feat(xwindow): New module "xwindow"

Add module to display title of active window.
Requires WM with support for the _NET_ACTIVE_WINDOW hint.

Ref #84

src/modules/xwindow.cpp

@@ -0,0 +1,123 @@
+#include "modules/xwindow.hpp"
+#include "x11/atoms.hpp"
+#include "x11/graphics.hpp"
+
+LEMONBUDDY_NS
+
+namespace modules {
+  /**
+   * Bootstrap the module
+   */
+  void xwindow_module::setup() {
+    connection& conn{configure_connection().create<decltype(conn)>()};
+
+    // Initialize ewmh atoms
+    if (!ewmh_util::setup(conn, &m_ewmh)) {
+      throw module_error("Failed to initialize ewmh atoms");
+    }
+
+    // Check if the WM supports _NET_ACTIVE_WINDOW
+    if (!ewmh_util::supports(&m_ewmh, _NET_ACTIVE_WINDOW)) {
+      throw module_error("The WM does not list _NET_ACTIVE_WINDOW as a supported hint");
+    }
+
+    // Add formats and elements
+    m_formatter->add(DEFAULT_FORMAT, TAG_LABEL, {TAG_LABEL});
+
+    if (m_formatter->has(TAG_LABEL)) {
+      m_label = load_optional_label(m_conf, name(), TAG_LABEL, "%title%");
+    }
+
+    // No need to setup X components if we can't show the title
+    if (!m_label || !m_label->has_token("%title%")) {
+      return;
+    }
+
+    // Make sure we get notified when root properties change
+    window root{conn, conn.root()};
+    root.ensure_event_mask(XCB_EVENT_MASK_PROPERTY_CHANGE);
+
+    // Connect with the event registry
+    conn.attach_sink(this, 1);
+
+    // Trigger the initial draw event
+    update();
+  }
+
+  /**
+   * Disconnect from the event registry
+   */
+  void xwindow_module::teardown() {
+    connection& conn{configure_connection().create<decltype(conn)>()};
+    conn.detach_sink(this, 1);
+  }
+
+  /**
+   * Handler for XCB_PROPERTY_NOTIFY events
+   */
+  void xwindow_module::handle(const evt::property_notify& evt) {
+    if (evt->time <= m_timestamp) {
+      return;
+    } else if (evt->atom == _NET_ACTIVE_WINDOW) {
+      update();
+    } else if (evt->atom == _NET_CURRENT_DESKTOP) {
+      update();
+    } else if (evt->atom == _NET_WM_VISIBLE_NAME) {
+      update();
+    } else if (evt->atom == _NET_WM_NAME) {
+      update();
+    } else {
+      return;
+    }
+
+    m_timestamp = evt->time;
+  }
+
+  /**
+   * Update the currently active window and query its title
+   */
+  void xwindow_module::update() {
+    xcb_window_t win{ewmh_util::get_active_window(&m_ewmh)};
+    string title;
+
+    if (m_active && m_active->match(win)) {
+      title = m_active->title(&m_ewmh);
+    } else if (win != XCB_NONE) {
+      m_active = make_unique<active_window>(win);
+      title = m_active->title(&m_ewmh);
+    } else {
+      m_active.reset();
+    }
+
+    if (m_label) {
+      m_label->reset_tokens();
+      m_label->replace_token("%title%", title);
+    }
+
+    // Emit notification to trigger redraw
+    broadcast();
+  }
+
+  /**
+   * Generate the module output
+   */
+  string xwindow_module::get_output() {
+    m_builder->node(static_module::get_output());
+    return m_builder->flush();
+  }
+
+  /**
+   * Output content as defined in the config
+   */
+  bool xwindow_module::build(builder* builder, string tag) const {
+    if (tag == TAG_LABEL) {
+      builder->node(m_label);
+    } else {
+      return false;
+    }
+
+    return true;
+  }
+}
+
+LEMONBUDDY_NS_END