This variable sets the horizontal border width for view
following. You can set the view to follow a specific instance using
the view_object variable
(or in the room
editor) and by setting this value you can control how near or
far from the edge of the view the instance needs to be before the
view will move. For example, if you have a view width of 320 and
set the horizontal view border to 160, the object that the view
must follow will always be in the middle of the view. However, make
the horizontal view border 0 and the instance must be right on the
edge of the view before it will move.
NOTE: if you are not setting the x and y position of the view manually, the view never leaves the boundaries of the room. This means that when the view reaches the edge of a room, the horizontal and vertical borders are ignored and the instance will move freely within the view.
view_hborder = view_wview / 2;
view_vborder = view_hview / 2;
The above code will set the view follow borders to half the width and height of the view, effectively forcing the view to always be centered on the follow object.