add protobuf
diff --git a/demo/sync-demo.pri b/demo/sync-demo.pri
new file mode 100644
index 0000000..88ab350
--- /dev/null
+++ b/demo/sync-demo.pri
@@ -0,0 +1,18 @@
+PROTOPATH += .
+PROTOPATHS =
+for(p, PROTOPATH):PROTOPATHS += --proto_path=$${p}
+
+protobuf_decl.name = protobuf header
+protobuf_decl.input = PROTOS
+protobuf_decl.output = ${QMAKE_FILE_BASE}.pb.h
+protobuf_decl.commands = protoc --cpp_out="." $${PROTOPATHS} ${QMAKE_FILE_NAME}
+protobuf_decl.variable_out = GENERATED_FILES
+QMAKE_EXTRA_COMPILERS += protobuf_decl
+
+protobuf_impl.name = protobuf implementation
+protobuf_impl.input = PROTOS
+protobuf_impl.output = ${QMAKE_FILE_BASE}.pb.cc
+protobuf_impl.depends = ${QMAKE_FILE_BASE}.pb.h
+protobuf_impl.commands = $$escape_expand(\n)
+protobuf_impl.variable_out = GENERATED_SOURCES
+QMAKE_EXTRA_COMPILERS += protobuf_impl