feat: Reload on XCB_RANDR_SCREEN_CHANGE_NOTIFY

include/components/bar.hpp

@@ -14,13 +14,14 @@
 POLYBAR_NS
 
 // fwd
+class screen;
 class tray_manager;
 class logger;
 class renderer;
 
 class bar : public xpp::event::sink<evt::button_press, evt::expose, evt::property_notify> {
  public:
-  explicit bar(connection& conn, const config& config, const logger& logger, unique_ptr<tray_manager> tray_manager);
+  explicit bar(connection& conn, const config& config, const logger& logger, unique_ptr<screen> screen, unique_ptr<tray_manager> tray_manager);
   ~bar();
 
   void bootstrap(bool nodraw = false);
@@ -45,12 +46,11 @@ class bar : public xpp::event::sink<evt::button_press, evt::expose, evt::propert
   connection& m_connection;
   const config& m_conf;
   const logger& m_log;
+  unique_ptr<screen> m_screen;
   unique_ptr<tray_manager> m_tray;
   unique_ptr<renderer> m_renderer;
 
-  xcb_screen_t* m_screen;
   xcb_window_t m_window;
-
   bar_settings m_opts;
 
   alignment m_trayalign{alignment::NONE};

include/components/screen.hpp

@@ -0,0 +1,45 @@
+#pragma once
+
+#include "common.hpp"
+#include "components/types.hpp"
+#include "x11/events.hpp"
+#include "x11/window.hpp"
+
+POLYBAR_NS
+
+// fwd
+class config;
+class logger;
+class connection;
+
+class screen : public xpp::event::sink<evt::randr_screen_change_notify> {
+ public:
+  explicit screen(connection& conn, const logger& logger, const config& conf);
+  ~screen();
+
+  struct size size() const {
+    return m_size;
+  }
+
+  xcb_window_t root() const {
+    return m_root;
+  }
+
+ protected:
+  void handle(const evt::randr_screen_change_notify& evt);
+
+ private:
+  connection& m_connection;
+  const logger& m_log;
+  const config& m_conf;
+
+  xcb_window_t m_root;
+  xcb_window_t m_proxy;
+
+  struct size m_size{0U, 0U};
+  bool m_sigraised{false};
+};
+
+di::injector<unique_ptr<screen>> configure_screen();
+
+POLYBAR_NS_END

include/x11/connection.hpp

@@ -69,6 +69,30 @@ class connection : public xpp_connection {
 
   virtual ~connection() {}
 
+  template <typename Event, uint32_t ResponseType>
+  void wait_for_response(function<bool(const Event&)> check_event) {
+    auto fd = get_file_descriptor();
+    fd_set fds;
+    FD_ZERO(&fds);
+    FD_SET(fd, &fds);
+
+    while (true) {
+      if (select(fd + 1, &fds, nullptr, nullptr, nullptr) > 0) {
+        shared_ptr<xcb_generic_event_t> evt;
+
+        if ((evt = poll_for_event()) && evt->response_type == ResponseType) {
+          if (check_event(reinterpret_cast<const xcb_map_notify_event_t&>(*(evt.get())))) {
+            break;
+          }
+        }
+      }
+
+      if (connection_has_error()) {
+        break;
+      }
+    }
+  }
+
   void preload_atoms();
 
   void query_extensions();
@@ -77,6 +101,9 @@ class connection : public xpp_connection {
 
   xcb_screen_t* screen();
 
+  void ensure_event_mask(xcb_window_t win, uint32_t event);
+  void clear_event_mask(xcb_window_t win);
+
   shared_ptr<xcb_client_message_event_t> make_client_message(xcb_atom_t type, xcb_window_t target) const;
 
   void send_client_message(const shared_ptr<xcb_client_message_event_t>& message, xcb_window_t target,

include/x11/window.hpp

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <xcb/xcb.h>
 #include <xcb/xcb_aux.h>
 
 #include "common.hpp"

src/components/bar.cpp

@@ -3,6 +3,7 @@
 #include "components/bar.hpp"
 #include "components/parser.hpp"
 #include "components/renderer.hpp"
+#include "components/screen.hpp"
 #include "components/signals.hpp"
 #include "utils/bspwm.hpp"
 #include "utils/color.hpp"
@@ -34,6 +35,7 @@ di::injector<unique_ptr<bar>> configure_bar() {
       configure_connection(),
       configure_config(),
       configure_logger(),
+      configure_screen(),
       configure_tray_manager());
   // clang-format on
 }
@@ -41,12 +43,9 @@ di::injector<unique_ptr<bar>> configure_bar() {
 /**
  * Construct bar instance
  */
-bar::bar(connection& conn, const config& config, const logger& logger, unique_ptr<tray_manager> tray_manager)
-    : m_connection(conn)
-    , m_conf(config)
-    , m_log(logger)
-    , m_tray(forward<decltype(tray_manager)>(tray_manager))
-    , m_screen(conn.screen()) {}
+bar::bar(connection& conn, const config& config, const logger& logger, unique_ptr<screen> screen,
+    unique_ptr<tray_manager> tray_manager)
+    : m_connection(conn), m_conf(config), m_log(logger), m_screen(move(screen)), m_tray(move(tray_manager)) {}
 
