Lee Salzman
I messed up in the patch I sent you regarding gobbling up the GLX error codes signaled when trying to create a context. After reading the spec I realized those error codes are relative to a base error that needs to be queried when setting up the GLX extension...
So I have made a patch that fixes it for a user I had who was still getting the bug with my old patch.
Without this patch my previous one won't work, so it is recommended to merge this...
The SDL OpenGL context code is now properly thread aware. There are two new functions which return the current OpenGL window and context for the current thread.
There are still places in the cocoa driver where the OpenGL context needs to be updated when the view changes. These will need a different solution and still use the last globally set context to avoid changing behavior.
This lets us change things like this...
if (Failed) {
SDL_SetError("We failed");
return -1;
}
...into this...
if (Failed) {
return SDL_SetError("We failed");
}
Fixes Bugzilla #1778.
Lee Salzman
When using SDL_GL_CreateContext() to create a >= 3.0 version or core/forward-compatible context, internally glXCreateContextAttribsARB is used. Mesa in particular seems to be having trouble with this call and returning all sorts of errors, so it is dangerous to poll for the highest GL version by using calls to SDL_GL_CreateContext unless you are sure, a priori, that the call will suceed, defeating the point of its use.
X11 protocol errors are of the following form, with varying details depending on user, but the cause is always SDL_GL_CreateContext as above...
X Error of failed request: GLXBadFBConfig
Major opcode of failed request: 153 (GLX)
Minor opcode of failed request: 34 ()
Serial number of failed request: 215
Current serial number in output stream: 221
These sorts of errors can be temporarily filtered out by setting an X11 error handler to catch and ignore them, which is safe with respect to SDL_GL_CreateContext behavior because this function is allowed to return NULL to indicate failure.
A patch is attached to do this temporary filtering/catching of errors generated by trying to use glXCreateContextAttribs and friends...
This works around a bug in NVIDIA's implementation of
glXSwapIntervalEXT, where it ignores updates to what it *thinks* is the
current value, even though glXQueryDrawable returns a different value.
Bug reported to NVIDIA and will hopefully be a part of 319.xx.
Also a fix for invalidly treating glXSwapIntervalEXT as having an int
return value (it's void).
Our new X11 window was being created with the TrueColor attribute, and trying to set the gamma
on that would fail. This change checks for the visual_info extension, and uses that to ask for
DirectColor if available.
Matthias Bentrup 2012-08-09 12:53:17 PDT
With OpenGL 4.3 the ARB added a new context flag for context reset isolation
and renamed the existing ES2 profile bit to ES profile bit, as it can be used
to request GLES 3 compatible contexts, too.
This patch adds these changes to SDL on Linux and Windows.
Also SDL lacks the ability to create shared contexts. This patch also adds a
new GL attribute to enable context sharing. As casting a GL context to int is
not portable, I added only a boolean attribute
SDL_GL_SHARE_WITH_CURRENT_CONTEXT, which makes the new context share resources
with the context current on the creating thread.
This required a small public API change: SDL_GL_SetSwapInterval() now accepts
negative values, and SDL_GL_GetSwapInterval() doesn't report errors anymore
(if it can't work, it'll return zero as a reasonable default).
If you need to test for errors, such as a lack of swap_control_tear support,
check the results of SDL_GL_SetSwapInterval() when you set your desired
value.
From Scott Percival
Okay, I think I have something for this. Tested it on GL and GLES
machines, it seems to work okay.
- Add a new SDL GL attribute SDL_GL_CONTEXT_EGL:
- Only useful for the X11 video driver at the moment
- Set to 1 for an EGL context, 0 to use the default for the video driver
- Default is 0, unless library is built for EGL only
- Should be set after SDL init, but before window/context
creation (i.e. same place you'd specify attributes for major/minor GL
version)
- After a lot of agony pondering the least-terrible way to go about
it, made it so that X11_GL_LoadLibrary and X11_GLES_LoadLibrary check
SDL_GL_CONTEXT_EGL. If no GL context exists yet, and the attribute
choice doesn't match with the checking function, then it changes all
the function pointers in the video driver and passes control on to the
new LoadLibrary method.
- Likewise, make X11_CreateWindow check this attribute before firing
off a call to X11_GL_GetVisual/X11_GLES_GetVisual
- Added a sanity check to the start of X11_GL_LoadLibrary
- Tidied up SDL_x11opengles.h
- Moved ownership of the gles_data structure over to
X11_GLES_LoadLibrary/UnloadLibrary
- Should incorporate the 3 fixes posted by Andre Heider
This is obviously quite a bit to take in, but is (at least) a proof of
concept for the approach I think EGL/GLX mingling should take. Any
comments/criticism is much appreciated.
Matthias Bentrup 2011-10-30 03:58:24 PDT
I've updated the context creation patch to include the bugfixes by Martin
Schreiber and also included a profile bit to request a ES2 compatible profile.
The wgl context creation may use 2 call to wglChoosePixelFormat if no
acceleration attribute is selected, this should work around a bug with buggy
AMD drivers (see #1254).
Revision 6 of the GLX_EXT_swap_control spec has a typo; the function
signature they list is void, but the docs talk about a return value, and the
glxext.h headers list "int".
Matthias 2011-02-23 09:37:51 PST
Please view the attached source file. Using this minimal program (as attached),
it creates an OpenGL 2.0 context with a cleared color buffer. If I set the
OpenGL version to 3.2, the function SDL_GL_CreateContext fails (or more
specifically, glXMakeCurrent fails) with an X11 BadMatch error:
X Error of failed request: BadMatch (invalid parameter attributes)
Major opcode of failed request: 128 (GLX)
Minor opcode of failed request: 5 (X_GLXMakeCurrent)
Serial number of failed request: 153
Current serial number in output stream: 153
Also note that if I do not specify the alpha buffer size, the program works for
OpenGL 2.0 and OpenGL 3.2.
After some further analysis, I believe I have found the problem. The specific
issue is in:
SDL_x11opengl.c::X11_GL_CreateContext.
Note that for OpenGL 3.2 contexts, the GLXFBConfig to use is chosen as the best
match from glXChooseFBConfig. However, opengl attributes originally set with
SDL_GL_SetAttribute are not mapped to GLX attributes and then passed to the
glXChooseFBConfig function. According to the GLX 1.4 specification, if the
attributes are not specified, the function falls back to defaults (which, in
this particular case, prefer alpha channel size == 0).
For testing purposes, I modified the call to glXChooseFBConfig to look
something like this:
int glxAttribs[] =
{
GLX_RED_SIZE,8,
GLX_GREEN_SIZE,8,
GLX_BLUE_SIZE,8,
GLX_ALPHA_SIZE,8,
None
};
if (!glXChooseFBConfig ||
!(framebuffer_config = glXChooseFBConfig(display, DefaultScreen(display),
glxAttribs, &fbcount)))
{
...
}
The best match GLXFBConfig then supports 8 bit alpha channel. The program then
works as intended.
Hope this helps!
