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SDL2 Port #1137

Merged
merged 41 commits into from
Dec 2, 2020
Merged

SDL2 Port #1137

merged 41 commits into from
Dec 2, 2020

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ivan-mogilko
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Resolves #1096.

Replaces Allegro 4 backend with SDL2.

Main bulk of work was done by @sonneveld previously, now gathered it up, tidied the code, amended and fixed where necessary.
CMake changes by @ericoporto.

Library changes

  • SDL2 is used for window management, rendering and input.
  • SDL2_Sound library for decoding audio formats.
  • MojoAL (embedded) is an OpenAL implementation based on SDL2 and SDL2_Sound.
  • Allegro 4 (embedded) is kept in a stripped form, for memory bitmap handling and drawing, file/path functions, unicode text functions, decoding FLIC videos.
  • Apeg (embedded) is kept to play OGG Theora videos, rewritten by @sonneveld to use OpenAL api instead of Allegro 4 sound.

Notable issues / future todo:

  • Disabled Windows-only plugin functions that return DirectX interfaces from Allegro 4.
  • For the similar reason had to remove AVI/MPG video support, which was previously implemented through use of MS DirectShow (non-portable) and used DirectDraw interface. Might need to reimplement video differently in the future, and support all wanted formats similarily for all systems.

Audio

Audio playback is completely rewritten, uses OpenAL (through MojoAL currently) and SDL2_Sound.
Audio is now played only on a separate thread (this was optional previously).

Notable issues / future todo:

  • May need to add configuration options for audio device init;
  • Sync between audio and game events/animation may be broken in some situations (at least happened with threaded audio before). If such problem is found may need to invent some kind of a syncing mechanism.

Rendering

  • Direct3D and OpenGL work more or less same, except window is now created by SDL2 and OpenGL uses few SDL_GL functions for getting context etc (makes code more uniform between platforms).
  • Software renderer now is only software in how game's virtual screen is drawn, after that it presents final image using SDL_Renderer. In practice this means that it may output with DirectX or OpenGL.
  • For the same reason, had to remove Hqx scaling filters. Idk if they were much used nowadays anyway.

Notable issues / future todo:

  • May need to expand configuration option for renderer choice, e.g. to choose whether software mode uses hardware-accelerated output or not.
  • Apparently software mode works slow for non-32bit games (need to look if it's possible to improve the final rendering).

Building

Must update CI scripts. What is necessary here?

Notable issues / future todo:

  • Investigate if possible to remove Apeg dependency on libvorbis and libogg (as we have SDL2_Sound now).

@ivan-mogilko
Imported MojoAL, link SDL and SDL_sound in MSVS project
a44e4e1 
SDL2: general backend;
SDL_Sound: for reading and decoding sound formats;
MojoAL: a SDL-based implementation of OpenAL API.
@ivan-mogilko
Imported OpenALDecoder and Audio Core module
e75b560 
Based on the work of @sonneveld (Nick Sonneveld); only relevant code, plus tidied up a little.
@ivan-mogilko
Imported OPENAL_SOUNDCLIP module
92411a3 
Based on the work of @sonneveld (Nick Sonneveld); only relevant code, plus tidied up a little.
@ivan-mogilko
Replaced allegro audio with new OpenAL audio core
62d39e3 
Based on the work of @sonneveld (Nick Sonneveld).

Audio now plays only on a separate thread, unconditionally.

Removed:
* Allegro4-based SOUNDCLIP implementations;
* old audio thread (now implemented in audio core module);
* obsolete config settings;
* PSP sound cache (may be reimplemented later).
@ivan-mogilko
OpenALDecoder: factor out PollBuffers and fill some data before start
f782e84 
There's some kind of race condition with MojoAL which may try to mix-in our new clip before it gets properly initialized with data. When it does so, it drops the clip out of the slot.
Here we prevent this by polling at least some data in before calling alSourcePlay.
@ivan-mogilko
Replaced sound config with a simplier temporary on/off switch
a891e3c
@ivan-mogilko
Removed unnecessary Allegro4-based sound libraries
fe2f996
@ivan-mogilko
AudioCore: fixed notify_all() called after return statement
14a7bc1
@ivan-mogilko
Replaced allegro's main() with SDL main()
bfc5b0a
@ivan-mogilko
SDL-based window management
1692037 
Based on the work of @sonneveld (Nick Sonneveld).
@ivan-mogilko
Disabled allegro system drivers and added SDL events polling
a659581 
Unfortunately, game processing is not fit for a single event poll, as game thread may be looping in a certain state for a while before returning to the main loop (such as running a dialog script, waiting for a blocking action to complete, etc). Fixing this is a task for another time.
At the moment we are adding event polls into each sub-state.
@ivan-mogilko
Create and destroy SDL window in gfx driver class
19317b7 
Based on the work of @sonneveld (Nick Sonneveld).

