Drag and Drop GMod Panels

--ADAPTED FROM LUABEE'S CODE BLOCKS.

AccessorFunc( PANEL, "m_Dragging", "Dragging", FORCE_BOOL )
AccessorFunc( PANEL, "m_DragOffset", "DragOffset" )

function PANEL:OnMousePressed(mc)
    self.m_DragOffset = {0,0}
    if (mc == MOUSE_LEFT) then
        self:StartDragging()
    end
end

function PANEL:OnMouseReleased()
    local ox,oy = self:GetDragOffset()[1] or 0, self:GetDragOffset()[2] or 0
    local mx,my = self:GetParent():ScreenToLocal(gui.MousePos())
    self:SetPos(mx-ox,my-oy)
    self:StopDragging()
end

function PANEL:Think()
    if self.m_Dragging then
        local ox,oy = self:GetDragOffset()[1], self:GetDragOffset()[2]
        local mx,my =  self:GetParent():ScreenToLocal(gui.MousePos())
        self:SetPos(mx-ox,my-oy)
    end
end

function PANEL:StartDragging(t)
    self.m_Dragging = true
    self:MouseCapture(true)
    self:MoveToFront()
    local mx,my = self:ScreenToLocal(gui.MousePos())
    self:SetDragOffset({mx,my})
end

function PANEL:StopDragging()
    self.m_Dragging = false
    self:MouseCapture(false)
end