VMS DECwindows Guide to Xlib Programming: VAX Binding

```json {VMS DECwindows Guide to Xlib Programming: VAX Binding} [AA-MG25B-TE]

This document serves as a guide for experienced programmers on how to use Xlib routines within the VMS DECwindows programming environment, adhering to the VAX calling standard. It provides an overview of Xlib, explains error handling, and offers debugging techniques.

The manual is structured into chapters covering various aspects of Xlib programming, including: - Client-Server Connection: How clients interact with servers using Xlib, including establishing and closing connections, and retrieving display information. Xlib buffers client requests for efficiency, but this can delay error reporting, which can be managed with synchronous operation for debugging. - Windows: Fundamentals of windowing in the X Window System, including window hierarchy (root, parent, child windows), creation, destruction, mapping, unmapping, changing characteristics (size, position, border, attributes), and interaction with the window manager. It details how window visibility and occlusion are determined. - Graphics Characteristics: Defining various attributes of graphic objects (e.g., line width, style, color, font) using graphics contexts (GCs), and managing them efficiently through routines that create, copy, change, and free these contexts. - Color: Color management, including pixels, color maps, visual types (Pseudocolor, Gray scale, Direct color, True color, Static gray, Static color), sharing color resources, allocating colors for exclusive use, and querying color map entries. - Drawing Graphics: Routines for drawing and filling points, lines, rectangles, arcs, and polygons, as well as clearing and copying areas within windows and pixmaps. It also covers defining and managing regions for clipping graphics. - Using Pixmaps and Images: Working with off-screen graphics resources like pixmaps (for cursors, icons, tiling, backing store) and images, including their creation, management, and use in graphical operations. - Writing Text: Concepts of characters and fonts, specifying fonts, computing text size, retrieving font information, and drawing text on the screen. - Event Handling: Event processing, selection of event types (e.g., keyboard, pointer motion, window crossing, input focus, keymap state, exposure, window state notification, client communication), and management of the event queue. It also discusses error handling in Xlib, including default error handlers and enabling synchronous operation for debugging.

The document also includes appendices on using the VMS DECwindows font compiler, routines requiring protocol requests, a list of VMS DECwindows named colors, and VMS DECwindows font names for 75 DPI and 100 DPI displays.