Constant BUFFER_SIZE 

pub const BUFFER_SIZE: u32 = 200; // 200u32

The maximum number of ViewTreeSnapshots a client can expect in a Watch call’s response. The number of ViewTreeSnapshots can be less than BUFFER_SIZE when the size of a Watch call’s response exceeds the limit of a FIDL channel.

There is a limit on the number of ViewTreeSnapshots that can be included in a Watch call’s response due to the size restrictions of a FIDL channel. This limit was calculated by finding out the maximum number of ViewTreeSnapshots which can be included in a Watch call’s response when MAX_VIEW_COUNT is 1.

Note: This value would have to adjusted when modifying ViewTreeSnapshot or ViewDescriptor.