Feature: Selection

Add support for selection content in the dom.

src/ftxui/component/screen_interactive.cpp

@@ -576,6 +576,18 @@ void ScreenInteractive::ForceHandleCtrlZ(bool force) {
   force_handle_ctrl_z_ = force;
 }
 
+/// @brief Returns the content of the current selection
+std::string ScreenInteractive::GetSelection() {
+  if (!selection_) {
+    return "";
+  }
+  return selection_->GetParts();
+}
+
+void ScreenInteractive::SelectionChange(std::function<void()> callback) {
+  selection_on_change_ = std::move(callback);
+}
+
 /// @brief Return the currently active screen, or null if none.
 // static
 ScreenInteractive* ScreenInteractive::Active() {
@@ -751,6 +763,14 @@ void ScreenInteractive::RunOnce(Component component) {
     ExecuteSignalHandlers();
   }
   Draw(std::move(component));
+
+  if (selection_data_previous_ != selection_data_) {
+    selection_data_previous_ = selection_data_;
+    if (selection_on_change_) {
+      selection_on_change_();
+      Post(Event::Custom);
+    }
+  }
 }
 
 // private
@@ -781,7 +801,9 @@ void ScreenInteractive::HandleTask(Component component, Task& task) {
 
       arg.screen_ = this;
 
-      const bool handled = component->OnEvent(arg);
+      bool handled = component->OnEvent(arg);
+
+      handled = HandleSelection(handled, arg);
 
       if (arg == Event::CtrlC && (!handled || force_handle_ctrl_c_)) {
         RecordSignal(SIGABRT);
@@ -824,6 +846,59 @@ void ScreenInteractive::HandleTask(Component component, Task& task) {
   // clang-format on
 }
 
+// private
+bool ScreenInteractive::HandleSelection(bool handled, Event event) {
+  if (handled) {
+    selection_pending_ = nullptr;
+    selection_data_.empty = false;
+    selection_ = nullptr;
+    return true;
+  }
+
+  if (!event.is_mouse()) {
+    return false;
+  }
+
+  auto& mouse = event.mouse();
+  if (mouse.button != Mouse::Left) {
+    return false;
+  }
+
+  if (mouse.motion == Mouse::Pressed) {
+    selection_pending_ = CaptureMouse();
+    selection_data_.start_x = mouse.x;
+    selection_data_.start_y = mouse.y;
+    selection_data_.end_x = mouse.x;
+    selection_data_.end_y = mouse.y;
+    return false;
+  }
+
+  if (!selection_pending_) {
+    return false;
+  }
+
+  if (mouse.motion == Mouse::Moved) {
+    if ((mouse.x != selection_data_.end_x) ||
+        (mouse.y != selection_data_.end_y)) {
+      selection_data_.end_x = mouse.x;
+      selection_data_.end_y = mouse.y;
+      selection_data_.empty = false;
+    }
+
+    return true;
+  }
+
+  if (mouse.motion == Mouse::Released) {
+    selection_pending_ = nullptr;
+    selection_data_.end_x = mouse.x;
+    selection_data_.end_y = mouse.y;
+    selection_data_.empty = false;
+    return true;
+  }
+
+  return false;
+}
+
 // private
 // NOLINTNEXTLINE
 void ScreenInteractive::Draw(Component component) {
@@ -899,7 +974,12 @@ void ScreenInteractive::Draw(Component component) {
 #endif
   previous_frame_resized_ = resized;
 
-  Render(*this, document);
+  selection_ = selection_data_.empty
+                   ? std::make_unique<Selection>()
+                   : std::make_unique<Selection>(
+                         selection_data_.start_x, selection_data_.start_y,  //
+                         selection_data_.end_x, selection_data_.end_y);
+  Render(*this, document.get(), *selection_);
 
   // Set cursor position for user using tools to insert CJK characters.
   {
@@ -988,4 +1068,21 @@ void ScreenInteractive::Signal(int signal) {
 #endif
 }
 
+bool ScreenInteractive::SelectionData::operator==(
+    const ScreenInteractive::SelectionData& other) const {
+  if (empty && other.empty) {
+    return true;
+  }
+  if (empty || other.empty) {
+    return false;
+  }
+  return start_x == other.start_x && start_y == other.start_y &&
+         end_x == other.end_x && end_y == other.end_y;
+}
+
+bool ScreenInteractive::SelectionData::operator!=(
+    const ScreenInteractive::SelectionData& other) const {
+  return !(*this == other);
+}
+
 }  // namespace ftxui.