Brilliant.

[Jeff Mrochuk]

Well, I think I've figured out why our blanking technique was only
getting chunks of data, instead of a smooth row at a time.

The write fifo is using Byte masking to draw the triangle, so certain
bytes (where the triangle isn't) aren't overwritten. 

Now when you go back to vga_fifo_ctrl the data mask needs to be reset,
which it is, so that the entire words are written.  The problem with
setting the byte masks back to 0 in vga_fifo_ctrl is simple.

The data mask in vga_fifo_ctrl is not connected to anything.

I'll fix that.

-Jeff
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