GROBW/GROBH vs GROBW_P/GROBH_P

[Tim Wessman]

There are no bugs here and the explanation is correct. Because the screen is not an odd number of pixels, some internal adjustment happens internally on the Cartesian width to ensure plotted items remain "square" and can be centered properly. That manual simply does not show it because it would be very unpleasant to read a big decimal number and confusing to new readers. The same thing is in the UI itself which basically "lies" to round to a nice number there. This also allows your cursor to report nice numbers instead of crazy decimals.

The whole point of the Cartesian drawing commands is to enable drawing to existing plots, or to do plotting type applications. In this it works perfectly regardless of a small discrepancy by one pixel in the width. Any algorithm or code developed using them will work as expected. Changing it to be "exact" would simply cause a less pleasant user experience.

The manual does have the mistake you pointed out regarding 0,0 -> 320,240 (should be 319,239)