center town labels on minimap

--HG--
branch : openttd

src/viewport.cpp

@@ -1310,7 +1310,7 @@ static void ViewportAddSigns(DrawPixelInfo *dpi)
  * @param top    the new top of the sign
  * @param str    the string to show in the sign
  */
-void ViewportSign::UpdatePosition(int center, int top, StringID str)
+void ViewportSign::UpdatePosition(int center, int top, StringID str, StringID small_str)
 {
 	if (this->width_normal != 0) this->MarkDirty();
 
@@ -1323,6 +1323,9 @@ void ViewportSign::UpdatePosition(int center, int top, StringID str)
 	this->center = center;
 
 	/* zoomed out version */
+	if (small_str != STR_NULL) {
+		GetString(buffer, small_str, lastof(buffer));
+	}
 	this->width_small = VPSM_LEFT + Align(GetStringBoundingBox(buffer, FS_SMALL).width, 2) + VPSM_RIGHT;
 
 	this->MarkDirty();