text: /*
   * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *
   * 1. Redistributions of source code must retain the above copyright notice, this
   *    list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright notice,
   *    this list of conditions and the following disclaimer in the documentation
   *    and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #include <LibGUI/ScrollBar.h>
  #include <LibGUI/ScrollableWidget.h>
  
  namespace GUI {
  
  ScrollableWidget::ScrollableWidget()
  {
      m_vertical_scrollbar = add<ScrollBar>(Orientation::Vertical);
      m_vertical_scrollbar->set_step(4);
      m_vertical_scrollbar->on_change = [this](int) {
          did_scroll();
          update();
      };
  
      m_horizontal_scrollbar = add<ScrollBar>(Orientation::Horizontal);
      m_horizontal_scrollbar->set_step(4);
      m_horizontal_scrollbar->set_big_step(30);
      m_horizontal_scrollbar->on_change = [this](int) {
          did_scroll();
          update();
      };
  
      m_corner_widget = add<Widget>();
      m_corner_widget->set_fill_with_background_color(true);
  }
  
  ScrollableWidget::~ScrollableWidget()
  {
  }
  
  void ScrollableWidget::mousewheel_event(MouseEvent& event)
  {
      if (!m_scrollbars_enabled) {
          event.ignore();
          return;
      }
      // FIXME: The wheel delta multiplier should probably come from... somewhere?
      if (event.shift()) {
          horizontal_scrollbar().set_value(horizontal_scrollbar().value() + event.wheel_delta() * 60);
      } else {
          vertical_scrollbar().set_value(vertical_scrollbar().value() + event.wheel_delta() * 20);
      }
  }
  
  void ScrollableWidget::custom_layout()
  {
      auto inner_rect = frame_inner_rect_for_size(size());
      int height_wanted_by_horizontal_scrollbar = m_horizontal_scrollbar->is_visible() ? m_horizontal_scrollbar->preferred_size().height() : 0;
      int width_wanted_by_vertical_scrollbar = m_vertical_scrollbar->is_visible() ? m_vertical_scrollbar->preferred_size().width() : 0;
  
      m_vertical_scrollbar->set_relative_rect(
          inner_rect.right() + 1 - m_vertical_scrollbar->preferred_size().width(),
          inner_rect.top(),
          m_vertical_scrollbar->preferred_size().width(),
          inner_rect.height() - height_wanted_by_horizontal_scrollbar);
  
      m_horizontal_scrollbar->set_relative_rect(
          inner_rect.left(),
          inner_rect.bottom() + 1 - m_horizontal_scrollbar->preferred_size().height(),
          inner_rect.width() - width_wanted_by_vertical_scrollbar,
          m_horizontal_scrollbar->preferred_size().height());
  
      m_corner_widget->set_visible(m_vertical_scrollbar->is_visible() && m_horizontal_scrollbar->is_visible());
      if (m_corner_widget->is_visible()) {
          Gfx::IntRect corner_rect { m_horizontal_scrollbar->relative_rect().right() + 1, m_vertical_scrollbar->relative_rect().bottom() + 1, width_occupied_by_vertical_scrollbar(), height_occupied_by_horizontal_scrollbar() };
          m_corner_widget->set_relative_rect(corner_rect);
      }
  }
  
  void ScrollableWidget::resize_event(ResizeEvent& event)
  {
      Frame::resize_event(event);
      update_scrollbar_ranges();
  }
  
  Gfx::IntSize ScrollableWidget::available_size() const
  {
      int available_width = frame_inner_rect().width() - m_size_occupied_by_fixed_elements.width() - width_occupied_by_vertical_scrollbar();
      int available_height = frame_inner_rect().height() - m_size_occupied_by_fixed_elements.height() - height_occupied_by_horizontal_scrollbar();
      return { available_width, available_height };
  }
  
  void ScrollableWidget::update_scrollbar_ranges()
  {
      auto available_size = this->available_size();
  
      int excess_height = max(0, m_content_size.height() - available_size.height());
      m_vertical_scrollbar->set_range(0, excess_height, available_size.height());
  
      if (should_hide_unnecessary_scrollbars())
          m_vertical_scrollbar->set_visible(excess_height > 0);
  
      int excess_width = max(0, m_content_size.width() - available_size.width());
      m_horizontal_scrollbar->set_range(0, excess_width, available_size.width());
  
      if (should_hide_unnecessary_scrollbars())
          m_horizontal_scrollbar->set_visible(excess_width > 0);
  
      m_vertical_scrollbar->set_big_step(visible_content_rect().height() - m_vertical_scrollbar->step());
  }
  
