mouse drag line keep 90 angle,how to do

Development Programming & Scripting Blueprint
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[video]http://v.youku.com/v_show/id_XMjY0OTg0NTg3Ng==.html[/video]

90angle.PNG

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mouse drag line keep 90 angle,how to do

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When you set X,Y coordinates, keep either X or Y at the current value.