diff --git a/mozilla/gfx/src/xlib/nsFontMetricsXlib.cpp b/mozilla/gfx/src/xlib/nsFontMetricsXlib.cpp
index 09556ebc554..89925125dff 100644
--- a/mozilla/gfx/src/xlib/nsFontMetricsXlib.cpp
+++ b/mozilla/gfx/src/xlib/nsFontMetricsXlib.cpp
@@ -62,6 +62,7 @@ nsFontMetricsXlib::nsFontMetricsXlib()
   mStrikeoutOffset = 0;
   mUnderlineSize = 0;
   mUnderlineOffset = 0;
+  mSpaceWidth = 0;
 }
 
 nsFontMetricsXlib::~nsFontMetricsXlib()
@@ -419,6 +420,8 @@ void nsFontMetricsXlib::RealizeFont()
   // 56% of ascent, best guess for non-true type
   mXHeight = NSToCoordRound((float) mFontHandle->ascent* f * 0.56f);
 
+  int rawWidth = XTextWidth(mFontHandle, " ", 1);
+  mSpaceWidth = NSToCoordRound(rawWidth * f);
   unsigned long pr = 0;
 
   if (::XGetFontProperty(mFontHandle, XA_X_HEIGHT, &pr))
@@ -2184,4 +2187,11 @@ nsFontMetricsXlib::DrawString(nsDrawingSurfaceXlib* aSurface, nsFontXlib* aFont,
                 aX, aY, buf, (len / 2));
 }
 
+nsresult
+nsFontMetricsXlib::GetSpaceWidth(nscoord &aSpaceWidth)
+{
+  aSpaceWidth = mSpaceWidth;
+  return NS_OK;
+}
+
 #endif /* FONT_SWITCHING */
diff --git a/mozilla/gfx/src/xlib/nsFontMetricsXlib.h b/mozilla/gfx/src/xlib/nsFontMetricsXlib.h
index 658fb4dfd3f..8a227eaa823 100644
--- a/mozilla/gfx/src/xlib/nsFontMetricsXlib.h
+++ b/mozilla/gfx/src/xlib/nsFontMetricsXlib.h
@@ -102,6 +102,8 @@ public:
   NS_IMETHOD  GetFont(const nsFont *&aFont);
   NS_IMETHOD  GetFontHandle(nsFontHandle &aHandle);
 
+  virtual nsresult GetSpaceWidth(nscoord &aSpaceWidth);
+
 #ifdef FONT_SWITCHING
 
   nsFontXlib*  FindFont(PRUnichar aChar);
@@ -152,6 +154,7 @@ protected:
   nscoord             mStrikeoutOffset;
   nscoord             mUnderlineSize;
   nscoord             mUnderlineOffset;
+  nscoord             mSpaceWidth;
 
 #ifdef FONT_SWITCHING
 
diff --git a/mozilla/gfx/src/xlib/nsRenderingContextXlib.cpp b/mozilla/gfx/src/xlib/nsRenderingContextXlib.cpp
index 0a87387c157..19f156fffc5 100644
--- a/mozilla/gfx/src/xlib/nsRenderingContextXlib.cpp
+++ b/mozilla/gfx/src/xlib/nsRenderingContextXlib.cpp
@@ -958,6 +958,12 @@ NS_IMETHODIMP
 nsRenderingContextXlib::GetWidth(char aC, nscoord& aWidth)
 {
   printf("nsRenderingContextXlib::GetWidth()\n");
+  // Check for the very common case of trying to get the width of a single
+  // space.
+  if ((aC == ' ') && (nsnull != mFontMetrics)) {
+    nsFontMetricsXlib* fontMetricsXlib = (nsFontMetricsXlib*)mFontMetrics;
+    return fontMetricsXlib->GetSpaceWidth(aWidth);
+  }
   return GetWidth(&aC, 1, aWidth);
 }