ui: Add follow system theme option

source/window/linux_window.cpp

@@ -2,6 +2,9 @@
 
 #if defined(OS_LINUX)
 
+    #include <nlohmann/json.hpp>
+    #include <sys/wait.h>
+
     namespace hex {
 
         void Window::initNative() {
@@ -9,7 +12,28 @@
         }
 
         void Window::setupNativeWindow() {
+            bool themeFollowSystem = ContentRegistry::Settings::getSetting("hex.builtin.setting.interface", "hex.builtin.setting.interface.color") == 0;
+            EventManager::subscribe<EventOSThemeChanged>(this, [themeFollowSystem]{
+                if (!themeFollowSystem) return;
 
+                std::array<char, 128> buffer = { 0 };
+                std::string result;
+
+                // TODO: In the future maybe support more DEs instead of just GNOME
+                FILE* pipe = popen("gsettings get org.gnome.desktop.interface gtk-theme 2>&1", "r");
+                if (pipe == nullptr) return;
+
+                while (fgets(buffer.data(), buffer.size(), pipe) != nullptr)
+                    result += buffer.data();
+
+                auto exitCode = WEXITSTATUS(pclose(pipe));
+                if (exitCode != 0) return;
+
+                EventManager::post<RequestChangeTheme>(hex::containsIgnoreCase(result, "dark") ? 1 : 2);
+            });
+
+            if (themeFollowSystem)
+                EventManager::post<EventOSThemeChanged>();
         }
 
         void Window::updateNativeWindow() {