Complete or In-progress

• X Window System and ICCCM
• New font system (fontconfig/Xft)
• Clipboard behavior documentation
• Drag-and-drop specification
• Desktop entry specification
• XEMBED protocol
• "System tray" protocol
• Thumbnail/preview system
• Menu system
• Message bus IPC system (D-BUS)
• Icon themes
• Startup notification
• EWMH