If I set a pygame window to resizable and then click and drag on the border of the window the window will get larger but nothing blit onto the surface will get larger with it. (Which is understandable) How would I make it so that when I resize a window all blit objects resize with it and fill the window properly?
For example: Say I have a window of 200 x 200 and I blit a button at window_width/2 and window_height/2. The button would be in the center of the window at 100 x 100. Now if I resize the window to 300 x 300 the button stays at 100 x 100 instead of 150 x 150. 
I tried messing around with pygame.Surface.get_width ect, but had no luck.
Basically I'm trying to resize a program's window and have all blit images stay proportionate.
Recently with pygame2.0 You can use the SCALED flag
Pygame. How do I resize a surface and keep all objects within proportionate to the new window size?