a question about the size of chart window

[FuliangQ]

hi,everybody .

 first , please forgive me for my poor english .  

 i come to face the question to know the size of the chart window . i try to get a clue by reading 

the docs and files included in include-file .

  here , the size of the chart window means the length and width of it .

 

    thanks in advance for your help .