tibia-client/modules/game_interface/widgets/uiitem.lua

function UIItem:onDragEnter(mousePos)
  if self:isVirtual() then return false end

  local item = self:getItem()
  if not item then return false end

  self:setBorderWidth(1)
  self.currentDragThing = item
  g_mouse.setTargetCursor()
  return true
end

function UIItem:onDragLeave(droppedWidget, mousePos)
  if self:isVirtual() then return false end
  self.currentDragThing = nil
  g_mouse.restoreCursor()
  self:setBorderWidth(0)
  self.hoveredWho = nil
  return true
end

function UIItem:onDrop(widget, mousePos)
  if not self:canAcceptDrop(widget, mousePos) then return false end

  local item = widget.currentDragThing
  if not item:isItem() then return false end

  local toPos = self.position

  local itemPos = item:getPosition()
  if itemPos.x == toPos.x and itemPos.y == toPos.y and itemPos.z == toPos.z then return false end

  if item:getCount() > 1 then
    modules.game_interface.moveStackableItem(item, toPos)
  else
    g_game.move(item, toPos, 1)
  end

  self:setBorderWidth(0)
  return true
end

function UIItem:onDestroy()
  if self == g_ui.getDraggingWidget() and self.hoveredWho then
    self.hoveredWho:setBorderWidth(0)
  end

  if self.hoveredWho then
    self.hoveredWho = nil
  end
end

function UIItem:onHoverChange(hovered)
  UIWidget.onHoverChange(self, hovered)

  if self:isVirtual() then return end

  local draggingWidget = g_ui.getDraggingWidget()
  if draggingWidget and self ~= draggingWidget then
    local gotMap = draggingWidget:getClassName() == 'UIMap'
    local gotItem = draggingWidget:getClassName() == 'UIItem' and not draggingWidget:isVirtual()
    if hovered and (gotItem or gotMap) then
      self:setBorderWidth(1)
      draggingWidget.hoveredWho = self
    else
      self:setBorderWidth(0)
      draggingWidget.hoveredWho = nil
    end
  end
end

function UIItem:onMouseRelease(mousePosition, mouseButton)
  if self.cancelNextRelease then
    self.cancelNextRelease = false
    return true
  end

  if self:isVirtual() then return false end

  local item = self:getItem()
  if not item or not self:containsPoint(mousePosition) then return false end

  if Options.getOption('classicControl') and
     ((g_mouse.isPressed(MouseLeftButton) and mouseButton == MouseRightButton) or
      (g_mouse.isPressed(MouseRightButton) and mouseButton == MouseLeftButton)) then
    g_game.look(item)
    self.cancelNextRelease = true
    return true
  elseif modules.game_interface.processMouseAction(mousePosition, mouseButton, nil, item, item, nil, item) then
    return true
  end
  return false
end

function UIItem:canAcceptDrop(widget, mousePos)
  if self:isVirtual() then return false end
  if not widget or not widget.currentDragThing then return false end

  local children = rootWidget:recursiveGetChildrenByPos(mousePos)
  for i=1,#children do
    local child = children[i]
    if child == self then
      return true
    elseif not child:isPhantom() then
      return false
    end
  end

  error('Widget ' .. self:getId() .. ' not in drop list.')
  return false
end