I uploaded an example of a print preview program.

[Step]

1. run the demo, then open the text file called "SmallText.txt"  I uploaded
2. click the print button, you can preview the file, and also you can see the file page count
3. but when you open a larger file(> 50M), you can see that the page count = 1, it's not true

[Hope]

        In my opinion, I think even if I open a very large text file, I should be able to get the correct number of pages of the file.

I uploaded a video reproducing the problem.