node.cpp

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// 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.
#include <ftxui/screen/box.hpp>  // for Box
#include <utility>               // for move
 
#include "ftxui/dom/node.hpp"
#include "ftxui/screen/screen.hpp"  // for Screen
 
namespace ftxui {
 
Node::Node() = default;
Node::Node(Elements children) : children_(std::move(children)) {}
Node::~Node() = default;
 
/// @brief Compute how much space an elements needs.
/// @ingroup dom
void Node::ComputeRequirement() {
  for (auto& child : children_) {
    child->ComputeRequirement();
  }
}
 
/// @brief Assign a position and a dimension to an element for drawing.
/// @ingroup dom
void Node::SetBox(Box box) {
  box_ = box;
}
 
/// @brief Display an element on a ftxui::Screen.
/// @ingroup dom
void Node::Render(Screen& screen) {
  for (auto& child : children_) {
    child->Render(screen);
  }
}
 
void Node::Check(Status* status) {
  for (auto& child : children_) {
    child->Check(status);
  }
  status->need_iteration |= (status->iteration == 0);
}
 
/// @brief Display an element on a ftxui::Screen.
/// @ingroup dom
void Render(Screen& screen, const Element& element) {
  Render(screen, element.get());
}
 
/// @brief Display an element on a ftxui::Screen.
/// @ingroup dom
void Render(Screen& screen, Node* node) {
  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: Draw the element.
  screen.stencil = box;
  node->Render(screen);
 
  // Step 4: Apply shaders
  screen.ApplyShader();
}
 
}  // namespace ftxui