We can retrieve the content of the selection

examples/component/selectable_input.cpp

@@ -27,18 +27,16 @@ Element LoremIpsum() {
 
 int main() {
   auto screen = ScreenInteractive::TerminalOutput();
-  int counter = 0;
-
-  screen.onSelectionModified([&]{
-    counter++;
-  });
+  int selectionChangeCounter = 0;
+  std::string selection = "";
 
   auto quit = Button("Quit", screen.ExitLoopClosure());
 
   // The components:
   auto renderer = Renderer(quit, [&] {
     return vbox({
-        text("Select: " + std::to_string(counter)),
+        text("Select changed: " + std::to_string(selectionChangeCounter) + " times"),
+        text("Currently selected: " + selection),
         window(text("Horizontal split"), hbox({
                                              LoremIpsum(),
                                              separator(),
@@ -75,5 +73,10 @@ int main() {
     });
   });
 
+  screen.onSelectionModified([&] {
+    selectionChangeCounter++;
+    selection = screen.GetSelectedContent(renderer);
+  });
+
   screen.Loop(renderer);
 }

include/ftxui/component/screen_interactive.hpp

@@ -69,8 +69,7 @@ class ScreenInteractive : public Screen {
   void ForceHandleCtrlZ(bool force);
 
   // Selection API.
-  // TODO: Implement somethings here.
-  std::string GetSelectedContent(void);
+  std::string GetSelectedContent(Component component);
   void onSelectionModified(std::function<void(void)> callback);
 
  private:

include/ftxui/dom/node.hpp

@@ -48,6 +48,8 @@ class Node {
   // Step 4: Draw this element.
   virtual void Render(Screen& screen);
 
+  virtual std::string GetSelectedContent(Selection& selection);
+
   // Layout may not resolve within a single iteration for some elements. This
   // allows them to request additionnal iterations. This signal must be
   // forwarded to children at least once.
@@ -66,6 +68,7 @@ class Node {
 void Render(Screen& screen, const Element& element);
 void Render(Screen& screen, Node* node);
 void Render(Screen& screen, Node* node, Selection& selection);
+std::string GetNodeSelectedContent(Screen& screen, Node* node, Selection& selection);
 
 }  // namespace ftxui
 

src/ftxui/component/screen_interactive.cpp

@@ -577,9 +577,12 @@ void ScreenInteractive::ForceHandleCtrlZ(bool force) {
 }
 
 /// @brief Returns the content of the current selection
-std::string ScreenInteractive::GetSelectedContent(void)
+std::string ScreenInteractive::GetSelectedContent(Component component)
 {
+  Selection selection(selection_start_x_, selection_start_y_,  //
+                    selection_end_x_, selection_end_y_);
 
+  return GetNodeSelectedContent(*this, component->Render().get(), selection);
 }
 
 /// @brief Sets a callback on modifications of the selection

src/ftxui/dom/node.cpp

@@ -57,6 +57,17 @@ void Node::Check(Status* status) {
   status->need_iteration |= (status->iteration == 0);
 }
 
+std::string Node::GetSelectedContent(Selection& selection) {
+
+  std::string content;
+
+  for (auto& child : children_) {
+    content += child->GetSelectedContent(selection);
+  }
+
+  return content;
+}
+
 /// @brief Display an element on a ftxui::Screen.
 /// @ingroup dom
 void Render(Screen& screen, const Element& element) {
@@ -105,4 +116,35 @@ void Render(Screen& screen, Node* node, Selection& selection) {
   screen.ApplyShader();
 }
 
+std::string GetNodeSelectedContent(Screen& screen, Node* node, Selection& selection) {
+
+  Box box;
+  box.x_min = 0;
+  box.y_min = 0;
+  box.x_max = screen.dimx() - 1;
+  box.y_max = screen.dimy() - 1;
+
+  Node::Status status;
+  node->Check(&status);
+  const int max_iterations = 20;
+  while (status.need_iteration && status.iteration < max_iterations) {
+    // Step 1: Find what dimension this elements wants to be.
+    node->ComputeRequirement();
+
+    // Step 2: Assign a dimension to the element.
+    node->SetBox(box);
+
+    // Check if the element needs another iteration of the layout algorithm.
+    status.need_iteration = false;
+    status.iteration++;
+    node->Check(&status);
+  }
+
+  // Step 3: Selection
+  node->Select(selection);
+
+  // Step 4: get the selected content.
+  return node->GetSelectedContent(selection);
+}
+
 }  // namespace ftxui

src/ftxui/dom/text.cpp

@@ -44,6 +44,7 @@ class Text : public Node {
   void Render(Screen& screen) override {
     int x = box_.x_min;
     const int y = box_.y_min;
+
     if (y > box_.y_max) {
       return;
     }
@@ -67,6 +68,29 @@ class Text : public Node {
     }
   }
 
+  std::string GetSelectedContent(Selection& selection) {
+    int x = box_.x_min;
+    std::string selected_text = "";
+
+    if (has_selection == false) {
+      return "";
+    }
+
+    for (const auto& cell : Utf8ToGlyphs(text_)) {
+      if (x > box_.x_max) {
+        break;
+      }
+
+      if ((x >= selection_start_) && (x <= selection_end_)) {
+        selected_text += cell;
+      }
+
+      ++x;
+    }
+
+    return selected_text;
+  }
+
  private:
   std::string text_;
   bool has_selection = false;