river-options: free options of destroyed outputs

This is done when river's internal Output struct is destroyed, not when
the advertised wl_output global is removed. This means that options will
persist when an output is disabled and re-enabled.

river/Option.zig

@@ -67,6 +67,7 @@ pub fn destroy(self: *Self) void {
     var it = self.handles.safeIterator(.forward);
     while (it.next()) |handle| handle.destroy();
     if (self.value == .string) if (self.value.string) |s| util.gpa.free(mem.span(s));
+    self.link.remove();
     util.gpa.destroy(self);
 }
 

river/OptionsManager.zig

@@ -44,6 +44,13 @@ pub fn init(self: *Self, server: *Server) !void {
     server.wl_server.addDestroyListener(&self.server_destroy);
 }
 
+pub fn handleOutputDestroy(self: *Self, output: *Output) void {
+    var it = self.options.safeIterator(.forward);
+    while (it.next()) |option| {
+        if (option.output == output) option.destroy();
+    }
+}
+
 fn handleServerDestroy(listener: *wl.Listener(*wl.Server), wl_server: *wl.Server) void {
     const self = @fieldParentPtr(Self, "server_destroy", listener);
     self.global.destroy();

river/Output.zig

@@ -487,6 +487,8 @@ fn handleDestroy(listener: *wl.Listener(*wlr.Output), wlr_output: *wlr.Output) v
 
     log.debug(.server, "output '{}' destroyed", .{self.wlr_output.name});
 
+    root.server.options_manager.handleOutputDestroy(self);
+
     // Remove the destroyed output from root if it wasn't already removed
     root.removeOutput(self);