diff --git a/src/Paragraph.cpp b/src/Paragraph.cpp
index f3040b5da1..c33712d416 100644
--- a/src/Paragraph.cpp
+++ b/src/Paragraph.cpp
@@ -3200,8 +3200,7 @@ docstring Paragraph::simpleLyXHTMLOnePar(Buffer const & buf,
 bool Paragraph::isHfill(pos_type pos) const
 {
 	Inset const * inset = getInset(pos);
-	return inset && (inset->lyxCode() == SPACE_CODE &&
-			 inset->isStretchableSpace());
+	return inset && inset->isHfill();
 }
 
 
diff --git a/src/TextMetrics.cpp b/src/TextMetrics.cpp
index 090e503cdc..befa7eb010 100644
--- a/src/TextMetrics.cpp
+++ b/src/TextMetrics.cpp
@@ -672,8 +672,7 @@ void TextMetrics::computeRowMetrics(pit_type const pit,
 	InsetList::const_iterator iend = par.insetList().end();
 	for ( ; ii != iend; ++ii) {
 		if (ii->pos >= endpos || ii->pos < row.pos()
-			|| (ii->inset->lyxCode() != SPACE_CODE ||
-			    !ii->inset->isStretchableSpace()))
+		    || !ii->inset->isHfill())
 			continue;
 		Dimension dim = row.dimension();
 		if (pm.hfillExpansion(row, ii->pos))
diff --git a/src/insets/Inset.h b/src/insets/Inset.h
index 63834eb6a0..5fcc892dba 100644
--- a/src/insets/Inset.h
+++ b/src/insets/Inset.h
@@ -431,8 +431,8 @@ public:
 	/// is this equivalent to a space (which is BTW different from
 	/// a line separator)?
 	virtual bool isSpace() const { return false; }
-	/// is this an expandible space (rubber length)?
-	virtual bool isStretchableSpace() const { return false; }
+	/// does this inset try to use all available space (like \\hfill does)?
+	virtual bool isHfill() const { return false; }
 
 	enum DisplayType {
 		Inline = 0,
diff --git a/src/insets/InsetIPAMacro.cpp b/src/insets/InsetIPAMacro.cpp
index 46d75194ef..7d5290d565 100644
--- a/src/insets/InsetIPAMacro.cpp
+++ b/src/insets/InsetIPAMacro.cpp
@@ -620,16 +620,4 @@ void InsetIPAChar::validate(LaTeXFeatures & features) const
 }
 
 
-bool InsetIPAChar::isLetter() const
-{
-	return true;
-}
-
-
-bool InsetIPAChar::isLineSeparator() const
-{
-	return false;
-}
-
-
 } // namespace lyx
diff --git a/src/insets/InsetIPAMacro.h b/src/insets/InsetIPAMacro.h
index ff07b4009c..dbcfc541ab 100644
--- a/src/insets/InsetIPAMacro.h
+++ b/src/insets/InsetIPAMacro.h
@@ -167,9 +167,7 @@ public:
 	/// should this inset be handled like a normal character?
 	bool isChar() const { return true; }
 	/// is this equivalent to a letter?
-	bool isLetter() const;
-	/// should we break lines after this inset?
-	bool isLineSeparator() const;
+	bool isLetter() const { return true; }
 private:
 	Inset * clone() const { return new InsetIPAChar(*this); }
 
diff --git a/src/insets/InsetSpace.cpp b/src/insets/InsetSpace.cpp
index f7a1cd92ae..4066e3954a 100644
--- a/src/insets/InsetSpace.cpp
+++ b/src/insets/InsetSpace.cpp
@@ -199,7 +199,7 @@ int const arrow_size = 8;
 
 void InsetSpace::metrics(MetricsInfo & mi, Dimension & dim) const
 {
-	if (isStretchableSpace()) {
+	if (isHfill()) {
 		// The metrics for this kinds are calculated externally in
 		// \c TextMetrics::computeRowMetrics. Those are dummy value:
 		dim = Dimension(10, 10, 10);
@@ -240,7 +240,7 @@ void InsetSpace::metrics(MetricsInfo & mi, Dimension & dim) const
 			break;
 		case InsetSpaceParams::CUSTOM:
 		case InsetSpaceParams::CUSTOM_PROTECTED: {
-			int const w = 
+			int const w =
 				params_.length.len().inPixels(mi.base.textwidth,
 							fm.width(char_type('M')));
 			int const minw = (w < 0) ? 3 * arrow_size : 4;
@@ -267,7 +267,7 @@ void InsetSpace::draw(PainterInfo & pi, int x, int y) const
 {
 	Dimension const dim = dimension(*pi.base.bv);
 
-	if (isStretchableSpace() || params_.length.len().value() < 0) {
+	if (isHfill() || params_.length.len().value() < 0) {
 		int const asc = theFontMetrics(pi.base.font).ascent('M');
 		int const desc = theFontMetrics(pi.base.font).descent('M');
 		// Pixel height divisible by 2 for prettier fill graphics:
@@ -459,7 +459,7 @@ void InsetSpaceParams::write(ostream & os) const
 		os <<  "\\hspace*{}";
 		break;
 	}
-	
+
 	if (!length.len().empty())
 		os << "\n\\length " << length.asString();
 }
@@ -837,7 +837,7 @@ void InsetSpace::forOutliner(docstring & os, size_t) const
 }
 
 
-bool InsetSpace::isStretchableSpace() const
+bool InsetSpace::isHfill() const
 {
 	return params_.kind == InsetSpaceParams::HFILL
 		|| params_.kind == InsetSpaceParams::HFILL_PROTECTED
diff --git a/src/insets/InsetSpace.h b/src/insets/InsetSpace.h
index 8055706c41..b5a628a456 100644
--- a/src/insets/InsetSpace.h
+++ b/src/insets/InsetSpace.h
@@ -142,9 +142,8 @@ public:
 	bool clickable(int, int) const { return true; }
 	///
 	InsetCode lyxCode() const { return SPACE_CODE; }
-	/// is this an expandible space (rubber length)?
-	bool isStretchableSpace() const;
-
+	/// does this inset try to use all available space (like \\hfill does)?
+	bool isHfill() const;
 	/// should this inset be handled like a normal character?
 	bool isChar() const { return true; }
 	/// is this equivalent to a letter?