This variable can be used to find out if a particular view port is currently visible or not. You can also set this variable to effectively turn "on" or "off" a view by setting the value to true (visible) or false (invisible). Note that even if you have a view port set to visible, if view ports are not enabled (using the built-in variable view_enabled or enabling them in The Room Editor) then they will not be drawn to the screen.
NOTE This variable does not hold a real GML array, so you cannot run any array functions on it or serialise it (convert it to a string). The only operation you can run on it is accessing a value at an index, with the view_visible[index] syntax.
view_visible[0 ... 7]
Boolean (true: enabled, false: disabled)
if !view_visible[0]
{
view_visible[0] = true;
}
The above code checks to see if view[0] is visible or not and if it is not, it then sets it to be visible.