Some months ago, I’ve modified the AGain plugin sample from the VST SDK to add a Qt window. At that time, I encountered an issue with Vsthost, which is a common VST host. The issue was that in windowed mode, the plugin’s UI wasn’t displayed. With Traktion, I didn’t have this problem, but the minihost (a sample from the SDK) also didn’t use the UI size.

When developing pyvst, I has to implement the retrieval of the size of the plugin, and I’ve decided to add this to QtAGain. I was surprised to see that it actually work with just giving back the UI size (so fixing this was less than 5 lines).

So now, I know that to impelment an UI for a VST plugin, I have to implement:

• open()
• close()
• but also getRect()

Don’t make the same mistake as I did, do implement all three of them, even if your favorite VST host can live without getRect().

P.S.: Mixing Qt for VST UIs and wxPython for pyvst works really fine!