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 a modular DXE3 architecture into a multitasking desktop environment. The bootstrap loader dynamically discovers and loads core libraries, widget plugins, and applications 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 across 26 DXE modules: 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
• Modular DXE architecture with dependency resolution -- core libraries, widget plugins, and applications are all separate loadable modules

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

DVX uses a modular DXE3 architecture. The bootstrap loader (dvx.exe) is a small executable that discovers, dependency-sorts, and loads all modules at startup. Core libraries, widget plugins, and applications are separate .lib, .wgt, and .app DXE shared libraries.

dvx.exe (bootstrap loader)
  |
  +-- platformRegisterDxeExports() -- platform + libc/libm symbols
  |
  +-- libs/ (scanned, dependency-ordered)
  |     libtasks.lib    -- cooperative task switching, stb_ds
  |     libdvx.lib      -- draw, comp, wm, app, widget infrastructure
  |     dvxshell.lib    -- shell, app lifecycle, crash recovery
  |
  +-- widgets/ (scanned, each calls wgtRegister)
  |     box.wgt, button.wgt, label.wgt, ... (26 modules)
  |
  +-- shellMain() -- found via dlsym, enters main loop
        |
        +-- apps/ (loaded on demand by shell)
              progman.app, notepad.app, clock.app, ...

Boot Sequence

1. dvx.exe starts, calls platformRegisterDxeExports() to register platform and libc/libm symbols for DXE modules
2. Scans libs/ recursively for *.lib files, reads .dep files, topologically sorts, and loads in dependency order
3. Scans widgets/ recursively for *.wgt files, loads each, and calls wgtRegister() on any module that exports it
4. Finds shellMain() across loaded modules via dlsym
5. Calls shellMain(), which initializes the GUI, loads the desktop app, and enters the main event loop

Dependency Resolution

Each DXE module may have a .dep file (same base name, .dep extension) listing the base names of modules that must be loaded before it. The loader reads all .dep files, builds a dependency graph, and loads modules in topological order. For example, libdvx.dep contains libtasks, and dvxshell.dep lists libtasks, libdvx, and all widget modules it requires.

Widget DXE Modules

The 32 widget types in the WidgetTypeE enum are implemented across 26 .wgt DXE modules. Some modules register multiple widget types:

Module	Widget Types
box.wgt	VBox, HBox, Frame
radio.wgt	RadioGroup, Radio
textinpt.wgt	TextInput, TextArea
tabctrl.wgt	TabControl, TabPage
treeview.wgt	TreeView, TreeItem

Each widget DXE exports a standard wgtRegister() function that registers its widget class(es) with the core widget infrastructure. Widget DXEs are discovered by directory scanning, not hardcoded.

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

Source Tree

dvxgui/
  core/               Core GUI infrastructure (-> libs/libdvx.lib)
    platform/            Platform abstraction (dvxPlatform.h, dvxPlatformDos.c)
    thirdparty/          stb_image.h, stb_image_write.h
  tasks/              Cooperative task switcher (-> libs/libtasks.lib)
    thirdparty/          stb_ds.h
  shell/              Desktop shell (-> libs/dvxshell.lib)
  widgets/            Widget modules (-> widgets/*.wgt, 26 files)
  loader/             Bootstrap loader (-> dvx.exe)
  apps/               Application modules (-> apps/*.app)
    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
  config/             Themes, wallpapers, dvx.ini, dependency files
  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 serial-to-telnet proxy (secproxy)
  termdemo/           Encrypted ANSI terminal demo (termdemo.exe)
  bin/                Build output
  lib/                Build output (static libraries)
  releases/           Release archives

