Feature: Selection

Add support for selection content in the dom.

src/ftxui/dom/node.cpp

@@ -1,3 +1,4 @@
+#include <iostream>
 // Copyright 2020 Arthur Sonzogni. All rights reserved.
 // Use of this source code is governed by the MIT license that can be found in
 // the LICENSE file.
@@ -27,6 +28,20 @@ void Node::SetBox(Box box) {
   box_ = box;
 }
 
+/// @brief Compute the selection of an element.
+/// @ingroup dom
+void Node::Select(Selection& selection) {
+  // If this Node box_ doesn't intersect with the selection, then no selection.
+  if (Box::Intersection(selection.GetBox(), box_).IsEmpty()) {
+    return;
+  }
+
+  // By default we defer the selection to the children.
+  for (auto& child : children_) {
+    child->Select(selection);
+  }
+}
+
 /// @brief Display an element on a ftxui::Screen.
 /// @ingroup dom
 void Node::Render(Screen& screen) {
@@ -42,15 +57,31 @@ 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) {
-  Render(screen, element.get());
+  Selection selection;
+  Render(screen, element.get(), selection);
 }
 
 /// @brief Display an element on a ftxui::Screen.
 /// @ingroup dom
 void Render(Screen& screen, Node* node) {
+  Selection selection;
+  Render(screen, node, selection);
+}
+
+void Render(Screen& screen, Node* node, Selection& selection) {
   Box box;
   box.x_min = 0;
   box.y_min = 0;
@@ -73,12 +104,49 @@ void Render(Screen& screen, Node* node) {
     node->Check(&status);
   }
 
-  // Step 3: Draw the element.
+  // Step 3: Selection
+  if (!selection.IsEmpty()) {
+    node->Select(selection);
+  }
+
+  // Step 4: Draw the element.
   screen.stencil = box;
   node->Render(screen);
 
-  // Step 4: Apply shaders
+  // Step 5: Apply shaders
   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