vertical_layout.hpp

// SPDX-License-Identifier: MIT
#ifndef LIBSBX_UI_VERTICAL_LAYOUT_HPP_
#define LIBSBX_UI_VERTICAL_LAYOUT_HPP_
 
#include <algorithm>
 
#include <libsbx/ui/layout.hpp>
#include <libsbx/ui/element.hpp>
 
namespace sbx::ui {
 
class vertical_layout : public layout {
 
public:
 
  std::float_t spacing{0.0f};
 
  vertical_layout() = default;
 
  vertical_layout(std::float_t spacing)
  : spacing{spacing} { }
 
  ~vertical_layout() override = default;
 
  auto arrange(const rectangle& bounds, std::vector<std::unique_ptr<element>>& children) -> void override {
    const auto content = content_rectangle(bounds);
 
    if (children.empty()) {
      return;
    }
 
    auto total_fixed = 0.0f;
    auto total_flex = 0.0f;
 
    for (auto& child : children) {
      if (child->sizing.flex > 0.0f) {
        total_flex += child->sizing.flex;
      } else {
        total_fixed += child->sizing.preferred.y();
      }
    }
 
    const auto total_spacing = spacing * static_cast<std::float_t>(children.size() - 1u);
    const auto remaining = std::max(0.0f, content.height - total_fixed - total_spacing);
 
    auto cursor_y = content.y + content.height;
 
    for (auto& child : children) {
      auto child_height = 0.0f;
 
      if (child->sizing.flex > 0.0f) {
        child_height = total_flex > 0.0f ? (child->sizing.flex / total_flex) * remaining : 0.0f;
      } else {
        child_height = child->sizing.preferred.y();
      }
 
      child_height = std::clamp(child_height, child->sizing.min.y(), child->sizing.max.y());
 
      auto child_width = child->sizing.preferred.x() > 0.0f ? std::clamp(child->sizing.preferred.x(), child->sizing.min.x(), child->sizing.max.x()) : content.width;
 
      cursor_y -= child_height;
 
      child->resolve_as_arranged(rectangle{content.x, cursor_y, child_width, child_height});
 
      cursor_y -= spacing;
    }
  }
 
}; // class vertical_layout
 
} // namespace sbx::ui
 
#endif // LIBSBX_UI_VERTICAL_LAYOUT_HPP_