Sets or gets the canvas height. Normally this value must be in device-independent pixels.
If you want your scrollcanvas to use physical pixels instead of device-independent ones,
you must set the Scrollcanvas.AutoScale attribute to False. See High-DPI support for details.
This is called "virtual height" because usually only a portion of it is actually visible. The user can
use the scrollbars to scroll through the complete canvas content.