[LyX/master] Better implementation for corssOutLines

[Jean-Marc Lasgouttes]

commit 94114fd1218df7d2d99888bd18bc5fee394ff515
Author: Jean-Marc Lasgouttes <lasgout...@lyx.org>
Date:   Mon Apr 10 10:27:08 2017 +0200

    Better implementation for corssOutLines
    
    When trying to do implement a LaTeX feature on screen, it is always
    good to see how LaTeX does it, just in case it is easy to implement on
    our side.
    
    Then we have a correct output at all DPI sizes.
---
 src/frontends/qt4/GuiPainter.cpp |   23 +++++++++++------------
 1 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/src/frontends/qt4/GuiPainter.cpp b/src/frontends/qt4/GuiPainter.cpp
index cfde181..93bf16c 100644
--- a/src/frontends/qt4/GuiPainter.cpp
+++ b/src/frontends/qt4/GuiPainter.cpp
@@ -26,8 +26,9 @@
 
 #include "insets/Inset.h"
 
-#include "support/lassert.h"
 #include "support/debug.h"
+#include "support/lassert.h"
+#include "support/lyxlib.h"
 
 #include <algorithm>
 
@@ -669,17 +670,15 @@ void GuiPainter::strikeoutLine(FontInfo const & f, int x, 
int y, int width)
 
 void GuiPainter::crossoutLines(FontInfo const & f, int x, int y, int width)
 {
-       FontMetrics const & fm = theFontMetrics(f);
-       int const bottom = fm.underlinePos();
-       int const middle = fm.strikeoutPos();
-
-       // we draw several lines to fill the whole selection with strokes
-       // use 5 as diagonal width since this is close to the PDf output
-       // with normal font zoom levels
-       for(int x_current = x; x_current < x + width - 5; x_current = x_current 
+ 5) {
-               line(x_current, y + bottom, x_current + 5, y - 2 * middle - 2 * 
bottom,
-                       f.realColor(), line_solid, fm.lineWidth());
-       }
+       FontInfo tmpf = f;
+       tmpf.setXout(FONT_OFF);
+
+       // the definition of \xout in ulem.sty is
+    //  \def\xout{\bgroup \markoverwith{\hbox to.35em{\hss/\hss}}\ULon}
+       // Let's mimick it somewhat.
+       double offset = max(0.35 * theFontMetrics(tmpf).em(), 1);
+       for (int i = 0 ; i < iround(width / offset) ; ++i)
+               text(x + iround(i * offset), y, '/', tmpf);
 }