wl_display_dispatch() will block if there are no events available, and
while we try to avoid this by using SDL_IOReady() to verify there are
events before calling it, there is a race condition between
SDL_IOReady() and wl_display_dispatch() if multiple threads are
involved.
This is made more likely by the fact that SDL_GL_SwapWindow() calls
wl_display_dispatch() if vsync is enabled, in order to wait for frame
events. Therefore any program which pumps events on a different thread
from SDL_GL_SwapWindow() could end up blocking in one or other of them
until another event arrives.
This change fixes this by wrapping wl_display_dispatch() in a new mutex,
which ensures only one thread can compete for wayland events at a time,
and hence the SDL_IOReady() check should successfully prevent either
from blocking.
Some wayland compositors report the refresh rate as 0. Since we want to
force a minimum refresh rate of 10 frames worth, we were dividing by the
reported refresh rate, causing a divide-by-zero.
If the refresh rate is 0, instead force a frame every second if no frame
callbacks are received.
This fixes bug #4785
If you hide a window on Mutter, for example, the compositor never requests
new frames, which will cause Mesa to block forever in eglSwapBuffers to
satisfy the swap interval.
We now always set the swap interval to 0 and manage this ourselves, handing
the frame to Wayland when it requests a new one, and timing out at 10fps just
to keep apps moving if the compositor wants no frames at all.
My understanding is that other protocols are coming that might improve upon
this solution, but for now it solves the total hang.
Fixes#4335.
OpenGL apparently needs to not do any drawing between wl_egl_window_resize
and eglSwapBuffers, but Vulkan apps don't use SDL to present, so they
never call into an equivalent of SDL_GL_SwapWindow where our Wayland code
was handling pending resize work.
Fixes Bugzilla #4722.
For starters, we need to correctly respond to 0,0 configure after unsetting
fullscreen. Also, turns out that there should be no drawing calls at all
in between eglSwapBuffers and wl_egl_window_resize, as otherwise EGL can
already allocate a wrongly sized buffer for a next frame, so handle those
together.
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().
