About a month ago I ported the Curves adjustment UI to use Direct2D for the transfer map (the interactive spline/grid). This meant that a rectangular portion of the form was carved out for Direct2D. If you’ve used WPF interop then you’ll be familiar with “airspace limitations”, and I was curious as to whether it would be possible to put a WinForms button on top of an area that is being rendered to with Direct2D. In other words, if you use Direct2D to render to an area of a Form, does it completely take over that rectangular area?


Now, you can always take a guess, “Well of course you could/couldn’t do that because of explanation involving logical deduction or other example setting precedent.” For engineering purposes, however, something like this must be shown to work before taking a dependency on it.

And what do you know, it does work:


This screenshot shows a Form that contains a single control of type “D2DThingy.” That control then has 5 children controls of various types, and they are all stock WinForms controls. Clearly, they are able to coexist peacefully and without artifacts like clipping or flickering. Like with any WinForms UI there is still a lot of work to make sure that the background of the Button matches up with what’s behind it, etc. but that is a known problem with known solutions.

This is of special importance to me because I want to write a new toolbar UI for Paint.NET v4.0. However, I absolutely do not want to write my own ComboBox or TextBox controls. I could spend a full 12 months on a globalized TextBox that can work with all languages, input types, etc. Thankfully I won’t have to.

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