 /**
  * Cleanup signal handlers and destroy the bar window
@@ -465,7 +464,7 @@ void bar::setup_monitor() {
   m_log.trace("bar: Create monitor from matching X RandR output");
 
   auto strict = m_conf.get<bool>(m_conf.bar_section(), "monitor-strict", false);
-  auto monitors = randr_util::get_monitors(m_connection, m_screen->root, strict);
+  auto monitors = randr_util::get_monitors(m_connection, m_screen->root(), strict);
 
   if (monitors.empty()) {
     throw application_error("No monitors found");
@@ -534,7 +533,7 @@ void bar::restack_window() {
  * and moving it to the correct position
  */
 void bar::reconfigure_window() {
-  auto geom = m_connection.get_geometry(m_screen->root);
+  auto geom = m_connection.get_geometry(m_screen->root());
   auto w = m_opts.size.w + m_opts.offset.x;
   auto h = m_opts.size.h + m_opts.offset.y;
   auto x = m_opts.pos.x;

src/components/screen.cpp

@@ -0,0 +1,86 @@
+#include <csignal>
+#include <thread>
+
+#include "components/config.hpp"
+#include "components/logger.hpp"
+#include "components/screen.hpp"
+#include "components/types.hpp"
+#include "x11/connection.hpp"
+#include "x11/randr.hpp"
+#include "x11/winspec.hpp"
+
+POLYBAR_NS
+
+/**
+ * Configure injection module
+ */
+di::injector<unique_ptr<screen>> configure_screen() {
+  return di::make_injector(configure_connection(), configure_logger(), configure_config());
+}
+
+/**
+ * Construct screen instance
+ */
+screen::screen(connection& conn, const logger& logger, const config& conf)
+    : m_connection(conn)
+    , m_log(logger)
+    , m_conf(conf)
+    , m_root(conn.root())
+    , m_size({conn.screen()->width_in_pixels, conn.screen()->height_in_pixels}) {
+  // Check if the reloading has been disabled by the user
+  if (!m_conf.get<bool>("settings", "screenchange-reload", false)) {
+    return;
+  }
+
+  // clang-format off
+  m_proxy = winspec(m_connection)
+    << cw_size(1U, 1U)
+    << cw_pos(-1, -1)
+    << cw_parent(m_root)
+    << cw_params_override_redirect(true)
+    << cw_params_event_mask(XCB_EVENT_MASK_PROPERTY_CHANGE)
+    << cw_flush(true);
+  // clang-format on
+
+  // Receive randr events
+  m_connection.randr().select_input(m_proxy, XCB_RANDR_NOTIFY_MASK_SCREEN_CHANGE);
+  m_connection.ensure_event_mask(m_root, XCB_EVENT_MASK_SUBSTRUCTURE_NOTIFY);
+
+  // Create window used as event proxy
+  m_connection.map_window(m_proxy);
+  m_connection.flush();
+
+  // Wait until the proxy window has been mapped
+  using evt = xcb_map_notify_event_t;
+  m_connection.wait_for_response<evt, XCB_MAP_NOTIFY>([&](const evt& evt) -> bool { return evt.window == m_proxy; });
+  m_connection.clear_event_mask(m_root);
+
+  // Finally attach the sink the process randr events
+  m_connection.attach_sink(this, 1);
+}
+
+/**
+ * Deconstruct screen instance
+ */
+screen::~screen() {
+  m_connection.detach_sink(this, 1);
+
+  if (m_proxy) {
+    m_connection.destroy_window(m_proxy);
+  }
+}
+
+/**
+ * Handle XCB_RANDR_SCREEN_CHANGE_NOTIFY events
+ *
+ * If the screen dimensions have changed we raise USR1 to trigger a reload
+ */
+void screen::handle(const evt::randr_screen_change_notify& evt) {
+  if (!m_sigraised && evt->request_window == m_proxy) {
+    m_log.warn("randr_screen_change_notify (%ux%u)... reloading", evt->width, evt->height);
+    m_sigraised = true;
+    kill(getpid(), SIGUSR1);
+  }
+}
+
+POLYBAR_NS_END

src/x11/connection.cpp

@@ -101,6 +101,26 @@ xcb_screen_t* connection::screen() {
   return m_screen;
 }
 
+/**
+ * Add given event to the event mask unless already added
+ */
+void connection::ensure_event_mask(xcb_window_t win, uint32_t event) {
+  auto attributes = get_window_attributes(win);
+  uint32_t mask{attributes->your_event_mask | event};
+
+  if (!(attributes->your_event_mask & event)) {
+    change_window_attributes(win, XCB_CW_EVENT_MASK, &mask);
+  }
+}
+
+/**
+ * Clear event mask for the given window
+ */
+void connection::clear_event_mask(xcb_window_t win) {
+  uint32_t mask{XCB_EVENT_MASK_NO_EVENT};
+  change_window_attributes(win, XCB_CW_EVENT_MASK, &mask);
+}
+
 /**
  * Creates an instance of shared_ptr<xcb_client_message_event_t>
  */

src/x11/window.cpp

@@ -41,12 +41,7 @@ window window::change_event_mask(uint32_t mask) {
  * Add given event to the event mask unless already added
  */
 window window::ensure_event_mask(uint32_t event) {
-  auto attributes = get_attributes();
-
-  if ((attributes->your_event_mask & event) != event) {
-    change_event_mask(attributes->your_event_mask | event);
-  }
-
+  connection().ensure_event_mask(*this, event);
   return *this;
 }