Software Engineering and Computer Games

31.2. Using a background bitmap

Suppose we want to use a background bitmap as a resource. The basic idea is that when we draw the view we want to do the following.

• Copy the background bitmap to a memory window.
• Write the critter sprites on top of the memory window as well.
• Copy the memory window to the screen.

What we need to do is to store our background bitmap in a ready-to-use form. At the high level, we wrap it up inside a cSpriteIcon object. In Windows graphics, we implement the image as a cMemoryDC, and in OpenGL we save it as a cTexture – both of which are classes invented for use in the Pop Framework.

A complication comes up. We want our program to be size-independent; that is, if we resize the window, we want the whole background ...