Return whether an explicit rectangle was set as the viewport.
This is useful if you're saving and restoring the viewport and want to know
whether you should restore a specific rectangle or null. Note that the
viewport is always reset when changing rendering targets.
Return whether an explicit rectangle was set as the viewport.
This is useful if you're saving and restoring the viewport and want to know whether you should restore a specific rectangle or null. Note that the viewport is always reset when changing rendering targets.