From aa3c2879992aa45eac229c3c522a990941be70d2 Mon Sep 17 00:00:00 2001
From: Axel Kohlmeyer <akohlmey@gmail.com>
Date: Mon, 29 Jul 2024 00:05:53 -0400
Subject: [PATCH] add wrapper to extract value of equal style and compatible
 variables

---
 tools/lammps-gui/lammpswrapper.cpp | 20 ++++++++++++++++++++
 tools/lammps-gui/lammpswrapper.h   |  1 +
 2 files changed, 21 insertions(+)

diff --git a/tools/lammps-gui/lammpswrapper.cpp b/tools/lammps-gui/lammpswrapper.cpp
index 1ccb225a0a..ed2bde1c9f 100644
--- a/tools/lammps-gui/lammpswrapper.cpp
+++ b/tools/lammps-gui/lammpswrapper.cpp
@@ -102,6 +102,26 @@ void *LammpsWrapper::extract_atom(const char *keyword)
     return val;
 }
 
+// note: equal style and compatible variables only
+double LammpsWrapper::extract_variable(const char *keyword)
+{
+    void *ptr = nullptr;
+    if (lammps_handle) {
+#if defined(LAMMPS_GUI_USE_PLUGIN)
+        ptr = ((liblammpsplugin_t *)plugin_handle)->extract_variable(lammps_handle, keyword, nullptr);
+#else
+        ptr = lammps_extract_variable(lammps_handle, keyword, nullptr);
+#endif
+    }
+    double val = *((double *)ptr);
+#if defined(LAMMPS_GUI_USE_PLUGIN)
+    ptr = ((liblammpsplugin_t *)plugin_handle)->free(ptr);
+#else
+    lammps_free(ptr);
+#endif
+    return val;
+}
+
 int LammpsWrapper::id_count(const char *keyword)
 {
     int val = 0;
diff --git a/tools/lammps-gui/lammpswrapper.h b/tools/lammps-gui/lammpswrapper.h
index 8719ef4491..9157bf77b5 100644
--- a/tools/lammps-gui/lammpswrapper.h
+++ b/tools/lammps-gui/lammpswrapper.h
@@ -34,6 +34,7 @@ public:
     void *extract_global(const char *keyword);
     void *extract_pair(const char *keyword);
     void *extract_atom(const char *keyword);
+    double extract_variable(const char *keyword);
 
     int id_count(const char *idtype);
     int id_name(const char *idtype, int idx, char *buf, int buflen);