When drawing a circle using the GXR the position of the cursor afterwards is the upper right point of the bounding box. On a BBC Master 128 (tested on JSBEEB) it is on the circumference of the circle at 45 degrees e,g, at offset cos(45).r sin(45).r from the circle centre .... probably because it draws the circle using reflection / Bresenham and this is where it ends up.
Now, this is arguably very dozy behaviour. I'd have implemented it so it drew an ellipse in a bounding box (not fun on a 65C02) or so it reset the position to the centre of the circle, useful for drawing rings with outlines.
I would suggest rather than copying this odd feature, which I doubt any developer has ever used, the documentation says that the position of the graphics cursor after drawing the circle is indeterminate.
When drawing a circle using the GXR the position of the cursor afterwards is the upper right point of the bounding box. On a BBC Master 128 (tested on JSBEEB) it is on the circumference of the circle at 45 degrees e,g, at offset cos(45).r sin(45).r from the circle centre .... probably because it draws the circle using reflection / Bresenham and this is where it ends up.
Now, this is arguably very dozy behaviour. I'd have implemented it so it drew an ellipse in a bounding box (not fun on a 65C02) or so it reset the position to the centre of the circle, useful for drawing rings with outlines.
I would suggest rather than copying this odd feature, which I doubt any developer has ever used, the documentation says that the position of the graphics cursor after drawing the circle is indeterminate.