niri/workspaces: Allow restricting the module to an output

man/waybar-niri-workspaces.5.scd

@@ -17,6 +17,10 @@ Addressed by *niri/workspaces*
 	default: false ++
 	If set to false, workspaces will only be shown on the output they are on. If set to true all workspaces will be shown on every output.
 
+*output*: ++
+	typeof: string ++
+	If set, only show workspaces for the output set.
+
 *format*: ++
 	typeof: string ++
 	default: {value} ++

src/modules/niri/workspaces.cpp

@@ -37,6 +37,8 @@ void Workspaces::doUpdate() {
   std::copy_if(workspaces.cbegin(), workspaces.cend(), std::back_inserter(my_workspaces),
                [&](const auto &ws) {
                  if (alloutputs) return true;
+                 if (config_["output"].isString())
+                   return config_["output"].asString() == ws["output"].asString();
                  return ws["output"].asString() == bar_.output->name;
                });