adapted from https://github.com/jaagr/polybar/pull/576

polybar-xwindow-monitor-locality.patch

diff --git a/include/modules/xwindow.hpp b/include/modules/xwindow.hpp
index 4378ed5..e4b0e5c 100644
--- a/include/modules/xwindow.hpp
+++ b/include/modules/xwindow.hpp
@@ -18,6 +18,7 @@ namespace modules {
 
     bool match(const xcb_window_t win) const;
     string title() const;
+    xcb_window_t get_window() const;
 
    private:
     xcb_connection_t* m_connection{nullptr};
@@ -45,11 +46,14 @@ namespace modules {
 
    private:
     static constexpr const char* TAG_LABEL{"<label>"};
+    bool active_window_on_monitor(xcb_window_t window, monitor_t monitor) const;
 
     connection& m_connection;
     unique_ptr<active_window> m_active;
     map<state, label_t> m_statelabels;
     label_t m_label;
+
+    bool m_pinoutput{false};
   };
 }
 
diff --git a/src/modules/xwindow.cpp b/src/modules/xwindow.cpp
index fbc23af..a2e2a43 100644
--- a/src/modules/xwindow.cpp
+++ b/src/modules/xwindow.cpp
@@ -1,6 +1,7 @@
 #include "modules/xwindow.hpp"
 #include "drawtypes/label.hpp"
 #include "utils/factory.hpp"
+#include "utils/bspwm.hpp"
 #include "x11/atoms.hpp"
 #include "x11/connection.hpp"
 
@@ -58,11 +59,55 @@ namespace modules {
     }
   }
 
+  xcb_window_t active_window::get_window() const {
+    return m_window;
+  }
+
+  // if any xcb request fails, assume true
+  bool xwindow_module::active_window_on_monitor(xcb_window_t window, monitor_t mon) const {
+    xcb_get_geometry_reply_t* geom = xcb_get_geometry_reply(m_connection,
+      xcb_get_geometry(m_connection, window), nullptr);
+    if (!geom) {
+      return true;
+    }
+
+    xcb_translate_coordinates_reply_t *trans = xcb_translate_coordinates_reply(m_connection,
+      xcb_translate_coordinates(m_connection, window, m_connection.root(), geom->x, geom->y), nullptr);
+
+    if (!trans) {
+      return true;
+    }
+
+    int win_x = 0; // top right
+    int win_y = 0; // bottom left
+
+    win_x = trans->dst_x;
+    win_y = trans->dst_y;
+
+    // bspwm workaround - translated coordinates are way off (about x2),
+    // coordinates relative to parent window in geom are correct, no translation needed
+    if (file_util::exists(bspwm_util::get_socket_path())) {
+      win_x = geom->x;
+      win_y = geom->y;
+    }
+
+    // if x pos is within monitor width range and y is within height range
+    bool in_x = win_x <= mon->x + mon->w - 1 && win_x >= mon->x;
+    bool in_y = win_y <= mon->y + mon->h - 1 && win_y >= mon->y;
+
+    free(geom); free(trans);
+    return in_x && in_y;
+  }
+
   /**
    * Construct module
    */
   xwindow_module::xwindow_module(const bar_settings& bar, string name_)
       : static_module<xwindow_module>(bar, move(name_)), m_connection(connection::make()) {
+
+    // read config values
+    m_pinoutput = m_conf.get(name(), "pin-output", m_pinoutput);
+
     // Initialize ewmh atoms
     if ((ewmh_util::initialize()) == nullptr) {
       throw module_error("Failed to initialize ewmh atoms");
@@ -122,7 +167,22 @@ namespace modules {
     if (m_active) {
       m_label = m_statelabels.at(state::ACTIVE)->clone();
       m_label->reset_tokens();
-      m_label->replace_token("%title%", m_active->title());
+
+      if (!m_active) {
+        m_label->replace_token("%title%", "");
+        return;
+      }
+
+      if (m_pinoutput) {
+        if (active_window_on_monitor(m_active->get_window(), m_bar.monitor)) {
+          m_label->replace_token("%title%", m_active->title());
+          return;
+        } else {
+          m_label->replace_token("%title%", "");
+        }
+      } else {
+        m_label->replace_token("%title%", m_active->title());
+      }
     } else {
       m_label = m_statelabels.at(state::EMPTY)->clone();
     }