Feature: hyperlink support. (#665)

See the [OSC 8 page](https://gist.github.com/egmontkob/eb114294efbcd5adb1944c9f3cb5feda).
FTXUI support proposed by @aaleino in [#662](https://github.com/ArthurSonzogni/FTXUI/issues/662).

API:
```cpp
auto link = text("Click here") | hyperlink("https://github.com/FTXUI")
```

Fixed:https://github.com/ArthurSonzogni/FTXUI/issues/662

src/ftxui/component/input.cpp

@@ -1,6 +1,6 @@
-#include <stdint.h>    // for uint32_t
 #include <algorithm>   // for max, min
 #include <cstddef>     // for size_t
+#include <cstdint>     // for uint32_t
 #include <functional>  // for function
 #include <memory>   // for allocator, shared_ptr, allocator_traits<>::value_type
 #include <sstream>  // for basic_istream, stringstream

src/ftxui/dom/hyperlink.cpp

@@ -0,0 +1,72 @@
+#include <cstdint>  // for uint8_t
+#include <memory>   // for make_shared
+#include <string>   // for string
+#include <utility>  // for move
+
+#include "ftxui/dom/elements.hpp"        // for Element, Decorator, hyperlink
+#include "ftxui/dom/node_decorator.hpp"  // for NodeDecorator
+#include "ftxui/screen/box.hpp"          // for Box
+#include "ftxui/screen/screen.hpp"       // for Screen, Pixel
+
+namespace ftxui {
+
+class Hyperlink : public NodeDecorator {
+ public:
+  Hyperlink(Element child, std::string link)
+      : NodeDecorator(std::move(child)), link_(link) {}
+
+  void Render(Screen& screen) override {
+    uint8_t hyperlink_id = screen.RegisterHyperlink(link_);
+    for (int y = box_.y_min; y <= box_.y_max; ++y) {
+      for (int x = box_.x_min; x <= box_.x_max; ++x) {
+        screen.PixelAt(x, y).hyperlink = hyperlink_id;
+      }
+    }
+    NodeDecorator::Render(screen);
+  }
+
+  std::string link_;
+};
+
+/// @brief Make the rendered area clickable using a web browser.
+///        The link will be opened when the user click on it.
+///        This is supported only on a limited set of terminal emulator.
+///        List: https://github.com/Alhadis/OSC8-Adoption/
+/// @param link The link
+/// @param child The input element.
+/// @return The output element with the link.
+/// @ingroup dom
+///
+/// ### Example
+///
+/// ```cpp
+/// Element document =
+///   hyperlink("https://github.com/ArthurSonzogni/FTXUI", "link");
+/// ```
+Element hyperlink(std::string link, Element child) {
+  return std::make_shared<Hyperlink>(std::move(child), link);
+}
+
+/// @brief Decorate using an hyperlink.
+///        The link will be opened when the user click on it.
+///        This is supported only on a limited set of terminal emulator.
+///        List: https://github.com/Alhadis/OSC8-Adoption/
+/// @param link The link to redirect the users to.
+/// @return The Decorator applying the hyperlink.
+/// @ingroup dom
+///
+/// ### Example
+///
+/// ```cpp
+/// Element document =
+///   text("red") | hyperlink("https://github.com/Arthursonzogni/FTXUI");
+/// ```
+Decorator hyperlink(std::string link) {
+  return [link](Element child) { return hyperlink(link, std::move(child)); };
+}
+
+}  // namespace ftxui
+
+// Copyright 2023 Arthur Sonzogni. All rights reserved.
+// Use of this source code is governed by the MIT license that can be found in
+// the LICENSE file.

