I wanted to check out something I was working on a while ago and I noticed the transparency is just black now.

I tried reimporting the desktop friend example project and it does the same without changing anything. The desktop friend demo is still transparant though.

I haven't tried it with shapes, just the per-pixel transparency.

Microsoft have been rolling out the so-called “optimizations for windowed games” over the past year and some, which have it that if Windows thinks that a game isn’t going to use some feature (like window transparency!), it might render the game in a faster way that doesn’t allow for that.

And yet this doesn’t happen if you compile with YYC! A mildly mysterious black box.

Ah okay, good to know. Thanks for the link and the different workarounds!

Just wanted to come here and thank everyone who contributed to this thread. I've been scouring the web trying to figure out why I couldn't make the background of my own, unrelated game project transparent. This thread finally brought all the pieces together and allowed me to do it. 

For future readers, assuming you have this extension or are using a DLL extension of your own or something to accomplish a transparent background, make sure you're building for YYC and check "Use legacy DXGI_SWAP_EFFECT_DISCARD" in Game Options > Windows > Graphics.

And also make sure you're running draw_clear_alpha(c_black, 0) somewhere in a Draw Event before anything else is drawn, ideally in the Draw Begin Event of some game controller object.