Date: Sun, 15 Aug 93 16:25:07 PDT
From: akrause AT saturn DOT SDSU DOT Edu (Alan Krause)
To: djgpp AT sun DOT soe DOT clarkson DOT edu

Subject: LibGRX & Sprites

  I have been working with LIBGRX recently, and am doing some animation routines
, and have the following question:

  Is there anyway to make BitBlt not plot GRNOCOLOR pixels on the graphics
screen without re-writting much of the code??  What I am trying to do is to
animate a sprite which is not a perfect rectangle (i.e. a human, spaceships, 
etc.) so I let several of the pixels in the sprite be GRNOCOLOR so that the
backround will show through.  However, when I do a 
    BitBlt(NULL,xpos,ypos,*sprite,0,0,spritex,spritey,GrWRITE);

  it places the GRNOCOLOR pixels as black, and hence does not do what I want
it to do.  To get around this, I get the backround I'm going to write over in
a seperate context, copy it to the sprite context, and then write the sprite
data over the backround, then BitBlt this to the screen.

  I was hoping that there would be an easier/quicker way than having to 
reconstruct a new sprite each time the position changed.

  Any ideas??
     - Alan Krause