/window -CBdfkpa +xstn @test -1 -1 200 200
press f11
/window @test 50 50 200 200
if you resize a custom window while it is in fullscreen via /window, the window ends up being borderless. Tested on windows 7.
I believe that mIRC should be handling this and put the border back, not too sure
I also think having a property to check if a window is fullscreen would be a good idea: $window().fullscreen
If this is intended, we would need to be able to know when it occurs, I have made suggestion in the past for new event in menu { } for resizing, it has to be said that currently, making the display (typically picture window) bigger/smaller according to the window's size cannot be done in a smooth way, it requires a fast timer to check for change in size.
