Add example to use libRmlUi with SDL2 SDL_Renderer / SDL_RenderGeometry

[1bsyl]

for request #250
@baidwwy
I've updated the sample done for libRocket to match RmlUI sample/basics/sdl2
quickly tested.

[baidwwy]

That’s great. Thanks

[mikke89]

Very interesting, thank you!

Not sure how to handle this with regard to the CMake list. I guess it can be a bit confusing wrt. to the old SDL2 sample. Maybe rename the old one to eg. SDL2OpenGL, and add this as a separate sample? And further we should only enable this new one after testing the SDL version, after this has had a release.

Let me know if any of you have thoughts in this regard. For now it should be perfectly fine to merge it as is (after fixing the minor suggestions), and we can work on the CMake and sample things later, cheers!

[1bsyl]

I've just update the PR.
SDL2 is expected to be released soon, so you'll be able to try it.
Then fell free to change whatever you want.

[mikke89]

Perfect, thanks! I'll hold on with merging until I've had a chance to test with the release of the next version of SDL2.

[mikke89]

@1bsyl Thanks again! This works for me, I'm also in the process of adding CMake integration.

@aquawicket Those enhancements sounds very interesting! I'm very much looking forward to the PR(s) ;)

[mikke89]

For reference, see also SDL2 PR libsdl-org/SDL#4195.