Fix screen flicker on Wayland

Fixes Slackadays#190

The GUIClipboardDaemon created a new Wayland window every ~2 seconds to
interact with the clipboard. This steals focus from the currently active
window for a very short time, causing context menus and overlays to
close. It basically made Clipboard unusable on Wayland.

The simplest strategy of fixing this is to align Linux with all other
platforms by only reading data from the clipboard on-demand instead of
doing it continuously.

src/cb/src/clipboard.hpp

@@ -353,7 +353,6 @@ std::string formatBytes(const auto& bytes) {
 }
 
 void verifyClipboardName();
-void setupGUIClipboardDaemon();
 void syncWithRemoteClipboard(bool force = false);
 void syncWithGUIClipboard(bool force = false);
 void fixMissingItems();

src/cb/src/externalclipboards.cpp

@@ -304,70 +304,3 @@ void updateExternalClipboards(bool force) {
         if (!envVarIsTrue("CLIPBOARD_NOREMOTE")) writeToRemoteClipboard(thisContent);
     }
 }
-
-void setupGUIClipboardDaemon() {
-    if (envVarIsTrue("CLIPBOARD_NOGUI")) return;
-
-#if defined(__linux__) || defined(__APPLE__) || defined(__unix__)
-    auto pid = fork();
-    if (pid > 0) return;
-    if (pid < 0) {
-        perror("fork");
-        exit(EXIT_FAILURE);
-    }
-    if (setsid() < 0) {
-        perror("setsid");
-        exit(EXIT_FAILURE);
-    }
-    if (chdir("/") < 0) {
-        perror("chdir");
-        exit(EXIT_FAILURE);
-    }
-
-#if defined(__linux__)
-    // check if there is already a cb daemon by checking /proc for a process which has an exe symlink entry that points to a binary called "cb" and which does not have stdin or stdout file descriptors
-    // that point to a tty
-
-    for (const auto& entry : fs::directory_iterator("/proc")) {
-        try {
-            if (!fs::is_directory(entry)) continue;
-            auto exe = entry.path() / "exe";
-            if (!fs::exists(exe)) continue;
-            auto exeTarget = fs::read_symlink(exe);
-            if (exeTarget.filename() != "cb") continue;
-            auto fd = entry.path() / "fd";
-
-            auto pointsToFilesystemObject = [](const fs::path& path) {
-                auto target = fs::read_symlink(path);
-                if (fs::is_directory(target) || fs::is_regular_file(target)) return true;
-                return false;
-            };
-
-            if (fs::exists(fd / "0") && !pointsToFilesystemObject(fd / "0")) continue;
-            if (fs::exists(fd / "1") && !pointsToFilesystemObject(fd / "1")) continue;
-            if (fs::exists(fd / "2") && !pointsToFilesystemObject(fd / "2")) continue;
-
-            // found a cb daemon
-            _exit(EXIT_SUCCESS);
-        } catch (...) {}
-    }
-#endif
-
-    close(STDIN_FILENO);
-    close(STDOUT_FILENO);
-    close(STDERR_FILENO);
-
-#elif defined(_WIN32) | defined(_WIN64)
-
-#endif
-
-    while (fs::exists(path)) {
-        path.getLock();
-        syncWithGUIClipboard(true);
-        path.releaseLock();
-        std::this_thread::sleep_for(std::chrono::milliseconds(2000));
-        path = Clipboard(std::string(constants.default_clipboard_name));
-    }
-
-    exit(EXIT_SUCCESS);
-}

src/cb/src/main.cpp

@@ -45,14 +45,8 @@ int main(int argc, char* argv[]) {
 
         verifyAction();
 
-#if defined(__linux__)
-        setupGUIClipboardDaemon();
-        syncWithRemoteClipboard();
-        if (action != Action::Info) path.getLock();
-#else
         if (action != Action::Info) path.getLock();
         syncWithExternalClipboards();
-#endif
 
         fixMissingItems();