Fix stdin references.

Refactored the POSIX piped input handling to avoid redirecting stdin.
Instead, it now directly opens and reads from /dev/tty for keyboard input
when stdin is piped, allowing applications to process piped data while
still receiving interactive keyboard events.

This addresses the TODO comment in ScreenInteractive::InstallPipedInputHandling().

BUILD.bazel

@@ -169,13 +169,15 @@ ftxui_cc_library(
         "src/ftxui/component/util.cpp",
         "src/ftxui/component/window.cpp",
 
-
         # Private header from ftxui:dom.
         "src/ftxui/dom/node_decorator.hpp",
 
         # Private header from ftxui:screen.
         "src/ftxui/screen/string_internal.hpp",
         "src/ftxui/screen/util.hpp",
+
+        # Private header.
+        "include/ftxui/util/warn_windows_macro.hpp",
     ],
     hdrs = [
         "include/ftxui/component/animation.hpp",

CHANGELOG.md

@@ -27,6 +27,12 @@ Next
 - Remove dependency on 'pthread'.
 
 ### Component
+- Feature: POSIX Piped Input Handling.
+  - Allows FTXUI applications to read data from stdin (when piped) while still receiving keyboard input from the terminal.
+  - Enabled by default.
+  - Can be disabled using `ScreenInteractive::HandlePipedInput(false)`.
+  - Only available on Linux and macOS.
+  Thanks @HarryPehkonen for PR #1094.
 - Fix ScreenInteractive::FixedSize screen stomps on the preceding terminal
   output. Thanks @zozowell in #1064.
 

include/ftxui/component/screen_interactive.hpp

@@ -147,6 +147,8 @@ class ScreenInteractive : public Screen {
 
   // Piped input handling state (POSIX only)
   bool handle_piped_input_ = true;
+  // File descriptor for /dev/tty, used for piped input handling.
+  int tty_fd_ = -1;
 
   // The style of the cursor to restore on exit.
   int cursor_reset_shape_ = 1;

src/ftxui/component/screen_interactive.cpp

@@ -112,13 +112,13 @@ void ftxui_on_resize(int columns, int rows) {
 
 #else  // POSIX (Linux & Mac)
 
-int CheckStdinReady() {
+int CheckStdinReady(int fd) {
   timeval tv = {0, 0};  // NOLINT
   fd_set fds;
   FD_ZERO(&fds);                                          // NOLINT
-  FD_SET(STDIN_FILENO, &fds);                             // NOLINT
-  select(STDIN_FILENO + 1, &fds, nullptr, nullptr, &tv);  // NOLINT
-  return FD_ISSET(STDIN_FILENO, &fds);                    // NOLINT
+  FD_SET(fd, &fds);                             // NOLINT
+  select(fd + 1, &fds, nullptr, nullptr, &tv);  // NOLINT
+  return FD_ISSET(fd, &fds);                    // NOLINT
 }
 
 #endif
@@ -539,6 +539,8 @@ void ScreenInteractive::Install() {
   // https://github.com/ArthurSonzogni/FTXUI/issues/846
   Flush();
 
+  InstallPipedInputHandling();
+
   // After uninstalling the new configuration, flush it to the terminal to
   // ensure it is fully applied:
   on_exit_functions.emplace([] { Flush(); });
@@ -604,9 +606,10 @@ void ScreenInteractive::Install() {
   }
 
   struct termios terminal;  // NOLINT
-  tcgetattr(STDIN_FILENO, &terminal);
-  on_exit_functions.emplace(
-      [=] { tcsetattr(STDIN_FILENO, TCSANOW, &terminal); });
+  tcgetattr(tty_fd_, &terminal);
+  on_exit_functions.emplace([terminal = terminal, tty_fd_ = tty_fd_] {
+    tcsetattr(tty_fd_, TCSANOW, &terminal);
+  });
 
   // Enabling raw terminal input mode
   terminal.c_iflag &= ~IGNBRK;  // Disable ignoring break condition
@@ -634,7 +637,7 @@ void ScreenInteractive::Install() {
                              // read.
   terminal.c_cc[VTIME] = 0;  // Timeout in deciseconds for non-canonical read.
 
-  tcsetattr(STDIN_FILENO, TCSANOW, &terminal);
+  tcsetattr(tty_fd_, TCSANOW, &terminal);
 
 #endif
 
@@ -670,20 +673,13 @@ void ScreenInteractive::Install() {
   // ensure it is fully applied:
   Flush();
 
-  // Redirect the true terminal to stdin, so that we can read keyboard input
-  // directly from stdin, even if the input is piped from a file or another
-  // process.
-  //
-  // TODO: Instead of redirecting stdin, we could define the file descriptor to
-  // read from, and use it in the TerminalInputParser.
-  InstallPipedInputHandling();
-
   quit_ = false;
 
   PostAnimationTask();
 }
 
 void ScreenInteractive::InstallPipedInputHandling() {
+  tty_fd_ = fileno(stdin);  // NOLINT
 #if !defined(_WIN32) && !defined(__EMSCRIPTEN__)
   // Handle piped input redirection if explicitly enabled by the application.
   // This allows applications to read data from stdin while still receiving
@@ -692,29 +688,23 @@ void ScreenInteractive::InstallPipedInputHandling() {
     return;
   }
 
-  // If stdin is a terminal, we don't need to redirect it.
-  if (isatty(STDIN_FILENO)) {
+  // If stdin is a terminal, we don't need to open /dev/tty.
+  if (isatty(fileno(stdin))) {
     return;
   }
 
-  // Save the current stdin so we can restore it later.
-  int original_fd = dup(STDIN_FILENO);
-  if (original_fd < 0) {
-    return;
-  }
-
-  // Redirect stdin to the controlling terminal for keyboard input.
-  if (std::freopen("/dev/tty", "r", stdin) == nullptr) {
+  // Open /dev/tty for keyboard input.
+  tty_fd_ = open("/dev/tty", O_RDONLY);
+  if (tty_fd_ < 0) {
     // Failed to open /dev/tty (containers, headless systems, etc.)
-    // Clean up and continue without redirection
-    close(original_fd);
+    tty_fd_ = fileno(stdin);  // Fallback to stdin.
     return;
   }
 
-  // Restore the original stdin file descriptor on exit.
-  on_exit_functions.emplace([=] {
-    dup2(original_fd, STDIN_FILENO);
-    close(original_fd);
+  // Close the /dev/tty file descriptor on exit.
+  on_exit_functions.emplace([this] {
+    close(tty_fd_);
+    tty_fd_ = -1;
   });
 #endif
 }
@@ -1152,7 +1142,7 @@ void ScreenInteractive::FetchTerminalEvents() {
     internal_->terminal_input_parser.Add(out[i]);
   }
 #else  // POSIX (Linux & Mac)
-  if (!CheckStdinReady()) {
+  if (!CheckStdinReady(tty_fd_)) {
     const auto timeout =
         std::chrono::steady_clock::now() - internal_->last_char_time;
     const size_t timeout_ms =
@@ -1164,7 +1154,7 @@ void ScreenInteractive::FetchTerminalEvents() {
 
   // Read chars from the terminal.
   std::array<char, 128> out{};
-  size_t l = read(fileno(stdin), out.data(), out.size());
+  size_t l = read(tty_fd_, out.data(), out.size());
 
   // Convert the chars to events.
   for (size_t i = 0; i < l; ++i) {