & s, int const pos, bool const rtl,
                           double const wordspacing) const
 {
+       if (pos <= 0)
+               return rtl ? width(s) : 0;
        QTextLayout const & tl = getTextLayout(s, font_, rtl, wordspacing);
        /* Since QString is UTF-16 and docstring is UCS-4, the offsets may
         * not be the same when there are high-plan unicode characters