--- a/src/src.pro.orig	2018-12-13 09:54:51.989453243 +0100
+++ b/src/src.pro	2018-12-13 09:56:15.428141228 +0100
@@ -367,6 +367,54 @@
     SOURCES     += FileIO/SrmDevice.cpp
 }
 
+ 
+###==================
+### OPTIONAL => QXT
+###==================
+
+!isEmpty(QXT_INSTALL) {
+
+    # we will work out the rest if you tell use where it is installed
+    isEmpty(QXT_INCLUDE) { QXT_INCLUDE = $${QXT_INSTALL}/include }
+    isEmpty(QXT_LIBS)    { QXT_LIBS    = -L$${QXT_INSTALL}/lib -lQxtCore-qt5 }
+
+    DEFINES     += GC_HAVE_QXT
+    INCLUDEPATH += $${QXT_INCLUDE}
+    LIBS        += $${QXT_LIBS}
+}
+
+
+###==================
+### OPTIONAL => LMFIT
+###====================
+
+!isEmpty(LMFIT_INSTALL) {
+
+    # we will work out the rest if you tell us where it is installed
+    isEmpty(LMFIT_INCLUDE) { LMFIT_INCLUDE = $${LMFIT_INSTALL}/include }
+    isEmpty(LMFIT_LIBS)    { LMFIT_LIBS    = -L$${LMFIT_INSTALL}/$$LIB_SUFFIX -llmfit }
+
+    INCLUDEPATH += $${LMFIT_INCLUDE}
+    LIBS        += $${LMFIT_LIBS}
+    DEFINES     += GC_HAVE_LMFIT
+}
+
+
+###==================
+### OPTIONAL => LEVMAR
+###====================
+
+!isEmpty(LEVMAR_INSTALL) {
+
+    # we will work out the rest if you tell us where it is installed
+    isEmpty(LEVMAR_INCLUDE) { LEVMAR_INCLUDE = $${LEVMAR_INSTALL}/include }
+    isEmpty(LEVMAR_LIBS)    { LEVMAR_LIBS     = -L$${LEVMAR_INSTALL}/$$LIB_SUFFIX -llevmar }
+
+    INCLUDEPATH += $${LEVMAR_INCLUDE}
+    LIBS        += $${LEVMAR_LIBS}
+    DEFINES     += GC_HAVE_LEVMAR
+}
+
 
 ###=====================================
 ### OPTIONAL => GOOGLE KML IMPORT EXPORT