Build Output (bin/)

bin/
  dvx.exe             Bootstrap loader
  dvx.map             Linker map
  libs/
    libtasks.lib       Task switching DXE
    libdvx.lib         Core GUI DXE
    libdvx.dep         Dependencies: libtasks
    dvxshell.lib       Shell DXE
    dvxshell.dep       Dependencies: libtasks, libdvx, box, button, etc.
  widgets/
    box.wgt            VBox/HBox/Frame
    button.wgt         Button
    canvas.wgt         Canvas
    checkbox.wgt       Checkbox
    combobox.wgt       ComboBox
    dropdown.wgt       Dropdown
    image.wgt          Image
    imgbtn.wgt         ImageButton
    label.wgt          Label
    listbox.wgt        ListBox
    listview.wgt       ListView
    progress.wgt       ProgressBar
    radio.wgt          RadioGroup/Radio
    scrlpane.wgt       ScrollPane
    separatr.wgt       Separator
    slider.wgt         Slider
    spacer.wgt         Spacer
    spinner.wgt        Spinner
    splitter.wgt       Splitter
    statbar.wgt        StatusBar
    tabctrl.wgt        TabControl/TabPage
    terminal.wgt       AnsiTerm
    textinpt.wgt       TextInput/TextArea
    timer.wgt          Timer
    toolbar.wgt        Toolbar
    treeview.wgt       TreeView/TreeItem
  apps/
    progman/progman.app
    notepad/notepad.app
    clock/clock.app
    dvxdemo/dvxdemo.app
    cpanel/cpanel.app
    imgview/imgview.app
  config/
    dvx.ini
    themes/
      cde.thm
      geos.thm
      win31.thm
    wpaper/
      blueglow.jpg
      swoop.jpg
      triangle.jpg

Building

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

# Build everything (loader, core, tasks, shell, widgets, all apps)
make

# Build individual components
make -C loader    # builds dvx.exe
make -C core      # builds libs/libdvx.lib + widgets/*.wgt
make -C tasks     # builds libs/libtasks.lib
make -C shell     # builds libs/dvxshell.lib + config
make -C widgets   # builds widgets/*.wgt
make -C apps      # builds 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).

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

[colors]
desktop          = 0,128,128
windowFace       = 192,192,192
windowHighlight  = 255,255,255
windowShadow     = 128,128,128
activeTitleBg    = 48,48,48
activeTitleFg    = 255,255,255
inactiveTitleBg  = 160,160,160
inactiveTitleFg  = 64,64,64
contentBg        = 192,192,192
contentFg        = 0,0,0
menuBg           = 192,192,192
menuFg           = 0,0,0
menuHighlightBg  = 48,48,48
menuHighlightFg  = 255,255,255
buttonFace       = 192,192,192
scrollbarBg      = 192,192,192
scrollbarFg      = 128,128,128
scrollbarTrough  = 160,160,160
cursorColor      = 255,255,255
cursorOutline    = 0,0,0

[desktop]
wallpaper = C:\DVX\WPAPER\SWOOP.JPG
mode      = stretch

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

Colors Section

All 20 system colors as R,G,B triplets (0--255). Key names match the ColorIdE enum: desktop, windowFace, windowHighlight, windowShadow, activeTitleBg, activeTitleFg, inactiveTitleBg, inactiveTitleFg, contentBg, contentFg, menuBg, menuFg, menuHighlightBg, menuHighlightFg, buttonFace, scrollbarBg, scrollbarFg, scrollbarTrough, cursorColor, cursorOutline. Missing keys fall back to compiled-in defaults (GEOS Ensemble palette). Colors can also be loaded from standalone .thm theme files via the Control Panel.

Desktop Section

• wallpaper -- path to wallpaper image (BMP, PNG, JPEG, GIF)
• mode -- stretch, tile, or center

Bundled Applications

App	File	Type	Description
Program Manager	progman.app	Callback	App launcher grid with icons; Help menu opens the shell's Task Manager (Ctrl+Esc)
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	core/thirdparty/	Image loading (BMP, PNG, JPEG, GIF)
stb_image_write.h	core/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:

• core/README.md -- Core GUI library architecture and API
• tasks/README.md -- Task switcher API
• shell/README.md -- Shell internals and DXE app contract
• apps/README.md -- Writing DXE applications
• rs232/README.md -- Serial port driver
• packet/README.md -- Packet transport protocol
• security/README.md -- Cryptographic primitives
• seclink/README.md -- Secure serial link
• proxy/README.md -- Linux SecLink proxy
• termdemo/README.md -- Encrypted terminal demo