SDL2 | Port emulator to SDL2

[midwan]

The emulator currently uses SDL1 internally, for input events, graphics drawing (combined with DispManX), audio and joystick support.

We should move it to SDL2 which provides a more modern approach, hardware acceleration and enhanced joystick input features.

[midwan]

Note: Guichan is outdated, no longer updated and does not play well with SDL2.
Moving to Guisan instead seems like the obvious choice: https://github.com/kallisti5/guisan

[midwan]

The SDL2 packages available from the Jessie repository require/expect a X-environment and do not open a window from the console.

Will try compiling SDL2 from source with explicitly defining what features should be enabled/disabled, as mentioned here: https://solarianprogrammer.com/2015/01/22/raspberry-pi-raspbian-getting-started-sdl-2/

[midwan]

Confirmed, compiling SDL2 from source and defining the necessary options seems to produce a version that works without X11.

[midwan]

Note: Do NOT enable the experimental OpenGL driver on Raspbian. It breaks things like DispmanX and SDL2 without X11.

[midwan]

Proof of concept, using Guisan, SDL2 and hardware accelerated display:

[Fourdee]

@midwan

Note: Do NOT enable the experimental OpenGL driver on Raspbian. It breaks things like DispmanX and SDL2 without X11.

I ran into similar issues when compiling DXX-rebirth for RPi. I wanted to support both FBdev and OpenGL for RPi.
I had to compile 2 binaries. One for FBdev (--disable-video-opengl) and the other with OpenGL. Both work great :)

Might be worth a shot at compiling with --disable-video-opengl? Should work on the RPi OpenGL driver.

[midwan]

I tried compiling SDL2 with --disable-video-opengl but if the OpenGL driver is enabled, my applications don't start (no display is initialized). If I disable the OpenGL driver, they work again.

The same happens with any apps using DispManX directly, they fail when the OpenGL driver is enabled, work when it's not.

[midwan]

UAE's GUI is now working under SDL2, except one glitch in the Configurations list (only one entry appears, with a larger than normal row height). This needs to be fixed in the original Guichan (now Guisan) code that calculates the row height and list items there.

The emulation screen is not working correctly yet, needs more time to fix. It actually opens a screen 4 times larger than what was expected, with incorrect colors (maybe RGB format issue?) and it's very slow.

[midwan]

Note to self: the graphics corruption issue is related to the RGB format used (if it's 32-bit) in combination with the Pandora "copy to 16 bit" routines, located in picasso96.cpp. Investigate if those are really needed on the Pi and take them away if they are not.

[midwan]

Graphics corruption issue is now fixed.
Need to look into #41 next.