Specifying CSD/SSD Preference

Clients can ask the compositor to use server or client side decorations, or request the compositor to choose for them. miral::Decorations allows you to customize how the server deals with these requests.

This how-to will show you how to specify the behavior of the compositor regarding these requests.

Note: How to Specify Startup Apps is a prerequisite for this how-to.

---

To make the compositor prefer server side decorations when the client doesn’t specify a preference, you only need to change two lines:

@@ -1,6 +1,7 @@
 #include <miral/runner.h>
 #include <miral/configuration_option.h>
+#include <miral/decorations.h>
 #include <miral/external_client.h>
 #include <miral/minimal_window_manager.h>
 #include <miral/set_window_management_policy.h>
@@ -74,5 +75,6 @@ int main(int argc, char const* argv[])
             external_client_launcher,
             miral::ConfigurationOption{run_startup_apps, "startup-app", "App to run at startup (can be specified multiple times)"},
+            miral::Decorations::prefer_ssd(),
         });
 }

That’s it! You can now build and run your compositor and try running a Wayland compatible application to see how its decorations change:

./build/demo-mir-compositor --startup-app kgx --startup-app bomber

MirAL also has other strategies: miral::Decorations::prefer_csd(), miral::Decorations::always_ssd(), and miral::Decorations::always_csd(). Try playing around with different strategies and seeing how they behave differently.