Merge pull request #24477 from lupoDharkael/nouveau

Don't enable DRI_PRIME if nouveau is loaded

platform/x11/os_x11.cpp

@@ -243,7 +243,26 @@ Error OS_X11::initialize(const VideoMode &p_desired, int p_video_driver, int p_a
 	// Set DRI_PRIME if not set. This means that Godot should default to a higher-power GPU if it exists.
 	// Note: Due to the final '0' parameter to setenv any existing DRI_PRIME environment variables will not
 	// be overwritten.
-	setenv("DRI_PRIME", "1", 0);
+	bool enable_dri_prime = true;
+	// Check if Nouveau is loaded, we don't want to force dGPU usage with that driver.
+	if (FileAccess *f = FileAccess::open("/proc/modules", FileAccess::READ)) {
+		// Match driver name + space
+		String nouveau_str = "nouveau ";
+
+		while (!f->eof_reached()) {
+			String line = f->get_line();
+
+			if (line.begins_with(nouveau_str)) {
+				enable_dri_prime = false;
+				break;
+			}
+		}
+		f->close();
+		memdelete(f);
+	}
+	if (enable_dri_prime) {
+		setenv("DRI_PRIME", "1", 0);
+	}
 
 	ContextGL_X11::ContextType opengl_api_type = ContextGL_X11::GLES_3_0_COMPATIBLE;