Compatible resource directory determination

Previously, the resource directory is generated from `SNAP` if set,
`/usr/share/anbox` is used otherwise. This cannot work with binaries
installed via `make install` since the loading screen is mostly at
`/usr/local/share/anbox/ui/loading-screen.png`.

With this patch, anbox can get correct resource directory when it's
installed without snap.

src/anbox/cmds/launch.cpp

@@ -119,12 +119,6 @@ anbox::cmds::Launch::Launch()
     auto bus = std::make_shared<core::dbus::Bus>(bus_type);
     bus->install_executor(core::dbus::asio::make_executor(bus, rt->service()));
 
-    const auto snap_path = utils::get_env_value("SNAP");
-    if (!snap_path.empty()) {
-      const auto resource_path = fs::path(snap_path) / "usr" / "share" / "anbox";
-      SystemConfiguration::instance().set_resource_path(resource_path);
-    }
-
     std::shared_ptr<ui::SplashScreen> ss;
 
     // Instead of relying on the user session init system to start our

src/anbox/config.cpp

@@ -41,10 +41,6 @@ void anbox::SystemConfiguration::set_data_path(const std::string &path) {
   data_path = path;
 }
 
-void anbox::SystemConfiguration::set_resource_path(const fs::path &path) {
-  resource_path = path;
-}
-
 fs::path anbox::SystemConfiguration::data_dir() const {
   return data_path;
 }
@@ -88,3 +84,24 @@ anbox::SystemConfiguration& anbox::SystemConfiguration::instance() {
   static SystemConfiguration config;
   return config;
 }
+
+anbox::SystemConfiguration::SystemConfiguration() {
+  auto gen_resource_path = [] () -> fs::path {
+    const auto snap_path = utils::get_env_value("SNAP");
+    if (!snap_path.empty()) {
+      return fs::path(snap_path) / "usr/share/anbox";
+    }
+
+    const std::string exe = utils::process_get_exe_path(::getpid());
+    const std::size_t pos = exe.rfind("/bin/anbox");
+    if (pos != std::string::npos) {
+      const std::string leading_path = exe.substr(0, pos);
+      return fs::path(leading_path) / "share/anbox";
+    } else {
+      return "/usr/local/share/anbox";
+    }
+  };
+
+  resource_path = gen_resource_path();
+  data_path = "/var/local/lib/anbox";
+}

src/anbox/config.h

@@ -31,7 +31,6 @@ class SystemConfiguration {
   virtual ~SystemConfiguration() = default;
 
   void set_data_path(const std::string &path);
-  void set_resource_path(const boost::filesystem::path &path);
 
   boost::filesystem::path data_dir() const;
   std::string rootfs_dir() const;
@@ -44,10 +43,10 @@ class SystemConfiguration {
   std::string resource_dir() const;
 
  protected:
-  SystemConfiguration() = default;
+  SystemConfiguration();
 
-  boost::filesystem::path data_path = "/var/lib/anbox";
-  boost::filesystem::path resource_path = "/usr/share/anbox";
+  boost::filesystem::path data_path;
+  boost::filesystem::path resource_path;
 
 };
 }  // namespace anbox