Document debug settings in the default config

resources/default-config.kdl

@@ -318,3 +318,30 @@ binds {
 
     Mod+Shift+Ctrl+T { toggle-debug-tint; }
 }
+
+// Settings for debugging. Not meant for normal use.
+// These can change or stop working at any point with little notice.
+debug {
+    // Make niri take over its DBus services even if it's not running as a session.
+    // Useful for testing screen recording changes without having to relogin.
+    // The main niri instance will *not* currently take back the services; so you will
+    // need to relogin in the end.
+    // dbus-interfaces-in-non-session-instances
+
+    // Wait until every frame is done rendering before handing it over to DRM.
+    // wait-for-frame-completion-before-queueing
+
+    // Enable direct scanout into overlay planes.
+    // May cause frame drops during some animations on some hardware.
+    // enable-overlay-planes
+
+    // Disable the use of the cursor plane.
+    // The cursor will be rendered together with the rest of the frame.
+    // disable-cursor-plane
+
+    // Slow down animations by this factor.
+    // animation-slowdown 3.0
+
+    // Override the DRM device that niri will use for all rendering.
+    // render-drm-device "/dev/dri/renderD129"
+}