you're right, thank's for this hint
changed the code ...
--Draw a line from box position to current mouse position
local p0 = self.camera:Project(self.entity:GetPosition())
local p1 = self.window:GetMousePosition()
context:SetBlendMode(Blend.Alpha)
context:SetColor(1,0,0)
context:DrawLine(p0.x,p0.y,p1.x,p1.y)
context:SetBlendMode(Blend.Solid)
context:SetColor(0,0,0)
THANKS AGAIN to everyone for your help!