More Low-level Optimizations (3)

This test can be made a test against a value of zero if the inital value of scaledFraction has 2*dx subtracted from it. Giving outside the loop:

OffsetScaledFraction = dx + 2*dy - 2*dx = 2*dy - dx,

and the inner loop becomes

OffsetScaledFraction += 2*dy
if (OffsetScaledFraction >= 0) { 
	y = y +1; OffsetScaledFraction -= 2*dx; 
} 

The net result is that we might as well double the values of dy and dx (this can be accomplished with either an add or a shift).

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