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DVX_GUI/README.md
Scott Duensing 26c3d7440d Updated docs.
2026-03-20 20:00:05 -05:00

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DVX -- DOS Visual eXecutive

A windowed GUI compositor and desktop shell for DOS, built with DJGPP/DPMI. DVX combines a Motif-style window manager, dirty-rectangle compositor, cooperative task switcher, and DXE3 dynamic application loading into a multitasking desktop environment where applications are .app shared libraries loaded at runtime.

Targets real and emulated 486+ hardware with VESA VBE 2.0+ linear framebuffer. No bank switching -- LFB or fail.

Features

  • Motif/GEOS-style beveled window chrome with drag, resize, minimize, maximize, and restore
  • Dirty-rectangle compositor -- only changed regions are flushed to video memory, critical for acceptable frame rates on 486/Pentium hardware
  • 32 widget types: buttons, text inputs, list boxes, tree views, list views, tab controls, sliders, spinners, progress bars, dropdowns, combo boxes, splitters, scroll panes, ANSI terminal emulator, and more
  • Flexbox-style automatic layout engine (VBox/HBox containers with weighted space distribution)
  • Dropdown menus with cascading submenus, checkbox and radio items, keyboard accelerators, and context menus
  • Modal dialogs: message box (OK/Cancel/Yes/No/Retry) and file open/save with directory navigation and filter dropdown
  • 20-color theme system with live preview and INI-based theme files
  • Wallpaper support: stretch, tile, or center with bilinear scaling and 16bpp ordered dithering
  • Live video mode switching without restart
  • Mouse wheel support (CuteMouse Wheel API)
  • Screenshots (full screen or per-window) saved as PNG
  • Clipboard (copy/cut/paste within DVX)
  • Timer widget for periodic callbacks
  • Cooperative task switcher for apps that need their own main loop
  • DXE3 dynamic application loading with crash recovery (SIGSEGV, SIGFPE, SIGILL caught and isolated per-app)
  • INI-based preferences system with typed read/write accessors
  • Encrypted serial networking stack (DH key exchange, XTEA-CTR cipher)
  • Platform abstraction layer -- DOS/DJGPP production target, Linux/SDL2 development target

Target Hardware

  • CPU: 486 baseline, Pentium-optimized paths where significant
  • Video: VESA VBE 2.0+ with linear framebuffer
  • OS: DOS with DPMI (CWSDPMI or equivalent)
  • Supported depths: 8, 15, 16, 24, 32 bpp
  • Test platform: 86Box with PCI video cards

Architecture

The shell runs as a single DOS executable (dvx.exe) that loads applications dynamically via DJGPP's DXE3 shared library system.

+-------------------------------------------------------------------+
|                        dvx.exe (Task 0)                           |
|  +-------------+  +-----------+  +------------+                   |
|  | shellMain   |  | shellApp  |  | shellExport|                   |
|  | (event loop)|  | (lifecycle|  | (DXE symbol|                   |
|  |             |  |  + reaper)|  |  export)   |                   |
|  +-------------+  +-----------+  +------------+                   |
|         |               |              |                          |
|  +------+-------+  +----+-----+  +----+----+                     |
|  | libdvx.a     |  |libtasks.a|  | libdxe  |                     |
|  | (GUI/widgets)|  |(scheduler)|  | (DJGPP) |                     |
|  +--------------+  +----------+  +---------+                     |
+-------------------------------------------------------------------+
         |                    |
    +---------+          +---------+
    | app.app |          | app.app |
    | (Task N)|          | (Task M)|
    +---------+          +---------+

App Types

Callback-only (hasMainLoop = false): appMain creates windows, registers callbacks, and returns. The app lives through event callbacks in the shell's main loop. No dedicated task or stack needed.

Main-loop (hasMainLoop = true): A cooperative task is created for the app. appMain runs its own loop calling tsYield() to share CPU. Used for apps that need continuous processing (clocks, terminal emulators, games).

Crash Recovery

The shell installs signal handlers for SIGSEGV, SIGFPE, and SIGILL. If an app crashes, the handler longjmps back to the shell's main loop, the crashed app is force-killed, and the shell continues running. Diagnostic information (registers, faulting EIP) is logged to dvx.log.

Directory Structure

dvxgui/
  dvx/                  GUI compositor library (libdvx.a)
    platform/             Platform abstraction (DOS/DJGPP, Linux/SDL2)
    widgets/              Widget system (32 types, one file per type)
    thirdparty/           stb_image.h, stb_image_write.h
  tasks/                Cooperative task switcher (libtasks.a)
    thirdparty/           stb_ds.h
  dvxshell/             Desktop shell (dvx.exe)
  apps/                 DXE app modules (.app files)
    progman/              Program Manager -- app launcher grid
    notepad/              Text editor with file I/O
    clock/                Digital clock (multi-instance, main-loop)
    dvxdemo/              Widget system showcase / demo app
    cpanel/               Control Panel -- themes, wallpaper, video, mouse
    imgview/              Image Viewer -- BMP/PNG/JPEG/GIF display
  rs232/                ISR-driven UART serial driver (librs232.a)
  packet/               HDLC framing, CRC-16, Go-Back-N (libpacket.a)
  security/             DH key exchange, XTEA-CTR cipher (libsecurity.a)
  seclink/              Secure serial link wrapper (libseclink.a)
  proxy/                Linux SecLink-to-telnet proxy (secproxy)
  termdemo/             Encrypted ANSI terminal demo (termdemo.exe)
  themes/               Color theme files (.thm)
  wpaper/               Bundled wallpaper images
  bin/                  Build output (dvx.exe, apps/, config/)
  lib/                  Build output (static libraries)
  releases/             Release archives

Building

Requires the DJGPP cross-compiler (i586-pc-msdosdjgpp-gcc).

