There are some environment variables which houdini checks if the X server isn't reporting accurate window sizes.. You can set HOUDINI_OVERRIDE_XRES and HOUDINI_OVERRIDE_YRES to different values to adjust what Houdini thinks the actual resolution of the screen is.
I don't know if this will help as it has it's own peculiarities…
Cute, this helps So for now we need to fix a problem with “+” button