Created attachment 3055 [details]
Archive containing the mentioned files.

Overview:

Creating a Window and then creating a Renderer actually creates two windows in rapid succession with only the last window "surviving" - this leads to unexpected behaviour with some window managers (e.g. bspwm and the "preselect split" feature don't work correctly).

Steps to Reproduce:

Create a window as described here: https://wiki.libsdl.org/SDL_CreateWindow and call SDL_CreateRenderer() on the window. (See also attached sample source code.)

Actual Results:

Two windows are created.

Expected Results:

Only one window is created.

Build Date & Hardware:

SDL 2.0.7 on Void Linux x86_64 (glibc)
(2.0.7. was not an option in the "Version" field so I picked 2.0.6)

Additional Builds and Platforms:

Also encountered in Arch Linux on all the versions of SDL2 back to Dec 2015.

Additional Information: 

I've logged the output using bspwm's "external rules" feature, which runs a script each time a new window is created.

I've attached a minimal source code that produces the behaviour, output from the external_rules script after launching the compiled code once as well as the external_rules script itself.

Also see this issue for more information (with imv the window actually appeared to be created three times, suggesting that there might be other function calls that do this as well): https://github.com/eXeC64/imv/issues/56