Qt VNC GL Platform Plugin

A Qt 6 platform plugin that provides GPU-accelerated VNC server functionality using EGL/OpenGL ES offscreen rendering.

Unlike the software-only VNC plugin in Qt, this plugin uses EGL pbuffer surfaces and OpenGL ES for rendering, enabling hardware-accelerated graphics over VNC. All Qt rendering (including Qt Quick/QML scenes) is performed via OpenGL, with the framebuffer read back and served over the VNC protocol.

Features

• GPU-accelerated rendering via EGL/OpenGL ES pbuffer surfaces
• Full VNC server (RFB protocol 3.3) with keyboard and mouse input
• Supports Qt Quick, Qt Widgets, and any Qt application using the OpenGL rendering backend
• Configurable VNC port and physical screen size
• Screen automatically resizes to match the application window
• Client-side cursor support
• Cross-platform: Linux (native EGL) and Windows (EGL via ANGLE)

Supported Platforms

Platform	GPU Backend
Linux	EGL with native OpenGL ES drivers
Windows	EGL via ANGLE (OpenGL ES over Direct3D)

Requirements

• Qt 6 (qtbase with OpenGL and EGL support)
• EGL and OpenGL ES 2.0 capable GPU/driver
  • Linux: Mesa or vendor EGL driver
  • Windows: ANGLE (bundled with Qt)
• Network access for VNC client connections

Building

mkdir build && cd build
qt-cmake ..
cmake --build .

The plugin will be built as libqvncgl.so (Linux) or qvncgl.dll (Windows).

Usage

Run any Qt application with the vncgl platform:

./your_app -platform vncgl:port=5900

Platform Parameters

Parameter	Description	Default
port=N	VNC server listen port	15900 (auto-detect)
size=WxH	Initial screen resolution (resizes to match window)	1024x768
mmsize=WxH	Physical screen size in mm	auto (96 dpi)

Environment Variables

Variable	Description
QT_VNC_PORT	Override VNC server listen port (takes precedence over port=N parameter)

Port Selection

When no port is specified (neither port=N parameter nor QT_VNC_PORT), the server automatically scans for an available port starting from 15900. When a port is explicitly specified, only that port is used.

Examples

# Run with default auto-detect port (starting from 15900)
./your_app -platform vncgl

# Run with custom port via platform parameter
./your_app -platform vncgl:port=5910

# Run with custom port via environment variable
QT_VNC_PORT=5910 ./your_app -platform vncgl

# Run with explicit initial resolution
./your_app -platform vncgl:port=5910:size=1920x1080

# Force OpenGL backend for apps that default to Vulkan
./your_app -platform vncgl:port=5910 --opengl

Connect with any VNC client (e.g., TigerVNC, RealVNC) to localhost:<port>.

License

This project is licensed under the terms of the GNU General Public License v3.0 (GPL-3.0). See LICENSE.GPL3 for details.