From dfeb19b0a83b8ce57d28bf94a4f8d129993d1064 Mon Sep 17 00:00:00 2001
From: Joel Klinghed <the_jk@opera.com>
Date: Mon, 12 Jan 2026 23:06:20 +0100
Subject: Initial commit

---
 src/find_desktop.cc | 152 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 152 insertions(+)
 create mode 100644 src/find_desktop.cc

(limited to 'src/find_desktop.cc')

diff --git a/src/find_desktop.cc b/src/find_desktop.cc
new file mode 100644
index 0000000..a3a9330
--- /dev/null
+++ b/src/find_desktop.cc
@@ -0,0 +1,152 @@
+#include "find_desktop.hh"
+
+#include "xcb_atoms.hh"
+#include "xcb_connection.hh"
+#include "xcb_event.hh"
+#include "xcb_resource.hh"
+
+#include <cassert>
+#include <charconv>
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>
+#include <ctime>
+#include <optional>
+#include <string>
+#include <system_error>
+#include <xcb/xproto.h>
+
+namespace {
+
+int get_from_e17_using_window(xcb_connection_t* conn, xcb_window_t wnd,
+                              xcb_atom_t e_window_desk) {
+  if (e_window_desk == XCB_ATOM_NONE) {
+    return -1;
+  }
+
+  for (int i = 0; i < 2; ++i) {
+    auto cookie =
+        xcb_get_property(conn, 0, wnd, e_window_desk, XCB_ATOM_CARDINAL, 0, 2);
+    xcb::reply<xcb_get_property_reply_t> reply(
+        xcb_get_property_reply(conn, cookie, nullptr));
+
+    if (reply && reply->format == 32 &&
+        xcb_get_property_value_length(reply.get()) >= 8) {
+      auto* data = static_cast<uint32_t*>(xcb_get_property_value(reply.get()));
+      auto x = data[0];
+      auto y = data[1];
+      return static_cast<int>((x * 256) + y);
+    }
+
+    xcb_flush(conn);
+    struct timespec ts = {.tv_sec = 0, .tv_nsec = 250000000};  // 250ms
+    nanosleep(&ts, nullptr);
+  }
+  return -1;
+}
+
+std::string create_desktop(std::string const& prefix, int desktop,
+                           bool use_prefix) {
+  std::string ret;
+  if (use_prefix) {
+    ret.append(prefix);
+    ret.push_back('_');
+  }
+  auto const offset = ret.size();
+  ret.resize(offset + 10);
+  auto [ptr, ec] =
+      std::to_chars(ret.data() + offset, ret.data() + ret.size(), desktop);
+  if (ec == std::errc()) {
+    ret.resize(ptr - ret.data());
+  } else {
+    assert(false);
+    ret.resize(offset);
+  }
+  return ret;
+}
+
+}  // namespace
+
+std::optional<std::string> find_desktop(std::optional<std::string> display,
+                                        bool use_prefix) {
+  int screen_num = 0;
+  auto conn = xcb::make_shared_conn(xcb_connect(
+      display.has_value() ? display.value().c_str() : nullptr, &screen_num));
+  if (!conn || xcb_connection_has_error(conn.get())) {
+    return std::nullopt;
+  }
+
+  auto atoms = xcb::Atoms::create(conn);
+  if (!atoms) {
+    return std::nullopt;
+  }
+
+  auto* screen = xcb::get_screen(conn.get(), screen_num);
+  if (!screen) {
+    return std::nullopt;
+  }
+
+  xcb_window_t root = screen->root;
+
+  auto net_current_desktop_atom = atoms->get("_NET_CURRENT_DESKTOP");
+  auto e_window_desk_atom = atoms->get("__E_WINDOW_DESK");
+
+  if (!atoms->sync()) {
+    return std::nullopt;
+  }
+
+  auto* desktop_env = getenv("DESKTOP");
+  if (!desktop_env || strncmp(desktop_env, "Enlightenment-0.17", 18) != 0) {
+    /* Skip _NET_CURRENT_DESKTOP if we're in e17 */
+    /* Try to read the _NET_CURRENT_DESKTOP property */
+    auto net_current_desktop = net_current_desktop_atom.get();
+    if (net_current_desktop != XCB_ATOM_NONE) {
+      auto cookie = xcb_get_property(conn.get(), 0, root, net_current_desktop,
+                                     XCB_ATOM_CARDINAL, 0, 1);
+      xcb::reply<xcb_get_property_reply_t> reply(
+          xcb_get_property_reply(conn.get(), cookie, nullptr));
+
+      if (reply && reply->format == 32 &&
+          xcb_get_property_value_length(reply.get()) >= 4) {
+        auto* data =
+            static_cast<uint32_t*>(xcb_get_property_value(reply.get()));
+        return create_desktop("ewmh", static_cast<int>(data[0]), use_prefix);
+      }
+    }
+  }
+
+  /* Failing that, let's see if our owner knows */
+  auto* windowid_env = getenv("WINDOWID");
+  if (windowid_env) {
+    auto* const end = windowid_env + strlen(windowid_env);
+    unsigned long windowid;
+    auto [ptr, ec] = std::from_chars(windowid_env, end, windowid);
+    if (ptr == end && ec == std::errc{}) {
+      auto ret = get_from_e17_using_window(conn.get(),
+                                           static_cast<xcb_window_t>(windowid),
+                                           e_window_desk_atom.get());
+      if (ret != -1) {
+        return create_desktop("enlightenment", ret, use_prefix);
+      }
+    }
+  }
+
+  /* Try creating a bogus window then */
+  {
+    auto wnd = xcb::make_unique_wnd(conn);
+    xcb_create_window(conn.get(), XCB_COPY_FROM_PARENT, wnd->id(), root, 0, 0,
+                      1, 1, 0, XCB_WINDOW_CLASS_INPUT_OUTPUT,
+                      XCB_COPY_FROM_PARENT, 0, nullptr);
+    xcb_map_window(conn.get(), wnd->id());
+    xcb_flush(conn.get());
+
+    auto ret = get_from_e17_using_window(conn.get(), wnd->id(),
+                                         e_window_desk_atom.get());
+    if (ret != -1) {
+      return create_desktop("enlightenment", ret, use_prefix);
+    }
+  }
+
+  /* Don't know what else to do */
+  return std::nullopt;
+}
-- 
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