Call from OnDrawGizmos() to draw text at Unity3D glocal position in Editor

gistfile1.cs

public static void DrawString(Camera cam,string text, Vector3 worldPos, Color? colour = null)
{   
	if (IsValidCamera (cam) == false)
		return;

	UnityEditor.Handles.BeginGUI();
	Color c = GUI.color;
	if (colour.HasValue) GUI.color = colour.Value;
	var view = UnityEditor.SceneView.currentDrawingSceneView;
	if (view==null) return;
	Vector3 screenPos = view.camera.WorldToScreenPoint(worldPos);

	if (screenPos.y < 0 || screenPos.y > Screen.height || screenPos.x < 0 || screenPos.x > Screen.width || screenPos.z < 0)
	{
		GUI.color = c;
		UnityEditor.Handles.EndGUI();
		return;
	}

	Vector2 size = GUI.skin.label.CalcSize(new GUIContent(text));
	GUI.Label(new Rect(screenPos.x - (size.x / 2), -screenPos.y + view.position.height + 4, size.x, size.y), text);
	GUI.color = c;
	UnityEditor.Handles.EndGUI();

}

static bool IsValidCamera( Camera cam) {
	if (Camera.current == null) return false;
	if (Camera.current == cam) return true;
	#if UNITY_EDITOR
	if (SceneView.lastActiveSceneView != null && SceneView.lastActiveSceneView.camera != null && Camera.current == SceneView.lastActiveSceneView.camera) return true;
	#endif
	return false;
}