I solved the issue #4502.

The problem was that subsurface.fill, the function defined in surface.c, worked differently from the function pygame.draw.rect.

As the author of issue #4502 showed with the example of 100 * 100 square, even with the same coordinates, surface.fill filled all the 100 * 100 area and pygame.draw.rect filled only the 50 * 50 area.

However, subsurface.fill should work in the same way of pygame.draw.rect, and it means that the function needs to fill the area from the start coordinates (x, y) to the coordinates (x + dx, y + dy) and cut off the area with negative coordinates.

I implemented this, so please check it.