Centering+the+graphics+origin

//by Richard Russell, October 2010//

The following code will centre the graphics origin both horizontally and vertically, irrespective of the size and shape of the window: code format="bb4w" VDU 26 ORIGIN @vdu.tr%,@vdu.tb% code The reason it works is that after a **VDU 26** both the text and graphics viewports fill the entire window (client area). In that case **@vdu.tr%** and **@vdu.tb%** return the width and height of the text viewport in pixels, and since **one** pixel is equivalent to **two** BBC BASIC graphics units they also correspond to **half the width** and **half the height** of the graphics viewport, respectively. Therefore they are the correct values to use for centering the origin.