This allows you to bind surfaceless contexts on a background thread to, for
example, load assets in a separate context, for platforms that have different
requirements about sharing surfaces, etc.
Martin's notes on the matter:
"Here's a patch that enables passing NULL windows to SDL_GL_MakeCurrent, if
the involved APIs allow it. Currently, this is only the case for EGL, and
even then only if some specific extensions are present (which they usually
are).
If "surfaceless" contexts are not supported, SDL_GL_MakeCurrent continues to
generate an error (albeit with a more specific error message than it used to),
so this should not break anything that wasn't broken before."
(Please see https://bugzilla.libsdl.org/show_bug.cgi?id=3695 for more
discussion.)
Fixes Bugzilla #3695.
The Offscreen video driver is intended to be used for headless rendering
as well as allows for multiple GPUs to be used for headless rendering
Currently only supports EGL (OpenGL / ES) or Framebuffers
Adds a hint to specifiy which EGL device to use: SDL_HINT_EGL_DEVICE
Adds testoffscreen.c which can be used to test the backend out
Disabled by default for now
Rainer Sabelka
After I did an upgrade of my arch Linux installation (resulting in an update of Mesa to version 18.2.3), all my SDL2 applications which use the KMS/DRM driver stopped working.
Reason: Creating a Window with SDL_CreateWindow failed because the call to EGL
eglCreateWindowSurface() returns an error "EGL_BAD_MATCH".
After investigating with the debugger I figured, that the configuration, which has been selected from the output of eglChooseConfig(), has an "EGL_NATIVE_VISUAL_ID" which does not match the "format" of the underlying gbm surface.
The attached patch fixes the problem. It does so, by mimicking Weston's behavior.
All configurations returned from eglChooseConfig() which have an visual_id different from the gbm format are discarded, and only from the remaining ones the "best" match is selected.
tomwardio
Proposed patch loads eglCreatePbufferSurface in same manner as other 1.1 functors. This allows custom video drivers to create pbuffer surfaces.
tomwardio
Add support to be able to set EGL_SURFACE_TYPE bits when creating an EGL config. This is usefule when wanting to create pixel buffer surfaces in custom video drivers.
Manuel
The attached patch adds support for KMS/DRM context graphics.
It builds with no problem on X86_64 GNU/Linux systems, provided the needed libraries are present, and on ARM GNU/Linux systems that have KMS/DRM support and a GLES2 implementation.
Tested on Raspberry Pi: KMS/DRM is what the Raspberry Pi will use as default in the near future, once the propietary DispmanX API by Broadcom is overtaken by open graphics stack, it's possible to boot current Raspbian system in KMS mode by adding "dtoverlay=vc4-kms-v3d" to config.txt on Raspbian's boot partition.
X86 systems use KMS right away in every current GNU/Linux system.
Simple build instructions:
$./autogen.sh
$./configure --enable-video-kmsdrm
$make
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().
