EventSystem does not receive mouse input when fetching mouse input via an MQTT service (for working with a remote mouse setup)

1.8.X

Won't Fix

This appears to be an issue within the project and not a bug in the InputSystem. I verified the Mouse InputState events created by VirtualMouse and "injected" into the InputSystem via InputState.Change() are in fact processed and forwarded to the UI Input Module. I also verified the UI Events are properly dispatched and executed. The reason the UI doesn't respond is because the VirtualMouse creates an "indicator" GameObject that is parented to the UI Canvas, and all of the UI Events are dispatched to it, i.e. it's blocking input from reaching the UI controls. The problem is with this code in VirtualMouse.cs GameObject indicator = new GameObject(); indicator.name = "HRP_Mouse_Indicator"; indicator.transform.SetParent(referenceCanvas.transform); // <-- problem mouseImage = indicator.AddComponent<Image>(); mouseImage.color = Color.red; By creating a GO that's parented to the Canvas, it will be targeted by the Event System for handling pointer input, and since it's position is always set to current pointer position, it intercepts all pointer events blocking them from reaching the UI. By removing the indicator object from the Canvas hierarchy, the indicator visual won't display properly, but you can interact with the UI. Another (potential) issue with the project is around mouse position: the indicator doesn't match the position of the Windows mouse. This occurs because the received MQTT coordinates are in global Windows screen space and need to scaled to the rendering viewport. Note that VirtualMouse does invert the y-position (since Unity screen space y-axis increases going up) but the mouse position isn't scaled. I'm guessing this is expected, and doesn't matter for remote mouse input, but I wanted to call it out just in case.