Mart?n Golini
I'm having a very slow initialization of the video subsystem that locks the window creation for about 500 ms ( tested in at least 4 different systems ). What i found is that X11_InitModes_XRandR is using XRRGetScreenResources, that explicitly ask to poll the hardware for changes. This is not really necessary since if the data is already available you can use XRRGetScreenResourcesCurrent.
I attached a tentative patch that fix this issue. With the patch there's no lock when the subsystem is initialized and the window creation is instant in my applications. The patch only uses XRRGetScreenResourcesCurrent in X11_InitModes_XRandR but it could be potentially used in X11_GetDisplayModes and X11_SetDisplayMode.
Levi Bard
In some environments, xrandr modes initialization can fail even though xrandr support is present and of a sufficient version.
(The one I encountered was an AWS instance running a virtual display)
The attached patch allows SDL to keep trying other methods if xrandr modes initialization fails (still subject to SDL_VIDEO_X11_REQUIRE_XRANDR).
Ozkan Sezer
On systems with old glibc, such mine with glibc-2.8, the following warning
is issued and is fixed easily by defining _GNU_SOURCE:
/home/me/SDL2-2.0.5/src/video/x11/SDL_x11modes.c: In function 'CalculateXRandRRefreshRate':
/home/me/SDL2-2.0.5/src/video/x11/SDL_x11modes.c:263: warning: implicit declaration of function 'round'
/home/me/SDL2-2.0.5/src/video/x11/SDL_x11modes.c:263: warning: incompatible implicit declaration of built-in function 'round'
Michael
In SDL_x11modes.c the CalculateXRandRRefreshRate() function performs integer math on values that may return fractional results. This causes a value that would be calculated as 59.99972... to be returned as 59. In Linux the xrandr command returns 60Hz for this particular display mode yet SDL returns 59Hz.
I suggest this function be updated to correctly round the result of the calculation instead of truncating the result.
Notably: it sets the error string to inform you that your custom SDL is built
without xrandr support, which apparently has been a support issue for
Unreal Engine 4 developers.
The internal function SDL_EGL_LoadLibrary() did not delete and remove a mostly
uninitialized data structure if loading the library first failed. A later try to
use EGL then skipped initialization and assumed it was previously successful
because the data structure now already existed. This led to at least one crash
in the internal function SDL_EGL_ChooseConfig() because a NULL pointer was
dereferenced to make a call to eglBindAPI().
