validate-vst3-editorhost

name	validate-vst3-editorhost
description	Test VST3 plugin UIs (.vst3 bundles) using Steinberg's EditorHost without a full DAW. Use when user says "test the plugin UI", "open in editorhost", "show the .vst3 editor", or wants to visually inspect the VST3 editor. For functional validation use validate-vst3 instead.
compatibility	macOS, Windows, Linux. Built from VST3 SDK source.
metadata	{"author":"Oli Larkin","version":"0.0.1"}

VST3 EditorHost

Minimal VST3 host for testing plugin UIs without a full DAW.

Plugin Install Locations

editorhost accepts a direct path to a .vst3 bundle.

Platform	User Location	System Location
macOS	~/Library/Audio/Plug-Ins/VST3/	/Library/Audio/Plug-Ins/VST3/
Windows	%LOCALAPPDATA%\Programs\Common\VST3\	C:\Program Files\Common Files\VST3\
Linux	~/.vst3/	/usr/lib/vst3/ or /usr/local/lib/vst3/

Instructions

1. Build EditorHost from the VST3 SDK if not already built (see Building EditorHost below)
2. Run: editorhost /path/to/plugin.vst3
3. The plugin UI window should appear — verify layout, controls, and resizing
4. Test multiple editor instances with --secondWindow
5. If the UI doesn't appear, verify the plugin passes validator tests first

Usage

# Basic usage - load plugin and show UI
editorhost /path/to/plugin.vst3

# With component handler (tests host callbacks)
editorhost --componentHandler /path/to/plugin.vst3

# Open second window (tests multiple editor instances)
editorhost --secondWindow /path/to/plugin.vst3

# Specify a particular effect class by UID
editorhost --uid "ABCD1234..." /path/to/plugin.vst3

Binary Locations

Platform	Typical Path
macOS	<vst3sdk>/build/bin/Release/editorhost.app/Contents/MacOS/editorhost
Windows	<vst3sdk>\build\bin\Release\editorhost.exe
Linux	<vst3sdk>/build/bin/Release/editorhost

Building EditorHost

Clone the VST3 SDK if you don't have it, then build:

cd <vst3sdk>
cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=Release
cmake --build build --target editorhost

Linux: Requires X11 and GTK3 development libraries:

# Debian/Ubuntu
sudo apt install libx11-dev libgtkmm-3.0-dev libxcb-util-dev libxcb-cursor-dev libxcb-keysyms1-dev libxcb-xkb-dev

# Fedora
sudo dnf install libX11-devel gtkmm3.0-devel xcb-util-devel xcb-util-cursor-devel xcb-util-keysyms-devel libxkbcommon-x11-devel

Troubleshooting

Plugin doesn't load

• Check the plugin path is correct
• Verify the plugin passes validator tests first
• Check logs: Console.app (macOS), Event Viewer (Windows), or stderr (Linux)

UI doesn't appear

• The plugin might not have an editor (hasEditor() returns false)
• Check if createEditor() is returning a valid view
• Linux: Ensure X11 display is available (echo $DISPLAY)

UI appears but is blank/wrong size

• Check defaultEditorSize() returns valid dimensions
• For WebView UIs, check the HTML content is being set correctly
• Try with --secondWindow to see if the issue is with first-time setup