From 0b74a01313af5a94ac3dccea0dc053ac6aecdb20 Mon Sep 17 00:00:00 2001
From: houmain <houmain@posteo.net>
Date: Mon, 25 Jan 2021 15:56:41 +0100
Subject: [PATCH] Updating context when window title changes

---
 src/linux/client/FocusedWindow.cpp | 24 +++++++++++++-----------
 src/win32/FocusedWindow.cpp        | 13 ++++++++-----
 2 files changed, 21 insertions(+), 16 deletions(-)

diff --git a/src/linux/client/FocusedWindow.cpp b/src/linux/client/FocusedWindow.cpp
index be5bf295..3b573e3c 100644
--- a/src/linux/client/FocusedWindow.cpp
+++ b/src/linux/client/FocusedWindow.cpp
@@ -28,27 +28,29 @@ class FocusedWindow {
     m_net_active_window_atom = XInternAtom(m_display, "_NET_ACTIVE_WINDOW", False);
     m_net_wm_name_atom = XInternAtom(m_display, "_NET_WM_NAME", False);
     m_utf8_string_atom = XInternAtom(m_display, "UTF8_STRING", False);
+    XSetErrorHandler([](Display*, XErrorEvent*) { return 0; });
     return true;
   }
 
   bool update() {
     const auto window = get_focused_window();
-    if (window == m_focused_window)
+    auto window_title = get_window_title(window);
+    if (window == m_focused_window &&
+        window_title == m_focused_window_title)
       return false;
 
-    // TODO: is there a better way to prevent races?
-    const auto handler = XSetErrorHandler(&ignore_errors);
-    m_focused_window = window;
-    m_focused_window_class = get_window_class(window);
-    m_focused_window_title = get_window_title(window);
-    XSetErrorHandler(handler);
+    // window handles can become invalid any time
+    auto window_class = get_window_class(window);
+    if (window_class.empty() || window_title.empty())
+      return false;
 
+    m_focused_window = window;
+    m_focused_window_class = std::move(window_class);
+    m_focused_window_title = std::move(window_title);
     return true;
   }
 
 private:
-  static int ignore_errors(Display*, XErrorEvent*) { return 0; }
-
   Window get_focused_window() {
     auto type = Atom{ };
     auto format = 0;
@@ -68,7 +70,7 @@ class FocusedWindow {
 
   std::string get_window_class(Window window) {
     auto ch = XClassHint{ };
-    if (m_focused_window &&
+    if (window &&
         XGetClassHint(m_display, window, &ch) != 0) {
       const auto result = std::string(ch.res_name);
       XFree(ch.res_name);
@@ -84,7 +86,7 @@ class FocusedWindow {
     auto length = 0ul;
     auto rest = 0ul;
     auto data = std::add_pointer_t<unsigned char>{ };
-    if (m_focused_window &&
+    if (window &&
         XGetWindowProperty(m_display, window, m_net_wm_name_atom, 0, 1024,
           False, m_utf8_string_atom, &type, &format, &length,
           &rest, &data) == Success &&
diff --git a/src/win32/FocusedWindow.cpp b/src/win32/FocusedWindow.cpp
index 0f7042fc..ee5e2f5c 100644
--- a/src/win32/FocusedWindow.cpp
+++ b/src/win32/FocusedWindow.cpp
@@ -2,26 +2,29 @@
 #include "FocusedWindow.h"
 #include "win.h"
 #include <array>
+#include <cstring>
 
 class FocusedWindow {
 public:
-  HWND current() const { return m_current; }
   const std::string& get_class() const { return m_class; }
   const std::string& get_title() const { return m_title; }
 
   bool update() {
     const auto hwnd = GetForegroundWindow();
-    if (hwnd == m_current)
+
+    auto buffer = std::array<char, 256>();
+    GetWindowTextA(hwnd, buffer.data(), static_cast<int>(buffer.size()));
+
+    if (hwnd == m_current &&
+        !std::strcmp(buffer.data(), m_title.c_str()))
       return false;
 
     m_current = hwnd;
+    m_title = buffer.data();
 
-    auto buffer = std::array<char, 256>();
     GetClassNameA(hwnd, buffer.data(), static_cast<int>(buffer.size()));
     m_class = buffer.data();
 
-    GetWindowTextA(hwnd, buffer.data(), static_cast<int>(buffer.size()));
-    m_title = buffer.data();
     return true;
   }