Define new inPixels helper in BufferView

Length::inPixels(MetricsBase const &) and VSpace::inPixels(BufferView
const &) should be moved respectuvely to MetricsBase and BufferView:
core file are not supposed to use GUI files.

src/BufferView.cpp

@@ -368,6 +368,13 @@ int BufferView::leftMargin() const
 }
 
 
+int BufferView::inPixels(Length const & len) const
+{
+	Font const font = buffer().params().getFont();
+	return len.inPixels(workWidth(), theFontMetrics(font).em());
+}
+
+
 bool BufferView::isTopScreen() const
 {
 	return 0 == d->scrollbarParameters_.min;

src/BufferView.h

@@ -41,6 +41,7 @@ class FuncRequest;
 class FuncStatus;
 class Intl;
 class Inset;
+class Length;
 class PainterInfo;
 class ParIterator;
 class ParagraphMetrics;
@@ -105,6 +106,14 @@ public:
 	/// left margin
 	int leftMargin() const;
 
+	/// return the on-screen size of this length
+	/*
+	 *  This is a wrapper around Length::inPixels that uses the
+	 *  bufferview width as width and the EM value of the default
+	 *  document font.
+	 */
+	int inPixels(Length const & len) const;
+
 	/// \return true if the BufferView is at the top of the document.
 	bool isTopScreen() const;
 

src/Length.h

@@ -97,9 +97,11 @@ public:
 	 *	FontMetrics::em() to get this value.
 	 */
 	int inPixels(int text_width, int em_width = 0) const;
+
 	/** return the on-screen size of this length
 	 *
-	 *  This version of the function uses the right EM definition.
+	 *  This version of the function uses the current inset width as
+	 *  width and the EM value of the current font.
 	 */
 	int inPixels(MetricsBase const &) const;
 	/// return the value in Big Postscript points.

src/VSpace.cpp

@@ -228,7 +228,7 @@ int VSpace::inPixels(BufferView const & bv) const
 		return 3 * default_height;
 
 	case LENGTH:
-		return len_.len().inPixels(bv.workWidth());
+		return bv.inPixels(len_.len());
 
 	default:
 		LATTEST(false);