Macro layout 

macro_rules! layout {
    ($size:expr, $(($($line:tt)*) $(=> { $($row:tt)* })? ),+) => { ... };
    (@row %$val:expr $(, $($row:tt)*)?) => { ... };
    (@row #$val:expr $(, $($row:tt)*)?) => { ... };
    (@row >$val:expr $(, $($row:tt)*)?) => { ... };
    (@row <$val:expr $(, $($row:tt)*)?) => { ... };
    (@row $val:expr ; $val2:expr $(, $($row:tt)*)?) => { ... };
}

Generates a layout from given perameters. Formatting: Put size first. Then , Then (constraint) Constraints:

• %Num: Percentage

• #Num: Length

• Num: Min

• <Num: Max

• Num ; Num: Ratio

  Then Either , to make new row, or => {} to add horizontal limits to row. If horizontal limits, then constraint and optionally more

Ex: Custom Chunks Example