Method onSetViewScroll

src/ui/view.cpp:230–348

}

void View::onSetViewScroll(const gfx::Point& pt)
{
  Point oldScroll = viewScroll();
  Size maxsize = getScrollableSize();
  Size visible = visibleSize();
  Point newScroll(MID(0, pt.x, MAX(0, maxsize.w - visible.w)),
                  MID(0, pt.y, MAX(0, maxsize.h - visible.h)));

  if (newScroll == oldScroll)
    return;

  // This is the movement for the scrolled region (which is inverse to
  // the scroll position delta/movement).
  Point delta = oldScroll - newScroll;

  // Visible viewport region that is not overlapped by windows
  Region drawableRegion;
  m_viewport.getDrawableRegion(
    drawableRegion, DrawableRegionFlags(kCutTopWindows | kUseChildArea));

  // Start the region to scroll equal to the drawable viewport region.
  Rect cpos = m_viewport.childrenBounds();
  Region validRegion(cpos);
  validRegion &= drawableRegion;

  // Remove all children invalid regions from this "validRegion"
  {
    std::queue<Widget*> items;
    items.push(&m_viewport);
    while (!items.empty()) {
      Widget* item = items.front();
      items.pop();
      for (Widget* child : item->children())
        items.push(child);

      if (item->isVisible())
        validRegion -= item->getUpdateRegion();
    }
  }

  // Remove invalid region in the screen (areas that weren't
  // re-painted yet)
  Manager* manager = this->manager();
  if (manager)
    validRegion -= manager->getInvalidRegion();

  // Add extra regions that cannot be scrolled (this can be customized
  // by subclassing ui::View). We use two ScrollRegionEvent, this
  // first one with the old scroll position. And the next one with the
  // new scroll position.
  {
    ScrollRegionEvent ev(this, validRegion);
    onScrollRegion(ev);
  }

  // Move viewport children
  cpos.offset(-newScroll);
  for (auto child : m_viewport.children()) {