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x11: Deal with difference in GLX_EXT_swap_control_tear behavior. 

Mesa and Nvidia handle it differently, and one or the other may fix their
implementation in the future, so test which way it works at runtime.

Reference Issue #8004.
main
Ryan C. Gordon 2023-11-23 13:47:13 -05:00
parent 08fac5b1b2
commit 74a2542564
No known key found for this signature in database
GPG Key ID: FA148B892AB48044
3 changed files with 86 additions and 13 deletions
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68
src/video/x11/SDL_x11opengl.c
View File

@ -237,6 +237,8 @@ int X11_GL_LoadLibrary(SDL_VideoDevice *_this, const char *path)
return SDL_SetError("GLX is not supported");
}
_this->gl_data->swap_interval_tear_behavior = SDL_SWAPINTERVALTEAR_UNTESTED;
/* Initialize extensions */
/* See lengthy comment about the inc/dec in
../windows/SDL_windowsopengl.c. */
@ -902,7 +904,6 @@ int X11_GL_SetSwapInterval(SDL_VideoDevice *_this, int interval)
X11_GL_GetSwapInterval(_this, &currentInterval);
_this->gl_data->glXSwapIntervalEXT(display, drawable, currentInterval);
_this->gl_data->glXSwapIntervalEXT(display, drawable, interval);
status = 0;
swapinterval = interval;
} else if (_this->gl_data->glXSwapIntervalMESA) {
@ -925,6 +926,53 @@ int X11_GL_SetSwapInterval(SDL_VideoDevice *_this, int interval)
return status;
}
static SDL_GLSwapIntervalTearBehavior CheckSwapIntervalTearBehavior(SDL_VideoDevice *_this, Window drawable, unsigned int current_val, unsigned int current_allow_late)
{
/* Mesa and Nvidia interpret GLX_EXT_swap_control_tear differently, as of this writing, so
figure out which behavior we have.
Technical details: https://github.com/libsdl-org/SDL/issues/8004#issuecomment-1819603282 */
if (_this->gl_data->swap_interval_tear_behavior == SDL_SWAPINTERVALTEAR_UNTESTED) {
if (!_this->gl_data->HAS_GLX_EXT_swap_control_tear) {
_this->gl_data->swap_interval_tear_behavior = SDL_SWAPINTERVALTEAR_UNKNOWN;
} else {
Display *display = _this->driverdata->display;
unsigned int allow_late_swap_tearing = 22;
int original_val = (int) current_val;
/*
* This is a workaround for a bug in NVIDIA drivers. Bug has been reported
* and will be fixed in a future release (probably 319.xx).
*
* There's a bug where glXSetSwapIntervalEXT ignores updates because
* it has the wrong value cached. To work around it, we just run a no-op
* update to the current value.
*/
_this->gl_data->glXSwapIntervalEXT(display, drawable, current_val);
/* set it to no swap interval and see how it affects GLX_LATE_SWAPS_TEAR_EXT... */
_this->gl_data->glXSwapIntervalEXT(display, drawable, 0);
_this->gl_data->glXQueryDrawable(display, drawable, GLX_LATE_SWAPS_TEAR_EXT, &allow_late_swap_tearing);
if (allow_late_swap_tearing == 0) { /* GLX_LATE_SWAPS_TEAR_EXT says whether late swapping is currently in use */
_this->gl_data->swap_interval_tear_behavior = SDL_SWAPINTERVALTEAR_NVIDIA;
if (current_allow_late) {
original_val = -original_val;
}
} else if (allow_late_swap_tearing == 1) { /* GLX_LATE_SWAPS_TEAR_EXT says whether the Drawable can use late swapping at all */
_this->gl_data->swap_interval_tear_behavior = SDL_SWAPINTERVALTEAR_MESA;
} else { /* unexpected outcome! */
_this->gl_data->swap_interval_tear_behavior = SDL_SWAPINTERVALTEAR_UNKNOWN;
}
/* set us back to what it was originally... */
_this->gl_data->glXSwapIntervalEXT(display, drawable, original_val);
}
}
return _this->gl_data->swap_interval_tear_behavior;
}
int X11_GL_GetSwapInterval(SDL_VideoDevice *_this, int *interval)
{
if (_this->gl_data->glXSwapIntervalEXT) {
@ -935,6 +983,7 @@ int X11_GL_GetSwapInterval(SDL_VideoDevice *_this, int *interval)
unsigned int val = 0;
if (_this->gl_data->HAS_GLX_EXT_swap_control_tear) {
allow_late_swap_tearing = 22; /* set this to nonsense. */
_this->gl_data->glXQueryDrawable(display, drawable,
GLX_LATE_SWAPS_TEAR_EXT,
&allow_late_swap_tearing);
@ -943,12 +992,21 @@ int X11_GL_GetSwapInterval(SDL_VideoDevice *_this, int *interval)
_this->gl_data->glXQueryDrawable(display, drawable,
GLX_SWAP_INTERVAL_EXT, &val);
if ((allow_late_swap_tearing) && (val > 0)) {
*interval = -((int)val);
return 0;
*interval = (int)val;
switch (CheckSwapIntervalTearBehavior(_this, drawable, val, allow_late_swap_tearing)) {
case SDL_SWAPINTERVALTEAR_MESA:
*interval = (int)val; /* unsigned int cast to signed that generates negative value if necessary. */
break;
case SDL_SWAPINTERVALTEAR_NVIDIA:
default:
if ((allow_late_swap_tearing) && (val > 0)) {
*interval = -((int)val);
}
break;
}
*interval = (int)val;
return 0;
} else if (_this->gl_data->glXGetSwapIntervalMESA) {
int val = _this->gl_data->glXGetSwapIntervalMESA();