  void ScrollableWidget::set_content_size(const Gfx::IntSize& size)
  {
      if (m_content_size == size)
          return;
      m_content_size = size;
      update_scrollbar_ranges();
  }
  
  void ScrollableWidget::set_size_occupied_by_fixed_elements(const Gfx::IntSize& size)
  {
      if (m_size_occupied_by_fixed_elements == size)
          return;
      m_size_occupied_by_fixed_elements = size;
      update_scrollbar_ranges();
  }
  
  int ScrollableWidget::height_occupied_by_horizontal_scrollbar() const
  {
      return m_horizontal_scrollbar->is_visible() ? m_horizontal_scrollbar->height() : 0;
  }
  
  int ScrollableWidget::width_occupied_by_vertical_scrollbar() const
  {
      return m_vertical_scrollbar->is_visible() ? m_vertical_scrollbar->width() : 0;
  }
  
  Gfx::IntRect ScrollableWidget::visible_content_rect() const
  {
      Gfx::IntRect rect {
          m_horizontal_scrollbar->value(),
          m_vertical_scrollbar->value(),
          min(m_content_size.width(), frame_inner_rect().width() - width_occupied_by_vertical_scrollbar() - m_size_occupied_by_fixed_elements.width()),
          min(m_content_size.height(), frame_inner_rect().height() - height_occupied_by_horizontal_scrollbar() - m_size_occupied_by_fixed_elements.height())
      };
      if (rect.is_empty())
          return {};
      return rect;
  }
  
  void ScrollableWidget::scroll_into_view(const Gfx::IntRect& rect, Orientation orientation)
  {
      if (orientation == Orientation::Vertical)
          return scroll_into_view(rect, false, true);
      return scroll_into_view(rect, true, false);
  }
  
  void ScrollableWidget::scroll_into_view(const Gfx::IntRect& rect, bool scroll_horizontally, bool scroll_vertically)
  {
      auto visible_content_rect = this->visible_content_rect();
      if (visible_content_rect.contains(rect))
          return;
  
      if (scroll_vertically) {
          if (rect.top() < visible_content_rect.top()) {
              m_vertical_scrollbar->set_value(rect.top());
          } else if (rect.bottom() > visible_content_rect.bottom()) {
              m_vertical_scrollbar->set_value(rect.bottom() - visible_content_rect.height() + 1);
          }
      }
      if (scroll_horizontally) {
          if (rect.left() < visible_content_rect.left()) {
              m_horizontal_scrollbar->set_value(rect.left());
          } else if (rect.right() > visible_content_rect.right()) {
              m_horizontal_scrollbar->set_value(rect.right() - visible_content_rect.width() + 1);
          }
      }
  }
  
  void ScrollableWidget::set_scrollbars_enabled(bool scrollbars_enabled)
  {
      if (m_scrollbars_enabled == scrollbars_enabled)
          return;
      m_scrollbars_enabled = scrollbars_enabled;
      m_vertical_scrollbar->set_visible(m_scrollbars_enabled);
      m_horizontal_scrollbar->set_visible(m_scrollbars_enabled);
      m_corner_widget->set_visible(m_scrollbars_enabled);
  }
  
  void ScrollableWidget::scroll_to_top()
  {
      scroll_into_view({}, Orientation::Vertical);
  }
  
  void ScrollableWidget::scroll_to_bottom()
  {
      scroll_into_view({ 0, content_height(), 0, 0 }, Orientation::Vertical);
  }
  
  Gfx::IntRect ScrollableWidget::widget_inner_rect() const
  {
      auto rect = frame_inner_rect();
      rect.set_width(rect.width() - width_occupied_by_vertical_scrollbar());
      rect.set_height(rect.height() - height_occupied_by_horizontal_scrollbar());
      return rect;
  }
  
  Gfx::IntPoint ScrollableWidget::to_content_position(const Gfx::IntPoint& widget_position) const
  {
      auto content_position = widget_position;
      content_position.move_by(horizontal_scrollbar().value(), vertical_scrollbar().value());
      content_position.move_by(-frame_thickness(), -frame_thickness());
      return content_position;
  }
  
  Gfx::IntPoint ScrollableWidget::to_widget_position(const Gfx::IntPoint& content_position) const
  {
      auto widget_position = content_position;
      widget_position.move_by(-horizontal_scrollbar().value(), -vertical_scrollbar().value());
      widget_position.move_by(frame_thickness(), frame_thickness());
      return widget_position;
  }
  
  }
  