From 746644667cff9490d0f9a5f4ab70c76137dc80a2 Mon Sep 17 00:00:00 2001
From: Francesco Zanini <francesco@zanini.me>
Date: Mon, 6 Oct 2025 16:19:55 +0200
Subject: [PATCH] Allow management of resources and modules paths

SDR++ uses the config file to determine the location of modules and
resources to load. While this is mostly static in other distributions,
in Nix it changes very often.

This commit adds some functionality to the config manager to replace
`@prefix@` in the values of the keys `modulesDirectory` and
`resourcesDirectory` to a dynamic path. On save, the change is reverted.

The prefix path used is either the installation directory, or the
content of the `SDRPP_PREFIX` environment variable, if present.

NOTE: Paths are transformed using a *temporary copy* of the config. This fixes
the issue described here https://github.com/NixOS/nixpkgs/issues/467610.
---
 core/src/config.cpp | 34 ++++++++++++++++++++++++++++++++--
 core/src/config.h   |  4 +++-
 core/src/core.cpp   | 15 ++-------------
 3 files changed, 37 insertions(+), 16 deletions(-)

diff --git a/core/src/config.cpp b/core/src/config.cpp
index 6de1888f..dfde5628 100644
--- a/core/src/config.cpp
+++ b/core/src/config.cpp
@@ -41,13 +41,18 @@ void ConfigManager::load(json def, bool lock) {
         conf = def;
         save(false);
     }
+
+    transformPaths(conf, true);
+
     if (lock) { mtx.unlock(); }
 }
 
 void ConfigManager::save(bool lock) {
     if (lock) { mtx.lock(); }
     std::ofstream file(path.c_str());
-    file << conf.dump(4);
+    auto tmp_conf = conf;
+    transformPaths(tmp_conf, false);
+    file << tmp_conf.dump(4);
     file.close();
     if (lock) { mtx.unlock(); }
 }
@@ -98,4 +103,29 @@ void ConfigManager::autoSaveWorker() {
             termCond.wait_for(lock, std::chrono::milliseconds(1000), [this]() { return termFlag; });
         }
     }
-}
\ No newline at end of file
+}
+
+void ConfigManager::transformPaths(json& conf, bool expand) {
+    const char* env_prefix = std::getenv("SDRPP_PREFIX");
+    const std::string prefix = env_prefix ? env_prefix : INSTALL_PREFIX;
+
+    std::vector<std::string> directoryKeys = {
+        "modulesDirectory",
+        "resourcesDirectory"
+    };
+
+    const std::string from = expand ? "@prefix@" : prefix;
+    const std::string to = expand ? prefix : "@prefix@";
+
+    for (const auto& key : directoryKeys) {
+        if (conf.contains(key)) {
+            auto dir = conf[key].get<std::string>();
+
+            size_t pos = dir.find(from);
+            if (pos != std::string::npos) {
+                dir.replace(pos, from.length(), to);
+                conf[key] = dir;
+            }
+        }
+    }
+}
diff --git a/core/src/config.h b/core/src/config.h
index fbbdeb4a..f9deef01 100644
--- a/core/src/config.h
+++ b/core/src/config.h
@@ -33,4 +33,6 @@ private:
     std::mutex termMtx;
     std::condition_variable termCond;
     volatile bool termFlag = false;
-};
\ No newline at end of file
+
+    static void transformPaths(json& conf, bool expand);
+};
diff --git a/core/src/core.cpp b/core/src/core.cpp
index 37358062..f1b5396c 100644
--- a/core/src/core.cpp
+++ b/core/src/core.cpp
@@ -267,19 +267,8 @@ int sdrpp_main(int argc, char* argv[]) {
     defConfig["lockMenuOrder"] = false;
 #endif
 
-#if defined(_WIN32)
-    defConfig["modulesDirectory"] = "./modules";
-    defConfig["resourcesDirectory"] = "./res";
-#elif defined(IS_MACOS_BUNDLE)
-    defConfig["modulesDirectory"] = "../Plugins";
-    defConfig["resourcesDirectory"] = "../Resources";
-#elif defined(__ANDROID__)
-    defConfig["modulesDirectory"] = root + "/modules";
-    defConfig["resourcesDirectory"] = root + "/res";
-#else
-    defConfig["modulesDirectory"] = INSTALL_PREFIX "/lib/sdrpp/plugins";
-    defConfig["resourcesDirectory"] = INSTALL_PREFIX "/share/sdrpp";
-#endif
+    defConfig["modulesDirectory"] = "@prefix@/lib/sdrpp/plugins";
+    defConfig["resourcesDirectory"] = "@prefix@/share/sdrpp";
 
     // Load config
     flog::info("Loading config");
-- 
2.52.0