Feature: Virtual display streaming (second machine as wireless monitor)

[neang-mengseang]

Summary

Allow a second machine on the LAN to act as a virtual monitor for the main machine. No HDMI cable. The main machine creates a virtual display, streams its content over the network, and the sub machine renders it fullscreen. Input from the sub machine flows back to the main machine.

Architecture

`
Main machine (server):
VDD creates virtual monitor
-> DXGI captures virtual display
-> FFmpeg encodes to H.264/H.265
-> StreamChunker splits into chunks
-> SecureSocket encrypts
-> TCP sends to client

Sub machine (client):
TCP receives chunks
-> SecureSocket decrypts
-> StreamChunker reassembles
-> FFmpeg decodes
-> Qt renders in fullscreen window
-> Input forwarded back to server
`

Dependencies

Dependency	Purpose	License
Virtual Display Driver	Virtual monitor creation	MIT
FFmpeg (libavcodec)	Video encoding/decoding	LGPL 2.1
DXGI (Windows SDK)	Screen capture	Proprietary

Milestones

• Milestone 1: VDD detection, virtual display creation, DXGI capture, raw frame transmission (POC)
• Milestone 2: FFmpeg H.264 encoding, network streaming, client-side decoding and rendering
• Milestone 3: Input forwarding from display client back to server
• Milestone 4: GUI integration, VDD bundling, documentation, production release

New modules

src/lib/display/ DisplayManager.h/cpp # Virtual display lifecycle ScreenCapture.h/cpp # DXGI capture VideoEncoder.h/cpp # FFmpeg encoding DisplayStreamServer.h/cpp # Server-side streaming DisplayStreamClient.h/cpp # Client-side receiving DisplayViewer.h/cpp # Qt fullscreen viewer

Protocol extensions

New messages added to the wire protocol:

Message	Direction	Purpose
kMsgDisplayInit	Server -> Client	Start stream, send resolution
kMsgDisplayFrame	Server -> Client	Encoded video frame
kMsgDisplayEnd	Server -> Client	Stop stream
kMsgDisplayInput	Client -> Server	Input from display client
kMsgDisplayReady	Client -> Server	Client ready for frames

Full design doc

See docs/dev/virtual-display-plan.md in the repository.

Scope

• Windows first (IddCx virtual display driver)
• Linux and macOS support planned for later
• Hardware encoding (NVENC/AMF/QSV) where available
• Software fallback via FFmpeg libx264