Manuel Alfayate Corchete
I'm trying to build SDL2 with threads support here in GNU/Linux, both X86 and ARM, and it does not seem to be possible ATM:
/home/manuel/src/SDLLLL/src/core/linux/SDL_threadprio.c:233:26: error: 'rtkit_max_realtime_priority' undeclared (first use in this function)
Manuel Alfayate Corchete
This patch is needed so programs that do this work as expected:
1) Start in a different video mode than the mode used by the system and then...
2) Try to go fullscreen with the mode originally used by the system via SetWindowFullScreen() with the SDL_WINDOW_FULLSCREEN_DESKTOP flag.
An example would be pt2-clone in https://github.com/8bitbubsy/pt2-clone.
This program does this:
Starts with:
video.window = SDL_CreateWindow("", SDL_WINDOWPOS_CENTERED,
SDL_WINDOWPOS_CENTERED, screenW, screenH, windowFlags);
and then, *IF* the user has configured it in fullscreen mode in its .ini, it tries to go fullscreen with the desktop mode:
SDL_SetWindowFullscreen(video.window, SDL_WINDOW_FULLSCREEN_DESKTOP);
This sequence of operations is currently failing because SDL_SetDisplayModeForDisplay() in SDL_video.c fails because display->desktop_mode is not being initialized with its correct value: SetDisplayMode() in SDL_kmsdrmvideo.c will not be able to set the mode because it detects the mode to have a driverdata of 0x0 ("if (!modedata)") and rightfully returns an error.
So, the included patch fixes this small problem, and programs that first change the video mode and then try to go fullscreen with the system video mode will now work.
The patch simply fixes an small omission, but its really needed now that dynamic video mode changing was implemented on the KMSDRM backend.
Ryan C. Gordon
As discussed here:
https://discourse.libsdl.org/t/question-about-implementation-of-sdl-updatewindowsurfacerects/27561
"As you can see this function [WIN_UpdateWindowFramebuffer, in src/video/windows/SDL_windowsframebuffer.c] calls BitBlt on entire screen, even though it accepts the rects. Rects variable is not even used in this function at all. Now my question is why is that the case?"
Anthony Pesch
I was looking into my own input bug and noticed an issue in the HIDAPI code while looking over it. I don't have a controller that goes down this path to test and try to provoke the issue, but it looks pretty straight forward.
The memmove to shift the joystick id array on disconnect isn't scaling the size by sizeof(SDL_JoystickID), likely corrupting the ids on disconnect.
It currently behaves like a locking key which is pressed
when Caps Lock is enabled and released when disabled. This
means that apps that trigger events on Caps Lock key down will
only fire these events every other time Caps Lock is pressed.
Lacky
It looks like refactoring of SDL2 internal API has broken SDL_RenderFillRect for DirectFB. In new version function SDL_RenderFillRect returns 0, but rectangle is not visible.
Replacing "count" with "len" in the argument list for SDL_memcpy in DirectFB_QueueFillRects fixes problem.
Jan Bujak
I wrote a new driver for my gamepad on Linux. I'd like SDL to support it out-of-box, as currently it just treats it as a generic joystick instead of a gamepad. From what I can see the only way to do that is to either 1) pick one of the already supported controllers' PID, VID and button layouts and have my driver send that (effectively lying that it's something else), or 2) submit a preconfigured, hardcoded mapping to SDL.
Both of those, in my opinion, are silly when we already have the Linux Gamepad Specification which standarizes this:
https://www.kernel.org/doc/html/v4.15/input/gamepad.html
Unfortunately SDL doesn't make use of it currently. So I've took it upon myself to add it; patch is in the attachments.
Basically what the patch does is that if SDL finds no built-it controller mappings for a given joystick it then asks the joystick backend to autodetect it, and that uses the relevant evdev bits to figure out which button/axis is which. (See the specs for more details.)
With this patch applied my own driver for my controller works out-of-box with SDL with no extra configuration and is correctly recognized as a gamepad; this is also going to be the case for any other driver which follows the Linux Gamepad Specification.
Arithmatic operations promote Uint8 to signed int. If the top bit of a
Uint8 is set, and it is left shifted 24 places, then the result is not
representable in a signed 32 bit int. This would be undefined behaviour
on systems where int is 32 bits.
It makes it clearer who owns the memory, and more reasonable to free it on
failure in the creating function.
(and, of course, pacifies static analysis.)
Manuel Alfayate Corchete
On the KMSDRM backend, there is no such thing as a desktop, yet some programs could (and DO) use SDL_GetGlobalMouseState().
So I think its good idea that, in KMSDRM, it returns the same mouse coordinates anyway as SDL_GetMouseState() would return. There is nothing else it could return, as far as I can understand, since there is no desktop anyway.
This small patch does precisely that.
Manuel Alfayate Corchete
The KMSDRM backend was doing things wrong because of some small (but important) misconceptions on how KMS/DRM works: to implement a largely broken non-vsync refresh mechanism, the SwapWindow() function was issuing new pageflips before previous ones had completed, thus causing EBUSY returns, buffer mismanagement, etc... resulting in general breakage on vsync disabling from apps, that would not allow vsync to work again without KMSDRM video re-initialization.
To further clarify, on most DRM drivers async pageflips are NOT working nowadays, so all issued pageflips will complete on next VBLANK, NOT ASAP (calling drmModePageFlip() with the DRM_MODE_PAGE_FLIP_ASYNC flag will return error).
The old code was assuming that can just issue a synchronous (=on VBLANK) pageflip and then pass a 0 timeout to the pull() function so we do not wait for the pageflip event, thinking that this will lead to correct non-vsynced screen updates from the program: That is plain wrong.
Each pageflip has to be waite before issuing a new one, ALWAYS. And if we do not support ASYNC pageflips on the DRM driver level, then we are forced to wait for the next VBLANK. There is no way around it.
I have also added many comments on the KMSDRM code. This is needed for future reference for me or others who may need to look at this code: KMS/DRM terminology regarding what SYNC and ASYNC mean in pageflip terms, and where to do certain things and why, is not trivial. It is not desirable or possible to invest time on researching the same concepts every time there is need to dive into this code. So please leave all these comments in the patch.
1. Comment that SDL_SetThreadPriority will make any necessary system changes when applying priority.
2. Add a hint to override SDL's default behavior for scheduler policy.
3. Modify the pthreads SDL_SetThreadPriority so that instead of just using the current thread scheduler policy it will change it to a policy that should work best for the requested priority.
4. Add hint checks in SDL_SetThreadPriority so that #3 can be overridden if desired.
5. Modify the Linux SDL_SetThreadPriority so that in the case that policy, either by SDL defaults or from the hint, is a realtime policy it uses the realtime rtkit API.
6. Prior to calling rtkit on Linux make the necessary thread state changes that rtkit requires. Currently this is done every time as it isn't expected that SDL_SetThreadPriority will be called repeatedly for a thread.
Sam Lantinga
Ryan C. Gordon
Cameron Gutman
Tudor Brindus
James Legg
Brendan Shanks