Server: set and reuse capture_source per window

 river/Server.zig | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/river/Server.zig b/river/Server.zig
index f990fb0..592b915 100644
--- a/river/Server.zig
+++ b/river/Server.zig
@@ -566,5 +566,7 @@ fn handleToplevelCaptureRequest(
         return;
     };
 
+    window.capture_source = capture_source;
+
     _ = request.accept(capture_source);
 }