LENS(9.1) LENS(9.1) NAME lens - bitmap magnifier SYNOPSIS lens DESCRIPTION Lens is an interactive screen bitmap magnifier. When it starts, it displays an enlarged image of a magnifying glass in its layer, which becomes a setting sun when lens wants to confirm a command to exit. The first item in the button 2 menu, which rotates among go, peek and stop, determines the activity of the magnifier. Clicking button 1 serves as an abbreviation for selecting go or peek. When the magnifier is going, a crawling-bordered rectangle is drawn around the source, and the lens window contains the magnified image. The mouse controls the posi- tion of the source rectangle. During peeking, the rectangle last selected while going is re-examined periodically, and the contents are magnified, whether or not the lens window is currently selected. When stopped, the lens window is inactive. The button 2 menu also allows changing the magnification factor. The magnification factors are chosen from the Fibonacci numbers, and menu items for the next size smaller and larger are presented as, e.g., 3x or 8x. The current magnification factor is not displayed in the menu, only the next factors larger and smaller. The initial magnification factor is two. Button 2 may also be used to select the intervals at which peeking updates occur. These intervals are selected, in ticks, from among the powers of two, where a tick is one- sixtieth of a second. These choices are presented as, e.g., 32 ticks or 128 ticks. The initial interval between peeks is 64 ticks, approximately one second. The image window may be controlled by the button 2 menu item which toggles between inset and full size. In inset mode, the image is displayed inside the image window of the magni- fied lens icon. In full size mode, the image is displayed in the entire lens window. The final buton 2 menu entry is exit. A setting sun is dis- played, and button 3 must be clicked to confirm. LENS(9.1) LENS(9.1) BUGS While going, the display is only refreshed when the mouse is moved. Inconsistent results may be obtained when lens is used to examine its own image window. While peeking, it is assumed that the lens window contains an accurate magnification of what was on the screen at the time of the last magnification. If lens is used to examine its own image, strange things may occur. Due to the bitmap reshaping techniques employed by the mag- nification algorithms, high magnification factors will not work with large image windows. Precisely, if the product of the vertical magnification factor and the width of the des- tination rectangle overflows a signed short integer, pre- dictable but undesirable results will occur.