Plans for the future refactoring: make gfx driver *return* SDL_Window it creates from SetDisplayMode(), and let engine save it as current render window.
@ivan-mogilko
OGL, D3D: poll events during the looping fade-in/out effect
3148472
@ivan-mogilko
OpenGL: use SDL GL functions for uniform desktop code
251c934 
Based on the work of @sonneveld (Nick Sonneveld).

This simplifies the code and makes it uniform for Linux, Windows and MacOSX altogether.
@ivan-mogilko
Rewrote Software renderer using SDL_Renderer
0fddd6f 
Based on the work of @sonneveld (Nick Sonneveld).
@ivan-mogilko
Replaced few bare key codes with constants
f57767e
@ivan-mogilko
Replaced obscure mouse buttons constants with enum
7f385b3
@ivan-mogilko
SDL-based mouse input
d055087 
Based on the work of @sonneveld (Nick Sonneveld).
@ivan-mogilko
Rewrote mouse speed option relying on SDL, and made it off by default
6ec1876 
Mouse speed control was necessary mostly for Direct3D fullscreen, because Allegro4 had some issues with mouse input in that mode. SDL2 does not seem to have such problem.
But I'd like to keep this functionality in the engine just in case, at least for some time.
@ivan-mogilko
Hide system cursor in SDL window
16c4631
@ivan-mogilko
Added SDL-AGS key code conversions, amended keycode tables
45f4444 
Based on the work of @sonneveld (Nick Sonneveld) with certain simplifications.
@ivan-mogilko
SDL-based keyboard input
ee2f2d8 
Based on the work of @sonneveld (Nick Sonneveld) with certain simplifications.

This keeps original AGS keycodes (based on allegro scancodes, although that's irrelevant now) throughout the engine, and only replaces the way it's generated from backend events.
Note that this won't be compatible with unicode text events, and simple AGS code will have to be replaced with something to optionally store unicode text as well.
Also, in the future it may be beneficial to refactor event handling globally, and pass all wanted events to the engine components, either directly, or converted to convenient custom data.
@ivan-mogilko
Use SDL_Get/SetError instead of allegro_error
eda1755
@ivan-mogilko
Common: removed few unnecessary bitmap functions
82c2722
@ivan-mogilko
Cleanup wgt2allg.h and include allegro.h more explicitly
d86c185
@ivan-mogilko
Hide remaining allegro filepath functions, also remove unused code
8c74793
@ivan-mogilko
APEG: use OpenAL sound and SDL timers instead of Allegro's
00627fd 
Based on the work of @sonneveld (Nick Sonneveld) with minor modifications and fixes.
@ivan-mogilko
Cut out Windows-only video playback support based on DirectShow
c510546
@ivan-mogilko
Deprecated Windows-only plugin API
92f7146
@ivan-mogilko
Imported stripped Allegro source, link in MSVS project
ae8b736 
AGS still uses following from Allegro lib:
* bitmaps, drawing, blending and palette functions;
* functions for loading/saving bitmaps and pcx;
* playing FLIC;
* PACKFILE (used in limited situations, e.g. FLIC);
* fixed math functions;
* file path and find-file functions;
* unicode functions;
@ivan-mogilko ivan-mogilko added backend: allegro related to allegro 4 library ags3 related to ags3 (version with full backward compatibility) backend: sdl2 related to sdl2 library labels Nov 29, 2020
@ivan-mogilko ivan-mogilko added this to the 3.6.0 milestone Nov 29, 2020
@ivan-mogilko ivan-mogilko mentioned this pull request Nov 29, 2020
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@ivan-mogilko ivan-mogilko merged commit d4b4ec4 into adventuregamestudio:ags3--sdl2 Dec 2, 2020
@ivan-mogilko
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ivan-mogilko commented Dec 2, 2020 •
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Ok, I merged this into ags3--sdl2 branch, guess it's easier for letting more people test it and find issues to fix.

I wonder, when would be a good time to merge this into ags4? Considering ags4 branch does not have any deadline/milestone yet, doubt it needs preliminary release with allegro 4 backend?

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