backend: forward keyboard and mouse input from client

schema/input.fbs

@@ -0,0 +1,53 @@
+namespace InputEvent;
+
+
+enum KeyAction: byte {
+  DOWN,
+  UP,
+}
+
+
+table MouseMovement {
+  movement_x: int16;
+  movement_y: int16;
+}
+
+enum MouseButton: byte {
+  LEFT,
+  MIDDLE,
+  RIGHT,
+  X1,
+  X2
+}
+
+table MouseInput {
+  button: MouseButton;
+  button_action: KeyAction;
+}
+
+
+struct ModifierState {
+  shift: bool;
+  ctrl: bool;
+  alt: bool;
+  meta: bool;
+}
+
+table KeyboardInput {
+  key_code: int16;
+  key_action: KeyAction;
+  modifiers: ModifierState;
+}
+
+union Input {
+  Keyboard:KeyboardInput,
+  MouseMovement:MouseMovement,
+  MouseInput:MouseInput,
+}
+
+table InputEvent {
+  input: Input;
+}
+
+root_type InputEvent;
+