I just write a simple program to show the problem. I know I should clear,draw and display every frame. I just want to know:
When I use black text and white background, the edge of every letter is strange. I can describe the phenomenon in this way. A letter is printed on a paper,and you cut the paper in order to remove the margin,but you cut a little bit more. As a result, the letter is incomplete. The text on the screen is like this. My English is not good,but I hope I have described the problem clearly.
I really think it is a bug. I think it may due to the transformation between float type and int type,but I'm not sure.