text: /*
   * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
   *
   * SPDX-License-Identifier: BSD-2-Clause
   */
  
  #include <LibGUI/BoxLayout.h>
  #include <LibGUI/Painter.h>
  #include <LibGUI/Splitter.h>
  #include <LibGUI/Window.h>
  #include <LibGfx/Palette.h>
  
  REGISTER_WIDGET(GUI, HorizontalSplitter)
  REGISTER_WIDGET(GUI, VerticalSplitter)
  
  namespace GUI {
  
  Splitter::Splitter(Orientation orientation)
      : m_orientation(orientation)
  {
      REGISTER_INT_PROPERTY("first_resizee_minimum_size", first_resizee_minimum_size, set_first_resizee_minimum_size);
      REGISTER_INT_PROPERTY("second_resizee_minimum_size", second_resizee_minimum_size, set_second_resizee_minimum_size);
  
      set_background_role(ColorRole::Button);
      set_layout<BoxLayout>(orientation);
      set_fill_with_background_color(true);
      layout()->set_spacing(3);
  }
  
  Splitter::~Splitter()
  {
  }
  
  void Splitter::paint_event(PaintEvent& event)
  {
      Painter painter(*this);
      painter.add_clip_rect(event.rect());
  
      auto palette = this->palette();
  
      auto paint_knurl = [&](int x, int y) {
          painter.set_pixel(x, y, palette.threed_shadow1());
          painter.set_pixel(x + 1, y, palette.threed_shadow1());
          painter.set_pixel(x, y + 1, palette.threed_shadow1());
          painter.set_pixel(x + 1, y + 1, palette.threed_highlight());
      };
  
      constexpr size_t knurl_width = 2;
      constexpr size_t knurl_spacing = 1;
      constexpr size_t knurl_count = 10;
      constexpr size_t total_knurling_width = knurl_count * (knurl_width + knurl_spacing);
  
      if (m_hovered_index.has_value())
          painter.fill_rect(m_grabbables[m_hovered_index.value()].paint_rect, palette.hover_highlight());
  
      for (auto& grabbable : m_grabbables) {
          for (size_t i = 0; i < knurl_count; ++i) {
              auto& rect = grabbable.paint_rect;
              int primary = rect.center().primary_offset_for_orientation(m_orientation) - 1;
              int secondary = rect.center().secondary_offset_for_orientation(m_orientation) - (total_knurling_width / 2) + (i * (knurl_width + knurl_spacing));
              if (m_orientation == Gfx::Orientation::Vertical)
                  paint_knurl(secondary, primary);
              else
                  paint_knurl(primary, secondary);
          }
      }
  }
  
  void Splitter::resize_event(ResizeEvent& event)
  {
      Widget::resize_event(event);
      set_hovered_grabbable(nullptr);
  }
  
  void Splitter::set_hovered_grabbable(Grabbable* grabbable)
  {
      if (m_hovered_index.has_value()) {
          if (grabbable && grabbable->index == m_hovered_index.value())
              return;
          update(m_grabbables[m_hovered_index.value()].paint_rect);
      }
  
      if (grabbable) {
          m_hovered_index = grabbable->index;
          update(grabbable->paint_rect);
      } else {
          m_hovered_index = {};
      }
  }
  
  void Splitter::override_cursor(bool do_override)
  {
      if (do_override) {
          if (!m_overriding_cursor) {
              set_override_cursor(m_orientation == Orientation::Horizontal ? Gfx::StandardCursor::ResizeColumn : Gfx::StandardCursor::ResizeRow);
              m_overriding_cursor = true;
          }
      } else {
          if (m_overriding_cursor) {
              set_override_cursor(Gfx::StandardCursor::None);
              m_overriding_cursor = false;
          }
      }
  }
  
  void Splitter::leave_event(Core::Event&)
  {
      if (!m_resizing)
          override_cursor(false);
      set_hovered_grabbable(nullptr);
  }
  
  Splitter::Grabbable* Splitter::grabbable_at(Gfx::IntPoint const& position)
  {
      for (auto& grabbable : m_grabbables) {
          if (grabbable.grabbable_rect.contains(position))
              return &grabbable;
      }
      return nullptr;
  }
  
  void Splitter::mousedown_event(MouseEvent& event)
  {
      if (event.button() != MouseButton::Primary)
          return;
  
      auto* grabbable = grabbable_at(event.position());
      if (!grabbable)
          return;
  
      m_resizing = true;
  
      m_first_resizee = *grabbable->first_widget;
      m_second_resizee = *grabbable->second_widget;
      m_first_resizee_start_size = m_first_resizee->size();
      m_second_resizee_start_size = m_second_resizee->size();
      m_resize_origin = event.position();
  }
  
