Plot a signal, use plt.AxisAuto(0), then look at the bottom left corner. I think this is accurate - the zero tick marks the zero position (the first pixel column)... but it looks bad because the tick mark isn't perfectly aligned with the left edge of the frame.

What's the best solution here? Technically the tick is in the right spot. In reality, the figure might look better if a rule like this is added to straighten the left edge up.

if (majorTickPixelX == 1) 
     majorTickPixelX = 0;

I guess the alternative would be to move the left frame border right 1 pixel, but that would cover-up a column of real data, so I don't like that alternative.