fix stroke preview, use hmd pose instead of eye, fix vr fullscreen mode

src/hmd.h

@@ -59,7 +59,7 @@ struct Vive
     std::string dev_model{ "Vive" };
     std::string dev_tracksys{ "lighthouse" };
     std::string dev_manufacturer{ "HTC" };
-    std::function<void(const glm::mat4& proj, const glm::mat4& view)> on_draw = nullptr;
+    std::function<void(const glm::mat4& proj, const glm::mat4& view, const glm::mat4& pose)> on_draw = nullptr;
     std::function<void(const Controller&, Controller::Button, Controller::Action)> on_button = nullptr;
 
     Vive();