  Gfx::IntRect Splitter::rect_between_widgets(GUI::Widget const& first_widget, GUI::Widget const& second_widget, bool honor_grabbable_margins) const
  {
      auto first_widget_rect = honor_grabbable_margins ? first_widget.relative_non_grabbable_rect() : first_widget.relative_rect();
      auto second_widget_rect = honor_grabbable_margins ? second_widget.relative_non_grabbable_rect() : second_widget.relative_rect();
  
      auto first_edge = first_widget_rect.last_edge_for_orientation(m_orientation);
      auto second_edge = second_widget_rect.first_edge_for_orientation(m_orientation);
      Gfx::IntRect rect;
      rect.set_primary_offset_for_orientation(m_orientation, first_edge);
      rect.set_primary_size_for_orientation(m_orientation, second_edge - first_edge);
      rect.set_secondary_offset_for_orientation(m_orientation, 0);
      rect.set_secondary_size_for_orientation(m_orientation, relative_rect().secondary_size_for_orientation(m_orientation));
      return rect;
  }
  
  void Splitter::recompute_grabbables()
  {
      auto old_grabbables_count = m_grabbables.size();
      m_grabbables.clear();
      auto old_hovered_index = m_hovered_index;
      m_hovered_index = {};
  
      auto child_widgets = this->child_widgets();
      child_widgets.remove_all_matching([&](auto& widget) { return !widget.is_visible(); });
  
      if (child_widgets.size() < 2)
          return;
  
      size_t start_index = 0;
      size_t end_index = 1;
  
      while (end_index < child_widgets.size()) {
          auto const& first_widget = child_widgets[start_index];
          auto const& second_widget = child_widgets[end_index];
          m_grabbables.append(Grabbable {
              .index = m_grabbables.size(),
              .grabbable_rect = rect_between_widgets(first_widget, second_widget, true),
              .paint_rect = rect_between_widgets(first_widget, second_widget, false),
              .first_widget = first_widget,
              .second_widget = second_widget,
          });
          ++start_index;
          ++end_index;
      }
  
      if (old_hovered_index.has_value() && old_grabbables_count == m_grabbables.size())
          set_hovered_grabbable(&m_grabbables[old_hovered_index.value()]);
  }
  
  void Splitter::mousemove_event(MouseEvent& event)
  {
      auto* grabbable = grabbable_at(event.position());
      set_hovered_grabbable(grabbable);
      if (!m_resizing) {
          override_cursor(grabbable != nullptr);
          return;
      }
      auto delta = event.position() - m_resize_origin;
      if (!m_first_resizee || !m_second_resizee) {
          // One or both of the resizees were deleted during an ongoing resize, screw this.
          m_resizing = false;
          return;
      }
      auto new_first_resizee_size = m_first_resizee_start_size;
      auto new_second_resizee_size = m_second_resizee_start_size;
  
      new_first_resizee_size.set_primary_size_for_orientation(m_orientation, new_first_resizee_size.primary_size_for_orientation(m_orientation) + delta.primary_offset_for_orientation(m_orientation));
      new_second_resizee_size.set_primary_size_for_orientation(m_orientation, new_second_resizee_size.primary_size_for_orientation(m_orientation) - delta.primary_offset_for_orientation(m_orientation));
  
      if (new_first_resizee_size.primary_size_for_orientation(m_orientation) < m_first_resizee_minimum_size) {
          int correction = m_first_resizee_minimum_size - new_first_resizee_size.primary_size_for_orientation(m_orientation);
          new_first_resizee_size.set_primary_size_for_orientation(m_orientation, new_first_resizee_size.primary_size_for_orientation(m_orientation) + correction);
          new_second_resizee_size.set_primary_size_for_orientation(m_orientation, new_second_resizee_size.primary_size_for_orientation(m_orientation) - correction);
      }
      if (new_second_resizee_size.primary_size_for_orientation(m_orientation) < m_second_resizee_minimum_size) {
          int correction = m_second_resizee_minimum_size - new_second_resizee_size.primary_size_for_orientation(m_orientation);
          new_second_resizee_size.set_primary_size_for_orientation(m_orientation, new_second_resizee_size.primary_size_for_orientation(m_orientation) + correction);
          new_first_resizee_size.set_primary_size_for_orientation(m_orientation, new_first_resizee_size.primary_size_for_orientation(m_orientation) - correction);
      }
  
      if (m_orientation == Orientation::Horizontal) {
          m_first_resizee->set_fixed_width(new_first_resizee_size.width());
          m_second_resizee->set_fixed_width(-1);
      } else {
          m_first_resizee->set_fixed_height(new_first_resizee_size.height());
          m_second_resizee->set_fixed_height(-1);
      }
  
      invalidate_layout();
  }
  
  void Splitter::did_layout()
  {
      recompute_grabbables();
  }
  
  void Splitter::mouseup_event(MouseEvent& event)
  {
      if (event.button() != MouseButton::Primary)
          return;
      m_resizing = false;
      m_first_resizee = nullptr;
      m_second_resizee = nullptr;
      if (!rect().contains(event.position()))
          set_override_cursor(Gfx::StandardCursor::None);
  }
  
  }
  