src/ftxui/dom/hyperlink_test.cpp

@@ -0,0 +1,43 @@
+#include <gtest/gtest.h>  // for Test, EXPECT_EQ, Message, TestPartResult, TestInfo (ptr only), TEST
+#include <string>  // for allocator, string
+
+#include "ftxui/dom/elements.hpp"  // for text, hyperlink, operator|, Element, hbox
+#include "ftxui/dom/node.hpp"      // for Render
+#include "ftxui/screen/screen.hpp"  // for Screen, Pixel
+
+namespace ftxui {
+
+TEST(HyperlinkTest, Basic) {
+  auto element = hbox({
+      text("text 1") | hyperlink("https://a.com"),
+      text("text 2") | hyperlink("https://b.com"),
+      text("text 3"),
+      text("text 4") | hyperlink("https://c.com"),
+  });
+
+  Screen screen(6 * 4, 1);
+  Render(screen, element);
+
+  EXPECT_EQ(screen.PixelAt(0, 0).hyperlink, 1u);
+  EXPECT_EQ(screen.PixelAt(5, 0).hyperlink, 1u);
+  EXPECT_EQ(screen.PixelAt(6, 0).hyperlink, 2u);
+  EXPECT_EQ(screen.PixelAt(11, 0).hyperlink, 2u);
+
+  std::string output = screen.ToString();
+  EXPECT_EQ(output,
+            "\x1B]8;;https://a.com\x1B\\"
+            "text 1"
+            "\x1B]8;;https://b.com\x1B\\"
+            "text 2"
+            "\x1B]8;;\x1B\\"
+            "text 3"
+            "\x1B]8;;https://c.com\x1B\\"
+            "text 4"
+            "\x1B]8;;\x1B\\");
+}
+
+}  // namespace ftxui
+
+// Copyright 2023 Arthur Sonzogni. All rights reserved.
+// Use of this source code is governed by the MIT license that can be found in
+// the LICENSE file.

src/ftxui/screen/screen.cpp

@@ -1,7 +1,7 @@
-#include <cstdint>  // for uint8_t
+#include <cstdint>  // for size_t
 #include <iostream>  // for operator<<, stringstream, basic_ostream, flush, cout, ostream
 #include <map>      // for _Rb_tree_const_iterator, map, operator!=, operator==
-#include <memory>   // for allocator
+#include <memory>   // for allocator, allocator_traits<>::value_type
 #include <sstream>  // IWYU pragma: keep
 #include <utility>  // for pair
 
@@ -50,11 +50,13 @@ void WindowsEmulateVT100Terminal() {
 #endif
 
 // NOLINTNEXTLINE(readability-function-cognitive-complexity)
-void UpdatePixelStyle(std::stringstream& ss,
+void UpdatePixelStyle(const Screen* screen,
+                      std::stringstream& ss,
                       Pixel& previous,
                       const Pixel& next) {
-  if (next == previous) {
-    return;
+  // See https://gist.github.com/egmontkob/eb114294efbcd5adb1944c9f3cb5feda
+  if (next.hyperlink != previous.hyperlink) {
+    ss << "\x1B]8;;" << screen->Hyperlink(next.hyperlink) << "\x1B\\";
   }
 
   if ((!next.bold && previous.bold) ||  //
@@ -435,20 +437,20 @@ std::string Screen::ToString() {
 
   for (int y = 0; y < dimy_; ++y) {
     if (y != 0) {
-      UpdatePixelStyle(ss, previous_pixel, final_pixel);
+      UpdatePixelStyle(this, ss, previous_pixel, final_pixel);
       ss << "\r\n";
     }
     bool previous_fullwidth = false;
     for (const auto& pixel : pixels_[y]) {
       if (!previous_fullwidth) {
-        UpdatePixelStyle(ss, previous_pixel, pixel);
+        UpdatePixelStyle(this, ss, previous_pixel, pixel);
         ss << pixel.character;
       }
       previous_fullwidth = (string_width(pixel.character) == 2);
     }
   }
 
-  UpdatePixelStyle(ss, previous_pixel, final_pixel);
+  UpdatePixelStyle(this, ss, previous_pixel, final_pixel);
 
   return ss.str();
 }
@@ -517,6 +519,10 @@ void Screen::Clear() {
   }
   cursor_.x = dimx_ - 1;
   cursor_.y = dimy_ - 1;
+
+  hyperlinks_ = {
+      "",
+  };
 }
 
 // clang-format off
@@ -545,9 +551,28 @@ void Screen::ApplyShader() {
     }
   }
 }
-
 // clang-format on
 
+uint8_t Screen::RegisterHyperlink(std::string link) {
+  for (size_t i = 0; i < hyperlinks_.size(); ++i) {
+    if (hyperlinks_[i] == link) {
+      return i;
+    }
+  }
+  if (hyperlinks_.size() == 255) {
+    return 0;
+  }
+  hyperlinks_.push_back(link);
+  return hyperlinks_.size() - 1;
+}
+
+const std::string& Screen::Hyperlink(uint8_t id) const {
+  if (id >= hyperlinks_.size()) {
+    return hyperlinks_[0];
+  }
+  return hyperlinks_[id];
+}
+
 }  // namespace ftxui
 
 // Copyright 2020 Arthur Sonzogni. All rights reserved.