# Build everything (dvx lib, tasks lib, shell, all apps)
make

# Build individual components
make -C dvx         # builds lib/libdvx.a
make -C tasks       # builds lib/libtasks.a
make -C dvxshell    # builds bin/dvx.exe
make -C apps        # builds bin/apps/*/*.app

# Clean all build artifacts
make clean

Set DJGPP_PREFIX in the component Makefiles if your toolchain is installed somewhere other than ~/djgpp/djgpp.

Deployment

CD-ROM ISO (86Box)

The primary deployment method is an ISO image mounted as a CD-ROM in 86Box:

./mkcd.sh

This builds everything, then creates an ISO 9660 image with 8.3 filenames at ~/.var/app/net._86box._86Box/data/86Box/dvx.iso. Mount it in 86Box as a CD-ROM drive and run D:\DVX.EXE (or whatever drive letter is assigned).

Floppy Image

For boot floppy setups with CD-ROM drivers:

mcopy -o -i <floppy.img> bin/dvx.exe ::DVX.EXE
mcopy -s -o -i <floppy.img> bin/apps ::APPS
mcopy -s -o -i <floppy.img> bin/config ::CONFIG

The apps/ and config/ directory structures must be preserved on the target -- Program Manager recursively scans apps/ for .app files at startup.

Configuration

DVX reads its configuration from CONFIG\DVX.INI on the target filesystem. The INI file uses a standard [section] / key = value format. Settings are applied at startup and can be changed live from the Control Panel app.

[video]
width  = 640
height = 480
bpp    = 16

[mouse]
wheel        = normal
doubleclick  = 500
acceleration = medium

[desktop]
wallpaper     = C:\DVX\WPAPER\SWOOP.JPG
wallpaperMode = stretch
theme         = C:\DVX\THEMES\WIN31.THM

Video Section

  • width, height -- requested resolution (closest VESA mode is used)
  • bpp -- preferred color depth (8, 15, 16, 24, or 32)

Mouse Section

  • wheel -- normal or reversed
  • doubleclick -- double-click speed in milliseconds (200--900)
  • acceleration -- off, low, medium, or high

Desktop Section

  • wallpaper -- path to wallpaper image (BMP, PNG, JPEG, GIF)
  • wallpaperMode -- stretch, tile, or center
  • theme -- path to color theme file (.thm)

Bundled Applications

App File Type Description
Program Manager progman.app Callback App launcher grid with icons; also provides the Task Manager (Ctrl+Esc) for switching between running apps
Notepad notepad.app Callback Text editor with File/Edit menus, open/save dialogs, clipboard, and undo
Clock clock.app Main-loop Digital clock display; multi-instance capable
DVX Demo dvxdemo.app Callback Widget system showcase demonstrating all 32 widget types
Control Panel cpanel.app Callback System settings: color themes with live preview, wallpaper selection, video mode switching, mouse configuration
Image Viewer imgview.app Callback Displays BMP, PNG, JPEG, and GIF images with file dialog

Serial / Networking Stack

A layered encrypted serial communications stack for connecting DVX to remote systems (BBS, etc.) through 86Box's emulated UART:

Layer Library Description
rs232 librs232.a ISR-driven UART driver with FIFO support, automatic UART type detection (8250 through 16750), configurable baud rate
packet libpacket.a HDLC framing with byte stuffing, CRC-16 integrity checks, Go-Back-N sliding window for reliable delivery, 255-byte max payload
security libsecurity.a 1024-bit Diffie-Hellman key exchange (RFC 2409 Group 2), XTEA-CTR stream cipher, XTEA-CTR DRBG random number generator
seclink libseclink.a Convenience wrapper: multiplexed channels (0--127), per-packet encryption flag, bulk send helper
proxy secproxy Linux-side bridge: 86Box emulated serial port <-> secLink <-> telnet BBS; socket shim replaces rs232 API

Third-Party Dependencies

All third-party code is vendored as single-header libraries with no external dependencies:

Library Location Purpose
stb_image.h dvx/thirdparty/ Image loading (BMP, PNG, JPEG, GIF)
stb_image_write.h dvx/thirdparty/ Image writing (PNG export for screenshots)
stb_ds.h tasks/thirdparty/ Dynamic array and hash map (used by task manager)

Component Documentation

Each component directory has its own README with detailed API reference: