Introduce WithRestoredIO (#307)

This function allow running a callback with the terminal hooks
temporarily uninstalled.

Co-authored-by: ArthurSonzogni <sonzogniarthur@gmail.com>

CHANGELOG.md

@@ -24,6 +24,9 @@ unreleased (development)
 
 #### Component 
 - Add the `collapsible` component.
+- Add the `ScreenInteractive::WithRestoredIO`. This decorates a callback. This
+  runs it with the terminal hooks temporarilly uninstalled. This is useful if
+  you want to execute command using directly stdin/stdout/sterr.
 
 ### Bug
 

examples/component/CMakeLists.txt

@@ -31,3 +31,4 @@ example(slider_rgb)
 example(tab_horizontal)
 example(tab_vertical)
 example(toggle)
+example(with_restored_io)

examples/component/with_restored_io.cpp

@@ -0,0 +1,55 @@
+#include "ftxui/component/component.hpp"           // for Menu
+#include "ftxui/component/screen_interactive.hpp"  // for ScreenInteractive
+
+int main() {
+  using namespace ftxui;
+
+  auto screen = ScreenInteractive::Fullscreen();
+
+  // When pressing this button, "screen.WithRestoredIO" will execute the
+  // temporarily uninstall the terminal hook and execute the provided callback
+  // function. This allow running the application in a non-interactive mode.
+  auto btn_run = Button("Execute with restored IO", screen.WithRestoredIO([] {
+        std::system("bash");
+    std::cout << "This is a child program using stdin/stdout." << std::endl;
+    for (int i = 0; i < 10; ++i) {
+      std::cout << "Please enter 10 strings (" << i << "/10)" << std::flush;
+      std::string input;
+      std::getline(std::cin, input);
+    }
+        std::system("bash");
+  }));
+
+  auto btn_quit = Button("Quit", screen.ExitLoopClosure());
+
+  auto layout = Container::Horizontal({
+      btn_run,
+      btn_quit,
+  });
+
+  auto renderer = Renderer(layout, [&] {
+    auto explanation = paragraph(
+        "After clicking this button, the ScreenInteractive will be "
+        "suspended and access to stdin/stdout will temporarilly be "
+        "restore for running a function.");
+    auto element = vbox({
+        explanation | borderEmpty,
+        hbox({
+            btn_run->Render(),
+            filler(),
+            btn_quit->Render(),
+        }),
+    });
+
+    element = element | borderEmpty | border | size(WIDTH, LESS_THAN, 80) |
+              size(HEIGHT, LESS_THAN, 20) | center;
+    return element;
+  });
+
+  screen.Loop(renderer);
+  return EXIT_SUCCESS;
+}
+
+// Copyright 2022 Arthur Sonzogni. All rights reserved.
+// Use of this source code is governed by the MIT license that can be found in
+// the LICENSE file.

include/ftxui/component/screen_interactive.hpp

@@ -20,20 +20,28 @@ using Component = std::shared_ptr<ComponentBase>;
 
 class ScreenInteractive : public Screen {
  public:
+  using Callback = std::function<void()>;
+
   static ScreenInteractive FixedSize(int dimx, int dimy);
   static ScreenInteractive Fullscreen();
   static ScreenInteractive FitComponent();
   static ScreenInteractive TerminalOutput();
 
   void Loop(Component);
-  std::function<void()> ExitLoopClosure();
+  Callback ExitLoopClosure();
 
   void PostEvent(Event event);
   CapturedMouse CaptureMouse();
 
+  // Decorate a function. The outputted one will execute similarly to the
+  // inputted one, but with the currently active screen terminal hooks
+  // temporarily uninstalled.
+  Callback WithRestoredIO(Callback);
+
  private:
   void Install();
   void Uninstall();
+
   void Main(Component component);
   ScreenInteractive* suspended_screen_ = nullptr;
 

src/ftxui/component/screen_interactive.cpp

@@ -200,7 +200,7 @@ const std::string DeviceStatusReport(DSRMode ps) {
 }
 
 using SignalHandler = void(int);
-std::stack<std::function<void()>> on_exit_functions;
+std::stack<ScreenInteractive::Callback> on_exit_functions;
 void OnExit(int signal) {
   (void)signal;
   while (!on_exit_functions.empty()) {
@@ -211,10 +211,10 @@ void OnExit(int signal) {
 
 auto install_signal_handler = [](int sig, SignalHandler handler) {
   auto old_signal_handler = std::signal(sig, handler);
-  on_exit_functions.push([&]() { std::signal(sig, old_signal_handler); });
+  on_exit_functions.push([&] { std::signal(sig, old_signal_handler); });
 };
 
-std::function<void()> on_resize = [] {};
+ScreenInteractive::Callback on_resize = [] {};
 void OnResize(int /* signal */) {
   on_resize();
 }
@@ -230,6 +230,8 @@ class CapturedMouseImpl : public CapturedMouseInterface {
 
 }  // namespace
 
+ScreenInteractive* g_active_screen = nullptr;
+
 ScreenInteractive::ScreenInteractive(int dimx,
                                      int dimy,
                                      Dimension dimension,
@@ -275,7 +277,6 @@ CapturedMouse ScreenInteractive::CaptureMouse() {
 }
 
 void ScreenInteractive::Loop(Component component) {
-  static ScreenInteractive* g_active_screen = nullptr;
 
   // Suspend previously active screen:
   if (g_active_screen) {
@@ -311,7 +312,22 @@ void ScreenInteractive::Loop(Component component) {
   }
 }
 
+/// @brief Decorate a function. It executes the same way, but with the currently
+/// active screen terminal hooks temporarilly uninstalled during its execution.
+/// @param fn The function to decorate.
+ScreenInteractive::Callback ScreenInteractive::WithRestoredIO(Callback fn) {
+  return [this, fn] {
+    Uninstall();
+    fn();
+    Install();
+  };
+}
+
 void ScreenInteractive::Install() {
+  // After uninstalling the new configuration, flush it to the terminal to
+  // ensure it is fully applied:
+  on_exit_functions.push([] { Flush(); });
+
   on_exit_functions.push([this] { ExitLoopClosure()(); });
 
   // Install signal handlers to restore the terminal state on exit. The default
@@ -370,12 +386,6 @@ void ScreenInteractive::Install() {
   install_signal_handler(SIGWINCH, OnResize);
 #endif
 
-  // Commit state:
-  auto flush = [&] {
-    Flush();
-    on_exit_functions.push([] { Flush(); });
-  };
-
   auto enable = [&](std::vector<DECMode> parameters) {
     std::cout << Set(parameters);
     on_exit_functions.push([=] { std::cout << Reset(parameters); });
@@ -404,7 +414,9 @@ void ScreenInteractive::Install() {
       DECMode::kMouseSgrExtMode,
   });
 
-  flush();
+  // After installing the new configuration, flush it to the terminal to ensure
+  // it is fully applied:
+  Flush();
 
   quit_ = false;
   event_listener_ =
@@ -526,8 +538,8 @@ void ScreenInteractive::Draw(Component component) {
   }
 }
 
-std::function<void()> ScreenInteractive::ExitLoopClosure() {
+ScreenInteractive::Callback ScreenInteractive::ExitLoopClosure() {
-  return [this]() {
+  return [this] {
     quit_ = true;
     event_sender_.reset();
   };