diff --git a/headers/private/servers/app/DisplayDriver.h b/headers/private/servers/app/DisplayDriver.h
index fad12e1b59..d756c8d0db 100644
--- a/headers/private/servers/app/DisplayDriver.h
+++ b/headers/private/servers/app/DisplayDriver.h
@@ -43,6 +43,7 @@ class DrawData;
 class RGBColor;
 class ServerBitmap;
 class ServerCursor;
+class ServerFont;
 
 /*!
 	\brief Data structure for passing cursor information to hardware drivers.
@@ -257,6 +258,10 @@ class DisplayDriver {
 												int32 length,
 												const DrawData *d) = 0;
 
+	virtual	float				StringWidth(	const char *string,
+												int32 length,
+												const ServerFont &font) = 0;
+
 	virtual	float				StringHeight(	const char *string,
 												int32 length,
 												const DrawData *d) = 0;