The OpenGL functions gluOrtho2D and glViewport are displayed in this scrollable window. The parameters to gluOrtho2d set the boundaries of the current projection window while those of glViewport set the viewport boundaries. As usual, the parameters shown in green are changable. Left click on the value you wish to change and while holding the button down, drag the mouse up and down. The images in the display windows and the content of the technical content window are updated as you change a parameter.
While an input item is selected (drawn in yellow), you can also change its value using the Up-Arrow and Down-Arrow keys. The amount added to or subtracted from the selected item is fixed within the program. However, a multiplier is also used in making the change. You may adjust the multiplier through the Page-Up and Page-Down keys. Making the mulitiplier larger accelerates the change that is made to the selected item.