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!
Unfortunately the audio and cdrom systems do not build at all, and if you
disable those, SDL still fails to link with these errors:
Undefined symbols:
"_OBJC_IVAR_$_NSScreen._frame", referenced from:
-[NSScreen(NSScreenAccess) setFrame:] in SDL_cocoamodes.o
"_KLGetKeyboardLayoutProperty", referenced from:
_UpdateKeymap in SDL_cocoakeyboard.o
_UpdateKeymap in SDL_cocoakeyboard.o
"_KLGetCurrentKeyboardLayout", referenced from:
_UpdateKeymap in SDL_cocoakeyboard.o
ld: symbol(s) not found
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From michalziulek@gmail.com 2009-03-28 07:43:34 (-) [reply]
There is a bug in OpenGL 3.x context creation code.
Function glXGetProcAddress is used directly where it should be:
_this->gl_data->glXGetProcAddress. I have attached patch which fixes this on
x11 and win32. Thanks.
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From: Luke Benstead
Subject: OpenGL 3.0 Context Creation
I've attached a patch which implements OpenGL 3.x context creation on
the latest SVN. I've added two options to SDL_GL_SetAttribute, these
are SDL_GL_CONTEXT_MAJOR_VERSION and SDL_GL_CONTEXT_MINOR_VERSION.
These default to 2 and 1 respectively. If the major version is less
than 3 then the current context creation method is used, otherwise the
appropriate new context creation function is called (depending on the
platform).
Sample code:
if (SDL_Init(SDL_INIT_VIDEO) != 0) {
printf("Unable to initialize SDL: %s\n", SDL_GetError());
return 1;
}
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3); //Without these 2 lines, SDL will create a GL 2.x context
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
SDL_Surface* screen = SDL_SetVideoMode( 640, 480, 16, SDL_OPENGL | SDL_FULLSCREEN );
I've implemented context creation on both Win32 and X and run basic
tests on both. This patch doesn't provide access to all the options
allowed by the new context creation (e.g. shared contexts, forward
compatible contexts) but they can be added pretty easily.
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Make sure OpenGL library is loaded before working with OpenGL windows,
even those created with SDL_CreateWindowFrom()
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Port SDL 1.3 to the Nintendo DS
by Darren Alton, mentored by Sam Lantinga
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Using the following sequence
SDL_Init(..:)
SDL_CreateWindow(..., SDL_WINDOW_OPENGL)
SDL_DestroyWindow
SDL_CreateWindow(..., SDL_WINDOW_OPENGL)
SDL will crash in X11_GL_GetVisual. This is due to the fact that
during SDL_DestroyWindow X11_GL_Shutdown was called because the last window
has been closed.
On the next call to SDL_CreateWindow the library is still loaded and only the
memory is reinitialized. Function pointers such as gl_data->glXChooseVisual
will not be reinitialized.
Consequently, SDL will crash due to a NULL pointer access.
The attached patch corrects the behaviour.
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working earlier this week.
I added some more trace code to SDL_x11events.c
In SDL_X11opengl.c I modified SDL_GL_GetSwapInterval() so that it returns a pretty good value even if you have the SGI swap extension instead of the MESA swap
extension. I just saved the value you set and return it too you.
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One of the error was the result of an unitended recursive call to X11_GL_LoadLibrary which was also fixed.
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is incorrect. The result is that an illegal access is being made in X_PumpEvents when it tries to look up the windows ID of the source of an event. Taking out that
call does not seem to have any effect on the testgl. But, I would be happy if someone else took a look at this problem and found a fix higher up the stack.
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From: Couriersud
Subject: Some SDL1.3 patches
LoadLibrary will call X11_GL_Initialize. If LoadLibrary is called before
a window is created, it will crash since structures are not properly set
up.
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