10
src/video/x11/SDL_x11opengl.h
View File

@ -29,6 +29,14 @@
typedef void (*__GLXextFuncPtr)(void);
typedef enum SDL_GLSwapIntervalTearBehavior
{
SDL_SWAPINTERVALTEAR_UNTESTED,
SDL_SWAPINTERVALTEAR_UNKNOWN,
SDL_SWAPINTERVALTEAR_MESA,
SDL_SWAPINTERVALTEAR_NVIDIA
} SDL_GLSwapIntervalTearBehavior;
struct SDL_GLDriverData
{
int errorBase, eventBase;
@ -50,6 +58,8 @@ struct SDL_GLDriverData
int minor;
} es_profile_max_supported_version;
SDL_GLSwapIntervalTearBehavior swap_interval_tear_behavior;
Bool (*glXQueryExtension)(Display *, int *, int *);
__GLXextFuncPtr (*glXGetProcAddress)(const GLubyte *);
XVisualInfo *(*glXChooseVisual)(Display *, int, int *);

21
test/testgl.c
View File

@ -199,6 +199,17 @@ static void Render(void)
ctx.glRotatef(5.0, 1.0, 1.0, 1.0);
}
static void LogSwapInterval(void)
{
int interval = 0;
const int ret_interval = SDL_GL_GetSwapInterval(&interval);
if (ret_interval < 0) {
SDL_Log("Swap Interval : %d error: %s\n", interval, SDL_GetError());
} else {
SDL_Log("Swap Interval : %d\n", interval);
}
}
int main(int argc, char *argv[])
{
int fsaa, accel;
@ -211,8 +222,6 @@ int main(int argc, char *argv[])
int status;
int dw, dh;
int swap_interval = 0;
int interval = 0;
int ret_interval = 0;
/* Initialize parameters */
fsaa = 0;
@ -304,12 +313,7 @@ int main(int argc, char *argv[])
SDL_Log("Screen BPP : %" SDL_PRIu32 "\n", SDL_BITSPERPIXEL(mode->format));
}
ret_interval = SDL_GL_GetSwapInterval(&interval);
if (ret_interval < 0) {
SDL_Log("Swap Interval : %d error: %s\n", interval, SDL_GetError());
} else {
SDL_Log("Swap Interval : %d\n", interval);
}
LogSwapInterval();
SDL_GetWindowSize(state->windows[0], &dw, &dh);
SDL_Log("Window Size : %d,%d\n", dw, dh);
@ -421,6 +425,7 @@ int main(int argc, char *argv[])
SDL_GL_MakeCurrent(state->windows[i], context);
if (update_swap_interval) {
SDL_GL_SetSwapInterval(swap_interval);
LogSwapInterval();
}
SDL_GetWindowSizeInPixels(state->windows[i], &w, &h);
ctx.glViewport(0, 0, w, h);