[pygame] Dirty Rect updating

["etrek" <etrek@xxxxxxx>]

Hi,

I'm trying to update just the portions of my screen that change per frame.  The problem I'm having is that only the image I'm animating is showing up.  My background is not showing up -  background is now black. 

 

I'm not using Sprite/SpriteGroup, but I will soon, and I'm thinking I'll have the same problem when I try to render the dirty rects list returned by RnderUpdates.draw() method.

 

 

pseudocode:

 

background = pygame.image.load(background.png)

surface = pygame.image.load(spaceship)

while true:

    get events

    clear screen to white

    blit background

    blit spaceship 

    create rect of where surface is on screen

    pygame.display.update(rect)   # which in this case is a rectangle in the location of my animated surface

 

 

 

I'm following procedure from http://www.pygame.org/docs/tut/newbieguide.html:

1. Blit a piece of the background over the sprite's current location, erasing it.
2. Append the sprite's current location rectangle to a list called dirty_rects.
3. Move the sprite.
4. Draw the sprite at it's new location.
5. Append the sprite's new location to my dirty_rects list.
6. Call display.update(dirty_rects)

Thanks for help

Ethan