Review: Classic Mac OS the X Window System ("X") X
Review: Classic Mac OS The X Window System ("X") • Designed for the user, not the developer • Asente, Reid (Stanford): W window system for V OS, (1982) • First commercially successful GUI system • W moved BWS&GEL to remote machine, replaced local library calls with • Technically few advances synch. communication • One address space, one process, “no” OS • Simplified porting to new architectures, but slow under Unix • But revolutionary approach to UI consistency (HI Guidelines) • MIT: X as improvement over W (1984) • Macintosh Toolbox • Asynchronous calls: much-improved performance • Pascal procedures grouped into Managers, ROM+RAM • Application = client, calls X Library (Xlib) which packages and sends GEL • Extended as technology advanced (color, multiprocessing,...), but calls to the X Server and receiving events using the X Protocol. architecture was showing its age by late 90s • Similar to Andrew, but window manager separate • Inspiration for other GUIs, esp. MS Windows • X10 first public release, X11 cross-platform redesigned Jan Borchers 1 media computing group Jan Borchers 2 media computing group X: Architecture X Server • X11 ISO standard, but limited since static protocol Application • X server process combines GEL and BWS • X is close to Widget Set • Responsible for one keyboard (one EL), but n physical screens UITK our 4-layer WM Xt Intrinsics (GLs) architecture • One machine can run several servers Xlib model Xlib • Applications (with UITK) and WM are clients Network • GEL: Direct drawing, raster model, rectangular clipp. X Server BWS+GEL • X-Server layers: Device-dependent X (DDX), device-independent X (DIX) HW • BWS can optionally buffer output regions Jan Borchers 3 media computing group Jan Borchers 4 media computing group Typical Xlib application (pseudocode) X Protocol #include Xlib.h, Xutil.h Display *d; int screen; GC gc; Window w; XEvent e; main () { • Between X server process and X clients (incl.
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